STORM AND FLOOD OF JULY 5,1989, IN 

NORTHERN NEW CASTLE COUNTY, DELAWARE

By Gary N. Paulachok, Robert H. Simmons, and Anthony J. Tallman

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 94-4188

Dover, Delaware 

1995
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary 

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

For additional information write to: Copies of this report can be purchased from:

Hydrologist In-Charge, Delaware Office 

U.S. Geological Survey 

Federal Building, Room 1201 

300 S. New Street 

Dover, DE 19904

U.S. Geological Survey

Earth Science Information Center

Open-File Reports Section

Box 25286, MS 517

Denver Federal Center

Denver, CO 80225
CONTENTS

Glossary...........................................................................................................................................................vi

Abstract.............................................................................................................................................................1

Introduction......................................................................................................................................................2

Purpose and scope....................................................................................................................................2

Location of study area..............................................................................................................................2

Acknowledgments...................................................................................................................................2

Description of storm.........................................................................................................................................4

Spatial distribution of rainfall..................................................................................................................4

Temporal distribution of rainfall..............................................................................................................4

Description of flood..........................................................................................................................................9

Peak stage and discharge at streamflow-gaging stations.........................................................................9

Peak stage at selected sites.....................................................................................................................21

Summary.........................................................................................................................................................26

Selected references.........................................................................................................................................29

FIGURES

1 -2. Maps showing location of:

1. Study area and study region ........................................................................................................3

2. Rain gages and distribution of rainfall, July 4-6, 1989...............................................................7

3. Graphs showing hourly and cumulative rainfall at the University Farm, Newark, 

Delaware, and the New Castle County Airport, New Castle, Delaware, 

July 4-6, 1989 ................................................................................................................................10

4 -9. Photographs showing:

4. White Clay Creek flooding at Stanton, Delaware, July 5, 1989................................................ 11

5. Submergence of concrete-arch bridge along old Route 7 by floodwaters of White

Clay Creek at Stanton, Delaware..........................................................................................11

6. Damage to highway bridge and sidewalk from flooding of Shellpot Creek,

Wilmington, Delaware.......................................................................................................... 12

7. Damage to highway and parking lot caused by flooding of Shellpot Creek,

Wilmington, Delaware.......................................................................................................... 12

8. Floodwaters from Shellpot Creek at Market Street Shopping Center,

Wilmington, Delaware.......................................................................................................... 13

9. Floodwaters from White Clay Creek at Stanton, Delaware...................................................... 13

10. Map showing location of stream stage and discharge measuring stations.......................................... 15

11-17. Hydrographs showing discharge at:

11. Shellpot Creek at Wilmington, Delaware, July 4-6, 1989.......................................................20

12. Brandywine Creek at Wilmington, Delaware, July 4-6, 1989.................................................20

13. Red Clay Creek at Wooddale, Delaware, July 4-6, 1989........................................................20

14. Red Clay Creek near Stanton, Delaware, July 4-6, 1989........................................................20

15. White Clay Creek near Newark, Delaware, July 4-6, 1989....................................................21

16. Christina River at Coochs Bridge, Delaware, July 4-6, 1989.................................................21

17. Christina River near Bear, Delaware, July 4-6, 1989..............................................................21

Storm and flood of July 5, 1989, in Northern New Castle County, Delaware Hi
18-22. Maps showing location of peak-stage survey sites on:

18. Shellpot Creek in Delaware.................................................................................................... 24

19. Red Clay Creek in Delaware................................................................................................... 25

20. White Clay Creek in Delaware...............................................................................................26

21. Christina River in Delaware.................................................................................................... 27

22. Little Mill Creek in Delaware.................................................................................................27

TABLES

1. Rainfall data for sites in the study region, July 4-6, 1989................................................................. 5

2. Hourly and cumulative rainfall at the Univeristy Farm, Newark Delaware, and the

New Castle County Airport, New Castle, Delaware, July 4-6, 1989............................................ 8

3. Peak stages and discharges for previous flood of record and the flood of July 5,1989.................. 14

4-10. Selected values of stage and discharge for:

4. Station 01477800 Shellpot Creek at Wilmington, Delaware, July 4-6, 1989......................... 16

5. Station 01481500 Brandywine Creek at Wilmington, Delaware, July 4-6, 1989................... 17

6. Station 01480000 Red Clay Creek at Wooddale, Delaware, July 4-6, 1989........................... 17

7. Station 01480015 Red Clay Creek near Stanton, Delaware, July 4-6, 1989........................... 18

8. Station 01479000 White Clay Creek near Newark, Delaware, July 4-6, 1989....................... 18

9. Station 01478000 Christina River at Coochs Bridge, Delaware, July 4-6, 1989.................... 19

10. Station 01478040 Christina River near Bear, Delaware, July 4-6, 1989................................ 19

11 -15. Peak flood stage at selected sites on:

11. Shellpot Creek, Delaware, July 5,1989.................................................................................. 22

12. Red Clay Creek, Delaware, July 5, 1989 ................................................................................22

13. White Clay Creek, Delaware, July 5, 1989.............................................................................23

14. Christina River, Delaware, July 5, 1989 .................................................................................23

15. Little Mill Creek, Delaware, July 5,1989............................................................................... 24

iv Storm and flood of July 5,1989, in Northern New Castle County, Delaware
CONVERSION FACTORS AND VERTICAL DATUM

Multiply

inch (in.) 

foot (ft) 

mile (mi)

square mile (mi2)

inch per hour (in/hr) 

cubic foot per second (ft3/s) 

cubic foot per second per square mile [(fr/s)/mr]

By

25.4 

0.3048 

1.609

2.590

25.4 

0.02832 

0.01093

To obtain

millimeter 

meter 

kilometer

square kilometer

millimeter per hour 

cubic meter per second 

cubic meter per second per square kilometer

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1 929 a geodetic datum 

derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea 

Level Datum of 1929.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware
GLOSSARY

Crest-stage station. A stream site where information is collected systematically only on peak stage and 

discharge.

Cubic feet per second. A unit of measurement for water discharge. One cubic foot per second is equal to 

the discharge of a stream at a rectangular cross section 1 foot wide and 1 foot deep, flowing at an 

average velocity of 1 foot per second. Equivalent to 448.8 gallons per minute.

Cubic feet per second per square mile. The average number of cubic feet of water flowing per second 

from each square mile of area drained, assuming that the runoff is distributed uniformly in time and 

area.

Floodmark. A mark showing the highest level reached by a flood water, sometimes referred to as a "highwater mark."

Flood stage. The approximate stage of a stream at which property damage would begin.

Isohyetal. A contour line drawn on a map which connects points receiving equal rainfall.

Peak stage. The highest value of stage attained during a flood.

Recurrence interval. The average number of years between occurrences of an annual peak flood or storm 

greater than or equal to a specified magnitude. Because of the random nature of flood events, the times 

between annual peak discharges of a specified magnitude may differ greatly from the average. In any 

given year, the chance that the annual peak flow will exceed the discharge with a specified recurrence 

interval is the reciprocal of (or one divided by) the recurrence interval. In any year, for example, there 

is 1 chance in 100 that the annual peak flow will exceed the flow with a 100-year recurrence interval 

(the 100-year flood).

Runoff. That part of the precipitation that appears in surface-water bodies.

Stage. Height of the water surface in a river above a predetermined point that may be on or near the 

channel floor. Used interchangeably with gage height. In this report, stage is given in feet.

Station number. Identification numbers assigned by the U.S. Geological Survey to streamflow-gaging 

stations in a downstream direction along the main stream. Stations on tributaries are assigned numbers 

based on the location where they enter the main stream.

Streamflow-gaging station. A site on a stream, canal, lake, or reservoir where systematic observations of 

stage or discharge are made.

vi Storm and flood of July 5,1989, in Northern New Castle County, Delaware
STORM AND FLOOD OF JULY 5,1989, IN NORTHERN 

NEW CASTLE COUNTY, DELAWARE

By Gary N. Paulachok, Robert H. Simmons, and Anthony J. Tallman

ABSTRACT

On July 5, 1989, intense rainfall from the remnants of Tropical Storm Allison caused severe 

flooding in northern New Castle County, Delaware. 

The flooding claimed three lives, and damage was 

estimated to be $5 million. Flood conditions were 

aggravated locally by rapid runoff from expansive 

urban areas.

Rainfall developed from convcctive uplift in a 

regional trough of low pressure that extended over 

northern Delaware. Because upper-level winds 

were weak, the storm remained virtually stationaiy 

and produced substantial amounts of rain. At the 

New Castle County Airport, 6.63 in. (inches) of 

rainfall was recorded on July 5, 1989, the greatest 

24-hour amount ever measured officially at that location. A total of more than 9 in. of rainfall was reported unofficially at Arden, Delaware, and Carneys 

Point, New Jersey, during July 4-6, 1989.

