SPECIAL REPORT 96-17

Effects of Ice Boom Geometry

on Ice Capture Efficiency

Gordon Gooch September 1996
Abstract: An ice boom’s geometry is critical to the collection and retention of ice in small, fast-moving streams

and rivers. Ice booms are designed to quickly form a

solid ice cover much earlier than the ice cover would

form naturally. Once formed, the ice cover insulates the

river, eliminating the production of frazil ice locally. Frazil

leads to thick ice deposits, which reduce the river’s

available flow area and contribute to midwinter and

spring flooding. Model experiments, conducted at the

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Ice Engineering Facility at the Cold Regions Research

and Engineering Laboratory, have varied the ice boom

geometry to speed up the process of ice cover formation.

Model simulations have used floating plastic beads to

simulate real ice particles to determine what ice boom

design works best. Under controlled laboratory conditions, boom geometry clearly affects the boom’s ability

to captured more beads. Comparison of field and laboratory tests indicates similar results.
Special Report 96-17

Effects of Ice Boom Geometry

on Ice Capture Efficiency

Gordon Gooch September 1996

Prepared for

OFFICE OF THE CHIEF OF ENGINEERS

Approved for public release; distribution is unlimited.

US Army Corps


of Engineers

Cold Regions Research &


Engineering Laboratory
PREFACE

This report was prepared by Gordon Gooch, Civil Engineering Technician of the Ice

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

Regions Research and Engineering Laboratory. Funding was provided by the Office of the

Chief of Engineers under the Civil Works program, Work Unit CWIS 32587, Ice Jam Characterization.

The author thanks Donald Haynes and Andrew Tuthill of CRREL for technically reviewing this report. The author was assisted by Kathleen White of CRREL in developing the test

programs and conducting experiments.

ii
INTRODUCTION

An ice boom is a series of floating timbers joined

together with a cable and anchored to shore or

riverbed anchors. The purpose of an ice boom may

be to divert floating ice away from problem areas

or to collect it to encourage the formation of a solid

ice sheet on a river. The sheet will insulate the

water beneath, eliminating ice production in those

locations. A reduction in ice volume can significantly reduce water levels and prevent ice jam

flooding. Researchers have been testing low-cost

solutions to encourage ice sheet formation on

small, fast-moving, frazil-producing streams using

ice booms. Frazil ice has been found to be the leading cause of ice jam flooding. Frazil ice begins as

small ice particles and quickly forms into larger

ice pans, which can restrict the flow capacity of

rivers and streams.

In this report, laboratory and field tests of ice

boom geometries are discussed, along with their

ability to capture floating ice and form a solid ice

cover. How well this can be done is referred to as

the “ice capture efficiency.” In laboratory tests the

ice capture efficiency is dramatically improved

when the incoming ice is first directed to the shore,

where it becomes stationary and thickens.

Effects of Ice Boom Geometry on Ice Capture Efficiency

GORDON GOOCH

Model tests using synthetic plastic beads can

compare the ice retention capabilities of ice booms

under controlled laboratory conditions. Model and

prototype ice boom behaviors are compared in this

report to emphasize the similarities between field

and laboratory results.

BACKGROUND

Site assessment criteria for ice cover formation

The criteria for a properly designed and functioning ice boom include many of the same general principles as debris booms (Perham 1987, 1988).

Froude number, flow velocity, ice forces and site

layout must all be within acceptable limits. The

Froude number is the ratio of the velocity divided

by the square root of gravity times the flow depth.

It is very useful, along with pool length, in determining if a location will meet minimum requirements for an ice control structure (ICS). Based on

flow depth, an upper Froude number limit of 0.10

is commonly used in selecting a site. The river pool

length in open-water conditions should be greater

than two river widths (Table 1). Experience has

shown that without these two minimum requirements, a conventional ice formation boom may not

Table 1. River hydraulics at ICS sites.

