Floods in New York, Magnitude

and Frequency

GEOLOGICAL SURVEY 

CIRCULAR 454

PREPARED IN COOPERATION WITH NEW YORK STATE
Floods in New York, Magnitude 

and Frequency

By F. Luman Robison

Prepared in cooperation with New York State

GEOLOGICAL SURVEY CIRCULAR 454

Washington 1961
United States Department of the Interior

STEWART 1. UDALL, SECRETARY

Geological Survey

THOMAS B. NOLAN, DIRECTOR

Free on application to the U.S. Geological Survey, Washington 25, D. C
CONTENTS

Page

Abstract.......................................................................................... J

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

Data used......................................................................................... 1

Types of flood series .............................................................................. 1

Computation of flood-frequency curves............................................................... 1

Regional flood-frequency curves.................................................................. 6

Hydrologic area curves.......................................................................... 6

The design flood. .................................................................................. 6

Determination of design flood .................................................................... 8

Conclusions. ...................................................................................... 9

Selected bibliography .............................................................................. 10

ILLUSTRATIONS

Figure 1. Map of New York showing location of gaging stations used in the analysis ..................... 5

2. Map of New York showing flood-frequency regions. ......................................... '

3. Frequency of annual floods. ............................................................... 7

4. Variation of mean annual flood with drainage area........................................... 8

5. Map of New York showing hydrologic areas ................................................ 9

TABLES

Table 1. Inventory of data used to define regional flood-frequency relations ........................... 2

III
Floods in New York, Magnitude and Frequency

By F. Luman Robison

ABSTRACT

This report presents a practical means of predicting the probable magnitude of floods on streams 

in New York State. Because of the limited amount of 

data on small drainage basins this method is not 

applicable to sites where the drainage area is less 

than 10 square miles or to streams where flood peaks 

are affected materially by manmade regulation. 

Flood data based on records collected at gaging 

stations having 5 or more years of record not affected 

by unnatural regulation or diversion were used to define two types of curves. The first is a composite 

frequency curve. It expresses the relationship between the mean annual flood and floods of recurrence 

intervals ranging from 1.1 to 50 years. The second 

type defines the relation of the mean annual flood to 

the drainage area above the site. The result obtainable from the combination of the two curves is a 

flood-frequency curve for any site in the State, gaged 

or ungaged, within the range of drainage area and 

recurrence interval defined by the base data.

INTRODUCTION

In the design of dams, highways, bridges, or any 

other structures over or adjacent to a stream, consideration should be given to the probability of flood 

damage. The magnitude and frequency of floods at 

the site of the proposed structure become major 

factors in the design or in the flood protection that 

must be afforded. The method explained in this report will enable the designer to determine the probable 

magnitude and frequency of floods at most sites on 

streams in New York State.

Peak discharges at gaging stations used in the 

analysis are not listed in this report. Annual peaks 

can be found in the annual series of water-supply 

papers for Parts 1-B, 3-A, and 4 of. the U. S. 

Geological Survey and in the 1960 publication of the 

Albany District of the Surface Water Branch of the 

U. S. Geological Survey titled "Maximum Known Discharges of New York Streams".

This report was prepared in the Albany Office of 

the U. S. Geological Survey under the direction of 

D. F. Dougherty, district engineer, Surface Water 

Branch, in cooperation with New York State Department of Public Works. Valuable assistance was 

given-the author by K. I. Darmer, G. R. Ayer, and 

F. H. Ruggles of the Albany Office, and A. Rice 

Green of the Floods Section in Washington.

The streamflow records used were collected by 

the U. S. Geological Survey, the Corps of Engineers, 

and many other agencies who are given credit in the 

annual series of water-supply papers published by 

the U. S. Geological Survey.

DATA USED

Streamflow records for periods ranging from 5 

to 46 years in length from 128 gaging stations, not 

materially affected by regulation or diversion, were 

used in this analysis, together with a limited amount 

of historical information. The records for Long

Island could not be used because of rapidly changing 

and practically indeterminate drainage areas. 

