Ice Jam Flooding and Mitigation

Lower Platte River Basin, Nebraska

Kathleen D. White and Roger L. Kay January 1996

SPECIAL REPORT 96-1
Abstract

This report presents the results of the Corps of Engineers’ Section 22 study

of ice jam flooding in the Lower Platte River basin. The purpose of the study

was to gather and analyze historical data relating to ice jams, with the

intent of developing guidance that can be used to alleviate ice jam flooding

at seven sites within the study area. Ice event and related information is

summarized for each site. Ice event characteristics for the study area are

identified and analyzed. A model for predicting the occurrence of ice jams

or other ice events within the study area was developed based on data for

the Platte River at North Bend, Nebraska. The model provides the minimum

discharge associated with ice events for a given date, assuming a threshold value of accumulated freezing degree-days has been reached. A data

collection program for future field observations was developed and placed

in operation during the winter of 1993-94. General information on ice jam

mitigation measures, as well as specific information on such operations as

dusting and blasting, is provided. Specific recommendations include increased monitoring of ice conditions, installation of ice motion detectors

and water stage recorders, and further study of nonstructural and structural

mitigation measures. The use of dusting and blasting as mitigation measures is also presented. The study was divided into six phases. Phase 1

involved collection of historical information from all available data sources,

published and oral. Site visits were made to each identified site. Phase 2

entailed analysis and assessment of the collected hydrological, hydraulical,

meteorological and ice data. Aerial reconnaissance of each of the seven

sites was also made during the ice-covered season. The third phase involved the design of the data collection program and database. Personnel

from CRREL conducted a workshop to train ice observers and other interested parties in data collection, while the database design was done by the

Nebraska Natural Resources Commission. Phase 4 was the assessment of

mitigation and prediction techniques. Various mitigation techniques were

evaluated for feasibility, and several were recommended for further study. A

model was developed to forecast the occurrence and severity of ice jams

utilizing collectable data. The fifth phase involved the development of guidance on the application of specific preventive measures, such as dusting

and blasting. The final phase involved the compilation of all work into this

report.

For conversion of SI units to non-SI units of measurement consult ASTM

Standard E380-93, Standard Practice for Use of the International System

of Units, published by the American Society for Testing and Materials,

1916 Race St., Philadelphia, Pa. 19103.

This report is printed on paper that contains a minimum of 50% recycled

material.
Special Report 96-1

Ice Jam Flooding and Mitigation

Lower Platte River Basin, Nebraska

Kathleen D. White and Roger L. Kay January 1996

Prepared for

U.S. ARMY ENGINEER DISTRICT, OMAHA

STATE OF NEBRASKA GOVERNOR’S EMERGENCY FUND

STATE OF NEBRASKA NATURAL RESOURCES COMMISSION

Approved for public release; distribution is unlimited.

US Army Corps


of Engineers

Cold Regions Research &


Engineering Laboratory
PREFACE

This report was prepared by Kathleen D. White, Research Hydraulic Engineer, Ice

Engineering Research Division, Research and Engineering Directorate, U.S. Army Cold

Regions Research and Engineering Laboratory (CRREL); and Roger L. Kay, Hydraulic

Engineer, Hydrologic Engineering Branch, Engineering Division, U.S. Army Engineer

District, Omaha (CEMRO). Project funding was provided by the U.S. Army Engineer

District, Omaha, by the State of Nebraska Governor’s Emergency Fund and by the State of

Nebraska Natural Resources Commission.

The authors acknowledge the contributions of John Gagnon (CRREL) and Chris Horihan and Marty Cieslik (CEMRO) in assembling the large amount of data required in this

study. In addition, Steven Daly (CRREL) was a valuable resource in the development of

the predictive model, which used HECDSS routines written by Mr. Daly. The contributions of Jon Zufelt (data collection) and James Wuebben and Jean-Claude Tatinclaux

(overview of mitigation), all from CRREL, are also gratefully acknowledged. Additionally, the authors recognize the valuable information and assistance provided by Robert

Buchholz and Debra Brey (CEMRO), Ralph Medina (Nebraska Civil Defense), Brian

Dunnigan and Mahendra Bansal (Nebraska Natural Resources Commission), Glenn Engel (Lincoln, Nebraska, USGS), Roy Osugi (National Weather Service, Omaha), Marlin

Petermann (Papio–Missouri Natural Resource District) and Cheryl Mueller (Columbus,

Nebraska). The authors also acknowledge the staff of the Lower Loup, Lower Platte North

and Papio–Missouri River Natural Resource Districts for their assistance in providing

workshop sites. The authors also acknowledge the many citizens of the State of Nebraska

and staff of various local, state and Federal agencies not mentioned above who attended

meetings and workshops, providing much valuable information about ice jam locations

and dates.

The contents of this report are not to be used for advertising or promotional purposes.

Citation of brand names does not constitute an official endorsement or approval of the use

of such commercial products.

ii
CONTENTS

Page

Preface ................................................................................................................................. ii

Introduction........................................................................................................................ 1

Historical data .................................................................................................................... 2

Ice records ...................................................................................................................... 3

Hydrological data ......................................................................................................... 4

Meteorological records ................................................................................................ 4

Summary of historical data collected ........................................................................ 6

Analysis of data ................................................................................................................. 16

Historical data ............................................................................................................... 16

Hydraulic analysis........................................................................................................ 20

Predictive model for ice jam occurrence ........................................................................ 23

Past methods ................................................................................................................. 23

Lower Platte River predictive model ........................................................................ 24

Data collection program design ...................................................................................... 30

Freeze-up conditions .................................................................................................... 31

Ice cover characteristics ............................................................................................... 31

Jam formation and evolution ...................................................................................... 34

Other useful data .......................................................................................................... 34

Database structure............................................................................................................. 35

Ice jam mitigation measures ............................................................................................ 37

Permanent measures .................................................................................................... 38

Advance measures ....................................................................................................... 39

Emergency measures ................................................................................................... 40

Specific mitigation options within the study area .................................................. 41

Conclusions ........................................................................................................................ 53

Literature cited ................................................................................................................... 54

Appendix A: Model results for the Loup River near Columbus ............................... 57

Appendix B: Model results for the Platte River along Sarpy County, Nebraska .... 59

Appendix C: Nebraska Disaster and Civil Defense Act ............................................. 65

Appendix D: Legal opinion on Nebraska law concerning the removal of

ice jams ........................................................................................................................... 85

Abstract ............................................................................................................................... 87

ILLUSTRATIONS

Figure

1. Lower Platte River Section 22 study sites ............................................................ 1

2. AFDD at the national Weather Service Station at North Platte, Nebraska,

during water year 1960 ...................................................................................... 5

3. Identified recurring ice jam sites on the Loup River between Genoa

and Columbus ..................................................................................................... 6

4. Loup River flows and daily air temperatures ..................................................... 8

iii
Figure Page

5. Identified recurring ice jam sites on the Platte River between North Bend

and Ashland ......................................................................................................... 10

6. Ice-related peak annual stages at the USGS gage for the Platte River at

North Bend for the period 1949 through 1992 ............................................... 11

7. Normalized stage for ice events between 1950 and 1990 for the gages in the

study area plus the Elkhorn River at Waterloo .............................................. 16

8. Statistics for the ice events shown in Figure 7 ..................................................... 18

9. Relationships among normalized stage, maximum discharge and maximum

AFDD for January through March, water years 1950 through 1990 .......... 19

10. Relationships among dates of occurrence of maximum ice-related stage,

maximum discharge and maximum AFDD for January through

March, water years 1950 through 1990 ............................................................ 20

11. Typical Platte River partial valley cross section upstream of Highway 6

in Sarpy County .................................................................................................. 22

12. Relationship between the observed and predicted values of normalized

stage at North Bend ................................................................................................. 26

13. Average daily discharge at the time of the maximum ice stage vs.

Julian Day ............................................................................................................. 28

14. Minimum discharge required for ice jam vs. Julian Day .................................. 28

15. AFDD at Columbus vs. date for winter 1993-94 ................................................. 29

16. Minimum discharge required for ice jam for 1 February to 8 March 1994 ..... 29

17. Nebraska ice report data collection form ............................................................. 32

18. System connectivity ................................................................................................. 35

19. Schematic of data transfer from branch site to home base ................................ 36

20. Schematic of on-line data retrieval at branch site ............................................... 36

21. Schematic of complete data download before processing ................................ 37

22. Ice motion detector .................................................................................................. 40

23. Minimum charge placed below ice surface required to break ice.................... 50

24. Crater diameter for ANFO charges placed just below the underside of

the ice .................................................................................................................... 50

TABLES

Table

1. Locations and water years of ice thickness measurements obtained

from USGS ............................................................................................................ 3

2. USGS data sources ................................................................................................... 4

3. National Weather Service meteorological data sources ..................................... 4

4. Maximum annual gage heights associated with ice at the USGS gage on

the Loup River near Genoa ............................................................................... 6

5. Maximum annual gage heights associated with ice at the USGS gage on

the Loup River at Columbus ............................................................................. 9

6. Summary of ice events at North Bend with a stage greater than the flood

stage of 8 ft ........................................................................................................... 11

7. Summary of ice-related flooding at Big Island ................................................... 12

8. Summary of ice-related flood events near the Highway 92 Bridge over

the Platte River .................................................................................................... 14

9. Summary of ice-related flood events at the confluence of the Platte and

Elkhorn Rivers near Ashland ............................................................................ 15

10. Parameters used in characterization of ice events in the Lower Platte River

basin study area .................................................................................................. 16

iv
Table Page

11. Ice events with normalized stage greater than 1.0.............................................. 17

12. Discharges used in HEC-2 model of lower Platte River .................................... 22

13. Known ice events during the period 1950 through 1990 ................................... 25

14. Results of applying AFDD and discharge criteria to historic data at

North Bend ........................................................................................................... 27

15. Data to be collected in ice data collection program ............................................ 31

16. Ice-jam mitigation methods .................................................................................... 38

17. Ice-jam mitigation strategies .................................................................................. 38

18. Constituents of 1979 dusting material .................................................................. 43

19. Example dusting plan for the lower Platte River based on the 1982 plan ...... 44

20. Spreadsheet for use in planning dusting operations ......................................... 46

21. Sample calculations for blasting costs .................................................................. 52

v
with a discharge of 119,000 cubic feet per second

(cfs) and a gage height of 14.42 ft. The 1993 event

caused flooding in the area between the Loup and

Platte Rivers and nearly overtopped the levee on

the north bank of the Loup River. At Ashland,

two major levee breaks occurred, flooding about

14,000 acres of farmland on the east side of the

Platte River. A number of houses were destroyed

along the west side of the river, and the well fields

for the city of Lincoln were threatened. Fourteen

counties were included in the disaster area.

The overall basin damages during the

March 1993 event were more than $25

million, including road closures; road

failures; damage to bridge abutments

and water supplies; flooding of residential, agricultural, industrial and commercial areas; and damage to levees,

dikes and other river- training structures.

Over 74,000 acres were damaged by

sediment deposited during the floods

(USAED, Omaha 1993).

The March 1993 ice event was the

most damaging event since February

1978, when over $18 million in damages resulted from ice-jam flooding

(USAED, Omaha 1978). Flood damages

in 1978 were particularly severe in the

Valley–Fremont area, when an ice jam

overtopped and breached the Union

Dike, flooding 27,000 acres in Dodge

and Douglas Counties. Substantial damages were also incurred that year due

to an ice jam that formed just downstream from the confluence of the Platte

and Elkhorn Rivers near Ashland. In

all, over 60,000 acres were flooded, and

20 counties were included in the disaster area for the 1978 event.

Ice Jam Flooding and Mitigation

Lower Platte River Basin, Nebraska

KATHLEEN D. WHITE AND ROGER L. KAY

INTRODUCTION

Severe flooding due to the combination of ice

jams and rapid snowmelt occurred within the

Lower Platte River basin in Nebraska during

March 1993. The two areas most affected were

along the south side of the Loup River at Columbus and just downstream from the confluence of

the Elkhorn and Platte Rivers near Ashland (Fig.

1). Stages at Columbus exceeded the previous peak

stage set in August 1966, an open-water event

Figure 1. Lower Platte River Section 22 study sites.

1

6

7

4

3

2

5

Genoa to Columbus

Hwy. 79 at North Bend

Big Island at Fremont

West channel at Leshara

1.5 miles north of Hwy. 64 Bridge

Hwy. 92 Bridge

Confluence of Platte and Elkhorn R.

Fremont

SOUTH DAKOTA

IOWA

MISSOURI

KANSAS

NEBRASKA

Sioux

City

Lincoln

Missouri

River

Platte

River

South

Loup

R.

Middle

Loup

R.

North

Loup

R.

Elkhorn

R.

Cedar

R.

Calamus

R.

Cr.

Logan

6

7 4

3

2

1

5

Genoa

Columbus

North

Bend

Norfolk

Omaha

Grand

Island Cr.

Salt

West Point

Waterloo

Ashland

Study

Area

NEBRASKA
Following the March 1993 ice event, the Federal Emergency Management Agency (FEMA), Region VII, as required by 44 CFR Part 206, formed

an Interagency Hazard Mitigation Team to review

the flood events and suggest measures which

might be implemented to mitigate similar events

in the future. At the suggestion of representatives

from State agencies, Work Element 3 called for a

comprehensive investigation by the Corps of Engineers to gather historical ice data with the intent of developing guidance that could be used to

mitigate or alleviate recurring ice-jam-related

flooding on the Lower Platte, Loup and Elkhorn

Rivers.

The Governor enthusiastically supported the

concept, and after a series of meetings, the planned

scope of the Section 22 study was defined. The

State’s share of the funding was provided by the

Governor’s Emergency Fund and the Natural Resources Commission. The present study is the result of this hazard mitigation coordination.

The objective of the Corps’ year-long Section

22 study (authorized by Section 22 of the Water

Resources Development Act of 1974, as amended)

was to investigate the recurring ice-jam problems

in the Lower Platte, Loup and Elkhorn Rivers with

the goal of developing general guidance on the

likelihood of ice-jam occurrence and evaluating

potential ice-jam flood mitigation measures. Seven locations of recurring ice jams were chosen for

study following the recommendations of the Interagency Hazard Mitigation Team. These locations are shown in Figure 1.

There are a number of sites which experience

ice jams and ice-jam-related flooding in addition

to the seven sites identified above, including

Schuyler, Ames and Louisville on the Platte River

and Norfolk, Waterloo and West Point on the

Elkhorn River. Many of these sites have also experienced damaging open-water flood events and

have put into place mitigation measures ranging

from nonstructural measures such as detection,

monitoring, warning and emergency response

plans to structural measures such as levees and

dikes. These mitigation measures have been primarily designed for open-water events, although

they may provide some protection during ice

events as well.

Ice events, however, present hazards that may

not be adequately addressed using mitigation

measures designed for open-water events only.

Consequently one major purpose of this study

was to provide general guidance to facilitate adequate warning and response to ice-jam events.

This guidance is applicable to the overall study

area as well as to the seven sites shown in Figure

1. In addition, the study includes an assessment

of possible mitigation measures that may be suitable for implementation at different locations.

Based on an analysis of past ice, meteorological

and hydrological records, an initial predictive

model of ice-jam occurrence and severity was developed. Because data collection is important in

detection, warning and the refinement of the predictive model for ice jams, a plan for collecting

future ice-related data was designed.

HISTORICAL DATA

Collection of data from past ice events is necessary in order to characterize the ice jams or other ice events at the chosen sites as well as those

occurring within the region as a whole. Analysis

of historical ice records and meteorological and

hydrological data enables us to determine which

parameters affecting jam formation and progression are most important. Although ice events are

usually highly site-specific, there may be similarities between ice events that occur within a region.

It is these similarities that allow development of

general guidance on mitigation measures as well

as a regional ice-jam predictive model.

Ice event records are often more difficult to

obtain than open-water flood records. Information on ice events is lacking because most ice

events occur less frequently than open-water

floods, ice events are often short-lived and may

affect only a short reach of river, and access or

weather conditions can make it difficult to make

observations. Ice events can include:

• Ice jams that cause flooding (overbank);

• Ice jams that do not cause flooding (within

bank) that may not be identified as ice jams;

• Ice covers that raise water levels upstream

or decrease water levels downstream;

• Initial ice cover formation; and

• Ice cover breakup and movement.

Ice jams include those which occur in the early

winter as ice formation begins (freeze-up jams),

those which form as a result of the breakup of ice

covers (breakup jams), and those which contain

characteristics of both (combination jams). Historical ice records may not differentiate between

types of ice events, making it difficult to characterize them.

Historical ice records for the Lower Platte, Loup

and Elkhorn Rivers were obtained through a liter2
ature search, an examination of various State and

Federal agency records, and a series of local public meetings. Weather records and river discharge

and stage records were also collected from the

National Weather Service (NWS) and the U.S. Geological Survey (USGS). The Nebraska Civil Defense Agency also made available a number of

documents which provided additional information on ice events within the study reach.

Ice records

The initial search for records of ice events in

the study area utilized the Ice Jam Data Base*

developed at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL).

Some ice-jam events included in the database are

well documented, while only sketchy information exists for others. The database relies heavily

on USGS sources (e.g. USGS 1989) and, in particular, on data collected for the USGS report series

on the magnitude and frequency of floods (Matthai 1968). As a result the most frequently reported ice events are those which occurred at the sites

of USGS water-stage gages between the mid-1930s

(when many gage records were begun) and the

early 1960s. Ice events that occur away from USGS

gages are not well represented as yet. While gage

records often include such useful data as the local

stage and discharge, they rarely provide information on the thickness, extent, likely causes or damages associated with a particular ice event.

The ice events that can be identified through a

review of peak USGS records are most commonly

associated with the peak annual gage height (or

discharge) at a particular location. It is not always

clear whether the reported value is the actual peak

or the average value that occurred on the peak

day. Also, it is possible that ice events that did not

cause an annual peak gage height will not be reported. In some cases a gage height is reported as

being caused by an ice jam. Generally, without

further information, we assume that an ice jam

must have been observed at or very close downstream from the gage when this form of reporting

is used. In other cases the gage height might be

reported as being affected by backwater from ice.

We assume in these cases that an ice cover located

at or downstream from the gage is causing backwater effects to be felt at the gage. The ice cover

may range from smooth to rough or even a jam.

Ice thickness is measured by the USGS whenever possible during winter discharge measurements at gaging stations. Written ice thickness

data that have been collected in Nebraska are located at the USGS office in Lincoln. Obtaining all

of the historical ice thickness measurements made

by the USGS within the study area would be beyond the scope of this study; however, records for

particular locations for particular years were obtained (Table 1).

Once a number of ice events had been identified through literature searches and agency contacts, the Corps contacted local residents and agencies to corroborate and expand on the information.

A series of meetings was held in October 1993

with the objective of identifying additional sources of information and learning more about the ice

jams which occur at the seven sites identified in

Figure 1. The meetings were held at Columbus

(26 October), Gretna (27 October) and Fremont

(28 October). For convenience these meetings were

held in two parts: first, a meeting with local, State

and Federal agencies; and second, a meeting with

the general public. The agency portions of the

meetings were attended by city and county officials, representatives of irrigation districts and

Table 1. Locations and water years of ice thickness measurements obtained

from USGS.

 USGS gaging

station number USGS gaging station location Water years

06793000 Loup River near Genoa 1948, 1969, 1978, 1979, 1987, 1993

06794500 Loup River at Columbus 1948, 1969, 1978

06799000 Elkhorn River at Norfolk 1966, 1969, 1978, 1979, 1987, 1993

06800500 Elkhorn River at Waterloo 1966, 1969, 1978, 1979, 1987, 1993

06770500 Platte River near Grand Island 1971, 1978, 1979, 1987, 1993

06796000 Platte River at North Bend 1971,1978, 1979, 1987, 1993

06805500 Platte River at Louisville 1971, 1978, 1979, 1987, 1993

* The CRREL Ice Jam Data Base (White 1992) is a database of ice events in the United States. It is updated

periodically; the latest version can be found at

www.usace.army.mil/crrel on the World Wide Web.

3
Table 3. National Weather Service

meteorological data sources.

NWS station

 location Period of record

Columbus 1949–1991

Genoa 1948–1991

North Platte 1948–1991

Grand Island 1900–1991

Omaha (Eppley) 1948–1991

West Point 1892–1991

Ewing 1948–1991

Table 2. USGS data sources.

 Gaging station

number Gaging station location Period of wintertime record available

06793000 Loup River near Genoa 1930–1991

06792500 Loup River Power Canal near Genoa 1937–1990

06794500 Loup River at Columbus 1935–1979

06799100 North Fork Elkhorn River near Pierce 1961–1992

06798000 South Fork Elkhorn River at Ewing 1948–1953, 1961–1972, 1978–1992

06797500 Elkhorn River at Ewing 1948–1991

06798500 Elkhorn River at Neligh 1931–1958, 1961–1992

06799000 Elkhorn River at Norfolk 1946–1992

06799350 Elkhorn River at West Point 1973–1992

06800500 Elkhorn River at Waterloo 1929–1991

06770000 Platte River near Odessa 1939–1991

06770500 Platte River near Grand Island 1935–1992

06796000 Platte River at North Bend 1950–1992

06801000 Platte River near Ashland 1929–1960, 1989–1992

06805500 Platte River at Louisville 1954–1991

Natural Resources Districts, members of the Civil

Defense network, National Weather Service observers, Corps of Engineers personnel and a representative from CRREL. A number of sources of

information were identified in the meetings, and

several additional ice events were revealed.

Hydrological data

In addition to the stage data and ice notes

discussed previously, USGS gaging station data

also provided information about water discharge throughout the winter. Discharge is important in characterizing ice jams for several

reasons. First, discharge at freeze-up determines

the stage at which the ice cover initially forms.

Second, as the discharge rises or falls throughout the winter, the corresponding changes in

stage may result in ice conditions that are either

more or less likely to break up and jam. Third,

large increases in discharge and stage, such as

those due to rainfall, snowmelt or a combination of both, may increase stages to the point

that the ice cover begins to break up. The discharge at breakup can determine whether the

ice is transported downstream or whether it is

likely to jam at a particular location.

Fortunately there are several gages within the

study area which have long-term discharge

records. Many of these gages are located within

jam areas or are affected by backwater from ice

jams, depending on the jam length. Average daily

discharge records were obtained for several USGS

gaging stations, both within the study reach and

in the contributing drainage basins, for the

months of January through April. Table 2 lists the

gaging stations selected and the period of winter

records available. Important discharge parameters examined for each site include the maximum

average daily discharge Qmax and the date on

which it occurred. For ease in data handling, dates

were converted from a month–day format to a

Julian Day format, with Day 1 being 1 October,

the start of the water year. Thus, the date of Qmax

would be termed JD Qmax.

Meteorological records

The NWS operates a number of gages that collect meteorological data. Records obtained from

gages within the Lower Platte River basin (Table

3) included minimum and maximum air temperature, snowfall and precipitation. From these

records we calculated average daily air temperature (ADAT), freezing degree-days (FDD), accumulated freezing degree-days (AFDD) and accumulated thawing degree-days (ATDD) for the

winter, all of which are described in detail below.

Meteorological data, like discharge data, are

tracked by Julian Day (JD) starting with 1 October, the start of the water year. Average daily air

4
tor of ice thickness and rapidity of snowmelt. They

are calculated using the equation

TDD = ADAT – Tb (3)

where Tb is the base temperature at which snowmelt and ice deterioration are considered to begin. Because snowmelt and ice deterioration can

occur when the average daily air temperature is

less than 32°F, the base temperature can range

from about 25° to 32°F. Thawing degree-days accumulated after the JD start cold are called ATDD.

If the ATDD drops below zero, accumulation ends

and ATDD is considered to be equal to zero until

the next positive TDD.

Snowfall data are important because the presence of snow can affect ice thickness. Snow on top

of an ice cover will insulate the ice, slowing its

growth during cold weather. Conversely, if there

is no snow on top of the ice, the ice will thicken

more quickly during cold periods. Snowfall is also

an indicator of the amount of snowpack available

during the snowmelt. The combination of deeper

snowpacks and rapid snowmelt causes larger increases in stage and discharge than shallower

snowpacks under the same conditions. Also, the

timing of snowfall can be important since late

snows are more likely to still be on the ground

when the breakup season arrives. Finally, heavy

snowfall on ice can cause a depression of the ice

cover that allows water to flood the ice cover. The

saturated snow can freeze into snow ice, increasing the overall ice thickness. Data on precipitation other than snowfall are also collected because

precipitation combined with snowmelt can result

in rapid runoff and sharp increases in stage that

800

600

400

200

0

– 200

– 400

– 600

– 800

0 50 100 150 200 250

Julian Day (1 Oct is day 1)

Accumulated Freezing Degree-days (°F)

JD AFDDmax

ATDD

JD start cold

AFDDmax

temperature is simply the average of the minimum (Tmin) and maximum (Tmax) air temperatures:

 

ADAT = T T max min +

2 . (1)

Freezing degree-days (FDD) are calculated from

the ADAT using the relation

FDD = 32 – ADAT. (2)

A positive value of FDD means that the average daily air temperature is lower than 32°F, while

a negative value means that the average daily air

temperature is higher than 32°F. Accumulated

freezing degree-days (AFDD) are the sum of the

freezing degree-days during the winter, beginning 1 October (the start of the water year). Since

air temperatures are still relatively high in October in Nebraska, however, AFDDs are summed

until some minimum value is reached. The date

of the minimum AFDD is called the JD start cold.

Upon reaching the JD start cold, AFDD is reset

to zero and begins accumulating again until

some maximum value is reached (AFDDmax).

The date of the AFDDmax is called JD AFDDmax.

The AFDDmax marks the change from generally

colder weather (average daily air temperature

below freezing) to weather where the average

daily air temperature is above freezing. After the

AFDDmax is reached, FDDs continue to be accumulated until they drop below zero. Figure 2

illustrates the parameters derived from the minimum and maximum temperature data.

Negative freezing degree-days are termed

thawing degree-days (TDD). Thawing degreedays are of interest because they can be an indicaFigure 2. AFDD at the National Weather

Service Station at North Platte, Nebraska,

during water year 1960.

5
lead to ice breakup. Precipitation amounts less

than 0.05 inch were designated trace amounts.

Summary of

historical data collected

A review of the historical records collected during the initial phase of the study indicated that ice

events are relatively frequent on the Lower Platte,

Loup and Elkhorn Rivers. Some locations have

reported more ice-related damage than others, and

many of the locations are also subject to occasional open-water flood damages. Records are good

at some locations and sketchy at others. Historical data collected for the seven sites shown in

Figure 1 are summarized below and discussed in

the section Analysis of Historical Data.

Site 1. Loup River from

Genoa to Columbus

Several sites along the Loup River between

Genoa and Columbus have recurring ice-jam problems. Unfortunately, little specific data are available for jams which occur upstream from Columbus. Local residents and agency representatives

identified the sites shown in Figure 3.

The uppermost site is just downstream from

the USGS gaging station on the Loup River near

Genoa, which has operated continuously since

1944. Although no detailed ice-jam information

was reported at the site, the gaging station records

do confirm the presence of downstream ice jams,

which can cause significant backwater effects at

the gage. The maximum annual (water year) gage

height for the station was caused by backwater

from ice 22 times between 1962 and 1991, or about

73% of the time (Table 4). There were no reported

ice effects at the gage between 1944 and 1962.

This can be interpreted in several ways:

• There actually were no ice events between

1944 and 1962;

• There were ice events but subsequent openwater events in the same year had higher

stages than the ice events; or

• The ice events that occurred were not reported or were reported as open-water events.

Figure 3. Identified recurring ice jam sites on the Loup River between Genoa and Columbus.

Table 4. Maximum annual gage

heights associated with ice at the

USGS gage on the Loup River near

Genoa (period of record 1944–1991,

flood stage 9 ft).

Ice-related annual

Date maximum stage (ft)

16 February 1962 10.0

18 December 1963 7.83

1 April 1965 10.33

19 March 1969 10.8

23 February 1970 8.59

19 February 1971 10.37

28 February 1972 9.21

21 January 1973 8.36

15 February 1974 9.12

3 March 1975 8.36

9 February 1976 8.79

23 February 1977 10.2

18 March 1978 12.12

15 March 1979 10.87

18 January 1980 10.79

30 December 1981 11.83

21 February 1982 12.35

17 February 1983 9.35

27 February 1985 9.43

27 January 1986 10.14

24 February 1988 8.99

10 March 1989 9.4

Loup

River

Canal

Loup 

R.

Platte

R.

Lake

Babcock

Union Pacific R.R.

Burlington Northern

Union Pacific R.R.

Union Pacific R.R.

R.R.

Rte. 81

Rte. 30

Rte. 30

Rte. 22

Rte. 22

Rte. 39

Rte. 39

Rte. 81

Genoa

Monroe

Columbus

Duncan

Oconee

USGS Gages

Ice

Jams

0 5 miles

6
The flood stage at the gage (9 ft) was exceeded

by ice events occurring in 1962, 1965, 1969, 1971,

1972, 1974, 1977–1983, 1985, 1986 and 1989. The

1988 ice event may have exceeded flood stage; the

precision of ice-jam stage measurement is larger

than 0.01 ft. The maximum open-water stage at

the Genoa gage was 13.93 ft during the storm of

August 1966. In comparison, the peak ice-related

stage of 12.35 ft at the gage on 21 February 1982

was caused by an ice jam. According to Nebraska

Civil Defense records, this jam was about one mile

long and resulted in lowland flooding. The nexthighest ice-related stage was 12.12 ft on 18 March

1978. Civil Defense records indicate that ice jams

causing flooding in 1978 were located both east

and west of the bridge.

Two ice jams at Genoa were reported by other

sources. On Thursday, 20 March 1969, the Columbus Daily Telegram reported that the ice jam at

Genoa was still in place and water was 1 ft lower

than Wednesday, 19 March, but still “slightly” out

of bank. According to Nebraska Civil Defense

records (1971), a 5-mile-long ice jam formed at

Genoa during the storm of February 1971. No

information about water stages, or the exact location in reference to the gage, was provided. Although the date of jam formation was not specified, the jam was in place and causing flooding at

least between 24 February and 6 March 1971, and

perhaps for a longer period.

The Loup River Power Canal diversion structure, consisting of a gated dam and gated canal

headworks, is located on the Loup River about

six miles upstream from the USGS gage on the

Loup River near Genoa. Outflow from the canal

enters the Platte River below Columbus. The

canal system, which began diversions in December 1936, includes a settling basin, two hydropower plants and Lake Babcock.

A USGS gage is located at the settling basin

weir two miles downstream from the headworks.

No ice jams were reported at the Loup River Power Canal gage. Canal operations, however, are suspended in early winter when heavy frazil ice discharge might adversely impact power production.

Regular canal operations resume when frazil ice

concentrations are low or a sheet ice cover forms

on the canal. The average flow for the period 1938–

1989 at this gage was 1600 cfs, in contrast to the

average daily flow at the Loup River gage near

Genoa, which is about 680 cfs for the period 1944–

1989. Instantaneous Loup River Power Canal flows

during the period January through March have

varied from essentially zero to 3160 cfs.