Oil Creek boom Oil Creek weir Allegheny R. boom Salmon River boom

(1981–82) (1982–83) (1988) (1982–83) (1989–91)

Average depth

(ft) 2 2.80 5 4.2 3

(m) 0.60 0.85 1.52 1.28 0.91

Flow velocity

(ft/s) 1.4 1.2 0.5 0.94 2.0

(m/s) 0.42 0.36 0.15 0.28 0.6

Froude number 0.17 0.13 0.04 0.08 0.21

Discharge

(cfs) 538 460 900 1870 900

(cms) 15 3 25 52 25

Channel width

(ft) 190 151 351 540 230

(m) 57 46 106 164 70

Pool length

(ft) 323 250 2431 600–900 1478

(m) 98 76 740 182–274 450

Length/width ratio 1.7 1.6 6.9 1.6 6.4
work. To be successful an ice boom must cause an

ice cover to progress beyond the natural change in

water surface slope upstream of the structure. Further constraints on ice boom design include project

cost, benefits and environmental impact.

Boom shapes

The three ice boom shapes discussed in this

report are single-sag, multiple-sag and shear booms

(Fig. 1). The purpose of a sag boom is to collect the

maximum amount of floating ice and form a stable

solid ice sheet behind the boom as quickly as possible. This ice sheet then thickens, allowing an ice

cover to progress upstream, insulating the water

beneath and eliminating additional frazil ice proFlow

Deadman

Anchor

Boom

Cable

Salmon

River

Boom

Units

a. Single-sag boom on the Salmon River. b. Multiple-sag boom on the Allegheny River.

c. Shear boom on Lake St. Francis.

Figure 1. Ice boom designs.

2

duction in the process. Frazil ice forms in supercooled, turbulent water and is composed of fine

disc-shaped particles of ice. These small particles

are suspended in the full depth of the river flow

because they have very little buoyancy. When these

suspended ice particles reach a region of slower

water, they clump together to form a frazil floc,

which floats along the water surface until it becomes incorporated into a solid ice sheet. Large volumes of frazil can accumulate, contributing to

flooding problems. Since sag booms prevent frazil

from forming, the lower ice volume will reduce or

eliminate spring or midwinter ice jam flooding.

Single-sag booms are often used on small creeks

and rivers because of ease of installation and low
cost. Multiple-sag booms are used primarily on

large rivers. These rivers typically have much lower

flow velocities and greater flow depths, resulting

in more favorable river hydraulics for ice cover

formation. These booms help stabilize the ice, preventing large ice sheets from floating into a navigation channel. Multiple shore and bed anchors

distribute the loads the boom will experience and

also help maintain the desired geometry. Each boom

design may require a specific shore anchor design

to allow boat passage or to span a large river.

Shear booms are designed to direct incoming

ice and floating debris away from problem areas,

typically navigation channels and flow intakes at

power dams, but they can also be used as ice formation booms in high-velocity areas in fast-moving

streams and rivers.

Ice arching

When ice floes pass through a constriction in a

river, they can arch across, forming a stable ice

bridge across the opening. Calkins et al. (1982)

found a relationship in laboratory tests between

the open-water width between two structures, b,

and the size of the solid ice floes, a, passing through

that opening indicating when a stable ice arch

would form. The minimum a/b ratio for establishing a stable arch for rafted floes was approximately

0.8. Calkins et al. found in laboratory tests,

using plastic blocks to simulate ice, that when the

a/b ratio was greater than 0.3, ice arching was more

frequent. Conversely if the gap opening increases

and the ice floe size remains approximately constant, formation of an ice cover would be unlikely.

Calkins et al. also found that an increase in the a/b

ratio from 0.1 to 0.2 decreased the amount of ice

passing through the opening by tenfold. Although

solid plastic blocks were used in the model study,

similar limits seem to apply to frazil ice pans. If

the estimated floe size, for example, is 5 ft (1.5 m),

then the open-water width should be no more than

20 ft (6.1 m) (5.0/20.0 = 0.25) for an arch to form

(Fig. 2). As the gap decreases, the a/b value increases until it reaches the value of one, or 100%

ice cover.