Names of stations used are listed in table 1 and their 

locations are indicated on figure 1. The computed 

curves for the Delaware River basin shown in the 

open-file report "Delaware River Basin Flood Frequency" (Tice, 1958) were used for the streams in 

that basin in New York State. In addition, the completed reports of other neighboring States were 

examined to be sure that the New York curves were 

reasonably consistent with the curves for overlapping 

or contiguous basins.

TYPES OF FLOOD SERIES

Flood data for a gaging station may be analyzed 

in two ways: as an annual flood series or as a 

partial-duration series. The latter series is often 

termed "floods above a base". In the annual flood 

series the recurrence interval is the average interval of time within which a flood equal to or 

greater than a given magnitude will occur once as 

the maximum flood in the water year (October 1 to 

September 30). In the partial-duration series the 

recurrence interval is the average interval of time 

between floods of a given magnitude regardless of 

their relation to the year or any bfher period of time. 

For floods having recurrence intervals of 10 years 

or more both series give essentially the same results.

The following table by Langbein (1949) shows the 

comparative values of recurrence intervals for the 

two series and a means of transforming one to the 

other:

Recurrence intervals, in years 

Annual flood series Partial-duration series

1

1

2

2

5

10

20. 5

50.5

100. 5

0.5

1.0

1.45

2.0

5.0

10

20

50

100

The annual flood series has been used in this study 

because of its relative simplicity.

COMPUTATION OF FLOOD-FREQUENCY CURVES

A detailed step-by-step explanation of the method 

for computing individual station frequency curves is 

not included in this report. This information is 

available in flood-frequency reports previously published, some of which are listed in the bibliography.

Significant features of the method used by the 

Geological Survey for computing flood frequency are:

(1) Only the maximum momentary peak discharge 

for each water year (October 1 to September 30) is 

used.
Table 1. --Inventory of data used to define regional.flood-frequency relations

No.

2000

3120 

3135

3140 

3155 

3185

3190 

3210 

3280 

3295 

3300

3305 

3335 

3345 

3460 

3480

3490 

3500 

3575 

3585 

3610

3615 

3625 

3650 

3655 

3665

3680 

3685 

3690 

3700 

3715

3725 

3735 

3765 

4135 

4140

4145 

4}50 

4155 

4165 

4170

4175 

4180 

4185 

4195 

4200

4205 

4210 

4220 

4225 

4245

4255 

4260 

4265 

4275 

4280

Gaging Station

PART 1-A 

Tenmile River at Gaylordsville, Conn.

- PART 1-B 

Hudson River near Newcomb

Cedar River below Chain Lakes, near Indian 

Lake 

Hudson River at Gooley, near Indian Lake

Hudson River at Hadley 

East Branch Sacandaga River at Griffin

Bond Creek at Dunhatn Basin

Batten Kill at Battenville

Glowegee Creek at West Milton

Kayaderosseras Creek near West Milton

Little Hoosic River at Petersburg

East Canada Creek at East Creek

Otsquago Creek at Fort Plain

Mohawk River at Cohoes 

Poesten Kill near Troy

Kinderhook Creek at Rossman

Catskill Creek at Oak Hill 

Esopus Creek at Coldbrook 

Rondout Creek near Lowes Corners

Chestnut Creek at Grahamsville 

Wallkill River near Unionville

Rutgers Creek at Gardnerville

Pochuck Creek near Pine Island

Wallkill River at Gardiner 

Wappinger Creek near Wappingers Falls

Fishkill Creek at Beacon

East Branch Delaware River at Margaretville

Platte Kill at Dunraven

Mill Brook at Arena 

Tremper Kill near Shavertown

Terry Clove Kill near Pepacton 

Coles Clove Kill near Pepacton

East Branch Delaware River at Harvard

Beaver Kill near Turnwood

Beaver Kill at Craigie Clair

Willowemoc Creek near Livingston Manor

Beaver Kill at Cooks Falls

East Branch Delaware River at Fishs Eddy __ 

West Branch Delaware River at Delhi

Trout Creek at CannonsVille

Cold Spring Brook at China 

Oquaga Creek at Deposit

West Branch Delaware River at Hale Eddy __ 

Callicoon Creek at Callicoon

Tenmile River at Tusten

Drainage 

area 

(sq mi)

