Hawaii StreamStats: A Web Application for Defining

Drainage-Basin Characteristics and Estimating

Peak-Streamflow Statistics

R

U.S. Department of the Interior

U.S. Geological Survey

Prepared in 

cooperation with 

the State of Hawaii, 

Department of 

Transportation.

USGS Fact Sheet 2010–3052

July 2010

eliable estimates of the 

magnitude and frequency 

of floods are necessary for 

the safe and efficient design 

of roads, bridges, waterconveyance structures, 

and flood-control projects 

and for the management 

of flood plains and floodprone areas. StreamStats 

provides a simple, fast, 

and reproducible method 

to define drainage-basin 

characteristics and estimate 

the frequency and magnitude 

of peak discharges in 

Hawaii’s streams using 

recently developed regional 

regression equations 

(Oki and others, 2010). 

StreamStats allows the user 

to estimate the magnitude 

of floods for streams where 

data from stream-gaging 

stations do not exist. Existing 

estimates of the magnitude 

and frequency of peak 

discharges in Hawaii can 

be improved with continued 

operation of existing 

stream-gaging stations and 

installation of additional 

gaging stations for areas 

where limited stream-gaging 

data are available.

Hawaii StreamStats Web Application

Flash Floods in Hawaii

U.S. Department of the Interior | U.S. Geological Survey

URL: http://streamstatsags.cr.usgs.gov/hi_ss/default.aspx

Page Contact Information: StreamStats Help

Page Last Modified: 07/02/2010 10:16:09

http://water.usgs.gov/osw/streamstats/hawaii.html

Flow in Hawaiian streams is very flashy and may pose a threat to human lives and property. The 

amount of discharge in Hawaiian streams commonly changes by a factor of a hundred or more over 

periods of less than a few hours. The photographs above from Waihee River on the Island of Maui 

were taken from the same vantage point and show how dramatically conditions can change over 

short periods of time.

10 December 30, 2007 December 31, 2007 January 1, 2008

100

1,000

Discharge, in cubic feet per second

5,000

pre-flood condition

Date
StreamStats

Streamflow statistics, such as 

the 100-year flood, the mean flow, 

and the 7-day 10-year low flow, are 

used by engineers, land managers, 

biologists, and many others to help 

guide decisions in their everyday 

work. StreamStats is a Web-based 

geographic information system (GIS) 

application that was created by the 

U.S. Geological Survey (USGS) 

in cooperation with Environmental 

Systems Research Institute, Inc. 

(ESRI), to provide users with access to 

an assortment of analytical tools that 

are useful for water-resources planning 

and management. StreamStats allows 

users to easily obtain streamflow 

statistics, basin characteristics, and 

descriptive information for USGS datacollection stations and user-selected 

ungaged sites. This functionality can 

be accessed through a map-based user 

interface that appears in the user’s Web 

browser, or individual functions can 

be requested remotely as Web services 

by other Web or desktop computer 

applications (Ries and others, 2008). 

StreamStats Hawaii Application

Hawaii StreamStats delineates 

drainage basins by GIS methods using a 

USGS 10-meter digital elevation model 

(DEM). Once the GIS basin boundary is 

generated, it can then be edited by the 

user so that any necessary corrections 

are made to the automated delineation. 

After the basin boundary is verified, 

the user can then compute any desired 

combination of basin characteristics 

available for the State of Hawaii. The 

user-selected basin characteristics, 

which may include drainage area, 

rainfall characteristics, and land-cover 

classifications, are displayed in a table. 

The delineated basin boundary and 

any basin characteristics that were 

generated by the user are then available 

for download in formats suitable for 

other applications, including GIS. 

Estimating Peak-Streamflow 

Statistics

StreamStats can estimate 

streamflow statistics for ungaged 

sites either on the basis of regional 

regression equations or on the basis of 

the known flows from nearby streamgaging stations. Regression equations 

are developed by statistically relating 

the streamflow statistics to the basin 

characteristics for a group of datacollection stations within a region. 

Estimates of streamflow statistics for 

Benefits

Hawaii StreamStats can save 

users considerable time and 

effort with the automated process 

that computes reproducible 

basin characteristics and 

peak discharges for streams 

in Hawaii. StreamStats is a 

simple and effective tool for 

estimating streamflow statistics 

and incorporates recent floodfrequency regional regression 

equations developed for Hawaii 

(Oki and others, 2010). The 

Hawaii StreamStats application 

can be expanded in the future 

to include regional estimates 

of low-flow streamflow 

characteristics as additional 

equations are developed.

Hawaii StreamStats Basin Delineation

Basin Delineation

Delineation Point

USGS Stream-Gaging Station 16213000,

Oahu, Hawaii
ungaged sites can then be obtained by 

measuring the basin characteristics for 

the ungaged site and inserting them 

into the regression equations (Ries and 

others, 2008). 

Regional regression equations 

were developed for peak discharges 

with 2-, 5-, 10-, 25-, 50-, 100-, and 

500-year recurrence intervals for 

unregulated streams (those for which 

peak discharges are not affected to a 

large extent by upstream reservoirs, 

dams, diversions, or other structures) 

in areas with less than 20 percent 

combined medium- and high-intensity 

development on Kauai, Oahu, 

Molokai, Maui, and Hawaii. Each 

of the islands was divided into two 

regions, generally corresponding to a 

wet region and a dry region. Unique 

peak-discharge regression equations 

were developed for each region. The 

regression equations used in Hawaii 

StreamStats have standard errors of 

prediction ranging from 16 to 620 

percent, and errors generally are 

greatest for leeward Molokai (region 

5) and southern Hawaii (region 10). 