 A single-sag boom on Oil Creek in Oil City,

Pennsylvania, created an open-water gap between

two shore ice covers (Fig. 3) The gap opening increases with distance upstream of the structure and

therefore could not meet the arching criteria. The

Allegheny River ICS, in comparison, had large 20-

ft- (6.1-m-) diameter frazil pans and parallel ice

shear walls in the open-water approach to the ice

boom (Fig. 4). The a/b value was within acceptIce Arching

1.0

0.8

0.6

0.4

0.2

0 10 20 30 40 50

Gap Opening (ft)

a/b for 5-ft-Diameter Ice Floe

Figure 2. Gap opening vs. a/b value for a floe 5.0 ft

(1.5 m) in diameter. The opening must be 20.0 ft

(6.1 m) or less for an arch to form.

3

Figure 3. Funnel-shaped ice formation at Oil Creek,

Pennsylvania.

Figure 4. Parallel ice shear walls at the Allegheny River

ice boom.
Figure 5. Oil Creek ice boom screens.

able limits for an arch to form, joining the intact

ice sheets from both riverbanks and allowing the

incoming floating ice to be incorporated into this

newly formed ice sheet.

When frazil flocs are present, the situation is

more complicated. Although a 100% ice cover with

solid ice blocks would indicate a definite arching

condition, frazil floes can be compressed, even

though the surface concentration may be considered 100%. This means that cohesion and strength

must also be considered when calculating arching probability. The compacting of the frazil discs

increases in proportion to the force exerted on it.

If there is little compression of the frazil before it

reaches a structure, the ice floe may separate easily. Frazil floes may also develop strength due to

the freezing of the surface layer exposed to the air.

The combination of compression and freezing of

the floe determines its final behavior when it meets

a resistant ice cover.

BOOM TESTS

Allegheny River

Oil City, located in northwestern Pennsylvania, has been plagued by ice jam flooding since

the mid-1800s. In February 1979, Oil Creek flooded the downtown business district, causing an

estimated $800,000 in damages. As a result of this

flood the U.S. Army Engineer District, Pittsburgh,

asked CRREL to find a solution to the flooding on

Oil Creek. Deck and Gooch (1981) concluded that

controlling the production of frazil ice on the Allegheny River and Oil Creek would eliminate

future flooding.

In the winter of 1982-83 an ice boom was installed on the Allegheny River upstream of the

confluence with Oil Creek to alleviate ice jam

flooding. The configuration, design load and general design criteria for the ICS were furnished by

CRREL to the U.S. Army Engineer District, Pittsburgh. They developed the anchor and detailed

structural design and awarded the contracts to

fabricate and install the structure prior. The cost

of these contracts was about $650,000 (Deck and

Gooch 1984).

The Allegheny River ice boom has a multiplesag design (Fig. 1b) and is located about 1600 ft

(487 m) upstream of the mouth of Oil Creek at the

downstream end of a pool in the river. The ice

boom consists of 20 floating steel pontoons. Each

pontoon is attached by chains to a 60-mm-diam.

wire rope and is 613 cm long, 91 cm wide and 40

cm deep. Two 77-m spans of wire rope are used to

4

cross the river. Alterations of the streambed could

not be made to anchor the structure to the bed

because of strict environmental regulations. Therefore, four shore anchors were used. One wire rope

is attached to each anchor and joined at a junction

plate at the approximate centerline of the river.

Floats support the weight of this junction plate and

the two wire ropes to which the pontoons are

attached.