Peak discharges at three active, continuousrecord strcamflow-gaging stations in northern New 

Castle County exceeded previously recorded maximums. Estimated recurrence intervals for peak flow 

at these stations exceeded 100 years. Peak 

streamflow at Shellpot Creek at Wilmington was 

8,040 ft-Vs (cubic feet per second) at a stage of 

13.76 ft (feet). This discharge was about 30 percent 

greater than the 100-year flood, exceeding the

previous flood of record, recorded in 1971, by 

1,190 ft-Vs and 1.8 ft in stage. The Christina River at 

Coochs Bridge peaked at 5,530 ft-Vs at a stage of 

13.12 ft. This discharge was about 10 percent greater than the 100-year flood, exceeding the previous 

flood of record, recorded in 1947, by 1,200 ft-Vs and 

0.7 ft in stage. White Clay Creek near Newark 

peaked at 11,600 ft-Vs at a stage of 16.55 ft. This discharge was about 10 percent greater than the 100- 

year flood, exceeding the previous flood of record 

(resulting from Hurricane Agnes, 1972) by 

2,500 ft-Vs; the 1989 and 1972 stages arc not comparable because the flood of 1972 was recorded at a 

site 0.5 miles upstream and at a datum of 2.6 ft higher than that of the current streamflow station. Peak 

discharges also exceeded previously recorded maximums at one active crest-stage station and at two 

discontinued streamflow-gaging stations.

The U.S. Geological Survey conducted comprehensive post-flood surveys to determine peak 

water-surface elevations that occurred on affected 

streams and their tributaries during the flood of 

July 5,1989. Detailed surveys were performed near 

bridge crossings to provide additional information 

on the extent and severity of the flooding and the effects of hydraulic constrictions on floodwaters. Selected data from the surveys arc included in this 

report.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 1
INTRODUCTION

On July 5, 1989, intense rainfall from the remnants of Tropical Storm Allison caused record-breaking floods in northern New Castle County, Del. The 

storm also caused floods in adjoining parts of southeastern Pennsylvania, northeastern Maryland, and 

southwestern New Jersey, and, on a broader scale, 

from northern Virginia to New York City.

During July 4-6, 1989, more than 9 in. of rain fell 

in a narrow band from Arden, Del., to Carneys Point, 

NJ. In Delaware, the maximum storm-total rainfall 

reported unofficially was 9.52 in. at a nonrecording 

rain gage at Arden. More than 8 in. of rain was measured or reported in the region encompassing northeastern New Castle County, southeastern Delaware 

County, Pa., and the vicinity of Penns Grove, N.J.

Record-breaking floods occurred on many streams 

in northern New Castle County. Flood discharges 

exceeded previously recorded maximums at three 

active, continuous-record streamflow-gaging stations, 

at one active crest-stage station, and at two discontinued streamflow-gaging stations. In Delaware, the 

flooding claimed three lives, and damage to private 

property, highways, and bridges was estimated to be 

$5 million (Office of the County Executive, New Castle County, oral commun., 1992).

This report complements an earlier report (Talley, 

1989) on the flood. That report presented basic data to 

allow for early release of information to the public. 

This report provides additional, verified data on the 

flood, including measurements of peak stage at bridge 

crossings on major streams.

Purpose and Scope

This report presents a summary of the storm and 

resultant flood of July 5, 1989, in northern New Castle 

County, Del. The report provides fundamental information on this extreme hydrologic event and forms a 

technical basis for planning and management of flood 

plains and stream corridors in the affected localities.

The report documents the distribution of rainfall at 

20 sites and peak stages and discharges for previous 

floods of record and the flood of July 5, 1989, at 12 

streamflow-gaging stations in the study region. The

report also documents the time series of flood stage and 

discharge at seven continuous-record streamflow-gaging 

stations in the study area, and presents data on peakflood stage at 67 bridge crossings on five major streams 

in that area. Data are shown on maps, graphs, and 

tables, and flood conditions and damage are illustrated 

by photographs.

Location of Study Area

The study area, or area of primary focus in this 

report, is in northern New Castle County, Del., and occupies about 256 mi2. The area is bounded on the west by 

the Maryland State line, on the north by the Pennsylvania State line, on the east by the Delaware River, and on 

the south extending from Delaware City through Kirkwood to the Maryland State line (fig. 1). Wilmington, 

Stanton, and Newark are the principal municipalities in 

the study area.

A study region broader in area than the study area 

was delineated for this report to incorporate supporting 

meteorologic and hydrologic data for localities in adjacent states. This region occupies about 600 mi2 and is 

approximately bounded on the southwest by Elkton, 

Md., on the northwest by Cochranville, Pa., on the northeast by Woodlyn, Pa., and on the southeast by Alloway, 

N.J. (fig. 1). The study area and study region arc situated in the Coastal Plain and Piedmont Physiographic 

Provinces.

Acknowledgments

The authors are grateful to the government agencies 

that provided supporting data on the meteorologic and 

hydrologic conditions of this flood, and to the private 

citizens who provided photographs of the flood damage. 

The U.S. Army Corps of Engineers, Philadelphia District, provided funding for post-flood surveys of peak 

stage in five major stream basins in northern New Castle County. The Corps of Engineers, along with the Delaware Geological Survey and other State and local 

agencies, provide continued support for the network of 

streamflow-gaging stations in Delaware. Franz 

Schaefer of the U.S. Army Corps of Engineers and William S. Schenck of the Delaware Geological Survey provided fundamental information on benchmarks used for 

the post-flood surveys. Marian D. Peleski of the 

National Weather Service furnished real-time

Storm and flood of July 5,1989, in northern New Castle County Delaware
[| Study

I Study region, includes study

75-45'

Base from U.S. Geological Survey, 1:100.000 012345 MILES

012345 KILOMETERS

Figure 1. Location of study area and study region.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 3
information on storm conditions during July 5, 1989, 

and provided much of the technical information contained in the Description of Storm section of this report. 

Denis C. Quinn, a private citizen, provided photographs 

of flood conditions and property damage in the Shellpot 

Creek Basin that are used in the report.

DESCRIPTION OF STORM

On July 5, 1989, the remnants of Tropical Storm 

Allison caused extensive flooding in northern New 

Castle County, Del. In late June 1989, the tropical 

storm moved inland from the Gulf of Mexico and dissipated rapidly over Texas. The moisture associated 

with the storm persisted over the Southeastern United 

States, however, through the end of June. By 

July 4, 1989, the moisture had drifted northward and 

spread across the mid-Atlantic region.

By early morning of July 5, 1989, the tropical 

moisture was well established over Delaware. On a 

larger scale, a weak trough of low pressure formed in 

the area extending from northern Virginia to New 

York City. Because upper-level winds were weak, 

convective uplift remained stationary and localized, 

and resulted in record rainfall and flooding at several 

localities in and around northern New Castle County. 

On July 5, 1989, a record 24-hour rainfall of 6.63 in. 

was measured officially at the New Castle County Airport.

Spatial Distribution of Rainfall

Rainfall for the storm period (July 4-6) varied considerably across the study region, and generally 

increased from west to east. Total amounts of rainfall 

for the 3-day period rather than daily amounts are presented in this section because of inconsistencies in 

observation times for recording and nonrecording rain 

gages (table 1), and the resultant general incomparability of daily amounts.

Total rainfall in the study region ranged from 3.65 

in. at Kennett Square, Pa., to 9.52 in. at Arden, Del. 

(table I). The greatest amounts, more than 9 in., were 

concentrated in a narrow band trending from north to 

south and extending from Arden, Del., to Carneys

Point, N.J. (fig. 2). More than 8 in. of rain was measured 

or reported in a broader area encompassing parts of northeastern New Castle County, southeastern Delaware 

County, Pa., and adjacent parts of New Jersey (fig. 2). 

During July 4-6, 1989, average rainfall in the study area, 

as estimated by isohyetal analysis (Bedient and Huber, 

1988, p. 27), was about 6.5 in.

Temporal Distribution of Rainfall

The rainfall produced by the remnants of Tropical 

Storm Allison persisted in the study area from July 4 to 

July 6, 1989. The temporal (chronological) pattern of 

rainfall was recorded officially by rain gages at the University Farm in Newark and the New Castle County Airport in New Castle (table 1; fig. 2).

By July 4, the moisture associated with the tropical 

storm moved into the mid-Atlantic region. Localized 

thunderstorms developed early afternoon on July 4 and 

produced a reported 2 to 4 in. of rain in the vicinity of 

Elkton, Md. (M.D. Peleski, National Weather Service, 

written commun., 1990). Rainfall varied considerably 

over the study area, however, as indicated by official 

measurements of 0.90 in. at the University Farm and 

0.24 in. at the New Castle County Airport (table 2; fig. 