The effects of these fluctuations in Loup River

Power Canal diversions on discharge, ice formation and ice transport in the Loup River below the

diversion structure have not been quantified. Some

local residents have expressed the opinion that

the resulting fluctuations in water level cause or

exacerbate ice jams in the Loup River downstream

from the canal diversion. However, it would only

be possible to evaluate the situation after a detailed study. A quantitative analysis would be difficult given the lack of good ice records. A qualitative analysis might address such issues as the

potential effects of raising and lowering water

levels on the formation of border ice, frazil production, frazil ice transport and the effects of sudden decreases in river flow on ice movement (e.g.

stranding ice blocks, increased frazil deposition).

Changes in the sediment regime of the river resulting from canal operations may also have impacted ice formation and transport processes. The

difficulties involved in evaluating Loup River

Power Canal operations are illustrated in Figure

4, which presents measured flows at the Loup

River Power Canal gage, the Loup River gage

near Genoa, the combined flow in the canal and

the river, and air temperatures at Columbus during the period 15 November through 9 December

1993. The canal operated at fairly steady flows

between 15 and 23 November, while the river

flows were slowly decreasing. Canal flow decreased sharply on 23 November and remained

very low until 28 November, when flows were

increased. The increased canal flow fluctuated

roughly diurnally. In most cases, increases in

canal flows are associated with decreases in river

flows (see, for example, 6 December 1993).

The rather marked decrease in river flow measured at the Loup River gage on 26, 27 and 28

November may actually reflect water going into

storage when the frazil ice produced during the

low temperatures experienced during this period

increased flow resistance due to shore ice and

anchor ice buildup and the formation of freezeup jams. A transient peak flow of the magnitude

and duration experienced on 1 December is unusual. This high flow might be attributable either

to the release of water from storage as a result of

rising temperatures, or it could be an artifact of

increased stage due to backwater from ice accumulations downstream from the gage.

Ice jams and associated flooding have been reported in the vicinity of the Monroe Bridge, south

of Monroe. One jam was reported at this location

on 19 March 1969 in the Columbus Daily Telegram.

7
about 0.8 mile downstream from the Highway 30-

81 bridge is reflected in the records of the USGS

gaging station that was operated at the bridge

from 1935 through 1978. Gage records revealed

that peak stages due to backwater from ice (i.e.

the ice jam was downstream from the gage but

raised water levels at the gage) occurred in 1936,

1958, 1961, 1963, 1969–1971 and 1973–1977 (Table

5). The records also showed that the ice jam itself

extended beyond the gage in 1978.

Local residents provided information on an

additional jam that occurred in February 1948,

causing $72,000 in damages. This jam caused high

stages during the week of 14–21 February 1948,

but the maximum stage (not reported) did not

occur until 28 February 1948. An additional ice

jam was reported in Nebraska Civil Defense

records* on 15 February 1966. This ice jam, located in the Wagner Lake–Sand Pit area west of Co4000

3000

2000

1000

0

12 Nov ‘93 17 22 27 2 Dec 7 12

Discharge (cfs)

Loup

River

Power

Canal

70

60

50

40

30

20

10

0

– 10

12 Nov ‘93 17 22 27 2 Dec 7 12

Air Temperature (°F)

Maximum

Air Temperature

Minimum

b. Minimum and maximum daily

air temperatures measured at

Columbus.

a. Flows measured at USGS gages

on the Loup River near Genoa and

the Loup River Power Canal near

Genoa.

Figure 4. Loup River flows and daily air temperatures, 15 November through 9 December 1993.

Nebraska Civil Defense records indicate that icejam-related flooding also occurred at the Monroe

Bridge in January 1980. This ice jam resulted in

lowland flooding for several days before breaking up.

According to local residents, severe ice jams

also occur downstream at Oconee Bend, east of

Monroe and about a mile west of Oconee (Fig. 3).

The ice jam at this location is said to be a recurring one, with the toe at the downstream end of

the bend. On 14 March 1978, Nebraska Civil Defense records indicated that ice-related overbank

flooding was taking place at this location.

Some residents reported an ice jam at Oconee

Bend in March 1993. The Columbus Daily Telegram

reported overbank flooding at Oconee Bend on

Monday, 9 March 1993, but ice was not specifically mentioned. No other specific data on jam dates,

length of jam, stages or damages due to ice jams

at Oconee Bend were given.

The most damaging ice jams on the lower portion of the Loup River have occurred at Columbus. The presence of a recurring ice jam that forms

* Memorandum of aerial reconnaissance, William J.

Clark, 16 February 1966.

8
lumbus (upstream from the gage), caused overbank flooding. No other more specific information regarding jam formation or extent was given.

The flood stage at the Columbus gage is considered by the USGS to be 11 ft. The maximum

open-water gage height of record was 14.42 ft on

14 August 1966. Prior to 1993 the peak ice-related

stage at the Columbus USGS gage was 11.2 ft on

21 March 1969, with an average daily discharge of

about 16,500 cfs. This ice jam resulted in extensive

flooding along the route of the present Highway

81 and the area between the Loup and Platte Rivers. The Columbus Daily Telegram reported that the

jam began forming east of the Highway 81 bridge

at about 6:30 p.m. on Tuesday, 17 March, and eventually extended about one-half mile upstream and

downstream of the bridge. Within two hours water levels had risen enough to begin overbank

flooding. According to newspaper reports, blasting was done in the vicinity of the Highway 81

bridge. The blasting was eventually successful in

removing the jam, which went out about 7 p.m.

on 21 March 1969.

According to Nebraska Civil Defense records

(1971), the ice jam that occurred in 1971 formed

about five miles east of Columbus and extended

for three miles. The jam flooded low-lying areas

southeast of Columbus. Blasting was initially unsuccessful, but it finally caused the release of the

jam on 24 February 1971.

The ice jam of 7–10 March 1993, which extended a short distance upstream from the Highway

30-81 bridge, resulted in a stage of greater than

12.5 ft at the gage, based on high-water marks.

Local residents described the 1993 event as being

the worst in memory, with a local farm implement dealer noting that the high-water marks on

his building were 4.5–5 ft higher than during the

August 1966 flood, which had a stage of 14.42 ft

recorded at the USGS gage. High-water marks set

by Corps personnel indicated that the stages produced by the ice jam at Columbus were equivalent to those that might be expected from an openwater event of about 200,000 cfs (USAED, Omaha

1993).

Ice jams which form on the Platte River between the Burlington Northern Railroad bridge

and the tailrace of the Loup River Power Canal

(Fig. 3) can also affect Loup River stages at Columbus and cause lowland flooding along the

Loup and Platte Rivers. Jams are known to have

formed in this area in March 1978, March 1979,

February 1982 and late November 1993. The jam

of February 1971, which extended for five miles

up the Loup River, probably also formed in this

area.

On 30 November 1993, a freeze-up ice jam

formed upstream from the Burlington Northern

Railroad bridge (Fig. 3) following a sudden drop

in temperature beginning about 22 November (Fig.

4b). The sudden drop in discharge through both

the river and the canal coincident with low temperatures is indicative of significant frazil ice formation and blockage upstream. The jam extended upstream to the water plant on the north bank

of the Loup River. Lowland flooding was experienced on both sides of the river. With rising temperatures the jam eventually went out on its own.

Small ice accumulations typical of ice breakup

and movement were evident on the Loup River

upstream from the jam area. It is probable that the

Loup River was the primary source of ice which

formed this jam.

On 14 March 1979, an ice jam formed upstream

from the Union Pacific Railroad bridge (Fig. 3).

This jam extended about one-half mile above the

bridge and caused lowland flooding. The jam

eventually failed and moved downstream, rejamming downstream from the Highway 81 bridge.

Backwater from the jam reached bank level at the

bridge before the jam failed on 15 March 1979.

Site 2. Platte River:

Highway 79 at North Bend

The Platte River in the vicinity of Highway 79

at North Bend was also identified as a site of

Table 5. Maximum annual gage

heights associated with ice at the

USGS gage on the Loup River at

Columbus (period of record 1934–

1979, flood stage 11 ft).

Ice-related annual

Date maximum stage (ft)

5 March 1936 6.57

26 February 1958 7.53

5 March 1959 6.18

17 February 1961 6.38

16 February 1963 6.04

21 March 1969 11.2

3 January 1970 8.0

20 February 1971 9.3

20 January 1973 7.4

10 January 1974 6.7

11 January 1975 7.46

3 January 1976 8.58

24 February 1977 6.36

15 March 1978 8.87

7 March 1993 >12.5

9
recurring ice jams. According to local residents

the jams initiate at a point about 2–2.5 miles downstream from the Highway 79 bridge, in the reach

upstream from Pole Island (Fig. 5). Ice-jam-related flooding occurs primarily in the Morse Bluff

area, but lowland flooding could occur on both

sides of the river. Ice jams have also been noted

upstream from the Highway 79 bridge, but data

are sketchy. For example, Nebraska Civil Defense

records report that an ice jam located about 1.75

miles upstream from the bridge in February 1980

resulted in lowland flooding, but no other information about the jam (i.e. location of toe, length,

stages) was available. In February 1982, ice jams

were located both upstream and downstream from

the bridge. Sandbagging of the levee in the

McGinn’s Lake area about four miles west of North

Bend was begun when backwater from the jam(s)

approached within six inches of the top of the

levee.

A USGS gaging station is located on the left

bank of the river just upstream from the Highway

79 bridge. This gage has been operated continuously since 1949. Ice jams have been reported at

the gage in 1971, 1972 and 1978. In addition, peak

annual stages caused by backwater from downstream ice have occurred at the North Bend gage

relatively frequently—in 1950–1953, 1955, 1958–

1963, 1970, 1974, 1976–1977, 1979–1980, 1982–1983,

1985–1986 and 1988–1989.

The flood stage at this gage, 8 ft, has been exceeded during the period of record by 14 ice-related events, 11 of which occurred between 1971

and 1989 (Fig. 6, Table 6). Using the difference

between recorded stage and flood stage as a measure of severity, it appears there has been a trend

toward more severe ice events in recent years.

However, more detailed information about events

within and outside the period of record, as well as

changes in observers and observation methods,

would be required to verify this apparent trend.

In addition, changes in river morphology and

property development patterns may also affect

stages.

The maximum stage recorded at the North

Bend gage was 15.55 ft on 19 March 1978, during

Union Pacific R.R.

Burlington

Northern

R.R.

CB& Q

C & NW

North Bend

Morse

Bluff

Fremont

Leshara

Waterloo

Valley

Union Pacific R.R.

Chicago and Northwestern R.R.

C & NW

WASHINGTON

COUNTY

DODGE

COUNTY

DOUGLAS 

COUNTY SANDERS

COUNTY

Platte R.

Elkhorn R.

Hwy. 92

Hwy. 77 Hwy. 92 Hwy. 77

Hwy. 77

Chicago

and

R.R.

Union Pacific R.R.

Burlington

Norhern

R.R.

Burlington

Northern

R.R.

Hwy. 79

Union

Pacific

R.R.

Hwy. 36

Hwy. 30

Hwy. 30

Hwy. 64

Hwy. 275

Hwy. 275

Hwy. 64

North west ern

USGS

Gages Ice

Jams

Big Island

Pole

Island

Mercer

Ford Farm

Venice Sokol

Camp

Two

Rivers

Vencil's

Island

Thomas

Lakes

Camp

Ashland

UP

R.R.

0 5 miles

Figure 5. Identified recurring ice jam sites on the Platte River between North Bend and Ashland.

10
main channel discharge and an indirect measurement of flow over the roadway.

In contrast to this ice-jam event, the maximum open-water stage was 5.51 ft lower at

10.04 ft. This stage occurred on 29 March 1960,

with a reported discharge of 112,000 cfs. The

gage height was reported to be affected by backwater, however, so although it is reported as an

open-water event, it may have been related to

a downstream ice jam, which would also have

affected discharge calculations. The maximum

open-water stage of 10.04 ft was exceeded by

several other ice events in addition to the March

1978 event, including ice events that occurred

on 13 February 1952 (10.17 ft, ice jam reported

downstream from gage); 20 February 1971

(12.24 ft, ice jam at gage); 19 February 1972

(10.19 ft, ice jam at gage); 18 January 1980 (10.44

ft, ice jam downstream from gage); and 28 February 1985 (10.59 ft, ice jam downstream from

gage). During the 1980 event the Department

of Roads operated a crane equipped with a

wrecking ball from the Highway 79 bridge to

break ice in the jam. NWS records indicate that

lowland flooding along the south bank resulted

from the 1985 event.

Ice jams formed about two miles west and one

mile east of the Highway 79 bridge at North Bend

on 13 March 1979. By 14 March the upstream jam

was located one-half to three-quarters of a mile

upstream from the bridge. Backwater from this

jam eventually breached a dike along the south

Table 6. Summary of ice events at North Bend with a stage greater than the flood stage of 8 ft.

Date Stage (ft) Description

13 February 1952 10.17 ice jam at gage

29 March 1960 10.04 gage affected by backwater from ice

20 February 1971 12.24 ice jam at gage

29 February 1972 10.19 ice jam at gage

17 February 1974 8.6 gage affected by backwater from ice

19 March 1978 15.55 ice jam at gage, maximum gage height of record, one dead, many evacuated

14 March 1979 10.0 gage affected by backwater from ice, upstream jam flooded Hwy 79 and

Morse Bluff

18 January 1980 10.44 ice jam downstream from gage, lowland flooding reported, crane and wrecking ball operated from bridge

22 February 1982 9.25 gage affected by backwater from ice, sandbagging of levee at McGinn’s

Lake, Wolf Lake roads flooded

18 February 1983 9.49 gage affected by backwater from ice

28 February 1985 10.59 ice jam downstream from gage, lowland flooding south bank

24 February 1988 8.14 gage affected by backwater from ice

12 March 1989 8.19 gage affected by backwater from ice

8 March 1993 10.97 ice jams upstream and downstream from Hwy 79 bridge

16

12

8

4

Stage (ft)

Water Year

1950 ‘52 ‘55 ‘59 ‘61 ‘63 ‘71 ‘74 ‘77 ‘79 ‘82 ‘85 ‘88

‘51 ‘53 ‘58 ‘60 ‘62 ‘70 ‘72 ‘76 ‘78 ‘80 ‘83 ‘86 ‘89

Flood Stage

an ice-jam event. This stage resulted in flooding

along both sides of the river. The Omaha WorldHerald reported that one person died in North

Bend during this event and another was injured

when a basement wall caved in. Highway 79 was

overtopped with water and ice. The average daily

discharge reported on this day was 54,000 cfs,

and the maximum instantaneous discharge was

calculated to be about 80,000 cfs, including the

Figure 6. Ice-related peak annual stages at the USGS gage for

the Platte River at North Bend for the period 1949 through

1992. Ice jams were reported in 1971, 1972 and 1978; all other

stages were affected by backwater from downstream conditions.

11
side of the river, resulting in flooding on Highway 79 and in the Morse Bluff area.

In February 1982, ice jammed intermittently at

the upstream side of the bridge, and a jam formed

about three-quarters of a mile downstream from

the bridge. Blasting was considered, but the jam

failed before blasting could be started. The

McGinn’s Lake and Wolf Lake areas were flooded. NWS records indicate that lowland flooding

along the south bank also resulted from the February 1985 event. Jamming upstream and downstream from the bridge caused lowland flooding

in March 1993.

Site 3. Platte River:

Big Island at Fremont

Big Island is located along the north bank of

the Platte River to the southwest of Fremont (Fig.

5) and includes several residential developments

built around lakes. There is some anecdotal evidence that an ice jam occurs in the reach along Big

Island, with the jam toe about 1 mile upstream

from the Highway 77 bridge.* According to local

residents, ice blocks which pile up at the Burlington Northern Railroad bridge can also raise the

water level sufficiently to cause backwater to flow

into the Big Island area. In most cases the backwater is probably formed by jams which form in

several places downstream from Fremont. One

recurring jam initiation location is about a half

mile downstream from the Highway 77 bridge,

and another is in the vicinity of Mercer, about 3–

3.5 miles downstream from the Burlington Northern Railroad bridge. Known ice-jam-related flooding events are summarized in Table 7.

In a review of ice-related flooding within the

Papio–Missouri Natural Resources District, Wehrspan (1978) reported ice-related flooding at Big

Island during the floods of 6–15 March 1949, when

overbank flow was observed between about onehalf mile downstream from the Highway 77 bridge

and a point about 4 miles upstream from the

bridge. It is possible that the area was flooded

again on 6–24 March 1950, although Big Island

was not specifically mentioned by Wehrspan, who

reported that “ice jams caused moderate overbank flow on the Platte River in the vicinity of

Fremont, Linwood, Schuyler and North Bend”

during this event.

Big Island was flooded in 1978, and 100 people

were evacuated by airboat, according to the Omaha World-Herald. No other details about the ice

jam causing this flood were given, although it is

probable that the ice jams at Mercer and downstream, which flooded the Valley area, contributed to elevated water levels at Big Island. In March

1979, Nebraska Civil Defense records reported

lowland flooding in the Big Island area due to ice

movement and jamming at the Burlington Northern Railroad bridge.

An ice jam formed about three-quarters of a

mile downstream from the Highway 77 bridge on

22 February 1982. This jam raised water levels in

the Big Island area, prompting some evacuations.

Nebraska Civil Defense records indicate that the

jam moved out by itself late in the afternoon but

rejammed between the Ford Farm and the Highway 64 bridge in the same location as the major

jam of 1978.

The NWS indicated that minor ice-related

flooding was affecting Big Island on 14 February

1984. By the next day, roads in the area were flooded, and on 16 February 1984, a number of residents were evacuated from the area. The jam was

not described, but it appears to have extended at

least as far as Ridge Road from an unknown point

downstream. The jam was observed from the air

Table 7. Summary of ice-related flooding at Big Island.

Date Description

6–15 March 1949 overbank flow 0.5 to 4 miles upstream from Highway 77 bridge

6–24 March 1950 possible overflow into Big Island

March 1978 100 evacuated by airboat

11–16 March 1979 lowland flooding, jam near BNRR Bridge

22 February 1982 jam three-quarters of a mile downstream from Highway 77 bridge

14–18 February 1984 roads flooded, residents evacuated

7 January 1985 evacuations due to ice-related high water

late February-early March 1989 minor ice-related flooding

* Marlin Petermann, personal communication.

12
on 17 February and reported to be 0.5 mile long.

The exact locations of the upstream and downstream ends of the jam were not identified. The

ice jam went out on 18 February 1984.

Nebraska Civil Defense records report evacuations in Big Island due to ice-related flooding

on 7 January 1985. NWS records indicate that

the ice jam was located between the Burlington

Northern Railroad bridge and the Highway 77

bridge. There was also minor ice-related flooding in Big Island at the end of February and into

early March 1985.

Site 4. Platte River:

West Channel at Leshara

Leshara has been plagued by open-water flooding as well as ice-related flooding. Because there

is no gage or large settlement near the jam area,

little has been reported about ice jams in the vicinity. However, it is thought that the jams which

adversely affect Leshara occur within the west

channel of the river. The jam that occurs north of

the Highway 64 bridge (see below) may also affect stages and ice conditions at Leshara. For example, a large ice jam that formed in the west

channel upstream from the Highway 64 bridge

on 16 March 1979 resulted in a dike breach and

flooding at Leshara the next day. This dike breach

may have been located in the same place as the

one that occurred in March 1978. The 1978 breach

was not specifically identified as being due to ice

action, but the presence of ice jams at the Highway 64 bridge that year and subsequent jamming

and flooding of the east channel of the river make

it highly likely that the 1978 event was, in fact, ice

related.

An ice jam in the Woodcliff area resulted in

lowland flooding and eventually in the failure of

a dike at Leshara on 27 February 1980. According

to Nebraska Civil Defense records, more extensive flooding occurred after the dike breached,

and some evacuations were necessary. The west

channel was plugged by a mile-long jam in February 1982, which caused lowland flooding

through the breach, which had not yet been fully

repaired.

A 28 February 1986 Omaha World-Herald news

article reported that residences in the Woodcliff

area were flooded during an ice event when the

dike failed at Leshara. According to the article,

the dike was originally breached during the 1978

ice jam event and had not been completely repaired by 1986.

Site 5. Platte River: 1.5 miles north

of the Highway 64 bridge

Details of this ice jam are sketchy. It is possible

that this ice jam is the one commonly described as

being located at the Ford Farm about 2.5 miles

upstream from the Highway 64 bridge, since the

upstream end of a jam is usually of more concern

to local observers than the downstream end.

The ice jam near the Ford Farm was associated

with the Union Dike breach, which resulted in

extensive flooding in the Valley area during the

March 1978. The jam was blasted in an effort to

release the jam and decrease flooding. A similar

event occurred in March 1929:*

 “...Valley, Nebraska, residents were prepared early today for the

second time within 24 hours to abandon their

homes as a huge ice gorge was forming six miles

above the town. A gorge that caused water to

break through a dike near the village Tuesday

night and threatened the city was blasted away

yesterday.”

On 1 March 1979, the ice in the vicinity of the

Ford Farm was dusted with fly ash in hopes of

increasing the rate of deterioration of the ice and

preventing the occurrence of an ice jam similar to

the 1978 jam (USAED, Omaha 1979). Although

ice jammed intermittently near the Ford Farm between 11 and 18 March 1979, no flooding occurred.

Nebraska Civil Defense records reveal that an

ice jam formed between Highway 64 and the Ford

Farm on 22 February 1982. The jam was reported

to be in the same place as the 1978 jam, which

caused so much flooding in Valley. The jam eventually failed naturally on 24 February before flooding occurred.

A minor jam was noted by Nebraska Civil Defense spotters upstream from the Highway 64

bridge on 12 February 1984. The NWS indicated

that the jam had caused overflows onto bottomlands and had flooded several cabins near Leshara on 16 and 17 February 1984. A minor jam upstream from the Highway 64 bridge was again

reported by the Nebraska Civil Defense on 26

February 1985.

The Omaha World-Herald reported that water

levels had come within 3 ft of overtopping the

Union Dike in the Ford Farm area on 27 February

1986, as a result of an ice jam. The location and

extent of the jam were not described, but it appar-

* Montpelier (Vermont) Evening Argus, Thursday, 14

March 1929.

13
ently formed somewhere upstream from the Highway 64 bridge. Ice was pushed up onto the top of

the dike during this event.

Site 6. Platte River: Highway 92 bridge

The recurring ice jam in the vicinity of the Highway 92 bridge appears to form both upstream

and downstream from the bridge and generally

affects the reach of river between the Two Rivers

State Recreation Area downstream from the bridge

and Sokol Camp upstream from the bridge. No

specific information regarding the usual locations

of the downstream end of the jam or the jam extent was obtained. Known ice-related flood events

are summarized in Table 8.

According to Nebraska Civil Defense records,

an ice jam formed near the Highway 92 bridge at

Venice in February 1971. The jam was first noted

on 23 February 1971, and the Highway 92 bridge

was closed soon after. Flooding occurred in the

Two Rivers area downstream from the bridge as a

result of this ice jam.

A 21 March 1978 Omaha World-Herald article

reported that an 80-ft-long section of dike was

washed away north of the Highway 92 bridge

near Yutan. No other details were given. An ice

jam formed downstream from the Highway 92

bridge, causing flooding at Sokol Camp and the

Two Rivers area.

On 14 March 1979, Civil Defense records report that ice began jamming on the west side of

the Highway 92 bridge. An ice jam also formed

downstream from the bridge. On 15 March, blasting took place both downstream and upstream

from the bridge. The blasting was reported to be

relatively unsuccessful, since little ice moved away

from the blasted areas.

Nebraska Civil Defense records reported an

ice bridge near Two Rivers on 22 February 1982.

Overbank flow was observed in the Two Rivers

area, but no other specific information was given

for this ice event.

The NWS noted a minor ice blockage occurring upstream from the Highway 92 bridge between Venice and Sokol Camp on 13 February

1984. On 14 February, local ice jam flooding was

reported in the Sokol Camp area. No other information on this jam was located.

Nebraska Civil Defense records reported an

ice jam on 26 February 1985 just upstream from

the Highway 92 bridge; the jam was threatening

the Lake Platte View development on the east

bank. No further mention was made of the jam or

of actual flooding.

Site 7. Platte River-Elkhorn River

confluence near Ashland

Ice jams frequently occur in the reach of the

Platte River between its confluence with the

Elkhorn River and the Highway 6 bridge. The

jams are formed by ice originating in the lower

Elkhorn River and the Platte River (probably

downstream from Highway 92). Flooding associated with these jams affects the Thomas Lakes

development, Camp Ashland (operated by the

National Guard) and Vencil’s Island, located between the Platte and Elkhorn Rivers. In addition,

several levee breaks have occurred along the east

bank during ice jams, flooding many acres. Known

ice events are listed in Table 9.

An ice jam formed in the Thomas Lakes area

on the Platte River in early February 1966. The

jam extended upstream beyond the Platte River’s

confluence with the Elkhorn River, with ice jamming both the Platte River and the Elkhorn River.

One major levee break occurred on the left bank

of the Elkhorn River, allowing Elkhorn River flows

to flood thousands of acres and damage the Interstate 80 (I-80) bridges over the Platte River. I-80

remained closed for several days while the damage was repaired. Because so much of the Elkhorn

River flow was diverted through the break in the

levee, Platte River water levels did not rise to

flood levels. Over 6500 lb of dynamite were reTable 8. Summary of ice-related flood events near the Highway 92 Bridge

over the Platte River.

Date Description

23 February 1971 Two Rivers area flooded, Highway 92 bridge closed

21 March 1978 80-ft-long section of dike washed out near Yutan

14 March 1979 blasting upstream and downstream from Highway 92 bridge

22 February 1982 Two Rivers area flooded

13–14 February 1984 Sokol Camp area flooded

26 February 1985 Lake Platte area threatened

14
portedly used to open a channel along the east

bank of the Platte and Elkhorn Rivers.

In March 1978, ice jams formed in many places

along the Platte River. Ice jams in the Elkhorn–

Platte confluence area flooded both sides of the

river and Vencil’s Island. A crane equipped with

a wrecking ball was operated from the Highway

6 bridge to facilitate ice movement through the

bridge. Blasting was done on 19 and 20 March in

an attempt to increase flow conveyance through

the area.

Nebraska Civil Defense records indicate that

on 24 February 1980 an ice jam was located between Memorial Hall and the north edge of Camp

Ashland. High stages caused by the jam were entering both Camp Ashland and the Thomas Lakes

development. The jam broke up on its own at

noon on 25 February.

Lowland flooding was first reported on 19 February 1982, in the vicinity of Highway 6 and the

Guard Camp. On 20 February it was reported

that an ice jam on Salt Creek was backing water

up into the Thomas Lakes area. Ice jammed in the

Thomas Lakes area and near Camp Ashland on

21 February 1982. According to Civil Defense reports, a number of homes were evacuated from

Thomas Lakes and from Vencil’s Island farther

upstream. Blasting of the ice jam began on 23

February but was cut short due to bad weather.

The jam failed soon after.

On 14 February 1984, an ice jam in the vicinity

of the Thomas Lakes development again forced

water into the development, flooding some cabins. There was solid ice between the jam and the

Highway 6 bridge downstream, with water flowing over the ice. A minor ice jam at the mouth of

the Elkhorn River was reported by the NWS on 16

February 1984. This jam was apparently affecting

the Vencil’s Island area. It is possible that the two

jams reported were actually the same jam.

In 1993 an ice jam formed in the vicinity of the

Thomas Lakes development on 7 February, following the breakup of the ice cover on the lower

Elkhorn River. The ice cover on the Platte River

below the confluence with the Elkhorn River did

not break up, and a solid ice cover extended about

two miles downstream from the Thomas Lakes

development (USAED, Omaha 1993). A jam

formed in this area when the movement of the

broken ice was stopped by the competent ice

cover. This jam did raise stages slightly, and levees

along the east bank were monitored. However,

the water stage remained within bank and the

jam eventually froze in place.

This jam was still in place when the rising temperatures, precipitation and snowmelt of early

March caused both an increase in discharge and

the breakup of additional ice upstream on the

Platte and Elkhorn Rivers. The jam both lengthened and thickened at this time, and by 8 March

the ice jam was about 2.5 miles long, causing water to overtop a levee on the east bank (Sarpy

County) and a levee on the west bank (Saunders

County). The Sarpy County levee failure reportedly occurred in the same general area as a break

during the 1966 and 1969 events. In addition, a

second levee failure occurred on the east bank

somewhat downstream from the first. The

Thomas Lakes development and Camp Ashland

were flooded, and the City of Lincoln’s well field

was threatened, with two pipelines washing out.

East bank flooding caused the closure of I-80 for

at least a day, and two Highway 6 bridges were

damaged. The discharge during the March 1993

event was estimated at 130,000 cfs (FEMA 1993),

but only about 55,000 cfs was measured at the

Table 9. Summary of ice-related flood events at the confluence of the Platte

and Elkhorn Rivers near Ashland.

Date Description

February 1966 levee break on Elkhorn River; I-80 damaged; blasting done

March 1978 flooding along east and west banks of the river; blasting done;

wrecking ball used at Highway 6 bridge

24 February 1980 flooding in Camp Ashland and Thomas Lakes

21 February 1982 flooding of Camp Ashland, Thomas Lakes, east side of river,

and Vencil’s Island; blasting done

14 February 1984 flooding in Thomas Lakes and Vencil’s Island

February–March 1993 Thomas Lakes flooded; levee break in same place as 1966 and

1969 and a second break downstream; Highway 6 bridges

damaged; blasting done

15
Ashland gage; the remainder of the flow was estimated in the overbanks. The previous maximum

discharge at the Ashland USGS gage was 107,000

cfs on 12 June 1944.

ANALYSIS OF DATA

Historical data

The available historical hydrological, meteorological and ice records presented previously were

examined to determine general characteristics or

trends associated with ice events in the study area.

Since it is difficult to quantify ice event occurrence at sites which are not gaged, the historical

analysis concentrates on gaged sites within the

study area. These sites include the Loup River

near Genoa, the Loup River at Columbus (until

1978) and the Platte River at North Bend and Louisville. Gaged sites outside of the study area on

the Elkhorn River are of value because of the

Elkhorn River contribution to ice jamming problems near Ashland, one of the more frequent and

costly jam sites within the study. Data from the

Elkhorn River at Waterloo are also included in

this preliminary analysis. The period included in

the historical analysis is 1950–1990.

Graphical analysis allows general characterization of various combinations of ice event data.

Parameters examined in the analysis are shown

in Table 10. Discharge at each gage can be compared by normalizing it as runoff per square mile

of contributing drainage area. Stages at different

locations are more difficult to compare because

they are a result of site-specific conditions such as

jam conformation, cross-sectional shape, width,

water slope and presence or absence of levees. As

a result, ice and discharge conditions that might

cause ice-related flooding at one location may not

cause flooding at another. However, stage is still a

valuable tool in comparing the severity of jamming at one locations vs. another. Therefore, we

have chosen to normalize stage at different locations by the reported flood stage for each location. The normalized stage, which is the maximum stage divided by the flood stage, is shown

in Figure 7 for each water year between 1950 and

1990. A normalized stage of 1.0 is at flood stage,

and normalized stages greater than 1.0 are above

flood stage. Table 11 lists the ice events for which

the normalized stage is greater than 1.0.

Figure 7 shows that about 44% of the known

ice events that occurred during the period 1950–

1990 resulted in water levels greater than flood

stage at Genoa, Columbus, North Bend and LouTable 10. Parameters used in characterization of ice events in the Lower Platte River basin study area.