Oil Creek

Single-sag ice booms were tested at two sites

on Oil Creek, for three successive winters (1981-

1984). The intent of the ICS is to encourage a stable ice cover to form upstream of the ICS, both to

capture transported surface ice and to suppress

ice production upstream. Unfortunately a floating

boom is effective in forming a stable ice cover only

if the surface velocity at the boom is less than a

critical velocity. This critical velocity is determined

by the properties of the ice floes arriving at the

boom: thickness, shape, overall density and

strength. If the surface velocity at the boom is

greater than this critical velocity, ice floes arriving

at the boom will tend to underturn and pass under the boom (Gooch and Daly 1994). These conditions typically result in Froude numbers above

0.10.

During the first winter the river site was 58 m

wide and 0.6 m deep, with an average velocity

across the river of 0.4 m/s and a pool length of 98

m. Ice collection screens hanging below each boom

unit (Fig. 5) captured frazil and resulted in a 0.3-m

increase in water level and a 200-ft ice cover

upstream (Fig. 3). The upstream open-water area

resembled a funnel, forcing the majority of the

floating frazil toward the center of the structure

and allowing nearly all of it to pass. As the
upstream ice approached the structure, the ice velocity increased because of the constriction caused

by the ice blockage in the channel, reducing the

structure’s ability to create an arch as the floating

ice made contact with the intact ice cover. The frazil flocs would shove against each other and compress, decreasing their diameter and allowing

them to pass through the constriction. At this point

the structure could no longer capture ice or influence the ice cover progression upstream. This

could explain the poor performance of the first Oil

Creek structure. Since frazil is difficult to capture

if the river velocity is above 2.0 ft/s (0.6 m/s) and

the water depth is less than 1.0 ft (0.3 m), the use

of a boom alone to initiate the formation of an ice

cover incorporating frazil ice may be ineffective

without some source of hydraulic control to reduce the velocity (Deck 1984).

In December 1983, researchers selected a site

with a water depth 0.8 ft (0.2 m) deeper than the

previous location but with only a 76-m pool length.

By increasing the depth the resulting velocity

would be reduced, thereby improving the ice formation potential. A stable ice cover formed in four

hours, with 70% of the cross-sectional flow area

restricted. All additional incoming frazil ice was

submerged, however, and transported downstream. The initial capture efficiency was excellent,

but the length of the pool and the stage rise were

inadequate to allow the ice cover to advance

through the steeper upstream reach. As a result,

the ice boom failed to effectively capture frazil ice

and cause significant ice cover formation.

In 1984 a more conventional and costly $2.2-

million, 306-ft (93-m) fixed-crest concrete weir with

a 45-ft (13.7-m) bascule gate was designed by the

Pittsburgh District. The Oil Creek ICS, which was

completed in 1988, provided the hydraulic control needed to form an ice cover. The gate is raised

by mid-December, creating a 5.0-ft- (1.5-m-) deep

pool, lowering the Froude number from above 0.10

to 0.04 and increasing the length of pool upstream

of the structure by a factor of 10 from previous

test sites (Table 1). A timber single-sag boom deployed approximately 200 ft upstream of the structure captured ice to form a stable ice cover during

high flows. The ice boom is no longer used because of continual cable failures. However, the

weir by itself provides the hydraulic control needed to form an adequate ice cover each winter. There

has been no ice jam flooding on Oil Creek since

the installation of the Allegheny River ice boom

in 1982-83.

The success of the double-sag Allegheny River

ice boom and the failure of the single-sag Oil Creek

boom initially spurred interest in capture efficiency

as a function of boom geometry. The Allegheny

River’s 650-ft (198-m) channel width required a

double-sag boom design to position the boom in

the low-velocity reach of the river without using

riverbed anchors. This design directs the very large

flocs or floating frazil ice pans to the shore, where

the pans accumulate and thicken due to the shoving action created by the increase in hydrostatic

forces acting on the ice accumulation. The ice capture efficiency is increased, and the load on the

structure is reduced as the ice comes in contact

with the shore and riverbed. This concept combines the direction feature of the shear boom and

the collection and thickening capability of the formation boom. As a result of this geometry, the ice

thickening process increases the upstream water

level, reduces the flow velocity upstream and narrows the open-water channel. This eventually allows ice to arch more easily, joining the right- and

left-bank ice sheets into one solid ice cover (Deck

and Gooch 1983).