3).

By 0200 hours on July 5, heavy rain developed over 

a widespread area of Maryland and Virginia and intensified as it moved northeasterly toward northern Delaware. Rain spread over the study area by 0600 hours 

and continued at moderate to high intensities through 

mid-day (fig. 3). From 0600 to 1200 hours, rainfall 

intensity at the University Farm ranged from 0.10 to 

1.20 in/hr and averaged about 0.61 in/hr; rainfall intensity at the New Castle County Airport ranged from 0 to 

1.64 in/hr and averaged about 0.90 in/hr. Rainfall intensity was greatest during 1000 to 1100 hours at the University Farm, and during 0700 to 0800 hours at the New 

Castle County Airport. The rain on July 5 ceased by 

early afternoon. On July 6, an additional 0.30 in. and 

0.26 in. of rainfall was measured at these sites, respectively, resulting in 3-day storm-total amounts of 5.80 in. 

at the University Farm and 7.13 in. at the New Castle 

County Airport (table 2; fig. 3).

Storm and flood of July 5,1989, in northern New Castle County Delaware
Table 1. Rainfall data for sites in the study region, July 4-6,1989

o

[ = degrees;' = minutes; > = greater than; in. = inches; = no data; e.d.t. = eastern daylight time; NWS = National Weather Service; 

Locations shown in figure 2]

Site 

no.

Location Latitude Longitude Date

Time of 

observation 

(e.d.t.)

Rainfall2 

(in.)

Type of 

rain gage/ 

Remarks

New Castle County, Delaware

1

2

3

4

5

6

7

8

9

10

11

Arden

Christiana

Choate

Claymont

Glasgow

Mt. Cuba

Newark 

(University Farm)

New Castle 

(New Castle Co.) 

Airport)

Ogletown

Stanton

Wilmington 

(Porter Reservoir)

39° 49' 75° 29

39°39? 75°40' 7/4/89 

7/5/89 

7/6/89

39°42 75°4l'

39°48 75°28 7/4/89 

7/5/89 

7/6/89

39°36' 75°44 7/4/89 

7/5/89 

7/6/89

39°37 75°38 7/4/89 

7/5/89 

7/6/89

39°40' 75°44 7/4/89 

7/5/89 

7/6/89

39°40' 75°35' 7/4/89 

7/5/89 

7/6/89

39° 39* 75° 42 7/4/89 

7/5/89

39°42' 75°38 7/4/89 

7/5/89

7/6/89

39°46' 75°32 7/4/89 

7/5/89 

7/6/89

-

0700 

0700 

0700

-

0800 

0800 

0800

0800 

0800 

0800

0800 

0800 

0800

3 2400 

3 2400 

3 2400

3 2400 

3 2400 

3 2400

~

0700 

0700

0700

3 2400 

3 2400 

3 2400

9.52

0.00 

.66 

6.07

6.73

>6

0.00 

4.75 

3.80

8.55

0.00 

3.75 

1.80

5.55

0.00 

3.00 

3.35

6.35

0.90 

4.60 

.30

5.80

0.24 

6.63 

.26

7.13

0.60 

4.85

5.45

0.00 

.37

6.43

6.80

0.24 

6.15 

.36

6.75

Nonrecording

Nonrecording

Nonrecording

Nonrecording

Nonrecording

Nonrecording

Recording; 

NWS Station no. 

07 6410 01

Recording; 

NWS Station no. 

07 9595 01

Nonrecording

Nonrecording

Recording; 

NWS Station no. 

07 9605 01

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 5
Table l.--Rainfall data for sites in the study region, July 4-6, 1989-Continued

Site Location 

no.

Latitude Longitude Date

Time of 

observation Rainfall 

(e.d.t.) (in.)

Type of 

rain gage/ 

Remarks

New Castle County, Delaware Continued

12 Wooddale

13 Yorklyn

39°45f 75°38'

39°48 75°4l'

7/4/89

7/5/89

7/6/89

-

0730

0730

0730

--

0.00

.76

5.56

6.32

5.50

Nonrecording

Nonrecording

Chester County, Pennsylvania

14 Kennett Square

15 London Grove

16 Mendenhall

17 Toughkenamon

39°53 75°4l'

39°52 75°47

39°49 75°38

39°49 75°44

-

7/4/89

7/5/89

7/4/89

7/5/89

7/5/89

7/4/89

7/5/89

7/6/89

-

0100

0715

1200

0800

0800

0800

3.65

1.10

2.68

3.78

0.49

.41

4.48

5.38

0.00

2.60

2.50

5.10

Nonrecording

Nonrecording

Nonrecording

Nonrecording

Delaware County, Pennsylvania

18 Chadds Ford

19 Marcus Hook

39°52 75°37

39°49 75°25

7/4/89 

7/5/89 

7/6/89

7/4/89 

7/5/89 

7/6/89

3 0700 

3 0700 

3 0700

3 2400 

3 2400 

3 2400

0.45 

4.15

4.60

0.39 

7.50 

.18

8.07

Recording; 

NWS Station no. 

36 1342 03

Recording; 

NWS Station no. 

36 5390 03

Salem County, New Jersey

20 Cameys Point 39°42 75°30' 7/5/89 - 9.22 Nonrecording

Location of nearest principal locality.

Daily amounts listed where known. In some cases, only storm totals are known. 

 Eastern Standard Time.

Storm and flood of July 5,1989, in northern New Castle County, Delaware
O 1 2 3 4 5 MILES I H-i i 1 i 'i ' '

012345 KILOMETERS

75°3O' Base from US. Geological Survey 1 tOO.OOO 1984

Figure 2. Location of rain gages and distribution of rainfall, July 4-6, 1989.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 7
Table 2.~Hourly and cumulative rainfall at the University Farm, Newark, Delaware, and the New Castle 

County Airport, New Castle, Delaware, July 4-6,1989

[Station numbers assigned by National Weather Service; e.s.t. = eastern standard time; Rainfall amounts in inches; Locations shown in 

figure 2]

Time 

Date (e.s.t.)

July 4 - 0100 

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

July 5 - 0100 

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

University Farm 

(Station 07641001

Hourly

0.00 

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.20

.50

.10

.00

.00

.00

.00

.00

.10

.00

.00

.00 

.00

.00

.00

.00

.20

.80

1.00

.50

1.20

.50

.10

.20

.10

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

Cumulative

0.00 

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.20

.70

.80

.80

.80

.80

.80

.80

.90

.90

.90

.90 

.90

.90

.90

.90

1.10

1.90

2.90

3.40

4.60

5.10

5.20

5.40

5.50

5.50

5.50

5.50

5.50

5.50

5.50

5.50

5.50

5.50

5.50

New Castle County Airport 

(Station 07959501)

Hourly

0.00 

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.06

.11

.05

.01

.00

.00

.00

.01

.00

.00

.00

.00

.00 

.00

.00

.00

.21

.95

1.64

1.30

1.00

1.07

.00

.42

.03

.00

.00

.00

.00

.00

.01

.00

.00

.00

.00

.00

Cumulative

0.00 

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.06

.17

.22

.23

.23

.23

.23

.24

.24

.24

.24

.24

.24 

.24

.24

.24

.45

1.40

3.04

4.34

5.34

6.41

6.41

6.83

6.86

6.86

6.86

6.86

6.86

6.86

6.87

6.87

6.87

6.87

6.87

6.87

8 Storm and flood of July 5,1989, in northern New Castle County, Delaware
Table 2.~Hourly and cumulative rainfall at the University Farm, Newark, Delaware, and the New Castle 

County Airport, New Castle, Delaware, July 4-6,1989-Continued

Time 

Date (e.s.t.)

July 6 - 0100 

0200

0300

0400

0500

0600

0700

0800

0900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

University Farm 

(Station 07641001

Hourly

.00 

.00

.00

.00

.00

.00

.00

.10

.00

.00

.10

.10

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

Cumulative

5.50 

5.50

5.50

5.50

5.50

5.50

5.50

5.60

5.60

5.60

5.70

5.80

5.80

5.80

5.80

5.80

5.80

5.80

5.80

5.80

5.80

5.80

5.80

5.80

New Castle County Airport 

(Station 07959501)

Hourly

.00 

.00

.00

.00

.00

.01

.03

.05

.04

.04

.04

.02

.01

.00

.00

.00

.00

.00

.02

.00

.00

.00

.00

.00

Cumulative

6.87 

6.87

6.87

6.87

6.87

6.88

6.91

6.96

7.00

7.04

7.08

7.10

7.11

7.11

7.11

7.11

7.11

7.11

7.13

7.13

7.13

7.13

7.13

7.13

DESCRIPTION OF FLOOD

The intense rainfall from the remnants of Tropical 

Storm Allison caused severe flooding in northern New 

Castle County. The flooding claimed three lives and 

caused extensive damage to public and private property. Flood damage to property, highways, and bridges 

in the study area totaled about $5 million. Damage was 

particularly severe in the highly urbanized Shellpot and 

Little Mill Creek Basins. Floodwaters from Shellpot 

Creek swept away several vehicles, dislodged large sections of concrete curbing and sidewalk, and damaged 

public and private property in the Wilmington area. 