For each region, the largest standard 

error of prediction is associated 

with regression equations for either 

the 2- or 500-year peak discharges, 

which represent the extremes of the 

recurrence intervals considered. These 

relatively large errors underscore 

the need to better understand the 

processes controlling floods in these 

areas and the need to collect additional 

peak-discharge data there. Because 

the regression equations for some 

regions contain substantial uncertainty, 

improved peak-discharge estimates 

for these regions may be required for 

proper design of engineering projects 

that could be affected by floods (Oki 

and others, 2010).

Limitations and User Warnings

The regression equations developed 

for the State of Hawaii have a number 

of limitations: 

• Use of a regression equation beyond 

its limits will produce peak-discharge 

estimates with unknown error 

and should therefore be avoided. 

StreamStats will provide a warning 

when an extrapolation beyond the 

limits of the regression equation occurs. 

• The regression equations were 

developed using peak-discharge 

data from streams that are mainly 

unregulated (not affected by 

regulation from upstream dams, 

reservoirs, diversions, or other 

structures), and they should not be 

used to estimate peak discharges in 

regulated streams.

• Streams in Hawaii commonly flow 

in natural, unmodified channels in 

their upper reaches, although some 

streams may flow through developed 

areas in their lower reaches. The 

equations developed for this study 

may not be reliable for streams with 

drainage basins in which more than 

20 percent of the area is affected 

by combined medium- and highintensity developments. 

• Hawaii StreamStats users are 

responsible for (1) checking the 

accuracy of delineated basins and 

(2) evaluating whether the errors 

associated with the predictions 

are acceptable for the desired 

application. For regions with 

limited data, particularly those on 

the Island of Hawaii, where regions 

cover large geographic areas 

that are hydrologically diverse, 

peak-discharge estimates from 

the regression equations may not 

accurately reflect local conditions 

and should be used with caution.

User-Selected Basin Characteristics
Zoom to the 

location of 

interest

Use the point 

delineation tool 

Estimate flows 

using regression 

equations

D

A

B

C

3610

7440

11000

16400

21100

26500

41000

Sarah N. Rosa and Delwyn S. Oki

Edited by

Peter H. Stauffer

Graphic design by

Jeanne S. DiLeo

References Cited

Ries, K.G., III, Guthrie, J.D., Rea, 

A.H., Steeves, P.A., and Stewart, 

D.W., 2008, StreamStats; a water 

resources web application: U.S. 

Geological Survey Fact Sheet 

2008–3067, 6 p. [http://pubs.usgs.

gov/fs/2008/3067/].

Oki, D.S., Rosa, S.N., and Yeung, 

C.W., 2010, Flood-frequency 

estimates for streams on Kaua‘i, 

O‘ahu, Moloka‘i, Maui, and 

Hawai‘i, State of Hawai‘i: U.S. 

Geological Survey Scientific 

Investigations Report 2010–5035, 

42 p. [http://pubs.usgs.gov/

sir/2010/5035].

Additional information on StreamStats:

The USGS StreamStats homepage: http://water.usgs.gov/osw/streamstats/

The StreamStats Description page: http://water.usgs.gov/osw/streamstats/ssinfo.html

The User Instructions-Version 2 page: http://water.usgs.gov/osw/streamstats/instructions1.html

The StreamStats Limitations page: http://water.usgs.gov/osw/streamstats/disclaimer.html

For further information please contact:

USGS Pacific Islands Water Science Center

677 Ala Moana Blvd., Suite 415

Honolulu, Hawaii 96813

(808) 587-2400

This Fact Sheet and any updates to it are available online at

http://pubs.usgs.gov/fs/2010/3052/

Streamflow Statistics Report

StreamStats automates the process of measuring the basin 

characteristics and solving the applicable regression equations 

for ungaged sites. When the process is complete, a Web browser 

window will appear that reports the (A) date and time of the 

analysis, (B) the location of the site, (C) the basin characteristics, 

and (D) the estimated streamflow statistics for the site. 

P A C I F I C O C E A N

Kauai

Oahu Molokai

Maui

Hawaii

1 2

3 4

6

4

5 6

8

8

9

10

7

EXPLANATION

Region Boundary

0 25

50250 75 KILOMETERS

50 MILES

159° 158° 157° 156° 155°

22°

21°

20°

19°

Equations for 10 Regions

The USGS has developed equations to 

estimate peak-discharge frequency 

statistics for ungaged sites on Kauai, Oahu, 

Molokai, Maui, and Hawaii. Regression 

equations have been developed for ten 

regions, two on each island.

Example Regression Equation

The equation to estimate the 100-year flood for ungaged sites in 

leeward Oahu (region 3) is:

Q100 = 539.5 (DRNAREA0.646)(PRECIP0.335)

where

Q100 is the peak flow that occurs, on average, once in 100 years 

(1-percent chance of occurrence in any year), in cubic feet per second,

DRNAREA is the drainage area, in square miles, and

PRECIP is the mean annual precipitation, in inches.

Hawaii Regression Equation Regions