Salmon River

Two single-sag ice booms were tested on the

Salmon River in Salmon, Idaho. Ice jams on the

Salmon River have caused millions of dollars in

damages in recent years. The Salmon River is characterized by a series of rapids and pools. The bed

slope is 0.003 in the study reach and therefore very

steep. Research efforts for a structural solution to

ice jam flooding in Salmon have been the major

focus. Because of cost and environmental constraints, the most favorable ice capture and freezeup structure design with the least impact on the

hydraulic conditions in the river is an ice formation boom.

The site chosen for an ICS was located about

nine miles upstream from the city of Salmon. At

this point the river is about 85 m wide and 1 m

deep, with a pool length of 450 m. Surface velocities are 2.0–3.0 ft/s (0.6–0.9 m/s) at the expected

winter flows of 25.0–37.0 m3/s (883–1300 cfs). This

site has a Froude number of 0.20 and would be

considered unsuitable by the current Froude criterion for ice cover formation (Fig. 6). A singlesag formation boom was tested at this site during

the winter of 1989-90. Field measurements and

observations at the site included river cross-section geometry, ice boom loading, orientation and

river velocity distribution. The ice boom failed,

allowing the incoming ice to pass under the structure and continue downstream. This indicated that

5
a. Sag boom.

b. Shear boom.

c. Sag and shear ice booms during testing.

Figure 8. Model booms.

the critical velocity had been exceeded at the boom

and a reduction in surface velocity was needed.

The current geometry of the boom carried incoming frazil ice pans to the outside of a riverbend,

6

Oil Creek 1988

(effective)

Allegheny River 1982-83

(effective)

Oil Creek1982-83

(ineffective)

Oil Creek 1981-82

(ineffective)

Salmon River 

1989-90 (ineffective)

1990-91 (effective)

Conventional Froude Limit 

For Ice Cover Formation

1.6

1.2

0.8

0.4

Flow Depth (m)

0 0.1 0.2 0.3

Froude Number

QSalmon River

42.5°

23.5°

34.7°

265'

280'

1989-'90

1990-'91

266'

Figure 6. Froude number vs. flow depth for prototype

booms.

Figure 7. Salmon River ice boom geometry.

where the velocity was at a maximum. The anchor

positions allowed the boom to sag in the direction

of maximum velocity rather than taking advantage of the lower velocities and shallower depth

on the left bank of the river (Fig. 7).

In May 1990, researchers at CRREL tested the

shear boom concept in the laboratory in an effort

to increase the frazil ice capture rate for the Salmon ice boom (Fig. 8). Model ice booms were built
7

4

3

2

1

Flow Depth (m)

0 0.1 0.2 0.3

Froude Number

Sag Boom Only (effective)

Sag Boom (ineffective)

Shear Boom (effective)

Conventional Froude Limit

For Ice Cover Formation

Figure 9. Froude number vs. flow depth for model

booms.

Figure 10. Water surface velocity distribution just upstream of a boom.

at a 1:25 scale and tested in an existing hydraulic

model and a 4-ft-wide rectangular flume. The performances of a shear boom and a single-sag boom

were compared (Fig. 9). A 3-mm plastic bead

material was used to simulate real ice. The plastic

beads were introduced upstream of each boom.

When the flow discharge was increased, the sag

boom released the bead particles while the shear

boom held them. By increasing the capture efficiency of the boom, the flow depth was increased

and the velocity upstream of the boom was reduced.