Floodwaters from Little Mill Creek forced evacuation of 

600 residents from an apartment complex in Elsmere, 

and destroyed 39 basement units in the complex. Damage in less urbanized drainage basins also was considerable. The photographs on the cover of this report 

and in figures 4-9 show flood conditions and property 

damage in the study area.

Peak Stage and Discharge at StreamflowGaging Stations

Peak stage and discharge on July 5, 1989, was 

recorded or measured at eight active continuousrecord streamflow-gaging stations, one active creststage station, and three discontinued recording stations (table 3). The location of these stations is shown 

in figure 10.

Storm and flood of July 5,1989, in northern New Castle County, Delaware
National Weather Service 

Station No. 07641001 

University Farm 

Newark, Del.

5.80

0100 0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 

HOURS (Eastern daylight time)

July 4,1989 JulyS. 1989 July 6,1989

0

0100

National Weather Service 

Station No. 07959501 

New Castle County Airport 

New Castle, Del.

7.13

0600 1200 1800 2400 0600 1200 1800 2400 0600 1200 1800 2400 

HOURS (Eastern daylight time)

July 4, 1989 July 5, 1989 July 6, 1989

Explanation 

| Hourly

 O Cumulative

Figure 3. Hourly and cumulative rainfall at the University Farm, Newark, Delaware, and the New Castle County Airport, New 

Castle, Delaware, July 4-6, 1989.

Peak discharge exceeded previously recorded maximums at continuous-record stations on Shellpot Creek, 

Christina River, and White Clay Creek. Estimated recurrence intervals for peak flow at these stations exceeded 

100 years. The recurrence interval for the peak discharge on Shellpot Creek was estimated using the methods presented in Sauer and others (1983). These 

methods were developed specifically for evaluating the 

flood-flow characteristics of streams in urban areas in 

the United States. Recurrence intervals for the other 

streams were estimated using a log-Pearson Type III 

analysis; this analysis is commonly used for evaluating 

the flood-flow characteristics of streams in basins that 

have not been highly urbanized.

Peak streamflow at Shellpot Creek at Wilmington 

was 8,040 frVs, or about 1,100 (ftVs)/mi2, at a stage of 

13.76 ft. This discharge was about 30 percent greater 

than the 100-year flood, and 1,190 ftVs more and the 

stage 1.8 ft higher than the previous flood of record in 

1971. The Christina River at Coochs Bridge peaked 

at 5,530 ft3/s, or 270 (ftVs)/mi2, at a stage of 13.12 ft. 

This discharge was about 10 percent greater than the 

100-year flood, and 1,200 fi*/s more and the stage 

0.7 ft higher than the previous flood of record in 

1947. White Clay Creek near Newark peaked at 

11,600 ftYs, or 130 (ftVs)/mi2, at a stage of 16.55 ft. 

This discharge was about 10 percent greater than the 

100-year flood and 2,500 ftVs more than the previous

10 Storm and flood of July 5,1989, in northern New Castle County, Delaware
Figure 4. White Clay Creek flooding at Stanton, Delaware, on July 5,1989. View looking downstream, right bank flood plain.

Figure 5. Submergence of concrete-arch bridge along old Route 7 by floodwaters of White Clay Creek at Stanton, Delaware. 

(Note debris accumulated against bridge.) View looking downstream.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 11
Figure 6. Damage to highway bridge and sidewalk from flooding of Shellpot Creek. Wilmington, Delaware. (View looking 

northeast along Market Street. [Photograph by Denis C. Quinn, private citizen.])

Figure 7. Damage to highway and and parking lot caused by flooding of Shellpot Creek, Wilmington, Delaware. (View 

looking southwest along Market Street. [Photograph by Denis C. Quinn, private citizen.])

12 Storm and flood of July 5,1989, in northern New Castle County, Delaware
Figure 8. Floodwaters from Shellpot Creek at Market Street Shopping Center, Wilmington, Delaware. (View looking northeast 

from left bank. [Photograph by Denis C. Quinn, private citizen.])

Figure 9. Floodwaters from White Clay Creek at Stanton, Delaware. (View looking downstream, right bank flood plain.)

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 13
Table 3. Peak stages and discharges for previous flood of record and flood of July 5,1989

[mi = square n liles; ft = foot; ft" /s = cubic foot per second; (ft /s)/mi) = cubic foot per second per square mile; > = greater than; < = less 

than; = no data; Locations shown in figure 10]

Station

no.

1 01477800

01478000

01478040

401478500

401478950

^1479000

^1480000

^14800 15

401480100

1 01481000

^1481500

'01495000

Station name

and location

Shell pot Creek

at Wilmington,

Del.

Christina River

at Coochs

Bridge, Del.

Christina River

near Bear, Del.

White Clay Creek

above

Newark, Del.

Pike Creek near

Newark, Del.

White Clay

Creek near

Newark, Del.

Red Clay Creek

at Wooddale,

Del.

Red Clay Creek

near Stanton,

Del.

Little Mill Creek

at Elsmere,

Del.

Brandywine

Creek at

Chadds

Ford, Pa.

Brandywine

Creek at

Wilmington,

Del.

Big Elk Creek

at Elks

Mills, Md.

Drainage

area

. .2.

(mi )

7.46

20.5

40.6

66.7

6.04

89.1

47.0

52.4

6.70

287

314

52.6

Period

of

record

(Water

years)

1945-89

1943-89

1979-82 ';

1983-89

1952-59;

1962-80

1969-75

1931-36;

1943-57;

1959-89

1943-89

1988-89

1963-80

1911-53;

1962-89

1946-89

1932-89

Previous flood of record Flood of lulv 5. 1989

Discharge Discharge

Stage Stage

T T O T ~J }

Date (ft) (ft /s) [(ft /s)/mi )] (ft) (fr /s) [(fr /s)/mi )]

DELAWARE RIVER BASIN

9/13/71 11.91 6,850 918 13.76 8,040 1,080

5/01/47 12.41 4,330 211 13.12 5,530 270

5/19/88 11.57 3,480 85.5 14.34 7,500 185

6/22/72 13.77 10,200 153 5 10.4 4,910 73.6

7/28/69 9.15 2,550 422 5 11.3 5,450 902

6/22/72 3 17.74 9,080 102 16.55 11,600 130

7/21/75 10.32 5,010 107 8.59 3,860 82.1

19.35 5,320 102

8/10/67 8.58 3,960 591 58.8 4,400 657

6/22/72 16.56 23,800 82.9 8.94 5,230 18.2

6/23/72 15.49 29,000 92.4 9.94 9,850 31.4

ELK RIVER BASIN

7/05/37 514.5 10,600 202 8.64 5,030 95.6

Recurrence

interval

(years)

>100

>100

-

>7

100

>100

>10

__

45

_

3

5

Active continuous-recording gage. 

Active crest-stage station.

At previous site 0.5 mi upstream and datum 2.6 ft higher than present datum. 

Discontinued recording gage. 

" From floodmark.

14 Storm and flood of July 5,1989, in northern New Castle County, Delaware
*\

J? E N N

M A R 't I A I

273>

,0 (896

EXPLANATION

j^^778 Active continuous-recording gage. 

A ^785 Discontinued recording gage 

^478040 Active crest-stage station

NOTE

Station numbers are those assigned by the U S Geological Survey 

and are abbreviated The first two digits {part number) and the last 

two digits (if zero) are omitted Example Station number 01479000 

is shown as 4790: Station number 01480015 is shown as 48O015 

Table 3 gives complete station numbers, station numbers, and 

other hydrologic information tor stations

75"45'

Base from U.S Geological Survey. 1:100.000 0123

012315 KILOMETERS

Figure 10. Location of stream stage and discharge measuring stations.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 15
flood of record in 1972. The flood of 1972 was 

observed at a previously operated streamflow-gaging 

station 0.5 miles upstream from and at datum 2.6 ft 

higher than the present station.

Peak discharge exceeded the previously recorded 

maximum at one active crest-stage station. The Christina River near Bear peaked at 7,500 ftVs, or 

185 (ft3/s)/mi2, at a stage of 14.34 ft. This discharge 

was about 4,000 fWs more and the stage 2.8 ft higher 

than the previous flood of record in 1988.