204

192

160

A. 1 Q

1,664 

114

14. 7

394

26.0

90

56. 1

C CC

291

59.2

3,456 

89

329

98 

192 

38. 5

20.9 

144

59. 7

98.0

ope

711 

182

186

O C C"

163

34. 7

25.0 

33.0

14.1 

28.0

«J § i

443

40.8

82

63

19 8

241

142

49.5

1.51 

66

593 

111

45.0

Mean 

annual 

flood 

(cfs)

3, 100

4,210

3,870

21,400 

5, 100

900

6. 700

704

1,800

2,000

9.440

6,280

16,000 

58, 200 

2,400

6, 150

4, 100 

14, 700 

2, 880

1, 300 

2,000

2, 300

1,130

11,400 

2,600

2,290

*toO

7,000

1, 550

1,810 

1,600

810 

1, 500

12. 700 

17,000

3,200

5,000

4,050

1 2, 500

4,200

2,200 

2, 400

85 

2, 540

5,200

1, 300

Period of record

8 2 8 8 3 S S o> en ro en o> -o> °>

jmm

__ 

_ _

 _

 L_

mm

mm

mm 

mm

mm

i

 

-5=

 jmmm

 _

mmmm 

Jmmmm 

mmmmLmmmmt 

 mmm-

 Lmmmmm 

mmmmt

 mmm

^

mmmmmt

 

mmmmL 

=i

mmmmL-

=t
Table 1. Inventory of data used to define regional flood-frequency relations--Continued

No.

4285

4340 

4350 

4365 

4370

4375 

4965 

4975 

4985 

4990

5005 

5010 

5020 

5025 

5030

5050 

5055 

5070 

5075 

5090

5100 

5105 

5125 

5135 

5140

5150 

5205 

5225 

5250 

5260

5265 

5270 

5275 

5280 

5295

5305 

5310

110 

115 

130

2135 

2145 

2150 

2155 

2165

2170 

2215 

2230 

2250 

2275

Gaging Station

PART 1-B- -Continued

Delaware River above Lackawaxen River near 

Barrvville

Neversink River near Claryville

Neversink River at Woodbourne

Neversink River at Godeffrov 

Oaks Creek at Index

Charlotte Creek at West Davenport 

Oteeo Creek near Oneonta

Susquehanna River at Unadilla 

Unadilla River near New Berlin 

Butternut Creek at Morris , Unadilla River at Rockdale 

Chenango River at Sherburne

Canasawacta Creek near South Plymouth 

Chenango River at Greene

Genegantslet Creek at Smithville Flats 

Tioughnioga River at Cortland

Otselic River at Cincinnatus 

Otselic River near Upper Lisle

Susquehanna River at Vestal

Susquehanna River near Waverly 

Tioga River at Lindley

Karr Valley Creek at Almond 

Bennett Creek at Canisteo

Tuscarora Creek near South Addison

Cohocton River at Cohocton

Cohocton River at Avoca 

Fivemile Creek near Kanona

Cohocton River near Camobell 

Newtown Creek at Elmira

PART 3 -A 

Great Valley Creek near Salamanca

Conewango Creek at Waterboro

PART 4 

Cattaraugus Creek at Gowanda

Buffalo Creek at Gardenville

Cayusa Creek near Lancaster 

Cazenovia Creek at Ebenezer

Tonawanda Creek at Batavia

Genesee River at Scio

Genesee River at Portageville

Genesee River at Jones Bridge, near Mt. 

Morris

Drainage 

area 

(sq mi)

2.023

65.6

113

302 

103

O C 1

167 

108

984 

196 

59. 6

518 

264

58. 3 

598

83. 1 

296

148 

216

3,960

4, 780 

770

27. 6 

95.8

114

53.3

157 

68.0

472 

79.8

142

290

428

145

93.3 

136

172

309

982

L tliJ

1.419

Mean 

annual 

flood 

(cfs)

60. 000

6. 200

7,000

10,000

11,000 

1, 570 

A onn

4,400 

2, 990

14.200 

4, 110 

1. 830

9,400 

5,060

2, 900 

9^400

2, 750 

6, 800

4, 800 

6, 500

54, 700

69, 000 

30, 000

3,480 

6. 350

8, 210

520

3,050 

1, 660

9, 700 

2, 500

6, 100

4, 280

18.000

8,200

5, 590 

7, 700

4,480

8,000

23,800

23, 500

Period of record

§

000 o o o 

 OJ K) '^ IO & CTJ CTJ CTJ CT) CT) CT:

li J __

___ 1

LJBJ

1

 

 ^

 _

 __

 

 "

JHBBHM 

 L.