During the tests a ripple line was observed on

the water surface, created by the floating structures. The ripple lines followed the shape of the

floating object and were distinctly different with

changes in the boom geometry and discharge. The

sag boom created a ripple line similar to the fun0.5

1.5

2.0 ft

21 ft

1860

1220

1060 gpm

Q

nel shape observed on Oil Creek, indicating the

water surface velocity distribution and the eventual freeze-up pattern (Fig. 10). The ripple lines

created by the shear boom were parallel to the

boom. The plastic particles decelerated once they

passed through this line. This line appears to separate the water surface areas affected by the floating

structure from those areas that are not.

The shear boom guided the incoming particles to the low-velocity collection zones along the

shore. The distribution of the particles became

more uniform as the accumulation of beads thickened, followed by a stage rise. The particles thicken due to shoving caused by the increase in a shear

force acting on the underside of the cover. The bead

cover progressed upstream at a rate dependent on

the incoming concentration of particles and the

amount of shoving and thickening. The capture

efficiency improved as the ice boom geometry was

changed (Table 2). A comparison between the

model and the field data indicate a substantial improvement in the capture efficiency. If we compare

Froude number (Fig. 6 and 9) prior to freeze-up at

field sites and also prior to simulated ice conditions in laboratory simulations, we find similar

results between the sag boom and shear boom

designs. The shear boom can capture ice at higher

flows and results in an immediate benefit by reducing the velocity further through the thickening of

the ice accumulation. The fact that prototype and

model measurements indicate a higher Froude

number indicates how important the shape is in

the ice collection ability of an ice boom and subsequent flow conditions upstream of the boom.
A similar experiment on the arch shape design was conducted in a model study by Burgi

(1971), with an ice boom named an “upstream V.”

Burgi noted that it provided a more stable ice cover than the sag boom configuration tested. The

“upstream V” ice boom formed a 45° angle to the

shoreline. Burgi concluded that the ice stability

was a result of the wedging of the floating ice between the boom and the riverbanks.

Following the lab experiments the Salmon ice

boom right-bank anchor was moved 266 ft upstream from its previous location (Fig. 7). This new

geometry and orientation directed more ice to the

lower-velocity zone on the left bank, increasing

water levels and ice collection. The resulting ice

cover progressed more than five miles upstream

and reduced the total volume of ice available to

cause a downstream ice jam. A detailed analysis

of historical winter temperature records established a method to predict when an ice jam would

reach the town of Salmon (Zufelt and Bilello 1992).

They concluded that the reduction in ice volume

could be attributed to the collection of frazil at the

ice boom upstream of Salmon.

 An evaluation of the performance of the Salmon River ice boom concluded that the change in

the shape of the ice boom resulted in an ice cover

formation upstream of the boom, preventing ice

jam flooding at Salmon in the winter of 1990-91

(White and Zufelt 1993).

CONCLUSIONS

 Full-scale tests in Salmon, Idaho, varied the

ice boom geometry dramatically, improving the

ice stability, capture efficiency and ice cover progression. Model and full-scale tests demonstrate

the importance and sensitivity of the ice boom

geometry. Use of this boom shape led to the sucTable 2. Modeling results for Salmon River ice booms.

Test 1 Test 2

Section 1 Section 2 Section 3 Section 1 Section 2 Section 3 Test 3

Average depth

(ft) 6.1 6.9 6.2 8.2 8.2 7.4 11.9

(m) 1.9 2.1 1.9 2.5 2.5 2.3 3.6

Velocity

(ft/s) 1.1 1.3 1.6 2.3 3.9 3.7 2.5

(m/s) 0.3 0.4 0.5 0.7 1.2 1.1 0.7

Froude number 0.08 0.08 0.11 0.14 0.24 0.24 0.12

Discharge

(cfs) 2.3 2.3 2.3 4.1 4.1 4.1 1.0

(cms) 0.07 0.07 0.07 0.12 0.12 0.12 0.03

Capture efficiency

Single-sag boom high high high negligible negligible negligible negligible

Shear boom high high high high

8

cess of the Salmon ice boom in a river where the

Froude criterion was considered unacceptable.