Peak discharge also exceeded previously recorded 

maximums at two discontinued streamflow-gaging stations. Peak streamflow at Pike Creek near Newark 

was 5,450 ftVs, or about 900 (ft3/s)/mi2 , at a stage of 

about 11.3 ft. This discharge was 2,900 ftVs more 

and the stage about 2.2 ft higher than the previous 

flood of record in 1969. Little Mill Creek at Elsmere 

peaked at 4,400 ftVs, or about 660 (ftVs)/mi2, at a 

stage of about 8.8 ft. This discharge was about 

440 ftVs more and the stage about 0.2 ft higher than 

the previous flood of record in 1967.

Selected values of stage and discharge for the 

period July 4-6, 1989, are presented in tables 4-10 for 

the active continuous-record streamflow-gaging stations on Shellpot Creek, Brandywine Creek, Red Clay 

Creek, White Clay Creek, and Christina River. All 

available values of discharge, recorded at a 5-minute 

frequency at Shellpot Creek at Wilmington and at a 

15-minute frequency at the other six continuousrecord stations in the study area, were used to prepare 

the hydrographs presented in figures 11-17. Comparison of the discharge hydrographs shows significant 

differences in streamflow response to rainfall. These 

differences are attributable mainly to differences in 

land use, size, and morphology of the drainage basins.

Table 4.~Selected values of stage and discharge foi 

Station 01477800 Shellpot Creek at 

Wilmington, Delaware, July 4-6,1989

[e.d.t. = eastern daylight time; ft = foot; ft" /s = cubic foot per 

second]

Date

July 4 

July 5 _ 

July 6 - -

Time 

(e.d.t.)

0600

1200

1800

2400

0600

0700

0715

0730

0745

0800

0815

0830

0845

0850

0855

0900

0905

0910

0915

0920

0925

0930

0935

0940

0945

0950

0955

1000

1005

1010

1015

1020

1025

1030

1035

1040

1045

1050

1055

1100

1105

1110

1115

1120

1125

1130

1135

1140

1145

1150

1155

1200

1215

1230

1245

1300

1315

1330

1345

1400

1415

1430

1500

1530

1600

1700

1800

2000

2200

2400

0200

0400

0600

1200

1800

2400

Stage 

(ft)

1.53

1.54

1.68

1.70

1.62

2.38

2.83

3.43

4.21

5.75

6.70

7.46

9.31

10.23

11.10

11.70

12.09

12.36

12.55

12.71

12.88

13.01

13.17

13.34

13.51

13.63

13.71

13.76

13.76

13.72

13.67

13.49

13.36

13.23

13.09

12.99

12.87

12.78

12.67

12.50

12.30

12.14

11.95

11.71

11.44

11.18

10.85

10.53

10.17

9.89

9.57

9.23

7.94

6.31

5.20

4.79

4.30

4.25

4.21

4.31

4.22

4.05

3.62

3.29

3.08

2.84

2.70

2.47

2.34

2.23

2.14

2.08

2.00

2.05

1.92

1.89

Discharge 

(ft3 /s

1.2

1.3

5.0

5.8

2.9

78

210

481

925

1,850

2,510

3,130

4,810

5,b60

6,270

6,690

6,960

7,130

7,260

7,360

7,470

7,560

7,660

7,770

7,880

7,960

8,010

8,040

8,040

8,020

7,990

7,870

7,780

7,700

7,610

7,540

7,470

7,410

7,340

7,220

7,100

6,990

6,870

6,700

6,500

6,320

6,090

5,870

5,620

5,390

5,060

4,730

3,550

2,220

1,490

1,250

974

947

925

980

931

829

585

409

309

203

147

76

50

36

26

21

15

18

17

15

16 Storm and flood of July 5,1989, in northern New Castle County Delaware
Table 5. Selected values of stage and discharge for 

Station 01481500 Brandywine Creek at 

Wilmington, Delaware, July 4-6,1989

[e.d.t. = eastern daylight time; ft = foot; ft~ /s = cubic foot per 

second]

Date

July 4 

July 5 -

July 6

Time 

(e.d.t.)

0600

1200

1800

2000

2200

2400

0200

0400

0600

0700

0730

0800

0830

0900

0930

1000

1015

1030

1045

1100

1115

1130

1145

1200

1215

1230

1245

1300

1315

1330

1345

1400

1415

1430

1445

1500

1515

1530

1545

1600

1615

1630

1645

1700

1730

1800

1830

1900

1930

2000

2030

2100

2130

2200

2300

2400

0300

0600

0900

1200

1500

1800

2100

2400

Stage 

(ft)

3.16

3.18

3.21

3.28

3.37

3.48

3.75

3.89

3.87

3.89

4.18

6.07

8.47

8.90

9.22

9.78

9.94

9.91

9.75

9.62

9.47

9.28

9.14

8.98

8.81

8.68

8.53

8.43

8.33

8.25

8.20

8.12

8.08

8.03

7.96

7.92

7.90

7.88

7.85

7.81

7.78

7.75

7.72

7.70

7.72

7.69

7.67

7.69

7.70

7.71

7.72

7.71

7.73

7.74

7.73

7.74

7.78

7.07

5.25

4.66

4.42

4.30

4.20

4.14

Discharge 

(ft3 /s

409

423

438

485

540

609

857

993

973

993

1,290

3,200

6,470

7,380

8,100

9,440

9,850

9,770

9,360

9,040

8,680

8,230

7,910

7,560

7,180

6,910

6,600

6,390

6,190

6,040

5,940

5,790

5,710

5,620

5,490

5,420

5,380

5,350

5,300

5,230

5,180

5,130

5,070

5,040

5,070

5,020

4,990

5,020

5,040

5,060

5,070

5,060

5,090

5,110

5,090

5,110

5,180

4,190

2,250

1,800

1,550

1,410

1,310

1,250

Table 6. Selected values of stage and discharge 

for Station 01480000 Red Clay Creek 

at Wooddale, Delaware, July 4-6,1989

[e.d.t. = eastern daylight time; ft = foot; ft /s = cubic foot per 

second]

Date

July 4 - 

July 5 

July 6 

Time 

(e.d.t.)

0600

1200

1800

2000

2200

2400

0200

0400

0600

0700

0730

0800

0830

0900

0930

1000

1015

1030

1045

1100

1115

1130

1145

1200

1215

1230

1245

1300

1315

1330

1345

1400

1415

1430

1445

1500

1515

1530

1545

1600

1615

1630

1645

1700

1730

1800

1830

1900

1930

2000

2030

2100

2130

2200

2300

2400

0300

0600

0900

1200

1500

1800

2100

2400

Stage 

(ft)

2.60

2.60

2.66

2.94

3.15

3.11

2.95

2.87

2.82

2.82

2.90

3.15

3.71

3.88

4.43

5.82

6.17

6.31

6.48

6.72

6.94

7.15

7.38

7.56

7.77

7.94

8.10

8.23

8.33

8.42

8.49

8.54

8.57

8.59

8.59

8.58

8.56

8.51

8.49

8.46

8.43

8.37

8.33

8.26

8.12

7.90

7.66

7.41

7.17

6.77

5.80

4.82

4.34

4.05

3.78

3.63

3.46

3.34

3.21

3.17

3.19

3.17

3.19

3.10

Discharge 

(ff /s)

48

48

58

129

215

196

131

108

93

93

118

210

530

638

970

1,860

2,100

2,200

2,320

2,490

2,660

2,810

2,980

3,110

3,270

3,400

3,520

3,610

3,680

3,740

3,790

3,820

3,840

3,860

3,860

3,850

3,830

3,800

3,790

3,770

3,750

3,700

3,680

3,630

3,530

3,370

3,190

3,000

2,820

2,530

1,850

1,220

916

748

573

482

379

312

241

225

230

225

230

191

Storm and flood of July 5,1989, in northern New Castle County, Delaware 17
Table 7. Selected values of stage and discharge 

for Station 01480015 Red Clay Creek 

near Stanton, Delaware, July 4-6, 1989

[e.d.t. = eastern daylight time; ft = foot; ft" /s = cubic foot per 

second]

Date

July 4 -

July 5- 

July 6 --

Time 

(e.d.t.)