 *_

 L-

 _

« _

 -

 K^
Table 1. Inventory of data used to define regional flood-frequency relations Continued

No.

2305 

2310 

2330 

2340 

2425

2435 

2440 

2450 

2525 

2545

2560 

2587.5 

2605 

2625

2650

2690 

2700 

2715 

2740

2750

2755 

2765

Gaging Station

PART 4 --Continued 

Oatka Creek at Garbutt

Black Creek at Churchville

Cayuga Inlet near Ithaca 

Fall Creek near Ithaca

Oneida Creek at Oneida

Chittenango Creek near Chittenango

Limestone Creek at Fayetteville

Deer River at Deer River

West Branch Oswegatchie River near Harrisville

Grass River at Pyrites

Salmon River at Chasm Falls

West Branch Ausable River (head of Ausable 

River) near Lake Placid

East Branch Ausable River at Au Sable Forks.

Bouquet River at Willsboro

Drainage 

area 

(sq mi)

208

123

36.7 

124

112

67. 7

85. 7

QC C

91 7

98.1

, oib 

258

335 

61 6

132

247 

116

275

Mean 

annual 

flood 

(cfs)

3. 100

1, 790

1,380 

3. 700

4,650

2, 190 '

3,240

2 090

4.380

& ot uuu 

4,100

4, 840 

7 750

1,770

> o, obU 

3, 950

4,500

Period of record

8 ' 2 8 ^ Si 8 8

en en en en en en en

__ 

1 I

1

=

 L-

 L-
Figure 1. --Map of New York showing location of gaging stations used in the analysis.
(2) Recurrence intervals are computed by the 

formula T=(n+l)/m, where T is in years, n is number 

of years of record, and m is the order number of 

each flood, the greatest Being numbered 1.

(3) Curves are fitted graphically.

(4) The mean annual flood is defined as the flood 

having a recurrence interval of 2. 33 years.

Recurrence interval is the average interval of 

time within which a flood of given magnitude will be 

equaled or exceeded once. Thus, a 25-year flood 

will be equaled or exceeded on the average once in 

25 years. Frequency of occurrence may also be expressed in terms of probability. For example, a 

25-year flood can be considered as one that has a 

4 percent chance of occurring in any one year.

Regional Flood-Frequency Curves

By combining the frequency curves for individual 

stations within a homogeneous region in the State, it 

was found that four different regional flood-frequency 

curves were applicable, in addition to those already 

computed by Tice (1958) for the Delaware River basin. 

The curves and regions in which each is applicable 

have been designated as A, B, C, D, E, F, and G 

(fig. 2). The curves represent the discharge as a 

ratio to the mean annual flood (fig. 3).

Region A. --Comprises most of the State, except 

the southeastern portion. From figure 1, it is evident that there are areas where records of sufficient 

length are not available. One such area borders on 

the southern and eastern shores of Lake Ontario. 

Since the topography and other characteristics of that 

area are similar to those in much of region A, curve 

A is used for the streams in that area. Two base 

periods, 1913-58 and 1939-58, were used in defining 

this region, and the frequency curve for the short 

period was adjusted to that for the long period.

Region B. --Includes the area west of the Hudson 

River, south of the Catskill Mountains and from the 

northern edge of the Catskills north to the foothills 

of the Adirondack mountains. On the east the northern portion of this region extends to the foothills of 

the Berkshire and Green mountains and north to the 

Poultney River and the Vermont State line. The 

southern part of this region consists principally of 

the Wallkill River basin. In this basin the storage 

effect of extensive flood plains reduces the mean 

annual floods, and the hurricanes and coastal storms 

cause a sharp rise at points on the curve above the 

10-year frequency. The northern part lies in an 

area with moderate precipitation. It is also affected 

by hurricane and coastal storm activity but to a 

slightly lesser degree than in the regions farther 

south. The base periods used for this region are 

1928-58 and 1939-58, and the frequency curve for the 

short period was adjusted to that for the long period.