Parameter Abbreviation Definition

Maximum stage max stage recorded ice-affected stage (ft), generally a maximum annual

gage height either due to an ice jam or to backwater from downstream ice jams

Julian Day of maximum stage JD max stage the date when the maximum stage occurred, in Julian Days,

where day 1 = 1 October, the start of the water year

Flood stage flood stage reported flood stage (ft)

Normalized maximum stage normalized stage ratio of maximum stage to flood stage

Maximum discharge max Q recorded maximum average daily discharge (cfs) between 1 January and 31 March

Julian Day of maximum Q JD max Q the Julian Day when the maximum discharge occurred

Maximum AFDD max AFDD the maximum absolute value of the accumulated freezing degree-days since the start of cold

Julian Day of maximum AFDD JD max AFDD the Julian Day when the maximum AFDD was reached

2

1

0

1950 ‘55 ‘60 ‘65 ‘70 ‘75 ‘80 ‘85 ‘90

Water Year

Normalized Stage

Figure 7. Normalized stage for ice events between

1950 and 1990 for the gages in the study area plus the

Elkhorn River at Waterloo.

16
Table 11. Ice events with normalized stage greater than 1.0.

Normalized

Location Flood stage (ft) Date(s) stage

Loup River at Genoa 9 16 February 1962 1.11

Loup River at Genoa 9 1 April 1965 1.15

Loup River at Genoa 9 19 February 1971 1.15

Loup River at Genoa 9 28 February 1972 1.02

Loup River at Genoa 9 15 February 1984 1.01

Loup River at Genoa 9 23 February 1977 1.13

Loup River at Genoa 9 18 March 1978 1.35

Loup River at Genoa 9 15 March 1979 1.21

Loup River at Genoa 9 18 January 1980 1.20

Loup River at Genoa 9 30 December 1980 1.31

Loup River at Genoa 9 21 February 1982 1.37

Loup River at Genoa 9 17 February 1983 1.04

Loup River at Genoa 9 27 February 1985 1.05

Loup River at Genoa 9 27 January 1986 1.13

Loup River at Genoa 9 10 March 1989 1.04

Loup River at Columbus 11 21 March 1969 1.02

Platte River at North Bend 8 13 February 1952 1.02

Platte River at North Bend 8 29 March 1960 1.01

Platte River at North Bend 8 20 February 1971 1.53

Platte River at North Bend 8 29 February 1972 1.27

Platte River at North Bend 8 17 February 1974 1.07

Platte River at North Bend 8 19 March 1978 1.94

Platte River at North Bend 8 14 March 1979 1.25

Platte River at North Bend 8 18 January 1980 1.31

Platte River at North Bend 8 22 February 1982 1.16

Platte River at North Bend 8 18 February 1983 1.19

Platte River at North Bend 8 28 February 1985 1.32

Platte River at North Bend 8 24 February 1988 1.02

Platte River at North Bend 8 12 March 1989 1.02

Platte River at Louisville 9 28 March 1962 1.01

Platte River at Louisville 9 19 February 1971 1.17

Platte River at Louisville 9 3 March 1979 1.09

Platte River at Louisville 9 22 February 1982 1.11

Note: There were no normalized stages greater than 1.0 at Waterloo

than of actual ice event occurrence. For example,

ice jams occurred at ungaged sites in 1966 and

1969. They may also have occurred at gaged sites,

but stages associated with large flows during the

summertime, particularly in 1966 (USAED,

Omaha 1966), may have obscured high ice-related

stages. A review of archived winter USGS stage

and discharge measurement records for the gaged

sites could be useful in identifying and verifying

ice event information. Large-scale climatic variations, increased development, modification of landuse practices, and changes in the sediment regime

of the rivers may also affect the apparent frequency of flooding, in addition to data uncertainties.

In addition to characterizing the frequency and

stage of ice events, it is also important to characterize the hydrological and meteorological conditions associated with ice events. The probability

distributions for the occurrence of discharge events

or temperatures can be developed with greater

isville. Stages greater than flood stage occurred

most frequently at Genoa (73%), followed by Louisville (50%) and North Bend (46%). Normalized

stages ranged between 0.34 and 1.94, with a mean

of 0.93 and standard deviation of 0.28. The frequency distribution of the normalized stages is

given in Figure 8a. The most frequently occurring

normalized stages fall between 1.0 and 1.1 (16.7%),

followed by 12.8% between 1.1 and 1.2. Assuming a log-normal distribution, the exceedance

probability of a given normalized stage is given

in Figure 8b. Flood stage is equaled or exceeded

about 40% of the time at the gaged sites in the

study area; however, factors unique to each site

may cause it to experience a significantly greater

or smaller probability of exceeding flood stage.

Although the ice events shown in Figure 7

which result in flooding appear to occur more

frequently after 1970, this may actually be more a

reflection of the quality and availability of data

17
14

12

10

8

6

4

2

0

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Number of Occurences

MaximumStage/Flood Stage

(Fig. 10a) it is evident that the maximum ice-related stage almost always occurs on or before the

date of the maximum discharge. This is because

ice jams generally form on the rising limb of the

hydrograph, and although a large-discharge event

is required to break up the ice and cause a jam, an

even larger discharge will cause the jam to fail

and wash out.

The relationship between the date of the maximum stage and the date of the maximum AFDD

is less clear (Fig. 10b). The maximum stage associated with ice events can occur either before and

confidence than for ice-related stages; therefore, it

is helpful to develop some idea of the relationships between them. From Figure 9 it appears

that normalized stage is roughly proportional to

both maximum discharge and maximum AFDD.

However, significant scatter in the data prevents

a clear relationship. There does not appear to be

any correlation between maximum discharge and

AFDD.

A comparison between the date of the maximum stage and the date of the maximum discharge shows a stronger correlation. In this case

Figure 8. Statistics for the ice events shown in Figure 7.

b. Exceedance probability.

0

0.4

1.2

1.6

2.0

Normalized Stage

99.99 99.9 99 95 90 80 70 50 30 20 10 5 1 0.1 0.01

0.8

Percentage of Time Equalled or Exceeded

a. Frequency distribution.

18
events occur after the weather begins warming.

For values close to zero, the maximum stage occurs near the time of the maximum AFDD, when

the ice would be thick, competent and most likely

to cause a damaging ice jam. However, the data

show that flood events (normalized stage greater

than 1) occur both before and after this date. Again,

values much lower than zero may indicate freezeup jams.

Ice events in the study area occur between late

December and late March, with ice events occurring most frequently between about 15 February

and 1 March. However, ice jams with significant

flood stages have occurred as early as late December and as late as the end of March. Ice events

most commonly cause stages within the range

after the weather begins to warm. Ice events occur before the maximum AFDD 42% of the time,

but 64% of these events are below flood stage.

Although not documented, it is possible that some

of the earlier events, say those occurring prior to

JD 100 (8 January), may be freeze-up events rather than breakup events. In addition, ice events

that occur before the maximum AFDD may also

have lower discharges, as snowmelt will not be a

significant component of the discharge. Figure 10c

presents the same data in another fashion. In this

figure the normalized stage is plotted against the

difference between the dates of the maximum

stage and the maximum AFDD. Negative values

indicate that ice events occur before the maximum cold, and positive values indicate that ice

60 x 103

40

20

0

4 8 12 16 20 x 102

Maximum Discharge (cfs)

Maximum AFDD

2

1

0

4 12 16 20 x 10 8 2

Maximum AFDD

a. Normalized stage vs. maximum discharge. b. Normalized stage vs. maximum AFDD.

c. Maximum discharge vs. maximum AFDD.

Figure 9. Relationships among normalized stage, maximum discharge and maximum AFDD for January through

March, water years 1950 through 1990.

2

1

0

Normalized Stage

20 40 60 x 103

Maximum Discharge (cfs)

19
plus or minus 50% of the flood stage at a given

location (normalized stage 0.5–1.5). However, ice

events may result in stages that are almost double

flood stages under worst-case conditions, such as

those experienced on the Platte River at North

Bend in 1978. In general, ice events occur only

after at least 400 FDD have accumulated.

Hydraulic analysis

Hydraulic analyses of ice-affected rivers can

often reveal possible causes of jam formation at

particular locations. According to profiles developed for the Platte River Basin Level B Study

(Missouri River Basin Commission 1975), the average Platte River water slope decreases from 4.6

ft/mile upstream of the Elkhorn confluence to 3.9

ft/mile downstream of the Elkhorn to the mouth.

The change in slope corresponds closely with historic jam locations and may be a contributing factor in the formation of breakup jams downstream

of the Elkhorn confluence. A second marked

change in slope occurs at a point approximately

2.5 miles upstream of the Highway 64 bridge,

where the stream slope decreases from 5.1 to 4.6

ft/mile. This location also corresponds closely

with the observed jamming location along Union

Julian Day of Maximum Discharge

200

150

100

50 100 150 200

Julian Day of Maximum Stage

b. Date of occurrence of the maximum ice-related stage

vs. the date of the maximum AFDD.

a. Date of occurrence of the maximum ice-related stage vs.

the date of the maximum discharge.

c. Normalized stage vs. the difference between the date

of maximum stage and the date of the maximum AFDD.

Figure 10. Relationships among dates of occurrence of maximum ice-related stage, maximum discharge and

maximum AFDD for January through March, water years 1950 through 1990 (October 1 = Julian Day 1).

0 100 150 200

Julian Day of Maximum AFDD

2

1

0

– 20 0 20 40 60

Normalized Stage

– 40

Date of Maximum Discharge – Date of Maximum AFDD

20
Dike. The third significant change in slope is at

the confluence of the Loup and Platte Rivers,

where the slope decreases from approximately 6

to 4.6 ft/mile. This location coincides also with a

historical jam location on the Platte River.

Using available HEC-2 models, we performed

a hydraulic analysis of two reaches within the

study area to determine whether any obvious hydraulic conditions conducive to ice jam formation

could be detected. The two locations were the

Platte and Loup Rivers at Columbus and the Platte

River near its confluence with the Elkhorn River.

We first developed open-water profiles, which can

be used to identify critical changes in water surface slope often associated with ice jam initiation.

We then modeled freeze-up jam conditions because frazil ice accumulations can result in areas

of localized thick ice that may be significant during breakup jam formation. Finally a stable ice

cover was modeled in both locations, and an equilibrium breakup ice jam was modeled for the lower

Platte River location. Open-water and stable ice

cover profiles were modeled with the HEC-2 step

backwater program (USACE 1990). Freeze-up and

breakup jam profiles were modeled using HEC-2

and the ICETHK utility (Wuebben and Gagnon,

in prep.).

Loup River near Columbus

The reach modeled extended from a point on

the Platte River from 0.5 mile downstream from

the Loup confluence to the Loup confluence and

then up the Loup River to about 7.25 miles upstream of the confluence. The HEC-2 model used

available cross-sectional geometry for a limited

map and maintenance study of the Loup River at

Columbus, Nebraska, performed for FEMA.*

However, while overbank information was relatively detailed, for many cross sections only one

point below the surveyed water surface was used

to describe the channel bottom. The computation

of water surface profiles at high discharges is not

significantly affected by the lack of detailed channel geometry but may decrease accuracy at low

discharges such as those used in this study. Channel geometry (cross-sectional area, top width, etc.)

fluctuates between adjacent sections within the

reach but not significantly. The overall bed slope

decreases from about 5 to 4 ft/mile downstream

of the Highway 81/30 bridge as the Loup enters

the Platte River valley, although local bed slopes

differ significantly from that.

Open-water, freeze-up and stable ice-cover

profiles were developed for a number of discharges ranging up to 3500 cfs, which is about the

maximum discharge experienced during freezeup. Open-water conditions show a flattening of

the profile near the downstream end of Wagners

Lake and about 3000 ft downstream of the Highway 81/30 bridge, as did profiles for a stable ice

cover and freeze-up conditions. The freeze-up ice

thicknesses computed by ICETHK ranged from

0.5 to 3.6 ft thick, with Manning’s n values ranging from 0.02 to 0.036. The stable ice cover was

represented by 1-ft-thick ice and a Manning’s n

value of 0.015. As can be seen in Appendix A, the

open-water profiles were lowest and the freezeup profiles were highest, as expected. This appendix includes profiles for 750, 2500 and 3500

cfs, although many other intermediate discharges

were modeled.

The thickest accumulations of ice computed

for the freeze-up case, up to 3.3 ft, were generally

located between the Highway 81/30 bridge and

the water treatment plant at all discharges. This

might be expected since the stream slope flattens

out slightly near the highway bridge. Significant

ice thickening was computed for all discharges

about 0.5 mile downstream of the highway bridge.

This location would correspond closely to the toe

of the 1969 ice jam. Another area of ice thickening

approximately 2000 ft upstream from the watertreatment plant was seen at discharges between

2000 and 3000 cfs. This location corresponds closely to the toe of the 1993 jam. Other discharges

showed slightly thicker ice in this area, but the

increase in stage was most noticeable for discharges between 2000 and 3000 cfs. Field observations

of the November 1993 freeze-up jam showed that

frazil accumulations upstream of the actual jam

were thickest from about 0.25 mile upstream of

the water treatment plant to just downstream of

the UPRR bridge west of Wagners Lake, with accumulations of up to 3 ft on top of sandbars and

along shore common. Ice accumulations of greater than 3 ft in thickness may be possible during

freeze-up due to river level fluctuations associated with Loup River Power Canal operations. The

formation of thick ice accumulations in the areas

with reduced slope would appear to contribute to

later breakup ice-jam formation near Columbus.

Platte River from

its mouth to near Highway 92

The area modeled on the Platte River extended

* LMMP study not yet published. from its confluence with the Missouri River up21
stream to near the Douglas–Sarpy County line.

The HEC-2 model was developed from available

HEC-2 input used for an ongoing Platte River

floodplain study performed by R. Michael Brenneman for the Nebraska NRC. Conditions modeled included open-water, freeze-up, stable ice

cover and breakup. Discharges used were approximately equal to the 50%, 25% and 1% seasonal flow duration values shown in Table 12 for

open-water, freeze-up and stable ice-cover profiles and the 1% seasonal flow duration value for

the breakup profile. ICETHK was used in conjunction with HEC-2 for the freeze-up and breakup profiles. Plots of the modeled profiles are

shown in Appendix B.

Some problems were encountered with the

HEC-2 input data. The numerous geometry errors

found in the model, especially at bridges, required

correction before the model would run properly.

Some cross sections had channel and valley dimensions that did not correspond well with the

location shown on the maps provided. Other cross

sections had detailed survey information within

the channel, while others had only two points

below the bank line. As a result the following discussion of results is qualitative, reflecting the uncertainty found in the model. Figure 11 shows a

typical cross section between the Elkhorn River

confluence and Highway 6 that illustrates why

floods are so damaging below the Elkhorn confluence. The overbank near the Western Sarpy Drain

is up to 5 ft lower than the Platte River high bank

and as much as 10 ft lower than the top of the

levee along the river. Once the levee is overtopped

or breached, it is evident that the depth of water

in the overbank can be quite large.

The thickest accumulations of ice shown in the

model correspond closely to observed ice-jam

locations. The most noticeable areas of ice accumulation were immediately downstream of the

Highway 6 bridge, near the north end of Camp

Ashland and north of Thomas Lakes. Ice thicknesses modeled for the 1% duration flow exceeded 3 ft for freeze-up and 5 ft for breakup. However, not enough field data are available to verify

the thickness and locations. The profiles for open

water and stable ice cover show localized decreases in water surface slope near each of these three

locations, but greater decreases were modeled just

upstream of the Elkhorn and just upstream of Salt

Table 12. Discharges used in HEC-2 model of lower Platte River.

50% exceedance 25% exceedance 1% exceedance

probability probability probability

discharge discharge discharge

Location (cfs) (cfs) (cfs)

Platte River downstream 4500 8000 12000

 of Elkhorn River

Platte River upstream 3500 6000 9000

 of Elkhorn River

1080

1075

1070

1065

1060

1055

1050

0 4 8 12 16 20 x 10 3

Distance (ft)

Elevation (ft)

Western

Sarpy Drain

Dike

Platte River

Figure 11. Typical Platte River partial valley cross section upstream of

Highway 6 in Sarpy County.

22
Creek. The jam profiles are up to several feet higher

than the open-water and stable-ice-cover profiles

as expected, but in some locations the breakup

profile approaches the open-water profile because

there is no ice. Better analysis of Platte River ice

jams could be accomplished with more detailed

geometry and field data relating to ice volume

and thickness.

PREDICTIVE MODEL FOR

ICE JAM OCCURRENCE

Past methods

The ability to forecast the occurrence and severity of an ice jam would provide early warning, which

could decrease damages due to ice jams within

the study area. As a result the Interagency Hazard

Mitigation Team requested the development of

some type of model that could be used to forecast

ice jams in the study area. While models have been

developed for use in predicting open-water flood

events, there are few existing models that can be

used to predict the occurrence and severity of

breakup ice jams. There have been a number of

attempts to develop a prediction scheme for ice

breakup, the prelude to breakup ice-jam formation.

For the most part these methods address the formation of cracks in the ice as a result of increases in

stage over the freeze-up stage (see, for example,

Beltaos 1990). The cracks, combined with increased

stage and discharge, result in ice-cover breakup

and movement. The thickness and deterioration

of the ice and the rate of the stage increase are

often considered, as well as river geometry and

meteorological and hydrological conditions.

Unfortunately, while ice-cover breakup is necessary for breakup ice-jam formation, the prediction of breakup alone is not sufficient to predict

the occurrence and severity of breakup ice jams.

The few methods to predict breakup ice-jam formation that presently exist are based on probabilistic or statistical analyses of past ice events and

the parameters associated with ice jams at a particular location. Shuliakovskii (1963) presented two

cases in which the probability of a breakup ice

jam occurring can be predicted based on a statistical analysis of historical events. The predictions

are based on the maximum stable ice stage in one

case and on the rise in water stage and the air temperature during jam formation in the second case.

Shuliakovskii also presented a technique for

forecasting the severity of a breakup ice jam using

the incremental increase in stage due to an ice jam

as the index of severity. His method assumes that

this incremental increase in stage is a function of

the ice thickness, the depth of snow, the rate of

rise of stage prior to ice jamming, the accumulated freezing degree-days during the ice breakup

or simply the existence of subfreezing temperatures, the character of the ice, the difference in

time between ice breakup on the main stem and

significant tributaries, and the ratio of total heat

input per unit surface area in the ice-jamming

region and the total heat input per unit surface

area in the flood-formation region.

Because detailed, long-term data for many of

these parameters may be difficult to obtain, Shuliakovskii presented a simplified application of the

prediction technique. For the case where no significant tributaries are present, the time of breakup on tributaries vs. the main stem may be neglected. If the ice-jam region is either coincident

with or very similar to the source of runoff in

terms of heat input, the heat terms may be neglected. Ice thickness may be estimated using

AFDD. The term describing the character of the

ice is neglected if the thickness and condition of

the ice cover contributing to the jam are relatively

uniform. Finally the temperature statistic of interest may be modified to more closely reflect conditions at the prediction site.

Zhukova (1979) discussed some important

parameters to consider in developing a method

to predict the occurrence of an ice jam. Working

with long-term stage and discharge data for several river basins, she developed a method to predict stages due to ice jams in particular river reaches. This method utilizes an observed relationship

between the long-term average normalized increase in stage due to ice jams and the ratio between long-term average ice-jam stages and openwater stages for the basins examined.

The prediction method relies on determining

the increase in stage due to ice over the long-term

average low-flow stage. The method for determining the long-term average low-flow stage was

not specified. Zhukova assumed that the total increase in stage due to an ice jam is the sum of the

incremental increase in stage due to the ice and

the increase in stage attributable to the jam discharge alone. For comparison between different

sites, the incremental stage increase due to ice is

normalized by the total increase in stage due to

an ice jam, and the stage increase due to discharge

during an ice jam is normalized by the stage increase due to the maximum open-water discharge.

Once these parameters are computed, long23
term average values can be determined. For Zhukova’s sites a plot of the long-term average values

of the normalized stage parameters exhibits a general relationship which can then be used to develop an expression useful in predicting ice-jam stages. Within each basin or other subarea, the data

could be further analyzed to determine the probability that a given increase in stage due to ice

will occur, assuming that an ice jam occurs at a

given discharge.

Galbraith (1981) developed a method for predicting the occurrence of significant ice jams on

the Saint John River in New Brunswick. His method was based on a review of data associated with

historical ice-jam formation. Three factors were

assumed to be important in the formation of ice

jams: the characteristics of the ice (e.g. strength,

piece size, quantity), its movement and river channel properties that restrict the movement of the

ice. Meteorological factors were thought to have a

major impact on both the characteristics and movement of ice, particularly the rate of snowmelt and

rainfall during the ice breakup period.

Galbraith’s method requires the determination

of indices for several meteorological parameters

following the start of the breakup period. These

include the number of days to reach an ATDD of

50, the rate of heat transfer over the breakup period, the number of days to reach a snowmelt index

of 90 mm, and the accumulated precipitation in

mm water equivalent. The rate of heat transfer

can be calculated from the incident solar radiation or hours of sunlight, incident atmospheric

radiation, air temperature, cloud cover, long-wave

radiation emitted from the surface and its emissivity, surface temperature, estimated conductive

heat transfer and wind speed. The snowmelt index is estimated from the mean daily wind speed,

air temperature (if greater than 0°C) and water

vapor pressure.

From past records the meteorological indices

were calculated for the years available and then

ranked in ascending (length of breakup period,

number of days to reach ATDD = 50 and snowmelt index = 90) and descending (rate of heat

transfer and accumulated precipitation) order. In

general, high-ranking or extreme values of the

indices were associated with damaging ice jams.

The time to ATDD = 50 and the snowmelt indices

were the best predictors of damaging ice jams.

Because these terms are related, Galbraith suggested that the snowmelt index might be the better predictor. Accumulated precipitation was not

useful in predicting the occurrence of ice jams. A

method using these four indices was developed

that rates the relative potential for significant (i.e.

damaging) ice jams.

Recently CRREL has been involved in several

attempts to develop prediction schemes for ice

events based on historical ice data. Wuebben and

Gagnon (1995), for example, developed a model

based on an evaluation of historical discharge,

stage and meteorological information for a reach

of the Missouri River near Williston, North Dakota. Ranges of parameters associated with low and

high potential for ice jams were identified, and a

method to predict ice-jam occurrence within this

reach was proposed.

Winter parameters examined were AFDD, the

Julian date of the maximum AFDD, the maximum

discharge, the Julian date of the maximum discharge, the difference in time between the maximum discharge and the maximum AFDD, the

stage of the downstream reservoir (which controls backwater levels affecting ice jamming), the

total snowfall, and the timing of the snowfall (i.e.

early or late in the season). Each parameter was

weighted and assigned a positive or negative rating factor according to its correlation with icejam events.

Wuebben’s prediction method involves calculating each parameter, determining the weight

and rating factor, and summing positive and negative weighting factors. The ratio of positive to

negative factors is used to predict the occurrence

of a breakup ice jam. During the winter of 1993-

94, when the method predicted a high ice-jam

potential, the most damaging ice-jam flood on

record occurred.

Lower Platte River

predictive model

The approach taken in developing an initial

predictive model of ice-jam occurrence within the

Lower Platte River basin study reach is similar to

the methods above in that it relies on an analysis

of hydrological and meteorological data associated with historical ice jams. The data presented in

the previous section, which encompasses the entire study area, do provide some information on

general trends and interrelationships between parameters. However, for various reasons it is not

possible to develop a model applicable to the entire study area at this time. These reasons include

uncertainties in the data, which might be rectified

over time as archived USGS records and old newspapers are searched. Also, the causes of ice-jam

formation at the different locations vary, along

24
with such important parameters as river hydraulics and geometry. We used both the regression

approach and the threshold approach to develop

a prediction model.

To select a site on which to base the predictive

model, the ice events described previously are

summarized in Table 13 for the period 1950–1990.

Of the seven sites chosen for detailed analysis in

the Section 22 Study, the Platte River at North

Bend provides the best combination of ice data

and long-term stage, discharge and meteorologiTable 13. Known ice events during the period 1950 through 1990.

Loup River

Water Loup River at Columbus Platte River Platte River Platte River Platte River Platte River Platte/Elkhorn

 Year between Columbus and Genoa at North Bend at Big Island at Leshara North of Hwy 64 at Hwy 92 Confluence

1950 X XX

1951 X

1952 XX

1953 X

1954

1955 X

1956

1957

1958 X X

1959 X X

1960 XX

1961 X X

1962 XX X

1963 X X X

1964

1965 XX

1966 X XX

1967

1968

1969 XX XX

1970 X X X

1971 XX XX XX XX

1972 XX XX

1973 X X

1974 XX X XX

1975 X X

1976 X X X

1977 XX X X

1978 XX X XX XX XX XX XX XX

1979 XX XX XX XX XX X XX X

1980 XX XX XX XX

1981 XX

1982 XX X XX X X XX XX

1983 XX XX

1984 XX X XX XX

1985 XX XX XX X X

1986 XX X XX X

1987

1988 X XX

1989 XX XX X

1990

Note: X = recorded ice event below flood stage

XX = recorded ice event above flood stage (not necessarily significant flooding)

cal records. Ice jams at North Bend are often associated with ice jams at other study locations, and

few jams occur at other locations in the absence of

some ice event at North Bend. Therefore, the predictive model developed for this study is based

on USGS gaging station records for gage #0679600

(Platte River at North Bend) and NWS data for

Columbus, Nebraska.

The normalized stage (i.e. the ratio between

the stage and flood stage) was used as an indicator of the severity of a given ice event. A high

25
normalized stage would be an indicator of a

severe or damaging ice event. For example, the

most damaging ice event at North Bend occurred

in March 1978. This event had a normalized stage

of more than 1.9, almost double the listed flood

stage of 8 ft. Using the regression approach, we

examined the relationships between a variety of

meteorological and hydrological parameters, including air temperature and discharge on the day

of the ice event, AFDD, ATDD, accumulated precipitation and accumulated snowfall. Because we

thought that the rate of increase in discharge (and

hence stage) might be important in ice-cover

breakup and jam formation, we also looked at the

difference between the average daily discharge

on the day of the event and one, two, three, four

and five days before the event.

An examination of the data showed that accumulated precipitation, accumulated snowfall and

air temperature on the day of the event were weakly correlated with the normalized stage of ice

events at North Bend. We also found little relationship between stage and the difference between

the discharge on the day of the ice event and one,

two, three, four and five days previously. ATDD

was slightly better correlated with the normalized stage. A stepwise linear regression selected

Julian date, AFDD and the discharge on the date

of the ice event (Q) as significant parameters. The

resulting model is:

NS = 1.60799 – 5.832 × 10–3 JD

+ 2.59 × 10–4 AFDD + 1.1 × 10–5 Q

where NS is the normalized stage. The r2 for the

model is 0.5419. Most of the variation is due to the

model rather than random error.

By definition a regression equation will overpredict and underpredict some values. Figure 12

is a graph of the normalized stages at North Bend

predicted for ice-event years by the regression

relationship vs. observed normalized stages. As

can be seen in the figure, the regression tends to

overpredict stage, but in eight cases it underpredicts stages. The most serious shortcoming is

illustrated by the two cases in which the regression predicts a stage less than flood stage, but stages

greater than flood stage occurred (1980 and 1955).

The normalized stage was underpredicted by 19%

and 32%, respectively, in these cases. In the remaining six cases the predicted normalized stage was

above flood stage but was between 7% (1983) and

23% (1978) lower than the observed normalized

stage. It is possible that an improved regression

Figure 12. Relationship between the observed

and predicted values of normalized stage at

North Bend.

2.0

1.6

1.2

0.8

0.4 0.8 1.2 1.6 2.0

Predicted Normalized Stage

Observed Normalized Stage

might be developed in the future with the inclusion of additional ice-event data. If so, this could

provide a useful prediction of the stages that might

be expected for an ice event at North Bend.

Although the regression does not result in a

conservative prediction of the occurrence or severity of ice jams, it does identify the important

parameters (date, AFDD and discharge) that

should be considered in developing a prediction

model. It also provides a mean value of expected

stage, which, if the uncertainty is recognized, can

be used to provide warning that damage is likely

or very likely.

The AFDD, discharge and Julian date of the ice

jam were considered in a threshold analysis, which

confirmed the conclusion reached during the evaluation of historic data for the study area—that

AFDD must reach at least 400 before an ice event

will occur. Similarly discharges must exceed at

least 6000 cfs for an ice event to occur. Also, ice

events occurred between Julian Day 131 and Julian

Day 182. From an examination of average daily

discharges at the time of maximum ice stages, a

relationship between ice-event discharge and

Julian date was developed:

26
Q = 0.39 (JD)1.96 (4)

where Q is the average daily discharge corresponding to ice events in cfs and JD is the Julian

Day (day 1 is 1 October of a given water year).

This relationship, shown in Figure 13, describes

the minimum average daily discharge required

for an ice event to occur on a given date. From

Figure 13 we can see that the relationship reasonably describes the minimum discharge conditions

associated with ice events at North Bend, at least

while the AFDD criterion is met. After examination of data for ice events at North Bend, the following criteria were then chosen to characterize

these ice events: AFDD>400 and Q >6000 cfs or

Q = 0.39 (JD)1.96, whichever is larger. Once these

criteria had been arrived at, they were applied to

the data for 1950–1990 to evaluate the effectiveness of this classification system. The first date

that met the criteria in a given year was selected

as an ice event.

Table 14 presents the results of application of

the criteria to the historic data. The second column identifies water years in which there was a

Table 14. Results of applying AFDD and discharge criteria to historic data at

North Bend.

Predicted

Recorded ice event

Water maximum ± one week of False Negative False negative

 year ice stage maximum ice stage prediction prediction prediction

1950 √ √

1951 √ √

1952 √ √

1953 √ √

1954 √

1955 √ √

1956 √

1957 √

1958 √ √

1959 √ √

1960 √ √

1961 √ √

1963 √ √

1964 √

1965 √

1966 √

1967 √

1968 √

1969 √

1970 √ √

1971 √ √

1972 √ √

1973 √ √

1974 √ √

1975 √

1976 √ √

1977 √ √

1978 √ √

1979 √ √

1980 √ √

1981 √

1982 √ √

1983 √ √

1984 √

1985 √ √

1986 √ √

1987 √

1988 √ √

1989 √ √

1990 √

Note: Water year 1962 was omitted due to significant amounts of missing meteorological

data.

27
Figure 13. Average daily discharge at

the time of the maximum ice stage vs.

Julian Day. The line represents the relationship Q = 0.39 (JD)1.96.

10 5

0 40 80 120 160 200

Julian Day (1 Oct is day 1)

Discharge (cfs)

4 10

3 10

10

9

8

7

6

5

Minimum Ice Jam Discharge (cfs)

0 50 100 150 200

Julian Day (1 Oct is day 1)

11 x 103

Figure 14. Minimum discharge required

for ice jam vs. Julian Day.

recorded maximum ice stage. The third column

indicates whether the criteria predicted an ice

event within one week of the actual recorded maximum ice stage. A false prediction is defined as

predicting a date farther than one week from the

actual date, or predicting an event and none occurred (such as in 1957). A negative prediction is

defined as predicting no ice event and none occurred. A false negative prediction is defined as

predicting no ice event and an ice event did occur.