0600 

1200 

1800 

2000 

2200 

2400

0200 

0400 

0600 

0700 

0730

0800 

0830 

0900 

0930 

1000

1015 

1030 

1045 

1100 

1115

1130 

1145 

1200 

1215 

1230

1245 

1300 

1315 

1330 

1345

1400 

1415 

1430 

1445

1500

1515 

1530 

1545 

1600 

1615

1630 

1645 

1700 

1730 

1800

1830 

1900 

1930 

2000 

2030

2100 

2130 

2200 

2300 

2400

0300 

0600 

0900 

1200 

1500 

1800 

2100 

2400

Stage Discharge 

(ft) (ft-/s

8.57 50 

8.58 51 

8.65 59 

8.69 64 

9.30 167 

10.25 362

9.43 191 

9.15 139 

9.02 114 

9.11 131 

9.98 296

12.35 945 

13.80 1,500 

15.30 2,270 

16.10 2,770 

16.80 3,250

17.00 3,400 

17.30 3,620 

17.50 3,770 

17.78 3,990 

17.96 4,130

18.14 4,280 

18.32 4,420 

18.50 4,580 

18.56 4,630 

18.62 4,680

18.74 4,780 

18.86 4,880 

18.96 4,970 

19.00 5,010 

19.06 5,060

19.13 5,120 

19.18 5,170 

19.22 5,200 

19.35 5,320 

19.32 5,300

19.28 5,260 

19.32 5,300 

19.30 5,280 

19.31 5,290 

19.34 5,310

19.27 5,250 

19.21 5,200 

19.17 5,160 

19.10 5,100 

18.90 4,920

18.70 4,750 

17.80 4,000 

17.32 3,630 

16.85 3,290 

16.38 2,960

15.90 2,640 

15.42 2,350 

14.95 2,070 

14.20 1,690 

13.30 1,280

11.33 644 

10.24 360 

10.01 302 

9.94 288 

9.89 278 

9.88 276 

9.90 280 

9.76 253

Table S. Selected values of stage and discharge for 

Station 01479000 White Clay Creek near 

Newark, Delaware, July 4-6, 1989

[e.d.t. = eastern daylight time; ft = foot; ft" /s = cubic foot per 

second]

Date Time Stage Discharge 

(e.d.t.) (ft) (ft /s)

July 4 - 0600 5.59 78 

1200 5.61 84 

1800 6.83 295 

2000 7.31 417 

2200 7.70 534 

2400 7.26 407

July 5 0200 6.92 319 

0400 6.64 255 

0600 6.46 222 

0700 6.98 330 

0730 8.46 785

0800 10.86 1,580 

0830 13.12 2,830 

0900 13.80 3,630 

0930 14.46 4,700 

1000 14.90 5,580

1015 15.12 6,180 

1030 15.36 6,990 

1045 15.59 7,850 

1100 15.82 8,800 

1115 16.16 10,200

1130 16.31 10,700 

1145 16.43 11,100 

1200 16.48 11,300 

1215 16.54 11,600 

1230 16.55 11,600

1245 16.53 11,500 

1300 16.55 11,600 

1315 16.43 11,100 

1330 16.37 10,900 

1345 16.23 10,400

1400 16.13 10,100 

1415 16.02 9,670 

1430 15.91 9,190 

1445 15.78 8,620 

1500 15.67 8,170

1515 15.58 7,810 

1530 15.52 7,580 

1545 15.41 7,170 

1600 15.34 6,920 

1615 15.24 6,570

1630 15.18 6,370 

1645 15.41 6,240 

1700 15.11 6,140 

1730 15.08 6,050 

1800 15.05 5,950

1830 15.02 5,860 

1900 14.96 5,710 

1930 14.93 5,650 

2000 14.88 5,540 

2030 14.80 5,370

2100 14.69 5,150 

2130 14.56 4,890 

2200 14.35 4,500 

2300 13.73 3,550 

2400 12.36 2,230

July 6 - 0300 8.80 906 

0600 8.14 668 

0900 7.85 559 

1200 7.89 573 

1500 7.87 566 

1800 7.75 518 

2100 7.60 462 

2400 7.46 411

18 Storm and flood of July 5,1989, in northern New Castle County Delaware
Table 9.-- Selected values of stage and discharge for 

Station 01478000 Christina River at 

Coochs Bridge, Delaware, July 4-6,1989

[e.d.t. = eastern daylight time; ft = foot; ft" /s = cubic foot per second]

Date

July 4

July 5

July 6- -

Time 

(e.d.t.)

0600

1200

1800

2000

2200

2400

0200

0400

0600

0700

0730

0800

0830

0900

0930

1000

1015

1030

1045

1100

1115

1130

1145

1200

1215

1230

1245

1300

1315

1330

1345

1400

1415

1430

1445

1500

1515

1530

1545

1600

1615

1630

1645

1700

1730

1800

1830

1900

1930

2000

2030

2100

2130

2200

2300

2400

0300

0600

0900

1200

1500

1800

2100

2400

Stage 

(ft)

3.37

3.38

8.16

7.46

5.63

4.82

4.38

4.12

4.01

7.42

9.86

10.72

11.04

11.20

11.40

11.64

11.85

11.76

12.01

12.19

12.16

12.17

[2.34

12.28

12.47

12.46

12.81

12.72

12.94

12.94

12.95

12.98

13.04

13.12

13.05

12.96

12.96

12.89

12.82

12.64

12.51

12.39

12.26

12.16

11.84

11.43

10.98

10.54

10.17

9.79

9.31

8.82

8.34

7.99

7.51

7.19

6.53

6.15

6.10

6.61

7.10

6.48

6.04

5.74

Discharge 

(ft3 /s>

23

24

476

363

168

105

76

61

55

358

1,020

1,810

2,140

2,310

2,610

3,070

3,480

3,300

3,820

4,230

4,160

4,180

4,430

4,350

4,600

4,590

5,080

4,950

5,260

5,260

5,280

5,320

5,410

5,530

5,430

5,290

5,290

5,190

5,090

4,840

4,660

4,500

4,330

4,160

3,460

2,670

1,930

1,520

1,220

980

758

599

503

443

350

291

191

139

133

203

278

184

127

95

Table 10. -Selected values of stage and discharge 

for Station 01478040 Christina River 

near Bear, Delaware, July 4-6, 1989

[e.d.t. = eastern daylight time; ft

second]

Date Time 

(e.d.t.)

July

July

July

4 0600

1200

1800

2000

2200

2400

5 0200

0400

0600

0700

0730

0800

0830

0900

0930

1000

1015

1030

1045

1100

1115

1130

1145

1200

1215

1230

1245

1300

1315

1330

1345

1400

1415

1430

1445

1500

1515

1530

1545

1600

1615

1630

1645

1700

1730

1800

1830

1900

1930

2000

2030

2100

2130

2200

2300

2400

6 0300

0600

0900

1200

1500

1800

2100

2400

= foot; ft3 /s

Stage 

(ft)

1.31

1.31

2.18

3.87

4.57

4.88

4.86

4.53

4.09

4.36

4.95

5.48

5.82

6.18

6.54

6.95

7.18

7.41

7.61

7.81

8.06

8.34

8.67

9.04

9.48

9.94

10.47

11.00

11.44

11.84

12.22

12.56

12.84

13.11

13.35

13.58

13.71

13.87

13.99

14.08

14.17

14.25

14.38

14.33

14.34

14.24

14.11

13.94

13.71

13.44

13.16

12.87

12.56

12.27

11.70

11.14

9.44

7.95

6.78

5.92

5.55

5.16

5.02

4.70

= cubic foot per

Discharge 

(ft3 /s)

18

18

71

244

337

382

379

331

272

308

392

494

568

651

739

830

883

938

1,000

1,090

1,190

1,320

1,480

1,660

1,890

2,180

2,550

2,790

3,350

3,800

4,260

4,680

5,060

5,450

5,820

6,180

6,390

6,660

6,870

7,030

7,190

7,330

7,390

7,480

7,500

7,310

7,080

6,780

6,390

5,960

5,530

5,100

4,680

4,320

3,630

3,080

1,870

1,140

792

590

468

430

404

355

Storm and flood of July 5,1989, in northern New Castle County, Delaware 19
DISCHARGE, IN CUBIC FEET PER SECOND

fi) 

I

ofi)O8

CO

I

ONfaCD 9> "

*<" SJ.

* DO

o

CD O

CQ

O <D

DISCHARGE. IN CUBIC FEET PER SECOND

S 

O ej «; 

p 3- "c_ w E.cB

 < CD

oCD

DISCHARGE. IN CUBIC FEET PER SECOND

3

CQ

i

P CD 

CD 7TtuI3

CQ

 n CQ'

SJ 55' 

p §- "c_ 0) EcS

»< CD 

J> U)->. CD*0 CD 

2

' 3

OCD CDoQ. BLCD

DISCHARGE IN CUBIC FEET PER SECOND
2400 0600 1200 1800 2400

HOURS (Eastern daylight time)

0600 1200

a

O 4.000

Site (01478040)

2400 0600 1800 2400 0600 1200 1800 2400 0600 

HOURS (Eastern daylight time)

July 4,1989 July 5. 1989

Figure 15. Discharge at White Clay Creek near Newark, 

Delaware, July 4-6, 1989.