This suggests that the criterion has exceptions and

warrants further study. The shear boom configuration should be considered for any future ICS

installation.

Plastic beads are very sensitive to minor

changes in water velocity and are difficult to capture, making them ideal for laboratory experiments studying model ice boom geometries. Laboratory experiments have shown conclusively that

a change in orientation and shape of an ice boom

can dramatically improve the plastic ice stability

and capture efficiency.

The design of low-cost ice control structures

is an ongoing research effort at CRREL. Total construction cost savings of $1 million or more may

result when compared to the $2.2-million conventional Oil Creek structure completed in 1988.

LITERATURE CITED

Burgi, P.H.(1971) Ice control structure on the North

Platte River, A hydraulic model study. Engineering and Research Center, Bureau of Reclamation,

REC-ERC-71-46.

Calkins, D.J., D.S. Deck and D.S. Sodhi (1982)

Hydraulic model study of Port Huron ice control

structure. USA Cold Regions Research and Engineering Laboratory, CRREL Report 82-34.

Deck, D.S. (1984) Frazil ice control on Oil Creek,

Pennsylvania. USA Corps of Engineers, report to

the Pittsburgh District.

Deck, D.S. and G. Gooch (1981) Ice jam problems

at Oil City, Pennsylvania. USA Cold Regions

Research and Engineering Laboratory, Special

Report 81-9.

Deck, D.S. and G. Gooch (1984) Performance of the

Allegheny River ice control structure (1983). USA
Cold Regions Research and Engineering Laboratory, Special Report 84-13.

Gooch, G. and S. Daly (1994) Oil City, Pennsylvania, ice management project. Ice control structures operations overview (1994) USA Corps of

Engineers, report prepared for the Water Control

Center, Pittsburgh District.

Perham, R.E. (1987) Floating debris control: A literature review. USA Cold Regions Research and

Engineering Laboratory, Technical Report REMRHY-2.

Perham, R.E. (1988) Elements of floating-debris

9

control system. USA Cold Regions Research and

Engineering Laboratory, Technical Report REMRHY-3.

White, K.D. and J.E. Zufelt (1993) Performance and

evaluation of freeze-up ice jam control at Salmon,

Idaho. USA Corps of Engineers, report prepared

for Walla Walla District.

Zufelt, J.E. and M.A. Bilello (1992) Effects of severe

freezing periods and discharge on the formation of

ice jams at Salmon, Idaho. USA Cold Regions Research and Engineering Laboratory, Special Report

92-14.
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For conversion of SI units to non-SI units of measurement consult Standard Practice for Use of the International System of Units (SI),

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September 1996

Effects of Ice Boom Geometry on Ice Capture Efficiency CWIS 32587

Gordon Gooch

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road Special Report 96-17

Hanover, New Hampshire 03755-1290

Office of the Chief of Engineers

Washington, DC 20314-1000

Approved for public release; distribution is unlimited.

Available from NTIS, Springfield, Virginia 22161.

An ice boom’s geometry is critical to the collection and retention of ice in small, fast-moving streams and rivers.

Ice booms are designed to quickly form a solid ice cover much earlier than the ice cover would form naturally.

Once formed, the ice cover insulates the river, eliminating the production of frazil ice locally. Frazil leads to thick

ice deposits, which reduce the river’s available flow area and contribute to midwinter and spring flooding.

Model experiments, conducted at the Ice Engineering Facility at the Cold Regions Research and Engineering

Laboratory, have varied the ice boom geometry to speed up the process of ice cover formation. Model simulations have used floating plastic beads to simulate real ice particles to determine what ice boom design works

best. Under controlled laboratory conditions, boom geometry clearly affects the boom’s ability to captured more

beads. Comparison of field and laboratory tests indicates similar results.

Ice booms 12

Ice jams

Model tests

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