For years when a maximum ice stage was recorded, the criteria identified 65% of the ice events

within one week of the time they actually occurred.

For the whole period the criteria predicted 55% of

the ice events within one week of occurrence or

correctly predicted that no ice events would occur. Also, 41% of the time, the criteria either predicted the wrong date (more than seven days different from the actual event) or that an ice event

would occur and one did not occur. Only once (in

water year 1961) did the criteria predict that no

ice event would occur and one actually did occur.

The ice-related stage of 6.93 ft in 1961, the second

smallest ice-related stage in the 26 years with ice

events, was more than a foot below flood stage

and may be considered a nondamaging ice event.

Considering the lack of detailed ice data, the

model performed quite well in hindcasting ice

events. This is particularly true if one considers

that the model may have accurately predicted ice

events for years where ice data at North Bend

was particularly sketchy, such as 1966 and 1969,

when serious ice jams occurred elsewhere in the

study area (Table 13). The model overpredicts the

occurrence of ice jams at North Bend. However, it

does provide good initial predictive model capa28
bilities that may be enhanced by the addition of

missing ice data.

Using the model to predict an ice jam requires

the calculation and updating of AFDD using observed minimum and maximum daily air temperatures at Columbus; also, some estimate of discharge at North Bend is necessary. Once the

minimum AFDD criterion of 400 has been met,

forecast discharges can be compared to the minimum discharge associated with an ice jam for a

given date, which can be estimated using Figure

14. If the AFDD criterion has been exceeded, and

the forecast discharge is greater than the discharge

for that date shown in Figure 14, there is a high

probability that an ice jam will occur in at least

one location in the study area.

Calculating or forecasting AFDD is relatively

simple. For example, the AFDD at Columbus

during the winter of 1993-94 had exceeded 400 by

17 January 1994 and remained above 400 through

the end of March (Fig. 15). The peak AFDD (924)

occurred on 1 March 1994. Forecasting discharge,

or even simply monitoring discharge, however, is

more complicated. The discharge criteria for the

prediction model are based on the reported discharges at North Bend, which are actually adjusted from the real-time, provisional discharges. The

provisional discharges are calculated from the

stages reported at the gage, which include the

effect of ice and are therefore too high. At the end

of each winter season, the provisional discharges

are adjusted to reflect the presence of ice and are

revised downward. The difference between the

provisional and adjusted discharges can be significant (Fig. 16).

If the minimum ice event discharge criteria

were applied to the provisional discharges, several ice events would have been predicted begin1000

800

600

400

200

0

Nov '93 Dec Jan '94 Feb Mar

Accumulated Freezing Degree-days (°F)

Figure 15. AFDD at Columbus vs. date

for winter 1993-94.

20

1 Feb 6 16 21 26 3 Mar 8

Discharge (cfs)

Provisional

Adjusted

Minimum

Ice Event

0

11

40 x 10 3

Figure 16. Minimum discharge required for ice jam for 1 February to

8 March, 1994.

29
ning in early January 1994. Using the adjusted

discharges would result in ice-event predictions

for 19 February and 2 March 1994. Although no

ice jams formed at North Bend during 1994, an ice

jam formed on the Platte River downstream of

the confluence with the Elkhorn River on 20 February 1994. Jams also reportedly formed on the

Platte River at Schuyler and upstream from Highway 64 on 5 March 1994.

Using the prediction criteria to predict ice jams

in the study area during 1994 was successful; however, the experience underscored the importance

of obtaining and forecasting real-time ice-affected

discharge. Before the model can be applied with

any confidence, a reliable method to adjust provisional discharges on a nearly real-time basis must

be developed. CRREL personnel are continuing

to develop a method to convert the provisional

ice-affected discharges into actual discharges for

use in the model.

DATA COLLECTION

PROGRAM DESIGN

The primary objective of an ice-data collection program in the Lower Platte River basin is

to develop information useful in developing

advance or emergency response measures to ice

jams. The secondary objective is to collect future data for input into the predictive model.

The data collection program design for the Lower Platte River basin is based on the guidelines

presented in White and Zufelt (1994). Table 15

lists the types of data that should be obtained to

meet the objectives of the data collection program. They may be categorized as either (1) historical, or background, data or (2) physical data

that must be collected in the field. Historical

data collection performed to date and the analysis of those data have been discussed in previous sections. Any additional historical data revealed during the course of the ice data

collection program should be added to the database. Collection of field data, described in

more detail below, may be categorized in chronological order: freeze-up conditions, ice cover

characteristics, breakup details, and ice-jam formation, progression and release.

Ice observations over a number of years will

be necessary to refine the predictive ice-jam model. Ice observations will also be a key part of an

ice-jam detection and warning system. The conditions which do not lead to jamming are as important to determine as those that do, so observations should be made carefully even during winters in which jamming is unlikely. Observations

of ice breakup and transport are particularly important, whether or not a jam forms. The characteristics of a jam which does not result in flooding

should be documented as completely as those of

a jam which does cause damaging floods.

Primarily because of safety constraints, the field

data collection portion of the program is to be

limited to visual observations and measurements that can be made on shore or from the air.

The USGS, the Corps of Engineers, the Papio–

Missouri River Natural Resources District (NRD)

and CRREL have personnel trained in making ice

measurements. These are the only persons who

should attempt to make any measurements from

the surface of the ice. Ice measurements should

never be made alone. Ice observers should be

aware of the possible safety hazards that are associated with data collection and should both minimize their exposure to these hazards and be prepared to deal with any hazards that might occur.

Ice-data-collection efforts may have to be suspended during particularly hazardous weather

or flooding conditions, so it is best to plan alternatives if it is not possible to obtain data using the

ideal method. Other constraints affecting the type

and quantity of data collected are budgetary

limitations, time (e.g. events may occur rapidly),

large geographic area and difficulty of access.

Representatives from the Omaha District office of the Corps of Engineers, CRREL, NWS

(Omaha), USGS (Lincoln), Nebraska Natural Resources Commission (NRC) and Nebraska Civil

Defense were involved in creating a network of

observers to make ice observations in the study

area. In January 1994, CRREL personnel presented a two-day workshop to the observers and others involved in ice-jam detection or response. The

workshop presented information on ice characteristics, river and ice hydraulics, mitigation options and data collection.

The observation form used by the observers,

the Nebraska Ice Report, is shown in Figure 17.

The form was developed mainly with input from

the NRC, CRREL, Corps of Engineers and Civil

Defense. Ice information collected using the Ice

Report is incorporated into the NRC database and

is available for use by the Nebraska Civil Defense, Corps of Engineers, NWS and others. In

addition, the USGS forwards information on ice

thickness measurements, which are also included

in the database.

30
concerns limit ground-based observations, aerial

reconnaissance would be desired. A particularly

useful application of aerial reconnaissance would

be to monitor the location of the main flow channel in the rivers at freeze-up, since effective application of some mitigation measures requires

this information. Ideally the channel should be

videotaped to record the location of the main channel, and the main channel location should be transferred to maps. In the future, as technology further develops, it may be possible to “mark” the

main channel directly on the videotape. Ideally

observations of freeze-up conditions should be

made in a consistent manner by the various ice

observers. It should be emphasized that the observers should include as many additional observations and comments as they desire when using

data collection forms. It is often the unexpected

observation that provides the most information.

Ice cover characteristics

As the winter continues, periodic observations

of general ice conditions should be made at selected locations. Observations of general ice conditions include monitoring the locations of the

downstream and upstream ends of the ice cover,

if possible, and any changes over time. Aerial reconnaissance is the easiest way to obtain this information, but with an adequate network of observation stations, ground-based observations

may be suitable. This is the case at several of the

seven recurring ice-jam locations, such as the Loup

River at Columbus and along the Union Dike,

where levees and dikes provide good access and

visibility along the jam reaches.

The relative roughness of the ice-cover surface

should be monitored over time, along with the

locations and sizes of open-water areas (leads)

within the ice cover. Changing water levels may

affect the ice cover in various ways. If the water

level drops after freeze-up, the ice cover may also

drop, forming a hinge crack along the shoreline.

It is important to note the presence of such cracks

parallel to the shore since they have a direct impact on breakup processes. The appearance and

location of cracks perpendicular to the shore

should also be noted. Since snow insulates an ice

cover, the dates of significant snowfall and the

change in estimated snow depths with time should

be reported.

The ice cover will begin to deteriorate as the

air temperature, length of day and sun angle increase during late winter and spring. The surface

of a formerly smooth ice cover may become pitTable 15. Data to be collected in ice data collection

program.

Historical data

past flood-fighting efforts

stages

discharges

meteorological conditions

ice records

Physical (field) data

Freeze-up conditions

general ice conditions in river

predominant ice type

location of main channel at freeze-up

Ice cover characteristics

general appearance

location of upstream and downstream boundaries

ice cover roughness

presence of leads or cracks

changes in water level affecting ice cover

Breakup details

thermal effects on ice cover

presence and growth of leads or cracks

changes in water level leading to breakup

breakup process

Jam formation and evolution

type of jam

location of jam toe

jam extent

ice characteristics

upstream ice supply

jam progression or regression with time

river geometry and hydraulics affecting jam

water stage

ice thickness

actual and potential ice jam flood areas

Freeze-up conditions

Visual observations of the freeze-up process

are quite valuable. In particular, the date of initial

ice formation and when and where the ice freezes

across the channel to form an ice cover are important. Border ice growth, as well as the types and

relative amounts of moving ice observed, should

be documented. The manner in which the ice cover actually forms in a reach where jams are known

to form would be of special value. It may also be

possible to determine whether the ice cover is

made up primarily of sheet ice or frazil ice through

observations of ice-cover formation and freezeup conditions. Identifying the type and the relative quantity of each type of ice that constitutes

the ice cover or jam can help both in estimating its

possible effects and in evaluating suitable mitigation measures.

Ground-based observations of freeze-up conditions at selected locations are usually adequate,

but if conditions are rapidly changing or if safety

31
32

ICE REPORT

 Section A

DATE: __________________mm/dd/yy TIME: _____________AM/PM RIVER NAME: __________________________________

OBSERVER’S NAME: _________________________________________

LOCATION OF OBSERVATION (See attached map grid):

Area/Site #: __________________________ or Lat: ______° ______' ______" Long: ______° ______' ______"

Location of nearest roads: ______________________________________________________________________________________

Location of nearest bridge: _____________________________________________________________________________________

Name of town: _________________________________________________________ County: _________________________

Is this a changed condition? Yes No Photographs: Yes No

LOCAL WEATHER

Temperature: Air: __________°F Water: __________°F

Precipitation: Rain: __________in. Snow: __________in.

Wind: Average speed: ______mph Direction: (circle one) NW N NE

W ⇑ E

SW S SE

RIVER CONDITION

Bankfull __________ft Estimate less than bankfull __________ft Nearest gage reading __________ft

 Section B

FREEZEUP

Border ice: Growth from shore __________ft __________% of channel remaining open

Moving ice: Types Frazil slush Frazil pans

 (Check all that apply) Fragmented sheet ice Large sheets

Other: __________________________

Percentage of open channel surface occupied by moving ice: ____________________%

Ice cover complete ______________________________________ (mm/dd/yy)

CHARACTER OF INTACT ICE COVER

Location of downstream end of ice cover: Lat: _____° _____' _____" Long: _____° _____' _____" or River Mi: ______

Location of upstream end of ice cover: Lat: _____° _____' _____" Long: _____° _____' _____" or River Mi: ______

Surface roughness (check one):

Smooth < 0.5 ft < 1.0 ft < 1.5 ft > 1.5 ft

Evidence of decay: Yes No Snow covered

If yes, check: Melting snow Melting ice Candled ice

Cracks in ice cover: Yes No

If yes, check: Parallel to shore Distance from shore: __________ft Estimate Measured

Perpendicular to shore

Evidence of fracturing along banks Yes No

If yes, check: (a) Ice thickness when fracture occurred: __________ft Estimate Measured

(b) Displacement: __________ft Estimate Measured

(c) Distance from shore: __________ft Estimate Measured

BREAKUP

Cracks (check one): Parallel to shore Distance from shore: __________ft Estimate Measured

Perpendicular to shore

Average distance between cracks: __________ft

Water on top of ice: Pooled Flowing None

Time ice started to more: _________AM/PM _____________________________mm/dd/yy

Time water was clear of ice: _________AM/PM _____________________________mm/dd/yy

Post movement: Height of shear walls along bank: _______________ft

ICE JAMS

Cause (check one): Freezeup Breakup

Condition at ice jam initiation point (check all that apply):

Solid ice sheet Bend Bridge Island Constriction

Reduction in water slope Other: _________________________

Jam length: ______________mi (approx)

Location of ice jam toe (downstream end), if known: Lat: _____° _____' _____"Long: _____° _____' _____" or River Mi: _____

Location of ice jam heat (upstream end), if known: Lat: _____° _____' _____" Long: _____° _____' _____" or River Mi: _____

Height of shear walls along bank after jam release: ________ft

Figure 17. Nebraska ice report data collection form.
33

Figure 17 (cont’d). Nebraska ice report data collection form.

 Section C

Observer: ___________________________________ Date: _________________________ Time: _________________________

River Name:_______________________________________________________________________________________________

Location: _________________________________________________________________________________________________

Sketches: Include approximate scale.

Illustrate character of ice cover, ice coverage, water level, etc.

1. River cross section:

2. River reach (use copy of map if available; show flow direction).

Comments on any aspect of ice quantity, quality, freezeup, breakup, jamming, weather, etc.:

CONTACT #1: CONTACT #2: CONTACT #3:

(Local) (Corps) Ice Engineering Research Division

CRREL

72 Lyme Road

Hanover, NH 03755-1290

(603) 646-4378

 Ice Report: Additional Information Page 2

Left

bank Right

bank

Looking downstream
ted or slushy in appearance. Deteriorated ice may

often appear darker. Pools of water may form on

top of the ice, enhancing the deterioration process. Water may also run over the top of the ice as

water levels increase. The shape and size of leads

and cracks change as ice melts because of contact

with warmer air and water. Changes in water level may also expose vertical sections of ice that can

provide information on the condition of the ice.

Sheet ice which has begun to deteriorate has a

characteristic appearance, termed candling. Candling will occur soon after exposure to sunlight

though, so it is best to check for candling soon

after an ice piece is exposed.

The ice cover may be monitored remotely by

satellite, although current technology is expensive, images are only occasionally available, and

the resolution of the images may not be desirable.

Two major satellites that could be used are Landsat (U.S.) and SPOT (European). The Landsat imagery covers an area roughly 100 × 100 miles, at

an approximate cost of $4400, while the SPOT

image covers an area roughly 40 × 40 miles at an

approximate cost of $2500. The SPOT image offers higher resolution (or in other words, the size

of the smallest distinguishable object) at 33–66 ft,

while the Landsat satellite offers resolution of only

100 ft. Cloud cover can obscure the target area,

rendering the collected image useless. The satellites also only pass over a specific area once every

16–18 days. A new radar system is being tested

that should be able to detect areas of river ice

with flowing water underneath. This technology

may prove useful for detecting the location of the

main channel for some mitigation techniques.

However, the cost of this is unknown, and an

image may not be available in time to be of use.

Jam formation

and evolution

Observations of ice-jam formation processes

are important in evaluating the effectiveness and

timing of mitigation measures. Important parameters include the location of the downstream end

of the jam; conditions at the jam initiation point,

such as stage, discharge and condition of ice cover, if any; any obvious cause for jam initiation,

such as obstruction to ice transport by a competent ice cover; and the time of jam formation relative to the occurrence of other events such as precipitation and increases in discharge.

It is important to identify the type of ice jam at

the different jam sites because different mitigation measures are suited to different types of ice

jams. Freeze-up ice jams generally occur during

the early to middle part of winter, during periods

of very cold weather and relatively steady discharge. Breakup jams occur from mid- to late winter and are usually associated with sudden large

increases in discharge due to snowmelt or precipitation or a combination of both. Breakup jams

commonly occur during periods of higher air temperatures and thaws. The dates and times of jam

formation should be recorded.

Locating the downstream end of the jam (the

jam toe) is essential because knowledge of the

conditions at the jam initiation point (e.g. open

water, solid ice cover, bridge) can help in identifying the cause(s) of the jam and in evaluating possible mitigation measures. Variability or lack of

variability of the jam toe location from year to

year is also important to note, since some longterm mitigation measures may rely on jam initiation at a particular location. Locating the upstream

and downstream ends of an ice jam may be difficult for a ground-based observer in the Lower

Platte River system, since the rivers cover a large

area and access may be limited. Aerial reconnaissance would be particularly useful in obtaining

this information as well as information about the

appearance of the jam and locations of flooded

areas.

The rate of upstream progression of an ice jam

should be monitored, if possible. The location of

the upstream end of the jam should be noted periodically, both to estimate progression between

reaches and to aid in emergency response decision-making. Again, aerial reconnaissance provides the most complete data on ice-jam progression when access is limited. River geometry and

hydraulic conditions affecting jam progression

should be noted. For example, it may take several

hours longer for the ice to progress upstream past

a riffle than through a relatively uniform reach.

Other useful data

Knowledge of the potential upstream ice supply is useful in estimating the extent, thickness

and possible stages associated with an ice jam.

Important parameters include the length and average width of the ice cover upstream from the

jam, the extent of open water between the jam

and the upstream ice cover, and the presence and

stability of upstream ice jams which might be additional sources of ice to the jam. Estimates of the

thickness and relative competence of any upstream

ice should be made, if possible. Again, actual ice

thickness measurements from the surface of an

34
ice cover should only be made by USGS, Corps of

Engineers or CRREL personnel. The competence

of an upstream ice cover might be assessed by

noting the existence of cracks or leads, the presence of water on top of the ice, and whether candling is visible.

Information on stage data at different locations

along an ice jam is extremely important because it

is stage that determines the level of flooding. Stage

data are collected at USGS gages, but it would be

more useful to develop a system of staff gages

within the jam reaches so that stage could be measured at several locations for each jam. A staff

gage could be as simple as painted markings on a

bridge pier that are monitored or photographed,

or it could be as complicated as a pressure transducer connected to a data acquisition system capable of relaying the information via telephone.

Monitoring of stages could be incorporated into a

detection and warning system as well as the datacollection program.

Stage data can also be obtained indirectly,

assuming that ice levels can be related to water

levels. Ice jams can damage trees, leaving scars

that can indicate the level of the ice. When ice

jams move downstream, they can leave behind

walls of ice along the bank, termed shear walls.

The height of these shear walls can also indicate

the ice levels, although if the river geometry is

favorable for pushing ice upwards, the shear walls

may be higher than the actual ice level. If the icejam flooding occurs during freezing weather, a

collar of ice may form around trees or other objects. When the water recedes, the ice collar may

remain. Photographs of buildings or other objects

showing water or ice levels may also be used to

determine stage.

DATABASE STRUCTURE

The Nebraska Natural Resources Commission

(NRC) was tasked with providing a database structure to allow easy entry and retrieval of information collected by the ice observers. The NRC will

set up each branch site and provide training for

entering the ice data, transferring the data to the

home base, and retrieving data on-line or through

file transfer. The Commission will also serve as

the long-term ice-data repository. A conceptual

overview of the connectivity between the NRC

(the home base) and other agencies responsible

for data collection and retrieval (branch sites) is

shown in Figure 18.

Figure 18. System connectivity.

Branch Site

HARD DISK

Ice Database

NRC

Home Base Branch Site

Branch Site Branch Site

The home base will act as the repository for the

Ice Report data. The database format and design

is standardized by the home base. It provides the

means (using Microsoft Access) for all the branch

sites to enter their local ice data. These local files

uploaded by the branch sites to the home base are

merged into one main database. The home base

also is responsible for system administration, log

tracking, data backups and security of the main

database. The minimum requirements for the

home base are a 486/66-MHz PC with 16 mb of

RAM, a 500-mb hard disk, a 14.4-kbps modem,

Internet connectivity using a bridge/router with

TCP/IP software, Microsoft Access software (version 2.0) and PC Anywhere software (version 4.5).

Observers at the branch sites will enter their

Ice Report data on their local PC using the Microsoft Access program provided by the home

base. That program also allows them to automatically transfer the updated and newly added data

to the home base. The branch sites have the capability to retrieve both raw and processed data from

the home base. The branch site is responsible for

the system administration, security and backup

of their local data. Minimum requirements for a

branch site are a 386/33-MHz PC, with 8 mb of

RAM, a 200-mb hard disk, a 14.4-kbps modem or

Internet connectivity using a bridge/router with

TCP/IP software, Microsoft Access software (version 2.0) and PC Anywhere software (version 4.5).

Figure 19 shows how data transfer can be

achieved from the branch site to the home base

using either a modem or Internet connection. Each

branch site is assigned a directory at the home

base. The branch site will transfer updated or newly added data to the home base over the modem

or through the Internet to an assigned directory.

The home base monitors these branch directories

and merges the uploaded data into the main

database automatically.

The two ways for a branch site to retrieve data

from the home base are by on-line access or by

downloading the complete database. Each method has its advantages and disadvantages. Access35
Phone 

Line

INTERNET

Bridge/Router

TCP/IP

UNIX FTP Server

Home Base

Home Base

Microsoft ACCESS

in Merge Mode

Branch Site

Modem Modem

Bridge/Router

TCP/IP

Branch Site

HARD DISK

Ice Database

Branch 

Upload Directories

Modem File Transfer

Protocol

Modem Connection

Internet Connection

Figure 19. Schematic of data transfer from branch site to home base.

Phone 

Line

INTERNET

Bridge/Router

TCP/IP

UNIX NFS Server

Home Base

Modem Modem

Bridge/Router

TCP/IP

Branch Site

(Microsoft ACCESS

in retrieval mode)

HARD DISK

Ice Database

Read Only

Read Only

Branch Site

Remote Control.

Control Home Base Computer Remotely.

Remote Access.

Share Main Database Files Remotely.

Home Base

Microsoft ACCESS in Retrieval Mode

PC Anywhere Host

Figure 20. Schematic of on-line data retrieval at branch site.

ing data on line allows the branch site to work

directly with the data residing at the home base.

It can be done over a modem using software such

as PC Anywhere, which allows the branch site to

control the home base PC, transferring only screen

outputs and keyboard and mouse inputs instead

of the entire data set. All the data processing is

done at the home base.

The data can be accessed over the Internet

through the Network File System (NFS) mechanism. This technique of remote access makes the

database files at the home base appear as local

files to the branch site, which can be directly processed by the Microsoft Access software at the

branch site. A schematic of each method is included in Figure 20. The advantages of on-line

access through the Internet are that direct access

to the latest data at the home base is possible, any

number of users on the Internet can share the

database, and session time is reduced because the

entire data set is not transferred. The disadvantages of on-line access are that only one user can

use the modem link at a time, on-line communication cost is based on the session time over the

modem link, and processing data over a slow Internet link (56 bps) for queries and reports can be

time consuming.

Figure 21 is a schematic of the second method

of working with data at the branch site: transferring the main database file from the home

base to the branch site and then processing it

locally without being connected to the home base.

The advantages of a complete data transfer are

that data are available locally for fast searches,

data can be modified and processed locally for

custom reports, and there is only a one-time

36
Phone 

Line

INTERNET

Bridge/Router

TCP/IP

FTP/NFS Server

Home Base

Home Base

PC Anywhere

Host

Modem Modem

Bridge/Router

TCP/IP

Branch Site

(Microsoft ACCESS

in retrieval mode)

HARD DISK

Ice Database

Read Only

Read Only

Branch Site

(Microsoft ACCESS

in retrieval mode)

File transfer over modem.

Download database to remote site.

File transfer over internet.

Download database to remote site.

Figure 21. Schematic of complete data download before processing.

communication cost for downloading (no session

costs). The disadvantages are that data may need

to be downloaded repeatedly to stay current, and

local changes to the database are not reflected

at the home base.

ICE JAM MITIGATION

MEASURES

A number of ice jam flood mitigation measures are possible, depending on the type, length,

thickness and accessibility of the jam and the available equipment, personnel and budget. These

measures may be broadly labeled as structural or

nonstructural; as measures appropriate to control

breakup or freeze-up jams; and finally, as measures that are permanent, deployed in advance of

an anticipated flood threat, or deployed under

emergency conditions when a jam has formed and

flooding has occurred. A brief overview of possible mitigation measures is followed by a discussion of measures that might be applied in the

study area.

Structural measures for ice-jam control, such

as levees, dikes and floodwalls, may incorporate

features that can be used to alleviate open-water

flooding as well. The costs of such measures include construction, operation and land acquisition, as well as costs associated with recreation

and environmental mitigation. Unfortunately,

while they are often very successful, structural

solutions tend to be expensive, and current budget climates make their funding less likely. They

remain appropriate for rivers where chronic or

particularly serious threats persist and where the

extent of damages justifies their cost. Although

the majority of the structural mitigation techniques are, by their very nature, permanent, some

are designed to be removable. These removable

structures are usually installed at the beginning

of winter and removed after spring breakup, when

the threat of ice-jam flooding no longer exists.

Nonstructural measures are those that modify vulnerability to flooding or reduce the severity of ice-jam-related floods. They are generally

less expensive than structural solutions. The

majority of the nonstructural techniques are

used for advance and emergency measures

when serious ice-jam flooding is imminent or

already occurring. For example, ice weakening

(ice cutting or dusting) may be implemented before an ice jam occurs, if sufficient warning is

provided, while blasting and mechanical removal

are often employed as emergency mitigation measures once ice jams have occurred. On the other

hand, the creation of ice-storage zones upstream

from a known jam site (to minimize the amount

of ice reaching the jam site) can be considered a

permanent measure, since these areas, once established and properly maintained, can be used

year after year.

Freeze-up ice-jam control usually targets the

production and transport of the frazil ice which

makes up the jam. This may be accomplished by

encouraging the growth of an ice cover, which

insulates the water beneath, decreasing the production of frazil ice. The ice cover can also incorporate frazil ice which is transported from upstream production areas, decreasing the supply

available to jam or deposit beneath a downstream

ice cover.

37
Ice booms are the most widely used type of

ice-control structure. They are relatively inexpensive and can be placed seasonally, thus decreasing environmental impacts. Booms are most commonly used to stabilize or retain an ice cover in

areas where surface water velocities are 2.5 ft/s

or less and relatively steady. Ice-control booms

are also used to promote ice-cover formation during freeze-up as an ice-jam mitigation effort. They

can be placed to direct ice pieces away from an

intake or navigation channel.

Breakup ice-jam frequency and flood levels can

be reduced by storing ice upstream from damageprone areas. Ice-storage zones reduce the volume

and/or rate of ice moving to a downstream jam

Table 16. Ice-jam mitigation methods.

Technique Jam type Type of mitigation

a. Structural

Dikes, levees, floodwalls F,B P

Dams and weirs F,B P

Ice booms F,B P,A

Retention structures F,B P

Channel modifications F,B P

Floodproofing F,B P,A

Ice storage zones B P,A

b. Nonstructural

Forecasting F,B A,P

Monitoring and detection F,B E,A,P

Thermal control F,B E,A,P

Land management F,B P

Ice cutting B A

Operational procedures F,B E,A,P

Dusting F,B E,A

Ice breaking F,B E,A

Mechanical removal F,B E,A

Blasting F,B E,A

c. Traditional techniques

Floodproofing P

Sandbagging A,E

Evacuation A,E

Levee closing A,E

F = Freeze-up jam

B = Breakup jam

P = Permanent measure

A = Advance measure

E = Emergency measure

Breakup ice-jam control focuses on affecting

the timing of the ice-cover breakup (thereby reducing the severity of the resulting jam to the

point where little or no flooding occurs) or controlling the location of the ice jam by forcing the

jam to occur in an area where flooding damages

will be inconsequential, or at least acceptable.

Table 16 summarizes the currently available

jam mitigation techniques. In the following sections, these methods are described in some detail.

Traditional flood-fighting methods, namely floodproofing, sandbagging, levee closing or evacuation, are obviously applicable to ice-jam floods.

Table 17 lists common ice-jam mitigation strategies and corresponding techniques.

Permanent measures

Dikes, levees and floodwalls physically separate the river from property to be protected. These

are used to protect against open-water floods as

well as ice-jam floods. However, designs adequate

for open-water protection may not be adequate for

the stages and physical damage caused by ice jams.

Table 17. Ice-jam mitigation strategies.

1. Protect surrounding areas from flood damages

• Dikes, levees, and floodwalls

• Floodproofing

• Floodplain land use management

• Flow diversion

• Sandbagging

• Levee closing

• Evacuation

2. Reduce ice supply

• Thermal control

• Revised operational procedures

• Ice booms

• Dams and weirs

• Ice storage zones

• Ice retention

3. Increase river ice and water conveyance

• Channel modifications

• Revised operational procedures

4. Control ice breakup sequence

• Detection and prediction

• Ice booms

• Ice retention

• Dusting

• Ice cutting

• Icebreaking

• Revised operational procedures

5. Displace ice jam initiation location

• Dams and weirs

• Ice piers, boulders and cribs

• Ice booms

• Channel modifications

• Dusting

• Ice cutting

• Icebreaking

6. Remove ice

• Thermal control

• Ice breaking

• Mechanical removal

• Blasting

38
Perhaps the best strategy for reducing flood

losses is to keep people and property out of the

floodplains. Proper land-use planning would dramatically reduce the flood damage potential. This

is particularly valuable in areas which experience

chronic flooding. If such land-use regulation is

not feasible, floodproofing should be considered.

There are four basic types of floodproofing to minimize damage to individual structures during

floods: raising or relocating a building, barrier

construction, dry floodproofing and wet floodproofing. Specific techniques of floodproofing are

presented in the U.S. Army Corps of Engineers

manual on floodproofing, Flood Proofing Techniques,

Programs and References (USACE 1991).

Advance measures

Mitigation measures that are put into place in

anticipation of actual ice-jam flooding are known

as advance measures. Some emergency measures,

such as ice removal, may also be initiated in advance of flooding. Monitoring and detection

should be addressed in any ice-jam mitigation

effort. Ice-cover breakup, jam formation and jam

progression are particularly important processes

to monitor. Simple remote gages to collect data on

river-ice movement and breakup are useful.

Water-level gages can be monitored to detect rapid increases in river stage, which often precede

ice breakup. Automated temperature sensors help

to verify whether conditions are conducive to icejam formation or breakup.

Ice motion detectors can be imbedded in intact

ice covers prior to breakup to warn of the initiation of breakup upstream from a likely jam site.

These can be connected to inexpensive burglar

alarm units that will automatically dial preselected telephone numbers when the unit detects ice

motion (Fig. 22), or existing USGS gages can be

augmented with telemetry transmitters that send

ice motion data directly to a local monitoring

center or to State and Federal agencies (e.g., NWS

or USGS) either through telephone, radio or satellite (Zufelt 1993).

Ice cutting involves creating slots in the ice,

either mechanically, using a chainsaw, trenching

machine, backhoe or other convenient device, or

thermally, using warm water or a substance that

reacts chemically with the ice, melting it. The slots

can be made to a partial depth or can extend the

full depth of the ice. They may follow the natural

thalweg of the river channel, be cut along the

edges of the channel to facilitate movement of the

ice sheet, or be cut into the ice in a pattern delocation. By developing low overbank areas where

ice can easily leave the channel during breakup,

perhaps supplemented by dikes or booms to redirect ice movement, the volume of ice passing

downstream can be substantially reduced. The

ice left behind settles in side channels, on floodplains or on the riverbanks.

