FLOOD MAGNITUDE AND FREQUENCY OF 

FRANKLIN POND TRIBUTARY AT THE CULVERT 

ON NEW JERSEY ROUTE 23, FRANKLIN BOROUGH, 

SUSSEX COUNTY, NEW JERSEY 

u.s. GEOLOGICAL SURVEY 

Open-File Report 96-327 

Prepared in cooperation with the 

NEW JERSEY DEPARTMENT OF TRANSPORTATION 
FLOOD MAGNITUDE AND FREQUENCY OF 

FRANKLIN POND TRIBUTARY AT THE CULVERT 

ON NEW JERSEY ROUTE 23, FRANKLIN BOROUGH, 

SUSSEX COUNTY, NEW JERSEY 

By Thomas Barringer 

u.s. GEOLOGICAL SURVEY 

Open-File Report 96-327 

Prepared in cooperation with the 

NEW JERSEY DEPARTMENT OF TRANSPORTATION 

West Trenton, New Jersey 

1996 
u.s. DEPARTMENT OF THE INTERIOR 

BRUCE BABBln, Secretary 

u.s. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director 

For additional information Copies of this report can be 

write to: obtained from: 

District Chief U.S Geological Survey 

U.S Geological Survey Earth Science Information Center 

Mountain View Office Park Open-File Reports Section 

810 Bear Tavern Road, Suite 206 Box 25286, MS 517 

West Trenton, NJ 08628 Denver Federal Center 

Denver, CO 80225 
CONTENTS 

Page 

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

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

Methods for determining flood magnitude and frequency ............................................................................ 1 

New Jersey Department of Environmental Protection Special Report 38 method ........................................ 3 

Results ............................................................................................................................................................ 3 

Selected references ........................................................................................................................................ 6 

ILLUSTRATIONS 

Figure 1. Map showing location of Franklin Pond tributary at the culvert at milepost 32.2 on New 

Jersey Route 23 and associated drainage basin, Franklin Borough, New Jersey ............. 2 

TABLES 

Table 1. Explanatory variables for the flood-magnitude and -frequency analysis of Franklin Pond 

tributary at the culvert on New Jersey Route 23, milepost 32.2, Franklin Borough, New 

Jersey ................................................................................................................................... 4 

2. Estimates of flood magnitudes for selected flood frequencies for Franklin Pond tributary at the 

culvert on New Jersey Route 23, milepost 32.2, Franklin Borough, New Jersey ............... 5 

III 
CONVERSION FACTORS 

Multiply By To obtain 

foot (ft) 0.3048 meter 

mile (mi) 1.609 kilometer 

square mile (mi2) 2.590 square kilometer 

foot per mile (ftlmi) 0.189 meter per kilometer 

cubic foot per second (ft3 /s) 0.0283 cubic meter per second 

iv 
FLOOD MAGNITUDE AND FREQUENCY OF FRANKLIN POND 

TRffiUTARY AT THE CULVERT ON NEW JERSEY ROUTE 23, 

FRANKLIN BOROUGH, SUSSEX COUNTY, NEW JERSEY 

By Thomas Barringer 

ABSTRACT 

Flood magnitude and frequency values are presented for the Franklin Pond tributary at the culvert 

at milepost 32.2 of New Jersey Route 23, Franklin Borough, New Jersey. The values were determined by 

using New Jersey Department of Environmental Protection Special Report 38 method. A description of the 

drainage-basin characteristics also is included in this report. The 100-year-flood estimate is 218 cubic feet 

per second. 

INTRODUCTION 

Information on the magnitude and frequency of floods is critical to the planning and design of 

highway culverts and bridges. Such information is not readily available for many stream crossings in New 

Jersey. To fulfill this information need, the U.S. Geological Survey (USGS), in cooperation with the New 

Jersey Department of Transportation, began an analysis of flood data from stream-crossing sites on New 

Jersey streams. 

TrdS report presents results of the analysis for FrarJilin Pond tributary at the culvert at milepost 

32.2 of New Jersey Route 23, Franklin Borough, New Jersey. The culvert is located about one-half mile 

north of the electrical substation south of Franklin Borough, New Jersey (fig. 1). The drainage area 

upstream from the site is estimated to be 0.82 mi2, A field reconnaissance was performed on May 18, 

1995, to verify the location of the drainage-basin divide and basin characteristics. Because the upper part 

of the drainage basin is steep, heavily wooded, and roadless, the calculated drainage area is approximate. 

Part of the subject basin lies within Franklin Borough. The flood-insurance study for Franklin 

Borough, Sussex County, New Jersey, (Federal Emergency Management Agency, 1983) does not include a 

detailed study of this stream; therefore, flood discharges were not determined previously. 

METHODS FOR DETERMINING FLOOD MAGNITUDE AND FREQUENCY 

Various widely used methods for calculating flood magnitude and frequency were considered for 

use in determining the flood magnitudes that are likely to be exceeded at this site within a given number of 

years (recurrence interval). The rational method (Chow and others, 1988), New Jersey Department of 

Environmental Protection (NJDEP) Special Report 38 method (SR 38) (Stankowski, 1974), the U.S. Soil 

Conservation Service (SCS) Technical Release 55 (TR-55) method (U.S. Soil Conservation Service, 

1986), the USGS transfer method (New Jersey Department of Environmental Protection, 1988), and the 

index-flood method (Thomas, 1964) were all considered for use in determining flood magnitude and frequency at the subject culvert. 