Figure 17. Discharge at Christina River near Bear, 

Delaware, July 4-6, 1989.

Site (01478000)

2400 0600 1200 1800 

HOURS (Eastern daylight tim

2400 0600 1800 2400

Peak Stage at Selected Sites

The U.S. Geological Survey conducted comprehensive post-flood surveys to determine peak watersurface elevations that occurred on affected streams 

and their tributaries during the flood of July 5, 1989, 

and to evaluate the physical and hydraulic characteristics of the stream channels. Detailed surveys were 

performed near bridge crossings to provide additional information on the extent and severity of 

flooding and the effects of hydraulic constrictions 

on floodwaters. Selected data from these surveys 

are presented in tables 11-15. Locations of the survey sites are shown in figures 18-22.

Julys, 1989

Figure 16. Discharge at Christina River at Coochs Bridge, 

Delaware, July 4-6, 1989.

Storm and flood of July 5,1989, In northern New Castle County, Delaware 21
Table 11. Peak flood stage at selected sites on Shellpot Creek, Delaware, July 5,1989

[All sites in Delaware; locations shown in figure 18]

Site

no.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Location

Amtrak railroad bridge at Wilmington

Governor Printz Boulevard (Route 13) highway bridge

at Wilmington

Lea Boulevard highway bridge at Wilmington

Colony Boulevard highway bridge at Wilmington

U.S. Geological Survey streamflow-gaging station

01477800 at Wilmington

Market Street highway bridge at Wilmington

Washington Street highway bridge at Wilmington

Shipley Road highway bridge at Wilmington

Carr Road highway bridge near Wilmington

Baltimore and Ohio railroad bridge near Wilmington

Baynard Boulevard highway bridge near Wilmington

Wilson Road highway bridge near Fairfax

Faulk Road (Route 261) highway bridge near Fairfax

Coachman Road highway bridge near Fairfax

Distance 

upstream 

from

mouth

miles)

1.4

1.6

1.7

1.9

2.3

2.5

3.0

3.1

3.3

3.9

4.3

5.0

5.4

6.0

Water-surface elevation, in feet 

(datum is sea level)

Upstream

13.1

18.6

20.0

27.0

,,

28.92

41.7

74.9

85.7

98.6

203.2

228.9

264.2

290.4

307.2

Downstream

10.7

14.2

18.6

26.0

31.6

67.9

77.2

92.8

199.3

223.5

262.5

288.4

304.7

Location of measurement at bridge crossing.

Recorded on water-stage recorder and adjusted to sea-level datum.

Table 12. ~Peak flood stage at selected sites on Red Clay Creek, Delaware, July 5,1989

(All sites in Delaware; locations shown in figure 19; = no data]

Site

no.

1

2

3

4

5

6

7

8

9

10

11

12

13

Location

Route 4 highway bridge at U.S. Geological Survey

streamflow-gaging station 01480015 near Stanton

Kiamensi Road highway bridge at Kiamensi

Baltimore and Ohio railroad bridge and dam at Kiamensi

Old Capital Trail highway bridge at Marshallton

Newport Road highway bridge near Cranston Heights

Kirkwood Highway (Route 2) bridge near Cranston Heights

Newport Gap Pike (Route 41 ) highway bridge near Faulkland

Greenbank Road highway bridge near Faulkland

Baltimore and Ohio railroad bridge near Faulkland

Baltimore and Ohio railroad bridge at Faulkland

Faulkland Road (Route 34) highway bridge at Faulkland

Baltimore and Ohio railroad bridge near Wooddale

Route 48 highway bridge at U.S. Geological Survey

streamflow-gaging station 01480000 at Wooddale

Distance 

upstream 

from

mouth

(miles)

0.9

1.5

1.6

1.8

1.9

2.3

2.6

2.8

2.9

3.4

3.6

4.3

4.9

Water-surface elevation, in feet 

(datum is sea level)

Upstream

20.5

25.8

35.8

38.3

39.8

50.9

55.6

56.1

58.1

70.3

72.7

86.0

J90.05

Downstream

219.35

-

37.7

39.6

45.9

53.0

56.4

68.2

71.6

85.0

89.7

Location of measurement at bridge crossing. 

.- Recorded on water-stage recorder. 

" Recorded on water-stage recorder and adjusted to sea-level datum.

22 Storm and flood of July 5,1989, in northern New Castle County, Delaware
Table l3.-Peak flood stage at selected sites on White Clay Creek, Delaware, July 5,1989

[All sites in Delaware; locations shown in figure 20]

Distance Water-surface elevation, in feet 

upstream (datum is sea level) 

from

Site 

no.

1

2

3

4

5

6

7

8

9

10

11

12

13

Location

Amtrak railroad bridge at Stanton

Abandoned Route 4 highway bridge at Stanton

Route 4 highway bridge at Stanton

Dam at Delaware Park near Stanton

Bridge on private road at Delaware Park at U.S. Geological Survey

streamflow -gaging station 01479000 near Newark

Baltimore and Ohio railroad bridge upstream from

Delaware Park near Newark

Old Harmony Road highway bridge near Newark

New Harmony Road highway bridge near Newark

Red Mill Road highway bridge near Newark

Kirkwood Highway (Route 2) bridge at Newark

Curtis Mill Road (Route 72) highway bridge at Newark

Dam 1.0 mile north of Newark

U.S. Geological Survey discontinued streamflow-gaging station

01478500 north of Newark

mouth 

(miles)

2.4

3.0

3.1

4.1

4.8

5.2

6.0

6.1

7.5

8.7

10.3

11.2

12.5

Upstream

15.9

18.2

18.4

23.5

27.2

30.4

33.0

33.6

41.5

50.1

68.0

78.7

89.0

Downstream

14.6

17.1

18.2

 > " *» 734 

-25.55

30.1

32.7

33.0

40.5

48.0

67.1

76.4

9 Location of measurement at bridge crossing.

" Recorded on water-stage recorder and adjusted to sea-level datum.

Table 14.~Peak flood stage at selected sites on Christina River, Delaware, July 5,1989

[AU sites in Delaware; locations shown in figure 21]

Site

no.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Location

Churchmans Road (Route 58) highway bridge

near Christiana (tidal marsh)

Route 7 highway bridge at Christiana

Route 273 highway bridge at Christiana

Smalleys Dam near Christiana

Walther Road highway bridge at U.S. Geological Survey

streamflow-gaging station 01478040 near Bear

Salem Church Road highway bridge near Coochs Bridge

Route 72 highway bridge at U.S. Geological Survey

streamflow-gaging station 01478000 at Coochs Bridge

Conrail railroad bridge at Coochs Bridge

Old Baltimore Pike highway bridge at Coochs Bridge

Dam northwest of Coochs Bridge

1-95 highway bridge near Newark

Route 896 highway bridge near Newark

Welsh Tract Road highway bridge near Newark

West Chestnut Hill Road highway bridge near Newark

Kirkwood Highway (Route 2) bridge at Newark

Barksdale Road highway bridge at Newark

Church Road highway bridge at Newark

Nottingham Road (Route 273) highway bridge near Newark

Wedgewood Road highway bridge near Newark

Distance 

upstream 

from

mouth

(miles)

10.1

13.8

14.4

15.2

17.0

19.2

21.7

21.8

22.4

22.9

Z3.0

23.4

23.6

23.9

26.1

27.2

28.1

28.3

29.5

Water-surface elevation, in feet 

(datum is sea level)

Upstream

9.7

14.8

16.1

17.1

T336

28.2

40.8

42.6

45.6

59.2

61.4

66.2

69.7

73.8

100.8

111.4

127.2

130.0

158.2

Downstream

9.1

14.4

15.5

16.7

23.3

-28.1

-38.66

40.8

43.4

53.9

59.2

64.6

68.2

71.2

98.3

108.6

126.3

128.6

157.6

 Location of measurement at bridge crossing. 

Recorded on water-stage recorder and adjusted to sea-level datum.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 23
Table 15. ~Peak flood stage at selected sites on Little Mill Creek, Delaware, July 5,1989

[All sites in Delaware; locations shown in figure 22]

Site

no.

1

2

3

4

5

6

7

8

Location

Amtrak railroad bridge near Elsmere

Maryland Avenue (Route 4) highway bridge at Elsmere

Dupont Road highway bridge at U.S. Geological Survey discontinued

streamflow-gaging station 01480100 at Elsmere

Wilmington Avenue (Route 2) highway bridge near Elsmere

Route 141 highway bridge near Elsmere

Faulkland Road (Route 34) highway bridge near Elsmere

Lancaster Pike (Route 48) highway bridge near Wilmington

Barley Mill Road highway bridge near VVooddale

Distance 

upstream 

from

mouth

(miles)

0.8

1.5

2.2

3.7

4.4

5.2

6.5

7.5

Water-surface elevation, in feet 

(datum is sea level)

Upstream

13.5

22.6

59.7

81.2

91.6

94.2

145.1

208.8

Downstream

9.8

22.4

57.4

80.8

88.7

90.9

139.6

201.9

Location of measurement at bridge crossing.