Diversion channels can be built to bypass ice

and water flow around the normal jamming sites,

lowering the upstream stage. If such diversion

channels are used, they should be designed to

remain dry except during flood events so they

will be available to function as open-water channels and not add to the ice supply reaching downstream ice-jam sites.

Ice-retention structures are used to control

freeze-up or breakup jams by promoting the initiation of an ice jam at a suitable location where

flooding will create little or no damage. Fragmented ice is captured and retained upstream from the

retention structure to create the ice jam. A variety

of structures can serve as ice-retention structures,

ranging from suspended structures such as a submarine net, to structures that project from the

streambed, such as concrete piers placed at regular intervals across the stream. Provision for icestorage zones or diversion channels may also be

required to limit the rise in upstream water level

and corresponding load on the structure elements

as well as the upstream flooding potential. Suspended structures are generally more suited to

smaller rivers and streams. Bed and bank scour

must be considered in the design of ice-retention

structures.

Thermal control of ice jams uses an existing

source of warm water to melt or thin a downstream ice cover or ice jam. Water even a fraction

of a degree above freezing can be quite effective

in melting ice over a period of days or weeks

(Wuebben and Gagnon 1995). External heat sources include cooling water effluent from thermal

power plants, wastewater treatment plant effluent and groundwater. The thermal reserve provided by water in nearby lakes and large reservoirs may also be a source of warm water for

thermal control. Because water reaches its maximum density at about 39°F, colder water in lakes

tends to stratify above warmer water. An ice cover can form on the water surface even though the

water at depth is still well above freezing. Warm

water can be brought to the surface using air bubblers, pumps or flow enhancers, or a low-level

outlet in a dam may be used to release warm

water.

39
signed to weaken it. Ice cutting must be carefully

timed to avoid refreezing of the slots. This technique may be used to cause a stable ice sheet to

break up earlier than normal, preventing it from

obstructing the movement of upstream ice. Ice

cutting in selected locations can also create a flow

path for ice and water at breakup, reducing the

probability of jamming.

Ice covers can be broken prior to natural breakup using icebreaking vessels or construction

equipment. The downstream movement of the

broken ice should be enhanced to prevent localized breakup ice jams. Air cushion vehicles (ACVs)

can be used to break large extents of relatively

smooth sheet ice covers, usually in areas where

the sheet ice may stop the ice run and initiate a

jam. The advantages of an ACV are its speed and

maneuverability and its ability to operate in shallow areas. The disadvantages are that it simply

breaks the ice but does not move it, it cannot

operate over rough ice accumulations because of

potential damages to its flexible skirts, and operations in cold weather can lead to severe icing of

the propulsion system. Also, the ACV must be

quite large; the smaller 2- or 4-person ACVs will

not break ice of average thickness in the Platte

River.

Dusting, or covering ice surfaces with a thin

layer of dark material, induces more rapid melting and ice weakening. Conventional materials

include coal dust, fly ash, topsoil, sand or riverbed material. Initial tests with biodegradable materials such as leaves, mulch and bark show promising results. This type of material is more easily

spread by commercially available seeders and

Anchored

Loops

Waterproof

Splice

#22 AWG

Phone Wire

Telephone

Dialer

Unit

AC

Power

Receiving

Parties

#28 AWG

Wire Loops

Ice

Cover

Stick

Wire

Loop

Plastic 

Tie

Ice

Cover

Figure 22. Ice motion detector.

spreaders than sand or coal dust. These materials

must be dry enough to flow freely for even distribution and to avoid freezing. Wind can be a problem, causing the fine materials to drift or the snow

to drift over the dust (Moor and Watson 1971).

The dusting material is usually applied two to

three weeks prior to breakup. The degree of melting depends on the quantity and properties of the

material deposited, solar radiation and snowstorms. In areas where late snowstorms occur, several applications may be necessary, although snow

of moderate depth over a dark material will melt

at an accelerated rate. The melting period may be

too short for significant reduction in ice volume

or weakening if breakup occurs soon after application. Whatever material is used, the possible

adverse environmental impacts of dusting must

be considered prior to application. The use of dusting as a mitigation measure within the study area

is discussed in detail below.

Emergency measures

Emergency measures are those that are taken

after an ice jam has formed and flooding is imminent or already occurring. The effectiveness of

emergency response may be reduced unless an

emergency action plan exists that specifically refers to ice jams. Comprehensive emergency management includes four phases: preparedness, response, recovery and mitigation. Emergency

planners should have a clear line of command for

multi-governmental management of ice-jam flooding events. Plans should be tested in advance to

be sure that all phases can be carried out and that

all necessary materials and equipment are avail40
able when needed. The Nebraska Disaster and

Civil Defense Act is attached in Appendix C for

reference. The act defines the legislated powers

and duties of the Nebraska State Civil Defense

Agency. Appendix D contains a legal opinion

drafted by the State indicating that both the State

and its political subdivisions are essentially protected from liability if emergency measures are in

accordance with the Nebraska Disaster and Civil

Defense Act and an emergency has been declared.

Prior to implementing emergency measures, it

is necessary to monitor the river ice conditions

upstream as well as downstream from the jam

site to select the best measures and to eliminate

those that may only displace the flooding problem to another location. Early ice monitoring can

also provide some lead time to allow other emergency measures to be taken. Downstream ice conditions also need to be assessed, if only to determine whether there is sufficient open-water area

to receive ice when the jam releases.

If ice-jam flooding has been predicted, levees

should be closed immediately and interior drainage pumps should be prepared for possible activation. Again, winter weather conditions such as

snowdrifts or frozen valves, which can hinder

levee closing, should be identified. Monitoring of

water levels at levees may aid in identifying possible overflow sites before serious damage can

occur.

Although ice can cause significant damage to

sandbags used as protective barriers, the use of

sandbagging as an emergency response measure

can be very effective in reducing damages at particular facilities or locations. For example, sandbagging around sewage treatment plants or low

points on roads or riverbanks can significantly

reduce flood losses. Overbank flow may be channeled away from flood damage areas using temporary levees constructed of sandbags.

Ice-jam emergency response measures include

icebreaking, mechanical ice removal and ice blasting, in addition to the traditional flood-fighting

efforts of evacuation, levee closing and sandbagging, all of which also qualify as advance measures. The principle behind evacuation is to move

people at risk from a place of relative danger to a

place of relative safety via a route that does not

pose significant danger. Local law enforcement

departments usually serve as lead organizations

and have standard operating procedures. Winter

weather conditions should be taken into account

when planning evacuation timing, equipment and

routes.

Construction equipment can be used to break

up an ice cover or an existing jam, either from the

shore or, if the ice is safe, from the river itself. It is

generally best to begin working from the downstream end of the ice cover toward the upstream

end so that the broken ice will be carried away. A

heavy weight or wrecking ball can be dropped

repeatedly on the ice surface to break up the ice.

Ice can be broken either to form a channel or to

weaken the ice in specific locations.

Mechanical removal involves taking the ice out

of the river and placing it elsewhere using bulldozers, backhoes, excavators or draglines, starting from the downstream end of the ice accumulation. This approach is most effective on small

rivers and streams because of the time required to

excavate and because of additional safety concerns associated with wide or deep rivers. Mechanical removal can be expensive and slow but

also quite effective. Access to the jam site by heavy

equipment is frequently an impediment to mechanical removal of ice.

Often a popular solution to ice-jam problems,

blasting breaks up an ice cover or loosens an ice

jam so that it is free to move. Absolute prerequisites to successful blasting are that enough flow is

passing down the river to transport the ice away

from the site and that sufficient open-water area

exists downstream to receive the ice. Otherwise,

the ice will simply rejam elsewhere and cause

problems for another community. Blasting has

been used to create a relief channel within a

grounded jam to pass water and decrease the upstream water level. As with icebreaking and mechanical removal, it is recommended that blasting

proceed upstream from the toe of the jam. Safety

and environmental concerns must be addressed

before implementation (USACE 1982).

Specific mitigation options

within the study area

The choice of mitigation options for a particular ice-jam location depends on a number of factors, including the characteristics of the ice jam,

weather, access and budget. Local residents and

officials, who are most familiar with the jam,

should be involved in selecting appropriate mitigation measures. Applying traditional flood mitigation techniques (e.g. floodproofing, sandbagging, evacuation and levee closing) should be

considered for areas affected by ice-jam flooding

Increased monitoring and detection of ice conditions, breakup and jamming is a nonstructural

mitigation option that should be implemented at

41
every ice-jam location within the study area. The

ice monitoring conducted under the aegis of the

Nebraska NRC should prove useful in the early

detection of ice breakup. The use of ice-motion

detectors will provide warning at a number of

locations in the study area. For example, a series

of ice-motion detectors on the Loup River upstream from Columbus will provide information

on the timing and location of ice breakup, which

can contribute to damaging jams at Columbus.

Knowledge of ice conditions on the Loup and

Platte Rivers downstream from Columbus and

estimates of broken ice volumes could be used to

assess the damage potential of a jam. The additional lead time provided by ice-motion detectors

will increase the effectiveness of early warning

and other advance measures, such as sandbagging or evacuation. Emergency measures such as

blasting or ice removal are most effective if they

are begun soon after a jam has formed, so early

detection is very important if such measures are

contemplated. Particular locations that would benefit from the use of ice-motion detectors include

the Loup River near Columbus and the Platte River

and lower Elkhorn River in the vicinity of their

confluence.

Water-stage recorders can also be used to alert

authorities when the stage reaches a certain level

or increases rapidly. Water-stage recorders could

be used singly or in conjunction with ice motion

detectors to provide early warning. Placing water-stage recorders both upstream and downstream from a known ice-jam location will allow

the observer to detect the formation of a jam which

causes backwater. If such an installation is not

possible, jam formation can also be detected by

combining discharge data from USGS gages and

information from a single water-stage recorder

upstream from a known jam location. Two likely

sites for water-stage recorders are Big Island and

Columbus.

Other nonstructural ice-jam mitigation measures that are suitable for application within the

study area are dusting, icebreaking, mechanical

removal and blasting. The formation and progression characteristics of a particular jam must be

known in order to design an effective plan of application. Dusting is best used when the ice jam is

caused by a competent ice sheet that impedes the

movement of broken ice. Icebreaking, mechanical

removal and blasting can be used to create a channel through a competent ice cover or through a

jam to increase flow and ice conveyance.

The application of structural ice-jam mitigation

techniques within the study area requires more

detailed analysis than is possible within the scope

of the present study. The available information

suggests that levees could prove effective in the

Big Island area. The existing levee at Leshara

should be evaluated to see what improvements

might increase its level of protection. An ice boom

located just upstream from the Loup River Power

Canal headworks could provide frazil-ice control,

which would decrease somewhat the amount of

ice available to downstream jams and might result in more efficient operation of the canal. The

effects of the canal operation must be studied in

detail before any conclusion can be reached as to

the impacts of fluctuations in stage and discharge

on the Loup River.

Ice dusting as a

mitigation alternative

Ice dusting refers to the practice of spreading

solid material on top of the ice surface to accelerate melting and decay of the ice. Dusting was

performed on the Platte River in 1979 at four locations (USAED, Omaha 1979). The dusting operation was done under the direction of the Nebraska Civil Defense Office and the Omaha District

Corps of Engineers; the Cold Regions Research

and Engineering Laboratory (CRREL) provided

technical assistance. The ice on the Platte River

just prior to breakup was as much as 3 ft thick in

1979, and the snowpack water equivalent was estimated at 2.5–3 inches in late February. The results of the dusting were inconclusive because of

the insufficient time between dusting and breakup, especially at the mouth of Salt Creek, where

breakup occurred two days after application. The

report noted that there may have been some positive effect in that no significant jamming problems occurred at the dusting sites, which had historically been problem areas, and jamming

occurred at other sites that were not dusted. The

report did conclude that dusting will reduce the

strength of river ice and reduce the problem of

jamming if an adequate time elapses between dusting and breakup.

Materials. The material used in 1979 for dusting was black-bottom slag from the Nebraska Public Power District power plant at Hallam, Nebraska. This material was chosen because of its dark

color and relatively low cost. The target application rate was 0.5 lb/yd2, and it was applied using

airplanes equipped with crop-dusting equipment.

The material was chemically analyzed for environmental reasons (Table 18). If this material is

42
in waterways from non-point pollution sources in

nonharmful levels. Another material that has recently been tried is leaf mulch (Haynes et al. 1994).

Equipment. The dust was applied by means of

crop-dusting airplanes in 1979. This was considered the only practical means of distributing the

material on the ice in a short time. Aircraft have

been the most commonly used method of application in other areas of the country and world as

well. Dusting in Alaska has been done with B-25

(USAED, Alaska 1968, 1969) and B-26 (Meyer 1976)

aircraft outfitted with gravity-flow hoppers. Helicopters have also been used, with the helicopter

carrying a hopper-type spreader. The crop-dusting airplanes used in 1979 were outfitted with

rectangular-shaped venturi-type funnels.

It is necessary to secure a means by which to

load the aircraft. In 1979 the material was put into

a plastic funnel-shaped bag with a 6-in. circular

bottom discharge port, which was hoisted above

the airplane hopper with a crane. The report on

the 1979 dusting recommended using augers to

load the material into the airplane; however, the

material may be excessively abrasive on auger

flights. Another option which may be less affected by abrasive material may be a portable elevator flight.

The areas to be dusted must be marked for the

pilots’ benefit. In the 1979 dusting operation, flight

paths were delineated with neon orange road

cones by using two cones to mark the beginning

and end of the path and individual cones at several intermediate points. The cones were placed

by helicopter.

Timing of application. The 1979 Platte River dusting operations were performed from 28 February

to 2 March, which was about a week later than

initially recommended based on experience. The

date will vary from year to year, depending on

weather conditions, such as snowfall or rainfall,

amount of sun and temperature. The recommended time of application in 1979 was for three weeks

prior to breakup. The report concluded that dusting should be done three to four weeks prior to

breakup, with trouble spots dusted even earlier.

Cavan (1969) stated that dusting should generally be carried out just before natural break-up

starts and that dusting is most effective when the

air temperature is 32°F or higher. Williams (1967),

as cited by Bolsenga (1969), reported that dusting

much before breakup is usually not worthwhile

because periods of freezing weather following

dusting freezes the meltwater produced. However, others have noted that the particles create tunTable 18. Constituents of 1979 dusting material.

Amount

Ingredient % by weight

Silica 50.00

Phosphorus pentoxide 0.25

Ferric oxide 7.50

Alumina 21.30

Titania 1.07

Lime 7.50

Magnesia 2.24

Sulfur trioxide 7.70

Potassium oxide 1.70

Sodium 0.20

Undetermined 0.54

used again for dusting, it should be chemically

analyzed again, since plant operations or fuel

source have changed since 1979.

Small-diameter particles are more desirable

because, for a given weight, the smaller particles

will cover a larger ice area than larger-diameter

particles. However, if particles are too small, they

may be blown off the target area before penetrating the ice cover. If particles are too large, they

may clog the spreader on the airplane. Bolsenga

(1968) cited Williams and Gold (1963), who stated

that field experience had shown the practical range

in particle size was 0.004–1.0 inches. The material

used in 1979 had fewer than 1% by weight outside this size range. Bolsenga also cited Konovalov and Miasnikov (1956), who recommended

particle sizes of 0.008–0.02 inches. However, it

would probably be prohibitively expensive to

screen bottom slag to this fine gradation (only

15% of the material used in 1979 was this fine).

The areal concentration in the past has varied from

0.01 to 0.08 lb/ft2 (Bolsenga 1968); for comparison, the application rate in 1979 was 0.02 lb/ft2.

Generally the lighter application rates were associated with smaller-diameter and less-dense particles.

Materials used in the past have included sand,

soil, coal dust, soot, fly ash, bottom slag, foundry

loam, phosphate fertilizer, potassium salt, calcium chloride, ammonium nitrate or mixtures of

the above (Bolsenga 1968). Some of these materials may not be environmentally acceptable today.

Dyes and powders in the form of a spray could be

used in areas where the cost of transporting and

applying dust is high, but these materials are not

as effective. Recently various agricultural products, such as grain, feed and fertilizer, have been

approved in certain areas, as these items are found

43
nels in the ice surface, which, if filled with water

and then frozen, tend to further break the ice since

water expands when frozen. Most dusting in the

past has been done much farther north than

Nebraska, so it is difficult to extrapolate timing

since Nebraska warms up quicker and the sun

angle gets higher sooner. The most critical aspects

of timing, though, appear to be adequate sunshine, near- or above-freezing temperatures and

lack of snowfall for several days following application. It is best to study past climate data to determine the earliest that dusting can be effective.

Dust can be applied far in advance of breakup

if the intent is to weaken a midwinter jam that

freezes in place. Midwinter jams may not be very

damaging at the time of formation but can cause

great damage at normal breakup if they freeze in

place and block a large portion of the flow channel. Dusting can weaken the ice and reduce the

volume in a midwinter jam enough so that it does

not pose a problem later. The rate of melting will

not be as effective as later, but since jams tend to

be several times thicker than the ice blocks composing it, more time is required to thin the ice.

Multiple applications may be necessary because

of the thickness and subsequent snowfalls. The

ice in some rivers may contain sediment that gives

it a dirty appearance and will accelerate the melting of this ice in a jam. Dusting to melt normal

spring breakup jams has not proven very effective because it generally takes too long to thin the

ice before damaging flooding occurs.

Planning an ice-dusting operation. Planning for

an ice-dusting operation is essential since weather conditions may limit the window of opportunity for applying dust. It is important to have the

material and equipment lined up ahead of time.

This does not mean actually having the equipment on hand but being able to mobilize operations in a short time. It is imperative to identify

the sites most likely requiring dusting ahead of

time, as resources and time are likely to be limited. Plans for dusting the Platte have been developed twice since 1979. The State of Nebraska requested initial technical planning assistance for

dusting operations from the Corps of Engineers

in 1980 and 1982. Dusting was not carried out in

either year because weather conditions became

favorable for natural melting prior to breakup,

although some ice jamming did occur. Table 19

summarizes the sites and materials required for

the ice-dusting operation planned in 1982. Eventually shorter or fewer strips were planned to reduce the cost of dusting, but dusting was not done.

The dusting strips were chosen on the basis of

historical ice-jamming problems. The effort that

went into planning these two proposed ventures

should serve as a guide for planning future dusting operations. Other items should be incorporated to form an overall plan of action for dusting.

The following is intended as a checklist in planning dusting operations, and a chart for estimating the cost of the operation is also included.

1) Identify sites for dusting. Sites of recurring

historical jamming problems should always be

identified as possible dusting sites. The need for

dusting these various sites may vary from year to

year, depending on conditions such as ice thickness and amount of open water. If possible, these

recurring jam sites should have aerial photography done just prior to freeze-up to identify the

location of the main channel or channels. Dusting

Table 19. Example dusting plan for the lower Platte River based on the 1982 plan. All flight information is

based on using Wahoo Airport as a base of operations.

Distance Number Total

Site Strip Cinder one way of passes Time for time

 no. Location length (ft) (tons)* (miles) (3 planes) each pass† (3 planes)

1 Louisville 9,000 7.5 27 4 47.4 min 3 hr 10 min

2** I-80\Salt Creek 16,000 13.3 22 7 41.4 min 4 hr 50 min

3** HWY #6 Bridge 5,200 4.4 19 2 37.8 min 1 hr 15 min

4** Elkhorn Exit 6,500 5.4 17 3 35.4 min 1 hr 45 min

5 Two Rivers 6,000 5.0 12 3 29.4 min 1 hr 28 min

6** Ford Farm 14,000 12.0 13 6 28.6 min 2 hr 52 min

7 Fremont 10,500 8.8 14 5 31.2 min 2 hr 36 min

8 C&NW Bridge 10,600 8.8 13 5 30.6 min 2 hr 33 min

9 North Bend 6,000 5.0 18 3 36.6 min 1 hr 50 min

* Based on concentration of 0.5 lb per sq yard.

† Includes 15 minutes for landing, taxiing, loading, fueling, etc.

** Sites dusted in 1979.

44
should be done from just downstream of the usual jam location to upstream of the jam location, so

maps showing the probable maximum upstream

and downstream ends of dusting should be prepared and on file. Maps showing the proposed

1982 dusting sites are on file in the Hydraulics

Section of U.S. Army Engineer District, Omaha.

2) Identify dusting material, availability and suitability. There are many suitable materials available for dusting, but not all may be available as

needed on short notice. A ready source of dusting

material should be identified. Dry material works

best, so it is important that a means of drying the

material be secured if necessary. The selected

source of material should be contacted every year

to assure that the required material can be delivered if needed. Alternate materials should be identified ahead of time in case the selected material is

unexpectedly unavailable or is designated as environmentally unacceptable.

3) Identify needed equipment. Equipment needs

and availability should be identified ahead of time.

This includes airplanes or helicopters equipped

for dusting, a means of conveying the dusting

material into the aircraft holding bay, and a means

of marking the dusting strips. An airport that is

central to the dusting sites should be identified as

a base of operations, and permission to use the

airport should also be secured.

4) Estimate the cost of planned dusting operations.

Unit costs of materials and equipment should be

periodically verified and updated if necessary.

Table 20 is designed to be used to assist in estimating operation costs. It is also helpful for identifying areas where dusting efforts can be cut back

if funding is limited.

5) Secure any applicable permits prior to the operation. Permit requirements will vary state by state

but will generally include some review by local,

state and Federal environmental agencies. USAED,

Omaha (1994) provided a complete discussion on

potentially applicable Federal regulations. In this

case the Nebraska Department of Environmental

Quality determined that the planned 1994 dusting would have no significant environmental impact and did not require a permit.

Summary of 1994 ice dusting

Three locations on the Platte River were dusted on 3 and 4 March 1994. The locations dusted

were:

• From Highway 64 bridge to about 3 miles

upstream;

• Both channels upstream of the Highway 92

bridge to about 1.25 miles upstream; and

• About 1 mile downstream of the Highway

92 bridge to about 1.5 miles downstream of

the Highway 92 bridge.

These three sites were selected based on previous

jamming locations and on aerial reconnaissance

flights on 5, 16 and 25 February. A brief warm-up

in mid-February broke up the lower Elkhorn River ice and cleared most of the Platte below the

Elkhorn. However, the river remained mostly icecovered above the Elkhorn, and the ice showed

few signs of deterioration at that time. By the end

of February, river-ice thickness still exceeded 2 ft

along Union Dike.

A decision to dust was made on 28 February,

and plans were finalized by 2 March. A rapid

warm-up began on 1 March and continued for

several days. The ice began to rapidly deteriorate

with the warmup as the remaining snow cover

melted and began to crack following completion

of the dusting operation. The dusting operation

used material from the same source as in 1979.

Three aircraft were used to apply the material.

Larger pieces of material applied after noon on 3

March were observed to have penetrated the ice

surface by as much as 4 inches by 5:00 p.m. the

same day. Smaller particles did not penetrate as

rapidly but made up the bulk of the material applied. The dusted strips showed significant decay, but the surrounding ice deteriorated rapidly

as well. The Platte River above the Elkhorn began

breaking up on 6 March with increasing flows,

and no ice jams were reported in the areas dusted,

although an ice jam causing minor overbank flows

was reported about one mile upstream of the uppermost dusting site.* No damage was reported.

Blasting as a

mitigation alternative

Blasting should be considered only as a last

alternative to ice-jam removal because of cost and

safety reasons. Explosives have been widely used

in ice and ice-jam removal in many countries, with

widely varying results. Explosives used in the past

have included TNT, dynamite, C-4, C-3, tetrytol,

ammonium nitrate–fuel oil (ANFO), ammonite,

black powder, thermite and even bombs and rockets. The relative effectiveness of various explosives varies. Often the explosive used has been

* Information from DATACOL (now called HYDROMET), the daily output of the NWS River Forecast Center and Pleasant Hills, Kansas.

45
46

NOTES:(1) Total length of all strips if more than one strip(2) Width was 30 feet in 1979(3) Rate was 0.056 lb/ft2 in 1979(4) Include trucking and handling costs

(5) Assumes airspeed of 100 mph. If different, multiply by ratio of (100/actual air speed, mph)(6) Includes taxiing, loading, dropping and landing. Computed as 15 minutes in 1979.(7) Does not include costs for planning, coordination, marking strips, etc.

Table 20. Spreadsheet for use in planning dusting operations.

 Col. 1 Col. 2 Col. 3 Col. 4 Col. 5 Col. 6 Col. 7 Col. 8 Col. 9 Col. 10 Col. 11 Col. 12 Col. 13 Col. 14 Col. 15 Col. 16 Col. 17 Col. 18 Col. 19 Col. 20 Col. 21 Col. 22

Dust One way Round Total Total Total Cost of Total cost

Base strip Strip Dusting Dust Dust Total flight trip Airplane flight Flight flight Down Time of Number time for loading of loading Total

 Dust site airport length width date weight cost dust cost distance flight time payload Number time cost cost time each pass of planes dusting equip. equip. cost

(ft) (ft) ( lb/ft2) (tons) ($/lb) ($) (mi) (min) (lb) of trips (hr) ($/hr) ($) (min) (min) used (hr) ($/hr) ($) ($)

c3 × c4 × c5

2000

c6 × c7 c9 × 1.2 c6 × 2000

c11

c10 × c12

60

c13 × c14 c10 × c16 c12 × c17

c18 × 60

c19 × c120 c8 + c15 +c21

(1) (2) (3) (4) (5) (6) (7)

 Totals of Columns

Col 1 Col 2 Col 3 Col 4 Col 5 Col. 20 Col. 18 Col. 16 Col. 14 Col. 11 Col. 9 Col. 7

Table 20. Spreadsheet for use in planning dusting operations.
chosen as a matter of convenience, in terms of

availability and cost. This report will discuss previous uses of explosives in Nebraska, steps to take

before and during blasting operations, selecting

proper charge sizes and placement, and estimating the quantity of explosives needed and the

time required.

The use of explosives to clear ice can be dated

back to Germany in 1758, when bombs were affixed below the ice and exploded (Bolsenga 1968).

Several researchers have studied blasting effects

on floating ice sheets (Van der Kley 1965, Mellor

1986, 1987), but there is little quantitative information available regarding blasting of ice jams.

Duego (1973) noted that thermally grown ice is

relatively easy to break up by blasting, while frazil ice is more difficult to break up since it absorbs

much of the blast energy. The guidance available

for blasting ice sheets can be useful in designing

an ice jam blasting plan, as long as the additional

difficulties posed by ice jams are taken into account. These include the fact that placement of

charges will be more difficult and hazardous, and

less exact, in an ice jam than in a stable ice sheet.

Also, the varying thickness, ice strength and porosity in an ice jam will cause more of the explosive energy to be absorbed than would be the case

in a uniform ice sheet, and therefore the crater

size will be smaller. At a minimum, one would

expect to use more and larger charges to achieve

the same effect in an ice jam as in an ice sheet.

Explosives have been used to break up ice jams

in Nebraska and surrounding states since at least

the 1920s, with varying degrees of success. Some

known applications of blasting for ice jam mitigation in Nebraska and the results, if known, are

presented below.

Missouri River, 1946. Tests were conducted in

1946 by several agencies, including Corps of Engineers employees in the Omaha District, to test

the effectiveness of ice-jam removal on the

Missouri River by means of various explosives.

Moran (1946) described efforts to remove an ice

jam near Corning, Missouri, on 8 and 9 February

1946. Weights and then live charges were dropped

from a helicopter to demonstrate the feasibility

and safety of such an operation. Following this,

15 charges of Composition C-3 ranging from 36 to

160 lb were dropped on the ice jam from a helicopter. However, the jam was resting on a bar,

and Moran observed “there was little or no flow

under or through the ice to aid its movement when

loosened.” Following this, tests were conducted

to determine the accuracy of dropping charges

from an airplane flying at about 65 mph at an

altitude of less than 20 ft. The accuracy of dropping charges in this manner was not as good as

when a helicopter is used, although accuracy improved with practice.

An ice jam in DeSoto Bend (prior to the bend

cut-off) was broken up using T37 rockets (7.2-

inch demolition rockets) and hand charges of Composition C-3. The rockets carried a 32.5-lb charge

of explosive in a steel casing, propelled by a

motor unit. The rockets had a maximum range of

300 yd and exploded upon impact. Eight rockets

were used on 23 February to break up the ice jam.

Four rockets were used on sheet ice 6–8 inches in

thickness. No appreciable effect was noticed from

the first three rockets, but immediately following

the fourth rocket the sheet ice broke loose 1000 ft

upstream of the target area, and a 1500-ft section

of sheet ice approximately 500 ft wide moved out.

Hand charges were then used on the remaining

sheet ice below the jam. The ice was too rotten to

walk on, so the charges were cast out onto the ice

from the shore. One 10-lb charge and 13 charges

from 4.5 to 6.75 lb were tossed 50–100 ft out onto

the ice at one- to five-minute intervals. Following

a series of two to four charges, a crack would

open up across the channel at a distance 100–300

ft upstream of the last hole produced, and a large

section of ice would then break away. Rockets

were then fired at the heavier jammed ice upstream (six hand charges had been tried but they

had no discernible effect). The first two rockets

produced no discernible breaking effect, but the

third rocket started ice movement approximately

1500 ft upstream. A fourth rocket was used merely to hasten the breakup.

Rockets and hand charges were also used on

an ice jam on 26 and 27 February at Tieville Bend

near Decatur but with less success. The hand

charges were thrown from the bank and were used

along a dike system. The ice was loosened but did

not move out. Charges were then placed from a

skiff, and the ice began moving through the dike

system. The next day fifty-two 18.5-lb charges were

used to break the ice clear of the dike system.

Hand charges were also used to clear 1.14 miles

of the main channel of sheet ice. The charges broke

the ice, but the flow was very slow, so it was

necessary to start the broken ice downstream from

the propeller wash of the outboard motor on the

skiff. It was also necessary to place additional

charges downstream along the dike system to prevent the ice from jamming there. Additional charges were placed from the motorboat when the

47
charges could not be thrown far enough out onto

the ice. Eleven rockets were fired on the 26th before a determination was made that a bar formation precluded movement in the desired direction. A twelfth rocket was fired in a different

location, but it failed to detonate and had to be

destroyed by means of a hand-placed charge. On

the 27th, nine more rockets were fired, and a small

area was cleared of ice. However, two of the rockets failed to explode, and the testing was suspended. It was also noted that the explosion of

each rocket threw steel fragments from the casing

and motor as much as 600 yd, which posed a

safety hazard for anyone in the area.

An attempt was made to remove an ice jam at

Black Bird Bend on 1 and 2 March using handplaced charges of Composition C-3. The jam was

800–1000 ft wide and 1 mile long and was composed of ice 10–34 in. thick and piled 5–6 ft above

the water surface. The jam was caused by a bar

formation over which the ice could not pass. Most

of the water was bypassing the toe of the jam, so

an effort was made to loosen the ice along one

shore so that a rise in stage would carry the ice

downstream. Eight-hundred and fifty pounds of

explosives were used over 1500 ft to loosen the

ice. Overnight a rise of approximately 2 ft cleared

the lower 300 ft of the ice that had been blasted,

but additional ice from upstream increased the

length of the jam to 1.5 miles. Approximately 1400

lb of explosives were used to clear a channel approximately 0.5 mile long, but the ice again

jammed at the lower end of the jam. The experiment was then stopped as there was insufficient

flow to carry the ice downstream.