1 
061~~~~~~~--~~~~~~~~~ 

Base from U.S. Geological Survey 1 :24,000, quadrangle, 

Franklin, 1954, photorevised 1971; Hamburg, 1954, photorevised 1971 

o 1 MILE 75' 74' 

I I 

I 

o 1 KILOMETER 

EXPLANATION 

_ •• - DRAINAGE-BASIN BOUNDARY 

o CULVERT SITE 

Figure 1. Location of Franklin Pond tributary at the culvert at milepost 32.2 on New Jersey 

Route 23 and associated drainage basin, Franklin Borough, New Jersey. 

2 
NEW JERSEY DEPARTMENT OF ENVIRONMENTAL PROTECTION SPECIAL 

REPORT 38 METHOD 

The Special Report 38 method (Stankowski, 1974) was developed for use with drainage basins of 

2 1 to 1,000 mi 2 . The subject basin has an area of 0.82 mi , but is sufficiently close to the 1 mi2 lower limit 

for this method to be acceptable. In addition, the estimates calculated with this method were in fairly close 

agreement with those made by using the USGS transfer method. 

Flood data from four streamflow gages located in basins with characteristics similar to the subject 

basin and located within a 41-mi radius of the culvert site were examined to determine whether the SR 38 

method provides reasonable estimates offlood magnitude when compared with USGS transfer method 

estimates of peak discharge. Flood magnitude and frequency computed by using the SR 38 method were 

also compared with estimates made by using the rational method and the TR-55 method. 

The estimates of the 100-year flood made for the New Jersey Route 23 site by using the rational 

method and the TR-55 method were 5.8 and 4.7 times, respectively, the estimates obtained by using the 

SR 38 method. The estimate of the I OO-year flood at the subject site using the SR 38 method was 1.3 times 

the average discharge estimate made by using the USGS transfer method with flood data from four gage 

sites (Furnace Brook at Oxford, New Jersey, station 01445490; Pequest River at Huntsville, New Jersey, 

station 01445000; Mulhockaway Creek at Van Syckel, New Jersey, station 01396660; and Quaker Creek at 

Florida, New York, station 01369500). The SR 38 estimate was chosen because of its close general agreement with the USGS transfer method estimates. Also, estimates made by using the rational and TR-55 

methods were not chosen because these methods produced overestimates offlood magnitude in some areas 

of New Jersey (R.D. Schopp, U.S. Geological Survey, oral commun., 1995). 

RESULTS 

Flood data from nearby streamflow or crest-stage gaging stations provide a good indication of the 

flood magnitude and frequency that can be expected at an ungaged site, particularly when the drainage area 

and other basin characteristics are similar. In this study, estimates obtained by using the New Jersey 

Department of Environmental Protection Special Report 38 method were compared with estimates made 

by using the USGS transfer method. In addition, the SR 38 estimate was compared with estimates made 

by using the rational method and the TR-55 method. 

Variables used In computing the SR 38 method flood-magnitude and -frequency estimates are 

listed in table 1. The estimates made by using the SR 38 method are listed in table 2. The estimate of the 

1 OO-year flood discharge at the culvert site is 218 ff Is. 

3 
Table 1. Explanatory variables for the flood-magnitude and -frequency analysis of Franklin Pond tributary 

at the culvert on New Jersey Route 23, milepost 32.2, Franklin Borough, New Jersey 

Drainage area: 0.82 square miles 

Latitude: 41 0 06' 31" 

Longitude: 740 34' 53" 

Highway: New Jersey Route 23 

Milepost: 32.2 

U.S.Geological Survey 7-1I2-minute quadrangles: Hamburg and Franklin, N.J. 

Variable Value Unit 

Drainage area 

Main-channel slope 

Surface-storage index 

Total stream length 

Population density (1990) 

Impervious cover 

Lake and swamp area 

= 

= 

= 

= 

= 

= 

= 

0.82 

447 

1l.0 

l.78 

385 

7.16 

10.0 

square miles 

feet per mile 

percent 

mile 

persons per square mile 

percent 

percent 

4 
Table 2. Estimates of flood magnitudes for selected fl'ood frequencies for Franklin Pond tributary at the 

culvert on New Jersey Route 23, milepost 32.2, Franklin Borough, New Jersey 

[Q, flood-magnitude estimates in cubic feet per second along with number, indicating recurrence interval 

in years; NJDEP, New Jersey Department of Environmental Protection; SR, Special Report]. 

Drainage area: 0.82 square miles 

Latitude: 41 ° 06' 31" 

Longitude: 74° 34' 53" 

Highway: New Jersey Route 23 

Milepost: 32.2 

U.S.Geological Survey 7-112-minute quadrangles: Hamburg and Franklin, N.J. 

Estimating method Q2 Q5 QIO Q25 Q50 QIOO 

NJDEP SR38 42 69 98 140 173 218 

5 
SELECTED ltEFERENCES 

Chow, Y.T., Maidment, D.R., and Mays, L.W., 1988, Applied hydrology: New York, McGraw-Hill, 572 p. 

Federal Emergency Management Agency, 1983, Flood insurance study of Franklin Borough, New Jersey: 

Federal Emergency Management Agency, September 15, 1983, 14 p., 3 pIs., 1 panel. 

New Jersey Deparunent of Environmental Protection, 1988, Technical manual for stream encroachment: 

New Jersey Department of Environmental Protection, Division of Water Resources, Bureau of 

Floodplain Management, 151 p. 6 app. 

Stankowski, SJ., 1974, Magnitude and frequency of floods in New Jersey with effects of urbanization: 

New Jersey Department of Environmental Protection, Special Report 38,46 p. 

Thomas, D.M., 1964, Floods in New Jersey, magnitude and frequency: New Jersey Department of 

Conservation and Economic Development, Water Resources Circular 13, 145 p. 

U.S. Soil Conservation Service, 1986, Urban hydrology for small watersheds: Engineering Division 

Technical Release 55, Washington, D.C., 162 p. 

6