75°35' 75°30' 75325'

39°45'

EXPLANATION

10 Location of peak-stage survey sites 

referenced in Table 11.

Base from U.S. Geological Survey map 1:100,000,1984. 3 MILES

I

1 2 3 KILOMETERS

Figure 18. Location of peak-stage survey sites on Shellpot Creek in Delaware.

24 Storm and flood of July 5,1989, in northern New Castle County, Delaware
75a45' 75C40' 75°35'

39°50'-

39°45' -

9 Location of peak-stage survey sites 

referenced in Table 12.

Base from U.S. Geological Survey map 1:100,000,1984.

I I I I 

0123 KILOMETERS

Figure 19. Location of peak-stage survey sites on Red Clay Creek in Delaware.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 25
75°40'

39°45' -

39-40' -

10 Location of peak-stage survey sites 

referenced in Table 13.

Base from U.S. Geological Survey map 1:100,000,1984.

I I I I 

0123 KILOMETERS

Figure 20. Location of peak-stage survey sites on White Clay Creek in Delaware.

SUMMARY

On July 5, 1989, intense rainfall from the remnants 

of Tropical Storm Allison caused record-breaking 

floods in northern New Castle County, Delaware. In 

Delaware, the flooding claimed three lives and caused 

an estimated $5 million damage to private property, 

highways, and bridges. The storm also caused floods in 

adjoining parts of southeastern Pennsylvania, northeastern Maryland, and southwestern New Jersey, and, on a 

broader scale, from northern Virginia to New York City.

The amounts of rainfall increased from west to east 

across the study region. Officially, 6.63 in. of rainfall 

was recorded on July 5, 1989, at the New Castle County 

Airport, the greatest 24-hour amount ever measured at

that location. Unofficially, a total of 9.52 in. of rainfall was reported during July 4-6, i 989, at Arden, Delaware. In the study area, average rainfall from the 

storm, as estimated from isohyets, was about 6.5 in.

Peak stage and discharge on July 5, 1989, were 

recorded or measured at eight active continuousrecord streamflow-gaging stations, one active creststage station, and three discontinued recording stations.

Peak discharge at continuous-record stations on 

Shellpot Creek, Christina River, and White Clay 

Creek exceeded previously recorded maximums. Estimated recurrence intervals for peak flow at these stations exceeded 100 years. Peak streamflow at

26 Storm and flood of July 5,1989, in northern New Castle County, Delaware
75°45' 75°40' 75°35'

39°45' -

39°40'

13 ~ Location of peak-stage survey sites 

referenced in Table 14

Base from U.S. Geological Survey map 1:100,000,1984

0123 KILOMETERS

Figure 21. Location of peak-stage survey sites on Christina River in Delaware.

75°40' 75°35' 75°30'

39°45' -

8 ~~ Location of peak-stage survey sites 

referenced in Table 15

0123 KILOMETERS

Base from U.S. Geological Survey map 1:100,000,1984.

Figure 22. Location of peak-stage survey sites on Little Mill Creek in Delaware.

Storm and flood of July 5,1989, in Northern New Castle County, Delaware 27
Shellpot Creek at Wilmington was 8,040 ftVs, or 

about 1,100 (ft3/s)/mi2 , at a stage of 13.76 ft. This 

discharge was about 30 percent greater than the 

100-year flood, and 1,190 ftVs more and the stage

I.8 ft higher than the previous flood of record in 

1971. The Christina River at Coochs Bridge peaked 

at 5,530 ft3 /s, or 270 (fWsymi2, at a stage of 13.12 

ft. This discharge was about 10 percent greater than 

the 100-year flood, and 1,200 ftVs more and the 

stage 0.7 ft higher than the previous flood of record 

in 1947. White Clay Creek near Newark peaked at

II,600 ft3 /s, or 130 (ft3/s)/mi2, at a stage of 16.55 ft. 

This discharge was about 10 percent greater than 

the 100-year flood and 2,500 ftVs more than the previous flood of record in 1972. The flood of 1972 

was observed at a previously operated streamflowgaging station 0.5 miles upstream from and at 

datum 2.6 ft higher than the present station.

Peak discharge exceeded the previously 

recorded maximum at one active crest-stage station. The Christina River near Bear peaked at 

7,500 ftVs, or 185 (ftVs)/mi2, at a stage of 

14.34 ft. This discharge was about 4,000 ft3 /s 

more and the stage 2.8 ft higher than the previous 

flood of record in 1988.

Peak discharge also exceeded previously 

recorded maximums at two discontinued streamflow-gaging stations. Peak streamflow at Pike 

Creek near Newark was 5,450 ftVs, or about 

900 (ft3/s)/mi2, at a stage of about 11.3 ft. This 

discharge was 2,900 ftVs more and the stage 

about 2.2 ft higher than the previous flood of 

record in 1969. Little Mill Creek at Elsmere 

peaked at 4,400 ft3/s, or about 660 (ft3 /s)/mi2 , at a 

stage of about 8.8 ft. This discharge was about 

440 ft3/s more and the stage about 0.2 ft higher 

than the previous flood of record in 1967.

Following the flood, comprehensive field surveys were conducted on affected streams and their 

tributaries to determine peak water-surface elevations during July 5, 1989, and to evaluate the physical and hydraulic characteristics of the stream 

channels. Detailed surveys were performed near 

bridge crossings to provide additional information 

on the extent and severity of flooding, and the 

effects of hydraulic constrictions on floodwaters. 

Data from these surveys and the streamflow-gaging stations provide fundamental information on 

this extreme hydro logic event and form a technical basis for planning and management of flood 

plains and stream corridors in the affected localities.

28 Storm and flood of July 5,1989, in northern New Castle County Delaware
SELECTED REFERENCES

Bailey, J.F., Patterson, J.L., and Paulhus, J.L.H., 

1975, Hurricane Agnes rainfall and floods, 

June-July 1972: U.S. Geological Survey 

Professional Paper 924,403 p.

Bedient, P.B., and Huber, W.C., 1988, Hydrology 

and flood plain analysis: Reading, Mass., 

Addison-Wesley Publishing Co., 650 p.

Bogart, D.B., 1960, Floods of August-October 

1955, New England to North Carolina: 

U.S. Geological Survey Water-Supply 

Paper 1420, 854 p.

Carpenter, D.H., and Simmons, R.H., 1969, 

Floods of August 1967 in Maryland and 

Delaware: U.S. Geological Survey OpenFile Report, 98 p.

Rostvedt, J.O., 1965, Summary of floods in the 

United States during 1960: U.S. Geological Survey Water-Supply Paper 1790-B, 

147 p.

Sauer, V.B., Thomas, W.O., Jr., Stricker, V.A., 

and Wilson, K.V., 1983, Flood characteristics of urban watersheds in the United 

States: U.S. Geological Survey WaterSupply Paper 2207, 63 p.

Simmons, R.H., and Carpenter, D.H., 1978,

Technique for estimating magnitude and 

frequency of floods in Delaware: U.S. 

Geological Survey Water-Resources Investigations Open-File Report 78-93, 69 p.

Talley, J.H., 1989, The storm of July 5, 1989-

Hydrologic conditions: Delaware Geological Survey Open-File Report no. 31, 29 p.

U.S. Geological Survey, 1991, National water

summary 1988-89 Hydrologic events and 

floods and droughts: U.S. Geological Survey Water-Supply Paper 2375, 591 p.

U.S. National Oceanic and Atmospheric Administration, 1970-92, Climatological data 

annual summaries, Maryland and Delaware: Asheville, N.C., U.S. Department of 

Commerce, Climatic Data Center (variously paginated).

___ 1989, Climatological data, Maryland and

Delaware, July 1989: Asheville, N.C., U.S. 

Department of Commerce, National Climatic Data Center, v. 93, no. 7.

___ 1989, Climatological data, Pennsylvania, 

July 1989: Asheville, N.C., U.S. Department of Commerce, National Climatic Data 

Center, v. 94, no. 7.

___ 1989, Hourly precipitation data, Maryland 

and Delaware, July 1989: Asheville, N.C., 

U.S. Department of Commerce, National 

Climatic Data Center, v. 39, no. 7.

___ 1989, Storm data: Asheville, N.C., U.S. 

Department of Commerce, National Climatic Data Center, v. 31, no. 7.

Storm and flood of July 5,1989, in northern New Castle County, Delaware 29