Platte River near Ashland, 9–11 February 1966.

Runoff from a rainfall event in early February

caused a breakup of the ice cover on the lower

Platte and its tributaries. An ice jam formed below the confluence of the Elkhorn and Platte Rivers, and private agricultural levees on both banks

were overtopped. Local interests spent about $6000

to remove the ice jam by blasting. The effort was

deemed unsuccessful in a Corps post-flood report. The floodwaters in the overbank froze in

place after temperatures dropped. Floodwaters

caused damage to the Interstate 80 bridge abutments, in excess of $30,000. The levees were repaired at a cost of $162,250 after it was determined that the river would not return to its

channel even after removal of the ice jam. Little

else is known of the blasting effort.

Columbus, Loup River, 18–21 March 1969. An ice

jam formed at Columbus on the Loup River at

about 6:30 p.m. on 18 March 1969, and within two

hours, it sent water spilling over the banks to the

north and south. A decision to blast the ice jam

was made by city officials on 21 March, according

to the 21 March Columbus Telegram, but the 22

March Columbus Telegram stated that the Platte

County Board of Supervisors decided late 20

March to blast. The ice jam extended 0.5 mile upstream and downstream from the Highway 81

bridge. Blasting operations began at 1:00 p.m. and

lasted until about 6:45 p.m. on 21 March. A total

of 1100 lb of explosives were used, but the length

of channel blasted was not reported. The Columbus Telegram reported that 12–30 sticks of dynamite were placed in 1- to 5-gallon cans weighted

with sand or bricks, which were then dropped in

holes in the ice jam from a helicopter. The helicopter pilot and explosives expert reported

progress in the blasting effort after each drop.

Fifteen minutes after the blasting operation was

suspended, the water level began to drop. Water

levels had dropped 3–4 ft by the next morning.

Platte and Elkhorn River west of Gretna and Platte

River near Yutan and near Ames, February 1971. Icejam flooding in late February caused breaks in

several private levees between Ashland and Fremont. A situation report describing the flooding

mentions local officials and private interests placing dynamite by helicopter west of Gretna and

near Yutan in efforts to break up ice jams on the

Platte and Elkhorn Rivers, but little else is known

of the blasting efforts or success. A long-time

resident near Fremont also recalled blasting from

a helicopter near Ames for the same flood event.

Platte River, 15 March 1979. Blasting operations

were conducted by the State of Nebraska downstream of the Highway 92 bridge for two days.

The blasting was reported to be relatively unsuccessful as little ice movement was observed in the

blast areas.

Confluence of Elkhorn and Platte Rivers, 8–18

March 1993. An ice jam formed near Thomas Lakes

in early February when the Elkhorn River ice broke

up and was stopped by an intact ice cover on the

Platte. Discharges soon dropped and temperatures

dropped, and the jam stayed in place until breakup in early March. A large increase in discharge

and a large volume of ice from upstream combined to overtop private levees and create numerous breaches on both sides of the river near and

just below the mouth of the Elkhorn on 8 March

1993. The breaches on the left bank allowed flow

to destroy two bridges on Highway 6 and close

Interstate 80 for parts of three days. The Sarpy

48
County Board of Supervisors gave the Western

Sarpy Drainage District permission to blast the

ice jam on 16 March.

Blasting began the afternoon of the 16th and

continued until the 18th. At the peak of the flooding, the jam extended nearly four miles, but it

was about 2–2.5 miles when blasting began. Initial blasting efforts began at the upstream end of

the jam in the hope of creating a channel to a

small levee breach at about the midpoint of the

jam, so that water levels would drop enough to

allow repair of other breaches. On the 17th, however, blasting began at the toe of the jam near

Thomas Lakes. According to the Omaha WorldHerald, charges up to 25 lb were used initially.

Charge sizes were reduced while blasting near

Thomas Lakes. A channel was blasted through

the jam on the 18th, and water levels began to

decrease gradually. Overflows through the breaches, however, were not stopped until the breaches

were repaired. An estimated 10,000 lb of explosives were used during the blasting operations.

Some other uses of explosives about which little is known include:

• Near Columbus on the Platte River near the

Burlington Northern Railroad bridge on or

about 24 February 1971;

• On the Platte River near Ashland on or

around 20 March 1978;

• Near the mouth of the Elkhorn River in February 1981; and

• Near Valley on the Platte River on or around

12 March 1929.

Suggested steps to take

for blasting operations

Blasting operations are hazardous because of

the potential for disaster if something goes wrong.

Untimely detonation of the charge could lead to

serious injury or death to one or more individuals.

Blasting can also cause property damage to facilities in the vicinity of operations. Explosives can

also have an adverse impact on the environment.

For these reasons, certain general steps and

precautions listed below (not in any particular

order) should be taken before initiating blasting

operations. Other guidelines for blasting operations are contained elsewhere in the report. These

guidelines should be incorporated into an emergency response plan so that exact details of each

step are known ahead of time so that blasting can

readily be accomplished.

• Obtain the services of an explosives expert to

advise on use and placement of explosives.

• Obtain the services of a professional helicopter pilot and use of a helicopter.

• Obtain necessary permits for explosives and

necessary quantities of explosives.

• Advise the Federal Aviation Administration

so that aircraft can be kept away from the

blast area.

• Contact the U.S. Fish and Wildlife Service to

determine if any endangered species are in

the blasting area.

• Designate an area reasonably close to the

blast site as a base of operations. All operations should be done from this site, including charge preparation and charge loading.

• Follow all safety precautions when handling

explosives. A good set of safety precautions

for ANFO has been developed by the U.S.

Bureau of Mines (1963).

• Notify those in the blasting area prior to

blasting so that nobody is in the proximity

of blasting.

• Have another helicopter or emergency rescue vehicle available at all times in case the

helicopter carrying explosives goes down.

• Coordinate with local law enforcement officials to keep “sightseers” out of the area.

Estimating charge size, total charge quantity and

time of blasting operation. Research on the use of

explosives on ice jams in rivers such as the Platte

is quite limited. However, the results of research

elsewhere can be used for estimating the size of a

blast crater created with a charge of a given weight.

For shallow rivers such as the Platte, complete

removal of an ice jam by using explosives is difficult, especially if flows are bypassing the jam. It is

possible to blast a “pilot” channel through the

length of the jam to allow more water back into

the main channel. In turn, this may help slowly

remove more ice from the jam. The selection of

charge size is often best based on experience but

will vary depending on the ice thickness and the

proximity to dwellings or other structures. It may

be necessary to adjust charge sizes after a few

drops. One guide for selecting the smallest effective charge size can be found in theoretical research done by Van der Kley (1965). Van der Kley

developed a relationship for the minimum charge

of TNT placed at varying depths below the ice

surface required to break ice of a given thickness

(Fig. 23).

Usually the ice thickness will not be known

but must be estimated by judging the amount of

ice above and below the water surface. Once the

ice thickness is estimated, then the depth below

49
is required to break ice as the charge depth increases. However, this is just a minimum charge;

larger charges can be used. Van der Kley also

developed curves for determining the crater diameters for various charge sizes and ice thicknesses. Figure 24 illustrates the crater diameters

for charges that explode just below the bottom

surface of the ice.

The crater diameter is defined as the distance

across the approximately circular hole from which

most ice is thrown clear. Larger charges create

larger craters, and larger charges are needed to

the bottom of the ice surface at which the charge

will explode must be estimated. It is important to

be sure the charge is below the bottom surface of

the ice because blasting above the ice takes a substantially larger charge to accomplish the same

thing. From Figure 23, the minimum charge required is found by first going to the appropriate

ice thickness and drawing a line straight up until

it intersects the curve for the depth at which the

explosive will detonate. A straight line is then

drawn to the left to find the minimum charge

weight required to break the ice. A larger charge

50

40

30

20

10

0 2 4 6 8 10

Ice Thickness (ft)

ANFO Charge Weight (lb)

Depth of Charge

Below Bottom of Ice Sheet

0 ft

0.6

1.6

2.5

3.3

6.6

3.0

Figure 23. Minimum charge placed below ice surface required to break ice.

(After Van der Kley 1965.)

Figure 24. Crater diameter for ANFO charges placed just below the

underside of the ice. (After Van der Kley 1965.)

0

200

20 40 60 80

Crater Diameter ( ft )

Weight of ANFO (lb)

Ice Thickness (ft)

–––––––––––––––

 00.66

 01.60

 02.50

 03.30

 06.60

 09.80

 13.10

 16.40

160

120

80

40

0 ft

0.6

1.6

2.5

3.3

6.6

3.0

50
create a crater of equal diameter as ice thickness

increases. The crater diameter for a given charge

is determined by finding the appropriate charge

weight on the left side of the figure and drawing a

straight line to the right until it intersects the curve

representing the estimated ice thickness. A straight

line is then drawn straight down to find the expected crater diameter. The crater diameter is important because it determines the length and width

of the channel created through the jam. It also determines the distance between charges. It is recommended that charges be placed a distance apart equal

to the diameter of the crater those charges create.

Thus, if a charge creates a crater 50 ft in diameter,

slightly over 100 charges would be required to

clear a channel one mile long and 50 ft wide.

If blasting is to be done, some quick computations can help determine a proper charge size.

Several items must be determined before doing

these computations. The extent of the ice jam must

be determined so that the length of channel to be

blasted is known. A plat map or USGS quadrangle map would be best for determining jam

lengths, since the pilot channel to be blasted is not

likely to be straight. Since access to the jam is

likely to be poor, the charges will need to be placed

from a helicopter. It would be necessary to know

how many charges a pilot will allow on his helicopter for either weight or space reasons. It is also

necessary to know how long it takes to complete

one round trip with the helicopter to load the

charges, drop the charges and return to the base

of operations. This can be estimated either from

experience or from the distance from the base of

operations to the blasting site. The last two items

are the cost of explosive per pound, including the

booster charge, and the cost of the helicopter per

hour, including the use of the helicopter, the pilot’s time and the blaster’s time.

Two examples are given below to illustrate the

methodology used to estimate quantities and time.

These are only examples and should not be used

for an actual blasting event. Diagrams illustrating

the use of the two figures above are shown, as

well as a chart for computing explosive quantities

and costs.

Example 1. An ice jam one mile in length is to

be blasted. The cost of explosives is $1.50 per

pound, and the use of helicopter is $350 per hour.

You would like to use charges of about 25–35 lb

and can take three charges per trip. The pilot estimates that one round trip will average ten minutes. You think the charges will detonate just below the ice bottom. The ice jam is estimated to

average 6 ft thick. What size of charge should be

used and what is the expected cost?

Step 1. Determine the minimum charge size

that can be used.

• From Figure 23, the minimum charge size

that could be used is approximately 7

lb. This is less than the size of charge

planned, so the planned charge size can

be used.

Step 2. Determine the cost of several charge

sizes. Compare costs for charges of 20,

30 and 40 lb.

• Use Table 21 and fill in columns 1, 3, 7, 9, 11

and 12 for charge size, length of channel to blast, number of charges per trip,

time for one round trip, cost of explosives per pound and cost of helicopter

per hour.

• Use Figure 24 to estimate the crater diameter. The crater diameter is 22 ft for the

20-lb charge, 27 ft for the 30-lb charge

and 31 ft for the 40-lb charge. Enter

these values in column 2 in the chart.

You can now complete the chart to compare costs.

• Complete column 4 by dividing column 1

by column 2. Column 5 is equal to column 3 times column 4 times 5280. Compute the number of charges, column 6,

by dividing column 5 by column 1, and

compute column 8 by dividing column

6 by column 7. Column 10 is equal to

column 8 times column 9 divided by

60. The cost of the explosives is determined by multiplying columns 5 and

11, the cost of the helicopter is determined by multiplying columns 10 and

12, and the total cost is the sum of columns 13 and 14. Any miscellaneous

costs can be added on to determine the

true total cost.

As can be seen, using 20-lb charges is the least

expensive alternative by about $750, but it takes

the most time by at least 2.5 hours. If time is important, it may be worthwhile to spend more for

larger charges.

Example 2. An ice jam 2 miles long needs to be

removed by blasting. You estimate the jam thickness to be 8 ft in the lower 0.5 mile and 3 ft in the

upper 1.5 miles. Explosives will cost $1.25 per

pound and the helicopter will cost $400 per hour.

The helicopter pilot will allow 80 lb of explosives

each trip and says each trip will take 10 minutes.

You think the explosives will explode just under

51
52

Table 21. Sample calculations for blasting costs.

Col (2) Col (4) Col (5) Col (6) Col (8) Col (10) Col (13) Col (14) Col (15)

Total Total

Weight Diameter Distance Number Round trip Total Cost of Cost of cost of cost of Total

of charge of crater to blast Pounds Total of Charges Number flight time flight time explosives helicopter explosives helicopter costs (lb) (ft) (mi) per foot pounds charges per trip of trips (min) (hr) ($/lb) ($/hr) ($) ($) ($)

from from col (1) col (4) × col (3) = 5280 col (5) at pilot’s col (6) Based on col (9) × col (8) col (5) × col (11) col (10) × col (12) col (13) × col (14)

Figure observation col (2) col (1) discretion col (7) experience 60

A2

Example 1

20 22 1 0.91 4800 240 3 80 10 13.33 1.50 350 7200.00 4666.67 11866.6730 27 1 1.11 5867 196 3 65 10 10.86 1.50 350 8800.00 3802.47 12602.47

40 31 1 1.29 6813 170 3 57 10 9.46 1.50 350 10219.35 3311.83 13531.18

Example 2

Lower 1/2 mile

20 8 0.5 2.50 6600 330 4 83 10 13.75 1.25 400 8250.00 5500.00 13750.0025 14 0.5 1.79 4714 189 3 63 10 10.48 1.25 400 5892.86 4190.48 10083.33

40 22 0.5 1.82 4800 120 2 60 10 10.00 1.25 400 6000.00 4000.00 10000.0080 36 0.5 2.22 5867 73 1 73 10 12.22 1.25 400 7333.33 4888.89 12222.22

Upper 1-1/2 miles

10 21 1.5 0.48 3771 377 8 47 10 7.86 1.25 400 4714.29 3142.86 7857.1415 25 1.5 0.60 4752 317 5 63 10 10.56 1.25 400 5940.00 4224.00 10164.0020 28 1.5 0.71 5657 283 4 71 10 11.79 1.25 400 7071.43 4714.29 11785.71

25 31 1.5 0.81 6387 255 3 85 10 15.61 1.25 400 7983.87 6245.16 14229.03

Col (1) Col (3) Col (7) Col (9) Col (12) Col (11)
the ice. What will be the most effective charge

size or sizes?

Step 1. Since the ice is considerably thicker at

the downstream end, larger charges

will probably be required, so compute

separately for the lower 0.5 mile and

the upper 1.5 miles.

• Divide the chart into two areas for the lower

0.5 mile and upper 1.5 miles. Fill in

column 3 for 0.5 mile and 1.5 miles in

the two separate groups. Fill in columns

9, 11 and 12 for round trip time, explosive cost and helicopter cost, using the

same numbers for each group.

Step 2. Determine the minimum charge weight

required.

• From Figure 23 the minimum charge size is

about 18 lb for 10-ft-thick ice and about

1–2 lb for 3-ft-thick ice.

Step 3. Determine the number of charges per

trip for various sizes of charges to blast

the 10-ft-thick ice.

• Since the load is limited to 80 lb, you could

have four 20-lb charges, three 25-lb

charges, two 40-lb charges or one 80-lb

charge. Put these numbers in columns

1 and 7.

Step 4. Determine the blast crater for the 10-ftthick ice.

• From Figure 24, find that a 20-lb charge has an

8-ft-diameter crater, a 25-lb charge has a

14-ft crater, a 40-lb charge has a 22-ft

crater and an 80-lb charge has a 36-ft

crater. Fill in column 2 with the blast

craters for the appropriate size of charge.

Step 5. Fill in the remainder of the chart for

the lower 0.5 mile.

• Compute columns 4, 5, 6, 8, 10, 13, 14 and 15

as in the previous example. As can be

seen, the 40-lb charges are the least expensive, but the 25-lb charges only cost

about $80 more and take only about 30

minutes longer to blast the lower part

of the jam. The larger charge may be

better because they will clear a wider

channel; the smaller charges may be

more convenient for handling.

Step 6. Determine the number of charges per

trip for various sizes of charges to blast

the 3-ft-thick ice.

• Since the ice is much thinner in the upper

1.5 miles, smaller charges can be used.

You could have eight 10-lb charges, five

15-lb charges, four 20-lb charges or

three 25-lb charges. Put these values in

columns 1 and 7 for the upper jam part

of the table.

Step 7. Determine the blast crater diameter for

the 3-ft-thick ice.

• From Figure 24, the crater size is 21 ft for 10-

lb charges, 25 ft for 15-lb charges, 28 ft

for 20-lb charges, and 31 ft for 25-lb

charges. Fill in column 2 with the appropriate crater diameter.

Step 8. Complete the rest of Table 21.

• Compute the values for columns 4, 5, 6, 8,

10, 13, 14 and 15 as before. As can be

seen, the 10-lb charges result in the lowest cost. Even if the pilot limited the

load to four charges per trip for safety

reasons due to the time it takes to light

more charges, the 10-lb charges would

still be slightly less expensive.

These examples illustrate how effective charge

sizes can quickly be determined. It is best if only a

few charge sizes are considered to reduce computation time, so it is important to have a good idea

of what charge sizes may be effective. It is also

important to remember that the cheapest alternative to getting the job done is not necessarily the

best alternative if it takes considerably longer to

accomplish.

CONCLUSIONS

The historical data-collection effort found much

available information, both published and oral. Some

information, such as ice-thickness measurements

from USGS stream-gaging records, is very time consuming to compile, while other information, such

as USGS discharge records, is relatively easy to access. In general, information about the physical

characteristics of ice and ice jams is the most difficult to obtain, simply because there has not been a

concerted effort in the past to collect such information, the information available is widely scattered,

and most people do not take particular notice of

the ice until it is causing problems. The data-collection program initiated as a result of this study

should begin to provide better ice information.

The analysis of the collected data attempted to

find relationships or trends among the various

hydrological, meteorological and ice records pertaining to ice events in the study area. The results

of the analysis were used to develop an ice-jam

predictive model based on hydrologic and meteorological data that are relatively easy to access.

53
Future refinement of the model, and development

of a separate model for each site, should be possible with additional data collected as part of the

ice-data-collection program.

Meetings with local citizens often yielded good

information on ice events but also some commonly mentioned themes. Many said there was not

enough communication between state agencies,

civil defense, local governments and the general

public. Many also expressed an interest in volunteering to help make ice observations—many more

than were needed. A number of people said they

were unfamiliar with or unaware of emergency

procedures, didn’t know who has the authority to

declare an emergency, and didn’t know who has

authority and assumes liability during an emergency. The Nebraska Disaster and Civil Defense

Act (App. C) describes the role and responsibility of

the State and its political subdivisions in dealing

with disaster emergencies, among other matters.

Local governments are the first agencies responsible for dealing with disasters. Advance

planning for disasters by county, city and other

local governments, and coordination of this planning between various governments, is important

for dealing with disasters when they begin, not

after they have reached great proportions. Appendix D contains a legal opinion drafted by the

State indicating that both the State and its political subdivisions are essentially protected from liability if emergency measures are in accordance

with the Nebraska Disaster and Civil Defense Act

and an emergency has been declared.

The Nebraska Ice Report will be an ongoing

effort and should be maintained for use in future

studies, as well as being able to provide “realtime” warnings of conditions upstream. The observations recorded on the data collection forms

will be reported to and stored in the ice database

to be maintained by the Nebraska Natural Resources Commission. The information collected

on the ice report will be able to be used to refine

the predictive model sometime in the future, perhaps leading to the development of models for

each individual site, rather than a generalized

model. Future studies will be able to utilize the

additional information collected by the ice report.

Perhaps more importantly the information contained in the database will be able to be called up

by various entities to check on ice conditions upstream that may impact conditions downstream.

The section of this report on specific mitigation options contains recommendations for specific measures that could be utilized at individual

locations for either controlling ice or monitoring

ice. More detailed studies would be required at

individual sites to determine the appropriateness

of specific structural measures. As mentioned in

the previous paragraph, the information collected by the ice report will provide much valuable

information on ice processes and characteristics,

which are presently very sketchy. Nonstructural

measures, such as monitoring, would not require

detailed study to implement, although some coordination efforts may be needed. A recommended future study would be to evaluate the impact,

if any, of the operation of the Loup Power Canal

on ice conditions downstream.

LITERATURE CITED

Beltaos, S. (1990) Fracture and breakup of river

ice cover. Canadian Journal of Civil Engineering, 17:

173–183.

Bolsenga, S.J. (1968) River ice jams: A literature

review. Lake Survey District, Corps of Engineers,

Research Report 5-5.

Cavan, B.P. (1969) A literature review of dusting

technology in deicing. Lake Survey District, Corps

of Engineers, Research Report 5-7.

Deugo, D. (1973) Ice control on the Rideau River,

Ottawa. National Research Council, Canada, Associate Committee on Geotechnical Research Technical Memorandum No. 107, p. 155–157.

FEMA (1993) Interagency Hazard Mitigation Team

Report. Federal Emergency Management Agency,

Region VII Interagency Hazard Mitigation Team

Report.

Galbraith, P.W. (1981) On estimating the likelihood of ice jams on the Saint John River using

meteorological parameters. In Proceedings, 5th Canadian Hydrotechnical Conference, May 26–27, 1981,

Fredericton, New Brunswick, p. 219–237.

Haynes, F.D., R.B. Haehnel and C.H. Clark

(1994) Weakening ice by dusting with leaves.

USA Cold Regions Research and Engineering

Laboratory, Ice Engineering Information Exchange Bulletin, No. 7.

Konovalov, I.M. and M.V. Miasnikov (1956) Utilizing solar radiation for increasing the navigation period. Rechnoi Transport, January 1956, 15(1):

13–18 (text in Russian). Translation by U.S. Lake

Survey, Detroit, 1967.

Matthai, H.F. (1968) Magnitude and frequency of

floods in the United States, Part 6-B: Missouri River

basin below Sioux City, Iowa. USGS Water-Supply Paper 1680.

54
Mellor, M. (1986) Revised guidelines for blasting

floating ice. USA Cold Regions Research and Engineering Laboratory, Special Report 86-10.

Mellor, M. (1987) Derivation of guidelines for

blasting floating ice. Cold Regions Science and Technology, 13: 193–206.

Meyer, R.L. (1976) The 1976 ice dusting and flood

reconnaissance program in Alaska. U.S. Army

Engineer District, Alaska, Corps of Engineers.

Missouri River Basin Commission (1975) Platte

River basin, Nebraska, Level B study. Hydrology

and Hydraulics Technical Paper. Missouri River

Basin Task Force on Hydrology and Hydraulics,

Omaha, Nebraska.

Moor, J.H. and C.H. Watson (1971) Field tests of

ice prevention techniques. Journal of the Hydraulics Division, American Society of Civil Engineers,

92(HY6): 777–789.

Moran, J.J. (1946) Memorandum report on research

toward breaking up of river ice jams. U.S. Army

Engineer District, Omaha, Corps of Engineers.

Nebraska Civil Defense (1971) After action report flood–blizzard 18 February–14 March 1971.

Shuliakovskii, L.G. (Ed.) (1963) Manual of forecasting ice-formation for rivers and inland lakes.

Israel Program for Scientific Translations TT 66-

51016, Jerusalem, Israel (1966).

USACE (1982) Ice Engineering. Engineer Manual

EM 1110-2-1612.

USACE (1990) HEC-2, Water Surface Profiles User’s

Manual. U.S. Army Corps of Engineers, Hydrologic Engineering Center.

USACE (1991) Flood proofing techniques: Programs and references report of the National Flood

Proofing Committee. Report prepared by Dewberry and Davis with French and Associates, Ltd.

USAED, Alaska (1968) Operation Dusty, Alaska.

U.S. Army Engineer District, Alaska, Corps of Engineers.

USAED, Alaska (1969) Operation Foresight 1969,

Alaska. U.S. Army Engineer District, Alaska, Corps

of Engineers.

USAED, Omaha (1966) Report on floods in the

Omaha District during calendar year 1966. U.S.

Army Engineer District, Omaha, Corps of Engineers.

USAED, Omaha (1978) Post flood report, Section

2—Data summary. U.S. Army Engineer District,

Omaha, Corps of Engineers.

USAED, Omaha (1979) Ice dusting of the Platte

River, 1979. U.S. Army Corps of Engineers, Omaha District.

USAED, Omaha (1993) Draft report: Great flood of

1993. Post flood report, Omaha District Upper Missouri River Basin, Tributaries and Reservoirs. U.S.

Army Engineer District, Omaha, Corps of Engineers.

USAED, Omaha (1994) Ice dusting of the Platte

River, 1994. U.S. Army Engineer District, Omaha,

Corps of Engineers.

U.S. Bureau of Mines (1963) Safety recommendations for sensitized ammonium nitrate blasting

agents. U.S. Bureau of Mines, Information Circular 8179.

USGS (1989) Water resources data, Nebraska,

water year 1989. U.S. Geological Survey WaterData Report NE-89-1.

Van der Kley, I.F. (1965) The use of explosives for

clearing ice. Rijkswaterstaat Communication, Nr. F.

Wehrspan, J.R. (1978) Summary of district activities related to March, 1978, flooding and recommendations. Memorandum, Papio-Missouri

Natural Resources District, Omaha, Nebraska.

White, K.D. (1992) Ice jam statistics recorded on

database. USA Cold Regions Research and Engineering Laboratory, Ice Engineering Information

Exchange Bulletin No. 2, November.

White, K.D. and J.E. Zufelt (1994) Ice jam data

collection. USA Cold Regions Research and Engineering Laboratory, Special Report 94-7.

Williams, G.P. and L.W. Gold (1963) Use of dust

to advance the break-up of ice on lakes and rivers. Division of Building Research of Canada, Technical Paper no. 165.

Williams, G.P. (1967) Ice-dusting experiments to

increase the rate of melting of ice. NRC, Division

of Building Research of Canada, Technical Paper

no. 239.

Wuebben, J.L. and J.J. Gagnon (1995) Ice jam

flooding on the Missouri River near Williston,

North Dakota. USA Cold Regions Research and

Engineering Labortory, CRREL Report 95-19.

Wuebben, J.L. and J.J. Gagnon (in prep.) ICETHK: A utility program for ice-affected water surface profile calculations using HEC-2. USA Cold

Regions Research and Engineering Laboratory,

CRREL Report.

Zhukova, M.A. (1979) Formation of ice jams and

their distribution. Soviet Hydrology: Selected Papers,

18(1): 7–13.

Zufelt, J.E. (1993) Ice motion detector system. USA

Cold Regions Research and Engineering Laboratory, Ice Engineering Information Exchange Bulletin, No. 4.

Zufelt, J.E. and A.M. Tuthill (1993) The ice motion detector: Advance warning for breakup. In

Proceedings, Workshop on the Environmental Aspects

of River Ice, August 18–21, 1993, Saskatoon, Saskatchewan, Canada, National Hydrology Research Institute Symposium Series No. 12, p. 59–74.

55
APPENDIX A: MODEL RESULTS FOR THE LOUP RIVER NEAR COLUMBUS

Figure A1. Open-water profiles.

56
57

Figure A3. Freeze-up water profiles.

Figure A2. Ice-flow water profiles.
APPENDIX B. MODEL RESULTS FOR

THE PLATTE RIVER ALONG SARPY COUNTY, NEBRASKA

58

Figure B1. Open-water flow profiles for the eastern section.
59

Figure B2. Open-water flow profiles for the western section.

Figure B3. Solid-ice-cover flow profiles for the eastern section.
60

Figure B5. Freeze-up flow profiles for the eastern section.

Figure B4. Solid-ice-cover flow profiles for the western section.
61

Figure B7. One-percent-duration flow profiles for open water, ice cover, freeze-up and breakup for the eastern section.

Figure B6. Freeze-up flow profiles for the western section.
62

Figure B8. One-percent-duration flow profiles for open water, ice cover, freeze-up and breakup for the western section.
APPENDIX C: NEBRASKA DISASTER AND CIVIL DEFENSE ACT

(Sections 81-829.31, 81-829.37 to 81-829.74 reproduced from the

Revised Statutes of Nebraska 1943, 1982 Supplement)

(c) DISASTER AND CIVIL DEFENSE

Cross Reference

Vital resource crises, see section 84 162 et seq.

81-825 to 81-829. Repealed. Laws 1947, c. 179 sec. 9.

81-825.01 to 81-828.01. Repealed. Laws 1953, c 336, sec. 5.

81-829.01 and 81-829.02. Expiration of act.

Note: According to the provisions of section 81-829.01, these sections expired by their own

limitation on March 1, 1945. They have therefore been omitted.

81-829.03. Repealed. Laws 1953, c. 336, sec. 5.

81-829.04. Repealed. Laws 1951, c. 315, sec. 16.

81-829.05. Transferred to section 81-829.36.

81-829-06. Transferred to section 81-829.37.

81-829.07. Transferred to section 81-829.38.

81-829.08. Transferred to section 81-829.39.

81-829.09. Transferred to section 81-829.40.

81-829.10 to 81-829.12. Repealed. Laws 1973, LB 494, sec. 34.

81-829.13. Transferred to section 81-829-52.

81-829.14. Transferred to section 81-829-53.

81-829.15. Transferred to section 81-829-54.

81-829.16 and 81-829.17. Repealed. Laws 1953, c. 336, sec. 5.

81-829.18. Transferred to section 81-829-46.

81-829.19. Transferred to section 81-829-48.

81.829.20. Repealed. Laws 1973, LB 494, sec. 34.

81-829.21. Transferred to section 81-829.55.

81-829.22. Transferred to section 81-829.49.

81-829.23. Transferred to section 81-829.51.

63
81-829.24. Transferred to section 81-829.58.

81-829.25. Transferred to section 81-829.59.

81-829.26. Transferred to section 81-829.60.

81-829.27. Transferred to section 81-829.61.

81-829.28. Transferred to section 81-829.62.

81-829.29. Transferred to section 81-829.63.

81-829.30. Transferred to section 81-829.64.

81-82931. Adjutant General; civil defense agency; administer. There is hereby created

in the office of the Adjutant General a civil defense agency. The Adjutant General shall

administer the provisions of sections 81.829.36 to 81.829.40, 81.829.46, 81-829.48, 81-829.49,

81-829.51 to 81-829.55, and 81-829.59 to 81-829.64.

Source: Laws 1953, c. 336, sec. 2, p. 1106.

Cross Reference

For provisions relating to the Adjutant General, see Chapter 55, article 1.

81-829.32. Transferred to section 81-829.65.

81-829.33 and 81-829.34. Repealed. Laws 1971, LB 105, sec 1.

81-829.35. Transferred to section 81-829.66.

81-829.36. Act, how cited. Sections 81-829.36 to 81-829.68 may be cited as the Nebraska

Disaster and Civil Defense Act of 1973.

Source: Laws 1951, c. 315, sec. 1, p. 1073; R.R.S.1943, sec. 81-829.05; Laws 1973, LB

494, sec. 1.