Region C. --Consists of the area east of the 

Hudson Kiver from about the Rensselaer-Columbia 

County line south to New York City. It also includes 

a small section west of the Hudson River, adjacent 

to New Jersey, drained by the Ramapo River. Snowfall is light so the mean annual floods are rather 

smatl. Hurricanes and coastal storms often bring 

heavy rains causing floods which have high ratios to 

the mean annual floods. This^accounts for the sharp 

rise in the frequency curve ab'ove a 10-year recurrence interval. The base periods and adjustment 

used for this region are the same as for region B.

Region D. --Includes the streams west of the 

Hudson River, draining the northern and eastern

slopes of the Catskill Mountains. Snowfall is heavy 

resulting in large mean annual floods. Hurricanes 

and coastal storms are responsible for many of the 

floods in this region. Also contributing to the flood 

magnitude is the orographic effect of the Catskill 

Mountain peaks, which causes the rainfall to be 

heavier on the eastern than on the western slopes. 

Curve D is also applicable to the Deer River and 

other streams draining the Tug Hill plateau, east of 

Lake Ontario. The periods and adjustment used for 

this region are the same as for regions B and C.

Region E. --The curve for region E applies only 

to the main stem of the Never sink River.

Region F. --The curve for region F applies to 

all the streams in the Delaware River basin in New 

York State, except the main stems of the Neversink 

and Delaware Rivers.

Region G. --The curve for region G applies to 

the main stem of the Delaware River.

Hydrologic Area Curves

The mean annual flood is influenced by many 

factors. Some of these are drainage area; shape of 

the basin and its alignment with the prevailing 

direction of storm travel; land and stream slopes; 

elevation; geology of the basin; flood water storage 

in stream channels, swamps and lakes; type of 

vegetal cover; and land use. On the basis of data 

presently available, this study indicated that drainage 

area is the only significant factor, therefore it is 

used to define the hydrologic area curves. By plotting 

the mean annual flood for all the stations used in the 

report against the respective drainage area, 10 

hydrologic areas were defined. Curves numbered 

1-11 (fig. 4) apply to areas as numbered on figure 5, 

except for the main stem of the Delaware River for 

which curve 11 applies.

An attempt was made to evaluate the effect of 

lakes and swamps on peak discharges, but on the 

basis of present records no significant effect could 

be defined. The damping effect of storage is no 

doubt reflected in the relatively low discharges from 

curve 7 of mean annual flood versus drainage area. 

Most of the unregulated Adirondack streams, although affected by considerable spring snowmelt, do 

not produce high mean annual floods, probably due 

to the effect of storage in lakes and swamps.

Slope of the stream was also investigated as a 

flood factor but considerably more data than now 

available would be necessary in order to define the 

effect. Where records have been obtained at a 

station in mountainous terrain and also at a station 

in the flat land of the same stream, the mean annual 

flood at the former station has a much higher ratio 

to drainage area than that at the latter.

THE DESIGN FLOOD

Before using the method described for determining the magnitude of the design flood it is necessary to decide on a recurrence interval. If the type 

of structure or its location are such that flooding 

would cause loss of life or great financial loss, then 

the design may be for a flood which will probably 

never be exceeded. However, for most structures 

the design will probably be for floods with a recurrence interval selected on the basis of economics. 

It is likely that most design floods will fall within the 

frequency range presented in this report.
Figure 2. --Map of New York showing flood-frequency regions.

1.1 1. 2 345 10 20 30 40 50 100 

RECURRENCE INTERVAL, IN YEARS

Figure 3. --Frequency of annual floods, regions A-G.
Determination of Design Flood

Once the recurrence interval of the design flood 

is selected, its magnitude may be determined by the 

following procedure:

1. Determine drainage area in square miles 

above the selected site.

2. From figure 5 determine the hydrologic area 

in which the site is located.

3. Determine the mean annual flood for the site 

from the appropriate curve in figure 4.

4. From figure 2 identify the flood-frequency 

region in which the site is located.

5. Determine ratio to mean annual flood for the 

selected recurrence interval from appropriate curve 

in figure 3.