81-82937. Nebraska Disaster and Civil Defense Act; policy. The purposes of sections

81-829.36 to 81-829.68 and the policy of the state are to:

(1) Reduce the vulnerability of people and communities of this state to damage, injury,

and loss of life and property resulting from natural or man-made disasters, civil disturbances, or hostile military or paramilitary actions;

(2) Prepare for prompt and efficient rescue, care, and treatment of persons victimized

or threatened by disasters;

(3) Provide a setting conducive to the rapid and orderly start of restoration and rehabilitation of persons and property affected by disasters;

(4) Clarify and strengthen the roles of the Governor, state agencies, and local governments in the prevention of, preparation for, and response to and recovery from disasters;

(5) Authorize and provide for cooperation in disaster prevention, preparedness, response, and recovery;

(6) Authorize and provide for coordination of activities relating to disaster prevention,

preparedness, response, and recovery by agencies and officers of this state, and similar state,

local interstate, federal-state, and foreign activities in which the state and its political

subdivisions may participate;

(7) Provide a disaster management system embodying all aspects of preparedness and

response;

64
(8) Assist in prevention of disasters caused or aggravated by inadequate planning for

and regulation of public and private facilities and land use; and

(9) Provide for the funding of activities incidental to carrying out the purposes of

sections 81-829.36 to 81-829.68.

Source: Laws 1951, c. 315, sec. 2(1), p.1074; R.R.S.1943, sec. 81-829.06; Laws 1973, LB

494, sec. 2.

81-82938. Nebraska Disaster and Civil Defense Act; purpose. Nothing in sections 81-

829.36 to 81-829.68 shall be construed to:

(1) Interfere with the course or conduct of labor dispute, except that actions otherwise

authorized by sections 81-829.36 to 81-829.68 or other laws may be taken when necessary

to forestall or mitigate imminent or existing danger to public health or safety;

(2) Interfere with dissemination of news or comment on public affairs, but any communications facility or organization, including but not limited to radio and television

stations, wire services, and newspapers, may be required to transmit or print public

service messages furnishing information or instructions in connection with a disaster

emergency;

(3) Affect the jurisdiction or responsibilities of police forces, fire fighting forces, units of

the armed forces of the United States, or of any personnel thereof, when on active duty,

but state, local, and interjurisdictional disaster emergency plans shall place reliance upon

the forces available for performance of functions related to disaster emergencies; or

(4) Limit, modify, or abridge the authority of the Governor to proclaim martial law or

exercise any other powers vested in him under the Constitution, statutes, or common law

of this state independent of, or in conjunction with, any provisions of sections 81-829.36 to

81-829.68.

Source: Laws 1951, c. 31S, sec. 2(2), p. 1074; R.R.S. 1943, sec. 81-829.07; Laws 1973, LB

494, sec. 3.

81-829.39. Terms, defined. As used in sections 81-829.36 to 81-829.68 unless the context

otherwise required:

(1) Civil Defense shall mean the preparation for and the carrying out of all emergency

functions, other than functions for which military forces are primarily responsible, to

prevent, minimize, and repair injury and damage resulting from disasters caused by

enemy attack, sabotage or other hostile action; or by fire, flood, earthquake, or other

natural causes. These functions include, without limitation, fire fighting services, police

services, medical and health services, rescue, engineering, air raid warning services,

communications, radiological, chemical and other special weapons defense, evacuation of

persons from stricken area, emergency welfare services, civilian war aid, emergency

transportation, existing or properly assigned functions of plant protection, temporary

restoration of public-utility services, and other functions related to civilian protection,

together with all other activities necessary or incidental to the preparation for and carrying out of the foregoing functions.

(2) Civil defense emergency shall mean an emergency declared by the President of the

United States or Congress pursuant to applicable federal law finding that an attack upon

the United States has occurred or is anticipated and that the national safety therefore

requires the invocation of the emergency authority provided for by federal law. Such

emergency also shall exist in the event of an enemy attack or other hostile action within

the State of Nebraska, or when the President determines that any attack has been made

upon or is anticipated within a designated geographic area which includes all or a part of

the State of Nebraska. Any such emergency shall terminate in the manner provided by

federal law, or by proclamation of the governor, or by resolution of the Legislature,

terminating such emergency.

(3) Disaster shall mean occurrence or imminent threat of widespread or severe damage, injury, or loss of life or property resulting from any natural or man-made cause,

65
including but not limited to fire, earthquake, wind, storm, wave action, oil spill, or other

water contamination requiring emergency action to avert danger or damage, volcanic

activity, epidemic, air contamination, blight, drought, infestation, explosion, riot, civil

disturbance, or hostile military or paramilitary action.

(4) Mobile support unit shall mean an organization for civil defense established in

accordance with the provisions of sections 81-829.52 by state or local authority to be

dispatched by the Governor to supplement local organizations for civil defense in a

stricken area.

(5) Local government shall mean counties, villages, and cities of all classes.

(6) Civil defense worker shall include any full-time or part-time paid, volunteer, or

auxiliary employee of this state or other states, territories, possessions, or the District of

Columbia, of the federal government or any neighboring country, or of any political

subdivision thereof, or of any agency or organization performing civil defense services at

any place in this state subject to the order or control of, or pursuant to a request of, the

state government or any political subdivision thereof and shall also include instructors

and students in recognized educational programs where civil defense services are taught.

A recognized educational program where civil defense services are taught. A recognized

educational program shall include programs in educational institutions duly existing

under the laws of this state and such other educational programs as shall be established

by the state Civil Defense Agency or otherwise under the provisions of sections 81-829.36

to 81-829.68.

Source: Laws 1951, c. 315, sec. 3, p. 1074; R.R.S. 1943, sec. 81-829.08; Laws 1973, LB

494, sec. 4.

81-829.40. Disaster and Civil Defense Agency; Governor; control.

(1) The Governor shall be responsible for meeting the dangers to the state and people

presented by disasters, and in the event of disaster beyond local control, he/she may

assume direct operational control over all or any part of the civil defense functions within

this state. He/she shall have general direction and control of the disaster response and the

state Civil Defense Agency and shall be responsible for carrying out the provisions of

sections 81-829.36 to 81-829.68.

(2) In order to effect the policy and purposes of sections 81-829.36 to 81-829.68, the

Governor may issue proclamations and make, amend, and rescind the necessary orders,

rules, and regulations to carry out the provisions of sections 81-829.36 to 81-829.68.

(3) A disaster emergency shall be declared by proclamation of the Governor if he/she

finds that a disaster has occurred or that the occurrence or threat thereof is imminent. The

state of disaster emergency shall continue until the Governor finds that the threat or

danger has passed or the disaster has been dealt with to the extent that emergency

conditions no longer exist and terminates the state of disaster emergency by proclamation, but no state of disaster emergency may continue for longer than thirty days unless

renewed by the Governor. The Legislature by resolution may terminate a state of disaster

emergency at any time, whereupon the Governor shall issue a proclamation ending the

state of disaster emergency. All proclamations issued under this subsection shall indicate

the nature of the disaster, the area or areas threatened, and the conditions which have

brought it about or which make possible the termination of the state of disaster emergency. All proclamations shall be disseminated promptly by means calculated to bring its

contents to the attention of the general public and, unless the circumstances attendant

upon the disaster prevent or impede, shall be promptly filed with the state Civil Defense

Agency, the Secretary of State, and the clerks of the local governments in the area to which

it applies.

(4) Proclamation of a state of disaster emergency shall activate the disaster response

and recovery aspects of the state, local, and interjurisdictional disaster and civil defense

plans applicable to the political subdivision or area in question and be the authority for

the deployment and use of any forces to which the plan or plans apply and for use or

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distribution of any supplies, equipment, and materials and facilities assembled, stockpiled, or arranged to be made available pursuant to sections 81-829.36 to 81-829.68 or any

other provision of law relating to disaster emergencies.

(5) During the continuance of any state of disaster emergency the Governor shall be

commander-in-chief of the organized and unorganized militia and of all other forces

available for emergency duty. To the greatest extent practicable, the Governor shall delegate or assign command authority by prior arrangement embodied in appropriate proclamations, orders, rules, and regulations, but nothing shall restrict his/her authority to do

so by orders issued at the time of the disaster emergency.

(6) In addition to any other powers conferred upon the Governor by law, he/she may:

(a) Suspend the provisions of any regulatory statute prescribing the procedures for

conduct of state business, or the orders, rules, or regulations of any state agency, if strict

compliance with the provisions of any statute, order, rule, or regulation would in any way

prevent, hinder, or delay necessary action in coping with the emergency;

(b) Utilize all available resources of the state government and of each political subdivision of the state as are reasonably necessary to cope with the disaster emergency;

(c) Transfer the direction, personnel, or functions of state departments and agencies or

units thereof for the purpose of performing or facilitating disaster response;

(d) Subject to any applicable requirements for compensation under section 81-829.57,

commandeer or utilize any private property if he/she finds this necessary to cope with the

disaster emergency;

(e) Direct and compel the evacuation of all or part of the population from any stricken

or threatened area within the state if he deems this action necessary for the preservation of

life or other disaster mitigation, response, or recovery

(f) Prescribe routes, modes of transportation, and destinations in connection with

evacuation;

(g) Control ingress and egress to and from a disaster area, the movement of persons

within the area, and the occupancy of premises therein;

(h) Suspend or limit the sale, dispensing, or transportation of alcoholic beverages,

firearms, explosives, and combustibles; and

(i) Make provisions for the availability and use of temporary emergency housing.

(7) In the event of a civil defense emergency, as defined in section 81-829.39, the

Governor shall assume direct operational control overall or any part of the civil defense

functions within this state.

Source: Laws 1951, c. 315, sec. 4(1), p. 1076; R.R.S. 1943, sec. 81-829.09; Laws 1973, LB

494, sec. 5.

81-829.41. Civil Defense Agency; Adjutant General; act; administer.

(1) The state Civil Defense Agency shall be maintained in the office of the Adjutant

General. The Adjutant General shall administer the provisions of sections 81-829.36 to 81-

829.68, subject to the direction and control of the Governor, and shall receive such compensation for these services as shall be determined by the Governor. The agency shall

have an assistant director and such other professional, technical, secretarial, and clerical

employees as are necessary for the performance of its functions.

(2) The agency shall maintain a state disaster plan and keep it current, which plan may

include:

(a) A history of Nebraska disasters;

(b) An analysis of past and potential disasters, including an identification of the functions and resources required to cope with such disasters. The expected frequency of

occurrence of disasters, along with the severity of their effect, shall indicate the priority of

preparedness efforts of the disaster agencies of the state;

(c) Measures to be undertaken to accomplish disaster damage assessment and situation

analysis, warning, direction and control, coordination of operating forces, emergency

resource management, emergency information and official instructions, communications

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and other necessary support to disaster response operations, and coordination and cooperation of federal, state, local, and nongovernmental agencies so as to provide a prompt

and effective response to disaster situations to prevent and minimize the injury and

damage caused by disasters;

(d) The provision of disaster relief and assistance to individuals, political subdivisions

of the state, and state agencies;

(e) Identification of areas of the state particularly vulnerable to a disaster;

(f) Recommendations for preventive and preparedness measures designed to eliminate

or reduce disasters or their impact, such as zoning, building, and other land-use control,

and safety measures for securing mobile homes or other nonpermanent or semipermanent structures;

(g) Authorization and procedures for the erection or other construction of temporary

works designed to protect against or mitigate danger, damage, or loss from flood, conflagration, or other disaster;

(h) Assistance to local officials in designing local disaster response plans;

(i) Preparation and distribution to the appropriate state and local officials of catalogs of

federal, state, and private disaster assistance programs; and

(j) Other necessary matters.

(3) The agency shall take an integral part in the development and revision of local and

interjurisdictional disaster and civil defense plans prepared under section 81-829.46. To

this end, it shall employ or otherwise secure the services of professional and technical

personnel capable of providing expert assistance to political subdivisions, their disaster

and civil defense agencies, and to interjurisdictionaI disaster and civil defense agencies.

Such personnel shall consult with subdivisions and agencies on a regularly scheduled

basis and shall make field examinations of the areas, circumstances, and conditions to

which particular local and interjurisdictional disaster and civil defense plans are intended

to apply, and may suggest or require revisions.

(4) In preparing and revising the state disaster plan and other civil defense plans, the

agency shall seek the advise and assistance of other agencies of government and the

private sector. In advising local and interjurisdictional agencies, the agency shall encourage them to also seek advise from these sources.

(5) The state disaster and other civil defense plans or any part thereof may be incorporated in rules or regulations of the agency.

(6) The state Civil Defense Agency shall:

(a) Determine the requirements of the state and its political subdivisions for basic

necessities such as food, clothing, shelter in various disaster situations;

(b) Procure and preposition supplies, medicines, materials, and equipment;

(c) Promulgate standards and requirements for local and interjurisdictional disaster

and civil defense plans;

(d) Periodically review local and interjurisdictional disaster and civil defense plans;

(e) Provide for mobile support units;

(f) Establish and operate or assist political subdivisions, their disaster and civil defense

agencies, and interjurisdictional disaster and civil defense agencies to establish and operate training programs and programs of public information;

(g) Make surveys of industries, resources, and facilities within the state, both public

and private, as are necessary to carry out the purposes of sections 81-829.36 to 81-829.69;

(h) Plan and make arrangements for the availability and use of any private facilities,

services, and property and, if necessary and if in fact used, provide for payment for use

under terms and conditions agreed upon;

(i) Establish a register of persons with types of training and skills important in disaster

prevention, preparedness, response, and recovery;

(j) Establish a register of mobile and construction equipment and temporary housing

available for use in a disaster emergency;

(k) Prepare, for issuance by the Governor, proclamations, orders, rules, and regulations

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as are necessary or appropriate in coping with disasters;

(l) Cooperate with the federal government and any public or private agency or entity in

achieving any purpose of sections 81-829.36 to 81-829.68 and in implementing programs

for disaster prevention, preparation, response, and recovery; and

(m) Do other things necessary, incidental, or appropriate for the implementation of

sections 81-829.36 to 81-829.68.

Source: Laws 1973, LB 494, sec. 6.

81-829.42. Governor’s Emergency Fund; established; use.

(1) While annual appropriations are adequate to meet the normal needs, the Legislature recognizes the necessity for anticipating and making advance provision to care for

the unusual and extraordinary burdens imposed on the state and its political subdivisions

by disasters or a civil defense emergency as defined in section 81-829.39. To meet such

situations, it is the intention of the Legislature to confer emergency powers on the Governor, acting through the Adjutant General and the state Civil Defense Agency, and vesting

him with adequate power and authority within the limitation of available funds in the

Governor’s Emergency Funds to meet any such emergency or disaster.

(2) There is hereby established a fund to be known as the Governor’s Emergency Fund.

It shall be expended, upon direction of the Governor, for any state of emergency. The

emergency declaration shall set forth the emergency and shall state that it requires the

expenditure of public funds to furnish immediate aid and relief. The Adjutant General

shall administer such fund. Any money in the fund available for investment shall be

invested by the state investment officer pursuant to the provisions of sections 72-1237 to

71-1259.

(3) It is the legislative intent that the first recourse shall be to funds regularly appropriated to state and local agencies. If the Governor finds that the demands placed upon these

funds are unreasonably great, he/she may make funds available from the Governor’s

Emergency Fund. Expenditures may be made upon direction of the Governor for any or

all of the civil defense functions as defined in section 81-829.39, or to meet the intent of the

state disaster plans as outlined in section 81-829.41. Expenditures may also be made to

state and federal agencies to meet the matching requirement of any applicable assistance

programs.

(4) Assistance shall be provided from the Governor’s Emergency Fund to political

subdivisions of this state which have suffered from a disaster to such an extent as to

impose a severe financial burden exceeding the ordinary capacity of the subdivision

affected. Applications for aid under this section shall be made to the state Civil Defense

Agency on such forms as shall be prescribed and furnished by the agency and which shall

require the furnishing of sufficient information to determine eligibility for aid and the

extent of the financial burden incurred. The agency may call upon other agencies of the

state in evaluating such applications. The Adjutant General shall review each application

for aid under the provisions of this section and recommend its approval or disapproval, in

whole or in part, to the Governor. If the Governor approves, he/she shall determine and

certify to the Adjutant General the amount of aid to be furnished. The Adjutant General

shall thereupon issue his voucher to the Director of Administrative Services, who shall

issue his warrants therefor to the applicant.

(5) When a disaster emergency has been proclaimed by the Governor, or in the event of

a civil defense emergency, the Adjutant General, upon order of the Governor, shall have

authority to expend funds to meet but not be limited to the following situations:

(a) The purposes of sections 81-829.36 to 81-829.68 to include civil defense functions as

defined in section 81-829.39, and the responsibilities of the Governor and the state Civil

Defense Agency as outlined in sections 81-829.40 and 81-829.41;

(b) Employing for the duration of the emergency additional personnel and contracting

or otherwise procuring all necessary appliances, supplies and equipment;

(c) Performing services for and furnishing materials and supplies to state government

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agencies, counties and municipalities with respect to performance of any duties enjoined

by law upon such agencies, counties, and municipalities which they are unable to perform

because of extreme climatic phenomena, and receiving reimbursement in whole or in part

from such agencies, counties, and municipalities able to pay therefor under such terms

and conditions as may be agreed upon by the Adjutant General and any such agency,

county, or municipality;

(d) Performing services for and furnishing materials to any individual in connection

with alleviating hardship and distress growing out of extreme climatic phenomena,

and receiving reimbursement in whole or in part from such individual under such terms

as may be agreed upon by the Adjutant General and such individual;

(e) Performing services to counties and municipalities with respect to quelling riots

and civil disturbances;

(f) Opening up, repairing, and restoration of roads and highways;

(g) Repairing and restoration of bridges;

(h) Furnishing transportation for supplies to alleviate suffering and distress;

(i) Restoration of means of communication;

(j) Furnishing medical services and supplies to prevent the spread of disease and

epidemics;

(k) Quelling riots and civil disturbances;

(l) Training of individuals or governmental agencies for the purpose of perfecting the

performance of emergency assistance duties as defined in the state disaster plans;

(m) Procurement and storage of special emergency supplies or equipment, determined

by the Adjutant General as required to provide rapid response by state government to

assist counties and municipalities in impending or actual emergencies;

(n) Clearing or removing from publicly or privately-owned land or water, debris and

wreckage which may threaten public health or safety; and

(o) Such other measures as are customarily necessary to furnish adequate relief in cases

of catastrophe or disaster.

(6) The Governor may receive such voluntary contributions as may be made from any

source to aid in carrying out the purposes of this section and shall credit the same to the

Governor’s Emergency Fund.

(7) All obligations and expenses incurred by the Governor in the exercise of the powers

and duties vested in him/her by the provisions of this section shall be paid by the State

Treasurer out of available funds in the Governor’s Emergency Fund, and the Director of

Administrative Services shall draw his warrants upon the State Treasurer or the payment

of such sum, or so much thereof as may be required, upon receipt by him of proper

vouchers duly approved by the Adjutant General.

(8) The provisions of this section shall be liberally construed in order to accomplish the

purposes of sections 81-829.36 to 81-829.68 and to permit the Governor to adequately cope

with any emergency which may arise, and the powers vested in the Governor by this

section shall be construed as being in addition to all other powers presently vested in

him/her, and not in derogation of any existing powers.

(9) Such funds as may be made available by the government of the United States for the

purpose of alleviating distress from disasters may be accepted by the State Treasurer, and

shall be credited to the Governor’s Emergency Fund unless otherwise specifically provided in the act of Congress making such funds available.

Source: Laws 1973, LB 494, sec. 7; Laws 1975, LB 612, sec. 2.

81-829.43. Disaster prevention, procedure.

(1) In addition to disaster prevention measures as included in the state, local, and

interjurisdictional disaster plans, the Governor shall consider on a continuing basis steps

that could be taken to prevent or reduce the harmful consequences of disasters. At his or

her direction, and pursuant to any other authority and competence they have, state

agencies, including but not limited to those charged with responsibilities in connection

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with flood plain management, stream encroachment and flow regulation, weather modification, fire prevention and control, air quality, public works, land use and land-use

planning, and construction standards, shall make studies of disaster prevention-related

matters. The Governor, from time to time, shall make recommendations to the Legislature, local governments, and other appropriate public and private entities as may facilitate measures for prevention or reduction of the harmful consequences of disasters.

(2) The appropriate state agencies, in conjunction with the state Civil Defense Agency,

shall keep land uses and construction of structures and other facilities under continuing

study and identify areas which are particularly susceptible to severe land shifting, subsidence, flood, or other catastrophic occurrence. The studies under this subsection shall

concentrate on means of reducing or avoiding the dangers caused by any such occurrence

or the consequences thereof.

(3) If the state Civil Defense Agency believes on the basis of the studies or other

competent evidence that an area is susceptible to a disaster of catastrophic proportions

without adequate warning, that existing building standards and land-use controls in that

area are inadequate and could add substantially to the magnitude of the disaster, and that

changes in zoning regulations, other land-use regulations, or building requirements are

essential in order to further the purposes of this section, it shall specify the essential

changes to the Governor. If the Governor upon review of the recommendation finds after

public hearing that the changes are essential, he or she shall so recommend to the agencies

or local governments with jurisdiction over the area and subject matter. If no action or

insufficient action pursuant to his recommendations is taken within the time specified by

the Governor, he shall so inform the Legislature and request legislative action appropriate

to mitigate the impact of disaster.

(4) The Governor, at the same time that he or she makes recommendations pursuant to

subsection (3) of this section, may suspend the standard or control which he finds to be

inadequate to protect the public safety and by regulation place a new standard or control

in effect. The new standard or control shall remain in effect until rejected by resolution of

the Legislature or amended by the Governor. During the time it is in effect, the standard

or control contained in the Governor’s regulation shall be administered and given full

effect by all relevant regulatory agencies of the state and local governments to which it

applies. The Governor’s action may be appealed, and the appeal shall be in accordance

with the Administrative Procedure Act.

Source: Laws 1973, LB494, sec. 8; Laws 1988, LB352, sec. 168.

Operative date July 1, 1989.

Cross Reference

Administrative Procedure Act, see section 84-920.

81-829.44. State Civil Defense Agency; duties. The state Civil Defense Agency shall

ascertain what means exist for rapid and efficient communications in times of disaster

emergencies. The agency shall consider the desirability of supplementing these communications resources or of integrating them into a comprehensive state or state-federal telecommunications or other communications system or network. In studying the character

and feasibility of any system or its several parts, the agency shall evaluate the possibility

of multipurpose use thereof for general state and local governmental purposes. The

agency shall make recommendations with respect there to the Governor as appropriate.

Source: Laws 1973, LB 494, sec. 9.

81-829.45. State Civil Defense Agency; weather condition, continuously apprise;

permits; issue; suspend. The state Civil Defense Agency shall keep continuously apprised of weather conditions which present danger of precipitation or other climatic

71
activity severe enough to constitute a disaster. If the agency determines that precipitation

that may result from weather modification operations, either by itself or in conjunction

with other precipitation or climatic conditions or activity, would create or contribute to

the severity of a disaster, it shall direct the officer or agency empowered to issue permits

for weather modification operation to suspend the issuance of the permits, and thereupon

no permits may be issued until the agency informs the officer or agency that the danger

has passed.

Source: Laws 1973, LB 494, sec. 10.

81-829.46. Civil Defense Agency; political subdivisions; suspension; Governor; director; salary; powers; duties; performance of functions.

(1) Each political subdivision within this state shall be within the jurisdiction of and

served by the state Civil Defense Agency and by a local or interjurisdictional civil defense

organization which is headed by a director or coordinator who shall devote full time his

duties, or shall be served by a part-time director or coordinator who has a full-time

assistant or deputy who shall be qualified as set forth in subsection (5) of this section.

(2) Each county shall maintain a civil defense agency or participate in a local or

interjurisdictional civil defense agency which, except as otherwise provided under the

provisions of sections 81-829.36 to 81-829.68, has jurisdiction over and serves the entire

county. Each city and village which is desirous of establishing a civil defense organization

may do so in accordance with the state civil defense plan and program. Each such local or

interjurisdictional civil defense organization shall have a director who shall be appointed

by the governing body or bodies of such government or governments, and who shall have

direct responsibility for the organization, administration, and operation of such local

organization for civil defense, subject to the direction and control of the governing body

or bodies of the political subdivision or subdivisions concerned. The director of any

country civil defense organization may also be appointed director for any city or village

within such county, and the director of any city or village civil defense organization may

also be appointed county director. Each local or interjurisdictional organization for civil

defense shall perform civil defense functions within the territorial limits of the political

subdivision or subdivisions within which it is organized, except that the interjurisdictional and county organizations for civil defense shall perform no civil defense functions

within the limits of a county or city which are already being performed by such county or

city civil defense organizations, unless the approval of the respective county or city civil

defense director be first obtained.

(3) The Governor may determine that some cities need civil defense organizations or

agencies of their own. He/she shall, after making such determination, require that such

civil defense organizations be established and maintained by issuing a directive in the

form of a rule or regulation. He shall make his determination on the basis of a city’s

disaster vulnerability and capability of response related to population size and concentration. The civil defense agency of a county shall cooperate with the civil defense agencies

of cities within the county but shall not have jurisdiction within a city having its own civil

defense agency. The state Civil Defense Agency shall publish and keep current a list of

cities required to have civil Defense agencies.

(4) Any provision of sections 81-829.36 to 81-829.68 or other law to the contrary notwithstanding, the Governor may require a local government to establish and maintain a

civil defense agency and organization jointly with one or more contiguous local governments, if he/she finds that the establishment and maintenance of an agency or participation therein is made necessary by circumstances or conditions that make it unusually

difficult to provide disaster prevention, preparedness, response, or recovery services

under the other provisions of sections 81-829.36 to 81-829.68. Such interjurisdictional

agencies shall be organized generally in accord with the Interlocal Cooperation Act and

pursuant to the provisions of section 84-143.

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(5) Local or interjurisdictional civil defense directors or coordinators, or their assistants

or deputies, who are required by sections 81-829.36 to 81-829.68 or rules and regulations

of the Governor to devote full time to their duties shall be qualified in accord with criteria

established for the state by the Governor and announced by him in a rule or regulation.

Such directors or coordinators shall be paid for their services in an amount comparable to

other officers of local governments. A minimum annual salary for such local or interjurisdictional civil defense director or coordinator shall be based on the combined population

of the jurisdictions served, as follows: Having a population of less than three thousand,

five thousand five hundred dollars; having a population of three thousand but less than

nine thousand, six thousand dollars; having a population of nine thousand but less than

sixteen thousand, six thousand five hundred dollars; having a population of sixteen

thousand but less than twenty thousand, seven thousand five hundred dollars; having a

population of twenty thousand but less than sixty thousand, eight thousand dollars; and

having a population of sixty thousand or more, comparable to other officer of local

governments as determined by the governing body or bodies.

(6) Each political subdivision, except those directly managing a local or interjurisdictional civil defense agency, shall have a liaison officer designated to facilitate the cooperation and protection of that subdivision in the work of disaster prevention, preparedness, response and recovery.

(7) The principal executive officer of each political subdivision of the state shall notify

the state Civil Defense Agency of the manner in which the subdivision is providing or

securing civil defense and disaster services, identify the person who heads the agency

from which the service is obtained, and furnish such additional information relating

thereto as the state agency requires.

(8) Each local and interjurisdictional civil defense agency shall prepare and keep

current a local or interjurisdictional disaster and civil defense plan for its jurisdiction.

Such plans shall be in conformance with the requirements established in section 81-

829.41.

(9) Each local or interjurisdictional civil defense agency shall prepare, keep current,

and distribute to all appropriate officials in written form a clear and complete statement

of the disaster responsibilities of all local agencies and officials and of the disaster chain of

command.

Source: Laws 1951, c. 315, sec. 7, p. 1079; Laws 1963, c. 516, sec. 1, p. l632;

R.R.S.1943, sec. 81-829.18; Laws 1973, LB 494, sec. 11.

81-829.47. Interjurisdictional arrangement;

Governor; findings.

(1) If the Governor finds that two or more adjoining counties would be better served by

an interjurisdictional arrangement than by maintaining separate disaster and civil defense agencies and services, he may delineate by order or regulation an interjurisdictional

area adequate to plan for, prevent, or respond to disaster in that area and direct steps to be

taken as are necessary, including the creation of an interjurisdictional relationship, a joint

disaster emergency plan, mutual aid, or an area organization for disaster planning and

services. A finding of the Governor pursuant to this subsection shall be based on one or

more factors related to the difficulty of maintaining an efficient and effective disaster

prevention, preparedness, response, and recovery system without such interjurisdictional

arrangement, such as:

(a) Small or sparse population;

(b) Limitations on public financial resources severe enough to make maintenance of a

separate disaster agency and services unreasonably burdensome;

(c) Unusual vulnerability to disaster as evidenced by a past history of disasters, topographical features, drainage characteristics, disaster potential, and presence of disasterprone facilities or operations;

(d) The interrelated character of the counties in a multi-county area; or

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(e) Other relevant conditions or circumstances.

(2) If the Governor finds that a vulnerable area lies only partly within this state and

includes: territory in another state or states and that it would be desirable to establish an

interstate relationship, mutual aid, or an area organization for disaster, he/she shall take

steps to that end as desirable. If this action is taken with jurisdictions that have enacted

the Interstate Civil Defense and Disaster Compact, any resulting agreement or agreements may be considered supplemental agreements pursuant to Article VI of that compact.

(3) If the other jurisdiction or jurisdictions with which the Governor proposes to

cooperate pursuant to subsection (2) of this section have not enacted that compacts he

may negotiate special agreements with the jurisdiction or jurisdictions. Any agreement,

if sufficient authority for the making thereof does not other wise exist, shall become

effective only after its text has been communicated to the Legislature and if the

Legislature has not disapproved it prior to adjournment of the next session competent

to consider it, or within thirty days of its submission, whichever is later.

Source: Laws 1973, LB 494, sec. 12.

81-829.48. Civil defense; local organization; mutual aid arrangements; interjurisdictional agreement.

(1) The director or coordinator of each local or interjurisdictional organization for civil

defense shall, in collaboration with other public and private agencies within this state,

develop or cause to be developed mutual aid arrangements for reciprocal civil defense aid

and assistance in case of disaster too great to be dealt with unassisted. Such arrangements

shall be consistent with the state civil defense plan and program, and in time of emergency it shall be the duty of each local or interjurisdictional organization for civil defense to

render assistance in accordance with the provisions of such mutual aid arrangements.

(2) The director or coordinator of each local or interjurisdictional organization for

civil defense may, subject to the approval of the Governor, enter into mutual aid

arrangements with civil defense agencies or organizations in other states for reciprocal civil defense aid and assistance in case of disaster too great to be dealt with

unassisted.

(3) In passing upon local disaster plans, the Governor shall consider whether they

contain adequate provisions for the rendering and receipt of mutual aid.

(4) It shall be a sufficient reason for the Governor to require an interjurisdictional

agreement or arrangement, pursuant to section 81-829.47, that the area involved and

political subdivisions therein have available equipment, supplies, and forces necessary to

provide mutual aid on a regional basis and that the political subdivisions have not

already made adequate provision for mutual aid, but in requiring the making of an

interjurisdictional arrangement to accomplish the purpose of this section, the Governor

need not require establishment and maintenance of an interjurisdictional agency or arrangement for any other disaster purposes.

Source: Laws 1951, c.31S, sec. 8(1), p. 1080; R.R.S.1943, sec. 81-829.19;

Laws 1973, LB 494, sec. 13.

81-829.49. Civil defense; political subdivision; interjurisdictional agreements; appropriations. Each political subdivision shall have the power to make appropriations in

the manner provided by law for making appropriations for the ordinary expenses of such

political subdivision for the payment of expenses of its local or interjurisdictional organization for civil defense and in furthering the purposes of sections 81-829.36 to 81-829.68.

Source: Laws 1951, c. 315, sec. 10(1), p. 1081; R.R.S.1943, sec. 81-829.22; Laws 1973,

LB 494, sec. 14.

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81-829.50. Local disaster emergency; declared; principal executive officer of a political subdivision; effect; interjurisdictional agency; disaster emergency; when.

(1) A local disaster emergency may be declared only by the principal executive officer

of a political subdivision. It shall not be continued or renewed for a period in excess of

seven days except by or with the consent of the governing board of the political subdivision. Any order or proclamation declaring, continuing, or terminating a local disaster

emergency shall be given prompt and general publicity and shall be filed promptly with

the clerk of the local government and the state Civil Defense Agency.

(2) The effect of a declaration of a local disaster emergency shall be to activate the

response and recovery aspects of any and all applicable local or interjurisdictional disaster or civil defense plans and to authorize the furnishing of aid and assistance thereunder.

(3) No interjurisdictional agency or official thereof may declare a local disaster emergency unless expressly authorized by the agreement pursuant to which the agency functions, but an interjurisdictional disaster or civil defense agency or organization shall

provide aid and services in accordance with the agreement and disaster or civil defense

plan pursuant to which it functions.

Source: Laws 1973, LB 494, sec. 15.

81-829.51. Civil defense; emergency; political subdivision; emergency expenditures;

election; when. In the event of a civil defense emergency, as defined in section 81-429.39,

each local government may make emergency expenditures, enter into contracts, and incur

obligations for civil defense purposes regardless of existing statutory limitations and

requirements pertaining to appropriation, budgeting, levies, or the manner of entering

into contracts; Provided, that in the event that any such expenditure, contract, or obligation will be in excess of or in violation of existing statutory limitations or requirements,

then before any such expenditure, contract, or obligation is undertaken it shall be approved by a vote of the governing body of such county, city, or village, as the case may be;

provided further, that such governing body may not vote its approval unless and until

they shall have secured the certificate of the local or interjurisdictional civil defense

director serving his government that such action is necessary in the public interest for civil

defense purposes.

Source: Laws 1951, c. 315, sec. 10(2), p. 1081; R.R.S.1943, sec. 81-829.23; Laws 1973,

LB 612, sec. 16.

81-829.52. Civil defense; mobile support rules; Governor; establish; commander of

unit; appointment; duties. The Governor or his/her duly designated representative is

authorized to establish such number of mobile support units as may be necessary to

reinforce disaster and civil defense organizations in stricken areas and with due consideration of the plans of the federal government and of other states. He/ she shall appoint a

commander for each such unit who shall have primary responsibility for the organization,

administration and operation of such battalion. The commander shall keep and maintain

a roster of members of said mobile support units, and only such persons whose names

appear on said roster shall be deemed members of such mobile support units and entitled

to the benefits provided by sections 81-829.53, and no political subdivision shall be entitled to reimbursement as provided in section 81-829.54 unless the individual on whose

behalf reimbursement is sought was duly enrolled on the roster as provided herein at the

time the obligation was incurred. Mobile support units shall be called to duty upon orders

of the Governor and shall perform their functions in any part of the state, or, upon the

conditions specified in mutual aid plans and agreements, in accordance with the Interstate Civil Defense and Disaster Compact, and in this section, in other states.

Source: Laws 1951, c. 315, sec. 6(1), p. 1077; R.R.S.1943, sec. 81-829.13;

Laws 1973, LB 494, sec. 17.

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81-829.53. Civil Defense; mobile support units; personnel; powers; duties; rights;

immunities; compensation. Personnel of mobile support units while on duty, whether

within or without the state, shall: (1) If they are employees of the state, have the powers,

duties, rights, privileges, and immunities, and receive the compensation incidental to

their employment; (2) if they are employees of a political subdivision of the state, and

whether serving within or without such political subdivision, have the powers, duties,

rights, privileges, and immunities, and receive the compensation incidental to their employment; and (3) if they are not employees of the state or a political subdivision thereof,

be entitled to compensation by the state at rates to be established by the Governor, and

shall be entitled to the same rights and immunities as are provided by law for the

employees of this state. All personnel of mobile support units shall, while on duty, be

subject to the operational control of the authority in charge of disaster and civil defense

activities in the area in which they are serving, and shall be reimbursed for all actual and

necessary travel and subsistence expenses in accordance with sections 84-306.01 to 84-

306.05 for state employees.

Source: Laws 1951, c. 315, sec. 6(2), p. 1078; R.R.S.1943, sec. 81-829.14;

Laws 1973, LB 494, sec. 18; Laws 1981, LB 204, sec. 176.

81-829.54. Civil Defense; mobile support units; employees; expenses; political subdivisions; reimbursement by state; rental of equipment; payment; damages.

(1) The state shall reimburse a political subdivision for (a) the compensation paid and

actual and necessary travel, subsistence, and maintenance expenses of employees of such

political subdivision while service as members of a mobile support unit as provided in

Sections 84-306.01 to 84-306.05 for state employees, (b) all payments for death, disability,

or injury of such employees incurred in the course of such duty, as provided in the

Nebraska Workmen’s Compensation Act, and (c) all losses of or damage to supplies and

equipment of such political subdivision resulting from the operation of such mobile

support unit.

(2) The state shall pay a fee for rental of privately-owned equipment used in the

operation of a mobile support unit, and shall also pay for any loss or damage to privatelyowned equipment used immobile support. The fee for rental of said privately-owned

equipment shall be fixed, and any loss or damage to said equipment shall be assessed by a

board consisting of three persons to be appointed by the Governor, one of whom shall be

the State Purchasing Officer.

Source: Laws 1951, c. 315, sec. 6(3), p. 1078; Laws 1953, c. 336, sec. 3, p. 1107;

R.R.S.1943, sec. 81-829.15; Laws 1973, LB 494, sec. 19; Laws 1981, LB 204, sec.

177.

81-829.65. Civil defense; immunity from liability for activities; covered by Workmen’s Compensation Act; licenses, not required; civil defense worker; powers, duties,

immunities, privileges.

(1) All functions provided for in sections 81-289.36. to 81-829.68 and all other

activities relating to civil defense are hereby declared to be governmental functions.

Neither the United States, the state, nor any political subdivision thereof nor other

agencies of the United States, the state, or political subdivision thereof, nor, except in

cases of willful misconduct, gross negligence or bad faith, any civil defense worker

complying with or reasonably attempting to comply with the provisions of sections

81-829.36 to 81-829.68 or Public Law 93-288, or any order, rule or regulation promulgated pursuant to any ordinance relating to black-out or other precautionary measures enacted by any political subdivision of the state shall be liable for the death of or

injury to persons, or for damage to property, as a result of any such activity. The

provisions of this section shall not affect the right of any person to receive benefits to

which he would otherwise be entitled under the provisions of section 81-829.36 to 81-

829.68, or under the Nebraska Workmen’s Compensation Act, or under any pension

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law, nor the right of any person to receive any benefits or compensation under any act

of Congress.

(2) Any requirement for a license to practice any professional, mechanical or other skill

shall not apply to any authorized civil defense worker who shall, in the course of performing his duties as such, practice such professional, mechanical or other skill during a

civil defense emergency or declared disaster emergency.

(3) Any civil defense worker, as defined in sections 81-829.36 to 81-829.68, performing civil defense services at any place in this state pursuant to agreements, compacts

or arrangements for mutual aid and assistance, to which the state or a political subdivision thereof is a party, shall possess the same powers, duties, immunities and

privileges he would ordinarily possess if performing his duties in the state, province

or political subdivision thereof in which is a party, shall possess the same powers,

duties, immunities and privileges he would ordinarily possess if performing his duties in the state, province or political subdivision thereof in which normally employed

or rendering services.

Source: Laws 1951, c. 315, sec. 9, p. 1080; Laws 1963, c. 517, sec. 1, p. 1633; R.R.S.

1943, sec. 81-829.21; Laws 1973, LB 494, sec. 29; Laws 1975, LB 612, sec. 3.

81-829.56. Interstate Civil Defense and Disaster Compact; enter into.

(1) This state hereby enacts into law and enters into the Interstate Civil Defense and

Disaster Compact with all states bordering this state which have enacted or shall hereafter enact the compact in the form substantially as adopted in this state.

(2) The Governor may enter into the compact with any state which does not border his

state if he finds that joint action with the state is desirable in meeting common intergovernmental problems of emergency disaster planning, prevention, response, and recovery.

(3) Nothing is subsections (1) and (2) of this section shall be construed to limit previous

or future entry into the Interstate Civil Defense and Disaster Compact of this state with

other states.

(4) If any person holds a license, certificate, or other permit issued by any state or

political subdivision thereof evidencing the meeting of qualifications for professional

mechanical, or other skills, the person may render aid involving that skill in this state to

meet an emergency or disaster, and this state shall give due recognition to the license,

certificate, or other permit.

Source: Laws 1973, LB 494, sec. 21.

81-829.57. Persons of state; conduct; personal services; compensation for property

claim; file.

(1) Each person within this state shall conduct himself and keep and manage his affairs

and property in ways that will reasonably assist and will not unreasonably detract from

the ability of the state and the public successfully to meet disaster emergencies. This

obligation includes appropriate personal service and use or restriction on the use of

property in time of disaster emergency. Sections 81-829.36 to 81-829.68 neither increases

nor decreases these obligations but recognizes their existence under the Constitution and

statutes of this state and the common law. Compensation for services or for the taking or

use of property shall be only to the extent that obligations recognized in this subsection

are exceeded in a particular case and then only to the extent that the claimant may not be

deemed to have volunteered his services or property without compensation.

(2) No personal services may be compensated by the state or any subdivision or

agency thereof, except pursuant to statute or local law or ordinance.

(3) Compensation for property shall be made only if the property was commandeered

or otherwise used in coping with a disaster emergency and its use or destruction was

ordered by the governor or a member of the disaster emergency forces of this state to

whom the Governor has duly delegated such authority.

(4) Any person claiming compensation for the use, damage, loss, or destruction of

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property under sections 81-829.36 to 81-829.68 shall file a claim therefore with the state

Civil Defense Agency in the form and manner the agency provides.

(5) Unless the amount of compensation on account of property damaged, lost, or

destroyed is agreed upon between the claimant and the state Civil Defense Agency, the

amount of compensation shall be calculated in the same manner as compensation due for

a taking of property pursuant to the condemnation laws of this state.

(6) Nothing in this section shall apply to or authorize compensation for the destruction

or damaging of standing timber or other property in order to provide a fire break or to the

release of waters or the breach of impoundments in order to reduce pressure or other

danger from actual or threatened flood.

Source: Laws 1973, LB 494, sec. 22.

81-829.58. Civil Defense; supplies; services; federal government; channeled through

Governor; funds deposited in Military Department Cash Fund. Whenever the federal

government or any agency or officer thereof shall offer to the state, or through the state to

any political subdivision thereof, services, equipment, supplies, materials, or funds by

way of gift, grant, or loan, for purposes of disaster response and civil defense, the state,

acting through the Governor, or such political subdivision, acting with the consent of the

Governor of the state or executive officer or governing body of such political subdivision

may authorize any officer of the state or such political subdivision, as the case may be, to

receive such services, equipment, supplies, materials, or funds on behalf of the state or

such political subdivision, and subject to the terms of the offer and the rules and regulations, if any, of the agency making the offer. All such funds received on behalf of the state

shall be deposited in the state treasury and by the State Treasurer credited to the Military

Department Cash Fund.

Source: Laws 1951, c. 315, sec. 10(3), p. 1081; Laws 1965, c. 342, sec . 2, p. 973,

R.R.S.1943, sec. 81-829.24; Laws 1973, LB494, sec. 23.

81-829.69. Civil Defense; supplies; services; channeled through Governor; funds

deposited in Military Department Cash Fund. Whenever any person, firm, or corporation shall offer to the state or to any political subdivision thereof, services, equipment,

supplies, materials, or funds by way of gift, grant, or loan, for purposes of disaster

response and civil defense, the state, acting through the Governor, or such political

subdivision, acting through its executive officer or governing body, may accept such offer

and upon such acceptance the Governor of the state or executive officer or governing

body of such political subdivision may authorize any officer of the state or of the political

subdivision, as the case may be, to receive such services, equipment, supplies, materials,

or funds on behalf of the state or such political subdivision, and subject to the terms of the

offer. All such funds received on behalf of the state shall be deposited in the state treasury

and by the State Treasurer credited to the Military Department Cash Fund.

Source: Laws 1951, c. 315, sec. 10(4), p. 1082; Laws 1965, c. 342, sec. 3, p. 974;

R.R.S.1943; sec. 81-829.25; Laws 1973, LB 494, sec. 24.

81-829.60. Civil defense; services, equipment, and supplies; utilization of services,

equipment, supplies, and facilities of existing departments and agencies of state. In

carrying out the provisions of sections 81-829.36 to 81-829.68, the Governor and the

executive officers or governing bodies of the political subdivisions of the state are directed

to utilize the services, equipment, supplies, and facilities of existing departments, offices,

and agencies of the state and of the political subdivisions thereof to the maximum extent

practicable, and the officers and personnel of all such departments, offices, and agencies

are directed to cooperate with and extend such services and facilities to the Governor and

to the disaster response arid civil defense organizations of the state upon request.

Source: Laws 1951, c. 315, sec. 11, p. 1082; R.R.S.1943, sec. 81-829.26; Laws 1973, SB

494, sec. 25.

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81-829.61. Disaster response; civil defense; organizations; political activities prohibited. No organization for disaster response and civil defense established under the authority of sections 81-829.36 to 81-829.68 shall participate in any form of political activity,

nor shall it be employed directly or indirectly for political purposes.

Source: Laws 1951, c. 315, sec. 12, p. 1082; R.R.S.1943, sec. 81-829.27; Laws 1973, LB

494, sec. 26.

81-829.62. Disaster response; civil defense; personnel; advocation of subversive activities against government; employment prohibited; oath. No person shall be employed or associated in any capacity in any disaster response and civil defense organization established under the provisions of section 81-829.36 to 81-829.68 who advocates or

has advocated a change by force or violence in the constitutional form of the government

of the United States or in this state or the overthrow of any government in the United

States by force or violence, or who has been convicted of or is under indictment or

information charging any subversive act against the United States. Each person who is

appointed to serve in an organization for disaster response and civil defense, shall before

entering upon his duties, take an oath, in writing, before a person authorized to administer oaths in this state; Provided, that the Adjutant General and any subordinate civil

defense officer within this state, designated by the Adjutant General in writing, shall be

qualified to administer any such oath within this state under such regulations as the

Adjutant General shall prescribe. The oath shall be substantially as follows:

I ......................................., do solemnly swear (or affirm) that I will support and defend

the Constitution of the United States and the Constitution of the State of Nebraska,

against all enemies, foreign and domestic; that I will bear true faith and allegiance to the

same; that I take this obligation freely, without any mental reservation or purpose of

evasion; and that I will well and faithfully discharge the duties upon which I am about to

enter. And I do further swear (or affirm) that I do not advocate, nor am I a member of any

political party or organization that advocates the overgrow of the government of the

United States or of this state by (name of civil defense organization), I will not advocate

nor become a member of any political party or organization that advocates the overthrow

of the government of the United States or of this state by force or violence. So help me God.

Source: Laws 1951, c. 315, sec. 13, p. 1082; Laws 1953, c. 336, sec. 4, p. 1108; R.R.S.

1943, sec. 81.829.28; Laws 1973, LB 494, sec. 27.

81-829.63. Civil defense; personnel; oath; affirmation. Whenever an oath is required

by section 81-829.62, the affirmation of a person conscientiously scrupulous of taking an

oath shall have the same effect.

Source: Laws 1951, c. 315, sec. 14, p. 1083; R.R.S.1943, sec. 81-829.29; Laws 1973, LB

494, sec. 28.

81-829.64. Disaster response and civil defense; organizations; enforce laws, orders,

rules, and regulations. It shall be the duty of every organization for disaster response and

civil defense established pursuant to the provisions of sections 81-829.36 to 81-829.68 and

of the officers thereof to execute and enforce such orders, rules, and regulations as may be

made by the Governor under authority of sections 81-829.36 to 81-829.68. Each such

organization shall have available for inspection at its office all orders, rules, and regulations

made by the Governor, or under his authority.

Source: Laws 1951, c. 315, sec. 15, p. 1083; R.R.S.1943, sec. 81-829.30; Laws 1973, LB

494, sec. 29.

81-829.65. Disaster or civil defense; fire departments; moving of equipment outside

of political subdivisions; insurance. The governing body of each political subdivision of

this state shall take the necessary action to permit the movement of its emergency equipment and personnel, or such equipment and personnel as defined in the state, local, or

79
interjurisdictional disaster or civil defense plans, outside the limits of such political subdivision in order to render aid, in the event of major disaster or civil defense emergency,

as such terms are defined in section 81-829.39, or in connection with any program of

practice or training for such disaster or civil defense emergency when such program is

conducted, or participated in by the state Civil Defense Agency or with any other related

training program. Such movement may be to any point in this state, or may be into any

adjoining state when mutual aid arrangements have been entered into on behalf of this

state with such other state as authorized by section 81-829.56. Each political subdivision

shall self-insure or contract for insurance against any liability for personal injuries or

property damage that may be incurred by it or by its personnel, as the result of any

movement made pursuant to this section. As used in this section, political subdivision

shall not include a district as defined in section 70.601.

Source: Law 1957, c. 380, sec. 1, p. 1323; R.R.S.1943, sec. 81-829.32; Laws 1973, LB

494, sec. 30. Laws 1988, LB961, sec. 1.

81-829.66. Civil defense or disaster; immunity from liability for licensors of shelter

space. Any person owning or controlling real estate or other premises who voluntarily

and without compensation grants a license or privilege, or otherwise permits the designation or use of the whole or any part or parts of such real estate or premises for the

purpose of sheltering persons during an actual, impending, mock or practice attack or

disaster shall, together with his successors in interest, if any, not be civily liable for

negligently causing the death of, or injury to, any person on or about such real estate or

premises, or loss of, or damage to, the property of such person, at any time such real estate

or premises are actually used for such purpose.

Source: Laws 1963, c. 499, sec. 1, p. 1591; R.R.S.1943, sec. 81-829.35; Laws 1973, LB

494, sec. 31.

81-829.67 and 81-829.68. Repealed. Laws 1976, LB 847, sec. 2.

81-829.69. Disaster emergency; proclaimed by Governor; powers. Whenever the Governor has proclaimed a disaster emergency pursuant to section 81-829.40, the Governor

shall be authorized:

(1) to enter into purchase, lease, or other arrangements with any agency of the United

States for temporary housing units to be occupied by disaster victims and to make such

units available to any political subdivisions of the state;

(2) To assist any political subdivision of the state which is the location of temporary

housing for disaster victims to acquire sites necessary for such temporary housing and to

do all things required to prepare such sites to receive and utilize temporary housing units;

and

(3) Under such regulations as he shall prescribe, to temporarily suspend or modify for

not to exceed sixty days any public health, safety, zoning, transportation, or other requirement of law or regulation within this state when by proclamation he deems such suspension or modification essential to provide temporary housing for disaster victims.

Source: Laws 1975, LB 612, sec. 4.

81-829.70. Temporary housing units; powers of political subdivisions. Any political

subdivision of this state is expressly authorized to acquire, temporarily or permanently,

by purchase, lease, or otherwise, sites required for installation of temporary housing units

for disaster victims, and to enter into whatever arrangements are necessary to prepare or

equip such sites to utilize the housing units.

Source: Laws l975, LB 612, sec. 5.

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81-829.71. Major disaster; powers of Governor; apply for federal community disaster

loans. Whenever a major disaster has been declared to exist in this state, the Governor

shall be authorized:

(1) Upon his determination that a local government of the state will suffer a substantial

loss of tax and other revenue from a major disaster and has demonstrated a need for

financial assistance to perform its governmental functions, to apply to the federal government, on behalf of the local government, for a loan, and to receive and disburse the

proceeds of any approved loan to any applicant local government subject to the terms of

the loan. The Governor shall determine the amount needed by any applicant local government to restore or resume its governmental functions, and certify such amount to the

federal government; and

(2) To recommend to the federal government, based upon his review, the cancellation

of all or any part of repayment when, in the first three full fiscal years following the major

disaster, the revenue of the local government is insufficient to meet its v operating expenses, including additional disaster-related expense of municipal operation. 

Source: Laws 1972, LB 612, sec 6.

81-829.72. Major disaster; powers of Governor; accept federal grant for disaster victims, Adjutant General; rules and regulations.

(1) Whenever a major disaster has been declared to exist in this state, the Governor is

authorized, upon his determination that financial assistance is essential to meet disasterrelated necessary expenses or serious needs of individuals or families adversely affected

by a major disaster that may not be otherwise met from other means of assistance, to

accept a grant by the federal government to provide such financial assistance, subject to

such terms and conditions as may be imposed upon the grant.

(2) The Adjutant General shall make such regulations as shall be necessary to carry out

the purposes of subsection (1) of this section, including, but not limited to: (a) Standards

of eligibility for persons applying for benefits; (b) procedures for application and administration; (c) methods of investigating, filing, and approving applications; and (d) formation of local or statewide boards to pass upon applications and procedure for appeals.

Such rules, regulations, and standards shall, upon approval thereof by the Governor, be

promulgated so as to meet disaster-related necessary expenses and serious needs of

individuals. For the purposes of this subsection, necessary expenses and serious needs

shall mean those essential requirements of food, health, clothing, and shelter.

Source: Laws 1975, LB 612, sec. 7.

81-829.73. Misstatement concerning financial assistance; penalties. Any person who

fraudulently or willfully makes a misstatement of fact in connection with an application

for financial assistance under sections 68-703, 81-829.42, 81-829.55, and 81-829.69 to 81-

829.74 shall, upon conviction of each offense, be subject to a fine of not more than five

thousand dollars, or imprisonment in the county jail for not more than one year, or both.

Source: Laws 1975, LB 612, sec. 8.

81-829.74. State of Nebraska; assents to federal law. The State of Nebraska, by the

adoption of sections 68-703, 81-829.42, 81-829.55, and 81-289.69 to 81-829.74, assents to the

provisions of the Disaster Relief Act of 1974, P.L.93-288, 93rd Congress, insofar as such

provisions are permissible under the Constitution of the State of Nebraska.

Source: Laws 1975, LB 612, sec. 9.

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Nebraska law does not address specifically the

questions of (1) who, if anyone, has authority to

approve ice jam removal (including by dynamiting) in the state’s watercourses, or (2) what liability exists for injury to person or damage to property as a result of any efforts extended toward

such removal or as a result of the removal itself.

However, the questions are answered in a general

way through the Nebraska Disaster and Civil Defense Act (hereinafter called the Disaster Act)

sections 81-829.36 to 81-829.68, R.R.S. 1943, as

amended.*

As is true for other emergency activities, if efforts to remove an ice jam take place in full accord

with the Disaster Act, both the state and its political subdivisions are authorized to approve that

activity and are essentially insulated from liability for any damages resulting therefrom. If such

action is not taken in accord with the Disaster Act,

the basis for such authority is unclear and the

chances of liability are much higher. The questions are analyzed in more detail below.

Authority to Approve

Ice Jam Removal

Section 82-829.39 of the Disaster Act defines

the term “civil defense” in relevant part to mean

“...the preparation for and the carrying out

of all emergency functions...to prevent,

minimize...damage resulting from disasters caused by...flood.... These functions

include, without limitation...other functions related to civilian protection, together with all other activities necessary or incidental to the preparation for and carrying

out of the foregoing functions.”

The same statute defines “disaster” to mean

“...occurrence or imminent threat of wide spread

or severe damage, injury, or loss of life or property resulting from any natural or manmade cause,

including but not limited to... flood...” Those two

statutes authorize virtually any activity that the

state or an appropriate local subdivision deems

necessary to prevent or minimize the consequences of flooding. However, it is very important that

the provisions of the Disaster Act be followed

carefully to take advantage of the protection granted by that act. Part of that compliance involves

the preparation of state and local disaster plans.

The authority and requirement for the state disaster plan is section 81-829.41, R.R.S. 1943. The authority and requirement for local disaster plans is

section 81-829.46(8), R.S. Supp, 1992. For disaster

declarations made by the Governor, section 81-

829.40(4), R.R.S. 1943 provides that “proclamation

of a state of disaster emergency shall activate disaster

response and recovery aspects of the state, local, and

interjurisdictional disaster and civil defense plans

applicable to the political subdivision or area in

question...” (emphasis added). A local disaster

emergency also may be declared by the principal

executive officer of any political subdivision (81-

829.50)(1)), R.R.S. 1943. The effect of any such local declaration is to “...activate the response and

recovery aspects of and all applicable local or interjurisdictional disaster or civil defense plan...” (emphasis added) (81-829.50)(2)), R.R.S. 1943. It is important to note from these two statutes that

whether the disaster declaration is by the Governor or by a local political subdivision, the effect is

to authorize the carrying out of what is included

in the applicable plan (state or local). It is therefore advisable for those plans to include provisions for relief from ice jams, including standards

or criteria for when the existence of those ice jams

will result in a disaster emergency declaration

and also the proposed measures to respond to

that situation. If it is anticipated that the response

may include dynamiting, when and how that will

be done must be addressed in the plan.

Limitation of Liability

If the activities undertaken are in accordance

with the Disaster Act, section 81-829.55 provides

extensive protection from liability. In relevant part,

that section provides as follows:

“Neither the United States, the state nor

any political subdivision thereof nor other agencies of the United States, the state

APPENDIX D: LEGAL OPINION ON NEBRASKA LAW

CONCERNING THE REMOVAL OF ICE JAMS

(Drafted by James R. Cook, February 15, 1994)

* NOTE: LB 1203, currently pending before the Nebraska Legislature, would rename the act the “Emergency Management Act” and would modify the laws

upon which this paper is based. If LB 1203 or similar

legislation passes, modifications to this paper will be

needed.

82
or political subdivision thereof, nor, except in cases of willful misconduct, gross

negligence or bad faith any civil defense

worker complying with or reasonably attempting to comply with the provisions of

[the Disaster Act]...or any order, rule or

regulation promulgated pursuant to the

provisions of [the Disaster Act]...shall be

liable for the death of or injury to persons,

or for damage to property, as a result of

any such activity.”

There are two different standards concerning

liability in the quoted material. For the governments—federal, state, or local—there is no liability as long as the activity is conducted in accordance with the Disaster Act (which means

pursuant to a state or local declaration and in

accordance with the previously prepared disaster

plan). For civil defense workers, which include

employees, volunteers, and auxiliary employees

of the government or “of any agency or organization performing civil defense services at any place

in this state subject to the order or control of, or

pursuant to a request of, the state government or

any political subdivision thereof... ,” there would

be liability only in the event there is willful misconduct, gross negligence, or bad faith.

Section 81-829.55, R.R.S. 1943 was used successfully to prevent the state and Department of

Roads employees from being held liable for damages caused by the removal in 1978 of an ice jam

on the Platte (Cain v. State, Case No. 10163, Saunders County, 1981). It is not clear whether this

protection for civil defense workers extends to

contractors although they may be included within the term “organization” as used in the statute.

Private contractors may, however, want to secure

insurance to protect them against an action based

on a regular negligence standard.

Actions Taken Other Than in

Accordance with the Disaster Act

If action to dynamite or otherwise remove ice

jams from rivers is taken and that is not in accordance with the Disaster Act, the defense of that

action would be much more difficult. There is no

separate and specific authority which the state,

counties, or other political subdivisions could use

for such action. And, it is clear that the rather

considerable protection from liability granted by

the Disaster Act would not be available. Without

the limits on liability imposed by that act, governmental liability would be determined in accordance with the State or Political Subdivisions Tort

Claims Act, whichever was applicable. The governing section of the Political Subdivision Tort

Claims Act is section 13-910, R.S. Supp, 1993. For

the state act, the governing section is section 81-

8219, R.R. Supp, 1993. Both effectively establish a

negligence test as the standard for liability. Under

those statutes, the state and its political subdivisions are liable for damages to the same extent as

private citizens would be for the same actions.

Nebraska Game

and Parks Authority

There is one other statute which deserves mention here. That is section 37-515, R.S. Supp, 1993,

which relates to the necessity of obtaining approval from the Game and Parks Commission before exploding any dynamite in any lake, river,

stream or other waters of the state. However, that

section specifically provides that the requirement

“. . . shall not apply where, to safeguard public or

private property from damage by ice gorges, immediate use of explosives is necessitated.” Unless

there is a question about the immediacy of the

action needed, approval by Game and Parks

would not be needed.

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VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

January 1996

Ice Jam Flooding and Mitigation: Lower Platte River Basin, Nebraska

Kathleen D. White and Roger L. Kay

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road Special Report 96-1

Hanover, New Hampshire 03755-1290

U.S. Army Engineer District, Omaha

State of Nebraska Governor’s Emergency Fund

State of Nebraska Natural Resources Commission

Approved for public release; distribution is unlimited.

Available from NTIS, Springfield, Virginia 22161

93

Ice jams Flooding Platte River

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

This report presents the results of the Corps of Engineers’ Section 22 study of ice jam flooding in the Lower Platte

River basin. The purpose of the study was to gather and analyze historical data relating to ice jams, with the intent

of developing guidance that can be used to alleviate ice jam flooding at seven sites within the study area. Ice event

and related information is summarized for each site. Ice event characteristics for the study area are identified and

analyzed. A model for predicting the occurrence of ice jams or other ice events within the study area was

developed based on data for the Platte River at North Bend, Nebraska. The model provides the minimum

discharge associated with ice events for a given date, assuming a threshold value of accumulated freezing degreedays has been reached. A data collection program for future field observations was developed and placed in

operation during the winter of 1993-94. General information on ice jam mitigation measures, as well as specific

information on such operations as dusting and blasting, is provided. Specific recommendations include increased

monitoring of ice conditions, installation of ice motion detectors and water stage recorders, and further study of

nonstructural and structural mitigation measures. The use of dusting and blasting as mitigation measures is also

presented. The study was divided into six phases. Phase 1 involved collection of historical information from all

available data sources, published and oral. Site visits were made to each identified site. Phase 2 entailed analysis

and assessment of the collected hydrological, hydraulical, meteorological and ice data. Aerial reconnaissance of
each of the seven sites was also made during the ice-covered season. The third phase involved the design of the data

collection program and database. Personnel from CRREL conducted a workshop to train ice observers and other

interested parties in data collection, while the database design was done by the Nebraska Natural Resources

Commission. Phase 4 was the assessment of mitigation and prediction techniques. Various mitigation techniques

were evaluated for feasibility, and several were recommended for further study. A model was developed to

forecast the occurrence and severity of ice jams utilizing collectable data. The fifth phase involved the development

of guidance on the application of specific preventive measures, such as dusting and blasting. The final phase

involved the compilation of all work into this report.

13. ABSTRACT (cont’d).

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