6. Multiply the ratio to mean annual flood 

(step 5) by the mean annual flood (step 3) to obtain 

the design-flood magnitude.

A complete flood-frequency curve for a specific 

site in New York State may be obtained by repeating 

steps 5 and 6 for various recurrence intervals. The 

frequency curve obtained by this method is generally 

a better indication of the frequency of future floods 

at a site than a curve from streamflow records at the 

site alone.

100

20 IK) 100 FOO 15001,000 2, 000 

DRAINAGE AREA, IN SQUARE MILES

Figure 4. --Variation of mean annual flood with drainage area in hydrologic areas 1-11.

,5,000
CONCLUSIONS

The accuracy of the information obtained from 

this report is a function of the data available. The 

curves presented are based on all known data existing 

through the 1958 water year. The frequency curves 

(recurrence interval-ratio to mean annual flood) 

cannot be extrapolated with confidence beyond 50 

years. Neither should the drainage area-mean annual 

flood curves be extended in either direction beyond 

the limits shown. Lack of information on drainage 

areas of less than 10 square miles limits the accuracy 

of the lower ends of the mean annual flood curves.

On Long Island the physiography is being changed 

so rapidly by construction of new housing, and commercial and industrial developments, that it is

practically impossible to compute even reasonably 

accurate drainage areas. Therefore, the curves 

here presented should not be used for Long Island 

streams. Also, extensive regulation prohibits the 

use of any of these curves on the Mohawk River below Delta Dam and on the Hudson River below Hadley.

Since this study was designed to produce a 

reasonable answer to frequency of floods in terms of 

the average occurrence of such events, it obviously 

cannot be used to predict the date of occurrence of 

any specific future flood. On the basis o£ present 

knowledge regarding the causes of floods, there 

seems to be no reason why several major floods could 

not occur in any given area within a single year or a 

short period of years. Conversely, many years may 

elapse without any major floods.

Figure 5. --Map of New York showing hydrologic areas.
10

SELECTED BIBLIOGRAPHY

Benson, M. A., 1960, Characteristics of frequency 

curves based on a theoretical 1, 000-year 

record, in Dalrymple, Tate, Flood-frequency 

analysis, Manual of hydrology, pt. 3, Floodflow techniques: U. S. Geol. Survey WaterSupply Paper 1543-A, p. 51-74.

Bigwood, B. L, , and Thomas, M. P., 1955, A

flood-flow formula for Connecticut: U. S. Geol. 

Survey Circ. 365.

Corbett, D. M., and others, 1943, Stream-gaging 

procedure: U. S. Geol. Survey Water-Supply 

Paper 888.

Cross, W. P., 

frequency:

7.

1946, Floods in Ohio, magnitude and 

Ohio Water Resources Board, Bull.

Dalrymple, Tate, 1960, Flood-frequency analysis, 

Manual of hydrology, pt. 3, Flood-flow techniques: U. S. Geol. Survey Water-Supply 

Paper 1543-A.

Gumbel, E. J., 1941, The return period of flood

flows: Annals of Math. Statistics, v. 12, no. 2, 

p. 163-190.

Kinnison, H. B., and Colby, B. R., 1945, Flood 

formulas based on drainage basin characteristics: Am. Soc. Civil Engineers Trans., 

v. 110, p. 849-904.

Langbein, W. B., 1949, Annual floods and the partialduration flood series: Am. Geophys. Union 

Trans., v. 30, p. 879-881.

Merrill, J. H., 1905, Map of surface configuration 

and catchments: State of New York, Museum 

Bull. 85.

Mordoff, R. A., 1949, The climate of New York 

State: N. Y., Cornell Univ., Ext. Bull. 764.

Powell, R. W., 1943, A simple method of estimating 

flood frequency: Civil Eng. v. 13, no. 2, 

p. 105-106.

Tice, R. H., 1958, Delaware River basin flood frequency: U. S. Geol. Survey open-file report, 

Trenton, N. J.

United States Weather Bureau, 1958, Local climatelogical summaries with comparative data.

Water Resources Division, 1960, Maximum known 

discharge of New York streams: U. S. Geol. 

Survey, Albany, N. Y.

INT DUP..D.C.61- 9784J