U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2012–3137

December 2012

StreamStats in North Carolina: A Water-Resources Web 

Application

Introduction

A statewide StreamStats application for North 

Carolina was developed in cooperation with the 

North Carolina Department of Transportation following completion of a pilot application for the 

upper French Broad River basin in western North 

Carolina (Wagner and others, 2009). StreamStats for 

North Carolina, available at http://water.usgs.gov/

osw/streamstats/north_carolina.html, is a Web-based 

Geographic Information System (GIS) application 

developed by the U.S. Geological Survey (USGS) 

in consultation with Environmental Systems 

Research Institute, Inc. (Esri)1

 to provide access 

to an assortment of analytical tools that are useful for water-resources planning and management 

(Ries and others, 2008).

The StreamStats application provides an 

accurate and consistent process that allows users 

to easily obtain streamflow statistics, basin characteristics, and descriptive information for USGS 

data-collection sites and user-selected ungaged sites. 

In the North Carolina application, users can compute 

47 basin characteristics and peak-flow frequency statistics (Weaver and others, 2009; Robbins and Pope, 

1996) for a delineated drainage basin. Selected 

streamflow statistics and basin characteristics for 

data-collection sites have been compiled from published reports and also are immediately accessible 

by querying individual sites from the web interface. 

Examples of basin characteristics that can be 

computed in StreamStats include drainage area, 

stream slope, mean annual precipitation, and percentage of forested area (Ries and others, 2008). 

Examples of streamflow statistics that were previously available only through published documents 

include peak-flow frequency, flow-duration, and 

precipitation data. These data are valuable for making decisions related to bridge design, floodplain 

delineation, water-supply permitting, and sustainable 

stream quality and ecology.

The StreamStats application also allows users 

to identify stream reaches upstream and downstream 

from user-selected sites and obtain information for 

locations along streams where activities occur that 

may affect streamflow conditions. This functionality can be accessed through a map-based interface 

with the user’s Web browser (fig. 1), or individual 

functions can be requested remotely through Web 

services (Ries and others, 2008).

The StreamStats Web site is http://streamstats.usgs.gov/. This Web site 

provides helpful information for the user, including definitions of basin characteristics, details about the functionality and limitations of the StreamStats 

application, user instructions, and links to access state applications.

StreamStats for North Carolina

The North Carolina (NC) StreamStats application is based on the best 

available elevation and stream data for the state. Basin delineations and topographic basin characteristics are generated from LiDAR-derived digital elevation models (DEMs) at 30-ft by 30-ft cell resolution. LiDAR-derived DEMs 

have several advantages over traditional elevation-data models, including better 

mapping of bare earth elevations in forested or vegetated areas, denser point 

spacing of elevation data (approximately 1 elevation point every 3 meters), 

and a high vertical accuracy (20 to 25 cm vertical RMSE). This is particularly 

important in eastern North Carolina where LiDAR data is considerably denser 

than previous elevation data determined using traditional methods (North 

Carolina Floodplain Mapping Program, 2003).

In 2007, the State of North Carolina developed a local-resolution National 

Hydrography Dataset (NHD) digital stream network (at an approximate 

1:4,800 scale) for 19 western counties in the State. For areas where localresolution NHD products are not available, StreamStats can be implemented by 

using the best-available hydrography, which currently (2012) is 1:24,000-scale 

NHD (U.S. Geological Survey, 2012). The local-resolution and 1:24,000-scale 

NHD are appended to make a continuous layer for streams across the entire 

State and in surrounding areas of adjacent States.

Figure 1. View of the user interface for the statewide North Carolina 

StreamStats application.
The NC StreamStats application uses the 

most current regional streamflow-regression 

equations and datasets of landscape characteristics. Basin characteristics, including rainfall data, 

topographic variables (such as slope and drainage 

area), and 1992, 2001, and 2006 National LandCover Datasets (NLCDs), are incorporated in the 

NC StreamStats application. The combination of 

accurate elevation surfaces for basin delineation, 

and basin-characteristics data available for use in 

regression equations is a powerful tool to evaluate changes in streamflow statistics as basins 

become more urbanized.

Application Functionality

The current (2012) functionality in the 

NC StreamStats application includes the 

following features:

• Navigating and viewing base-map features 

in the user interface, such as roads, streams, 

political boundaries, and USGS topographic 

maps. Current aerial imagery also is served 

through the NCOneMap Web-mapping service 

to provide the most up-to-date geospatial data 

available in participating counties in the State.

• Zooming in or out to different map scales 

based on user input of (1) a drawn rectangle 

surrounding an area of interest, (2) latitude 

and longitude coordinates, or (3) a 

specified scale.

• Accessing published peak-flow frequency and 

other streamflow statistics, basin characteristics, and descriptive information for USGS 

data-collection sites, plus a link to the USGS 

National Water Information System (NWIS) 

that provides access to historical and real-time 

data collected at selected sites.

• Delineating and editing a drainage-basin 

boundary for a user-selected ungaged 

site (fig. 2).

• Computing up to 47 basin characteristics, such 

as drainage area, stream slope, mean annual 

rainfall, soil type, and land cover from the 

1992, 2001, and 2006 NLCDs, for a selected 

site and ease of summarizing in tabular 

format (fig. 3).

• Estimating rural and urban peak-flow 

frequency statistics at ungaged locations and 

verifying the accuracy of the estimates for a 

specific site in tabular format (fig. 4).

• Downloading the basin boundary as an Esri1

shapefile for use in other applications, along 

with basin characteristics and streamflow statistics that have been computed for the site.

Figure 2. Example of an automated watershed delineation for a userdefined stream location in StreamStats where the drainage area is shaded 

magenta and streamgages are shown by the various colored triangles.

Figure 3. Partial summary table of basin characteristics for a user-defined 

stream site in StreamStats.

• Tracing information upstream or downstream from a selected site to 

identify the connected stream network and natural or manmade features 

that may affect the quantity or quality of the streamflow.

• Obtaining elevation profiles between selected points on the stream network or the land surface.

• Tracing the flow path of water or pollutants from a selected point on the 

land surface to the stream network and then downstream.

• Printing the results displayed in the user-interface map frame.
Streamflow Statistics for Ungaged Sites

By using the NC StreamStats application with regional regression 

equations, estimates of selected rural and urban peak-flow frequency statistics 

for ungaged sites can be obtained. Regression equations are developed by statistically relating streamflow data to basin characteristics for a group of datacollection sites within a region. Estimates of streamflow statistics for ungaged 

sites can then be obtained by using the basin characteristics for the ungaged 

site in the regression equations (Weaver and others, 2009; Robbins and Pope, 

1996; see inset below concerning rural peak-flow frequency estimates).

StreamStats automates the process of 

computing the basin characteristics and solving the 

applicable regression equations for ungaged sites. 

The drainage-basin boundary can be determined 

for a selected site by using a digital representation of the stream network. StreamStats users can 

(1) locate an ungaged site of interest on the map, 

(2) use the Watershed Delineation from a Point 

tool to delineate the drainage basin for the site, 

and then (3) use either the Basin Characteristics

tool to obtain a summary table of computed basin 

characteristics (fig. 3) or the Estimate Flows using 

Regression Equations tool to obtain estimates 

of ungaged rural and urban peak-flow frequency 

statistics (fig. 4).

Stream-Network Navigation

Information about other points of interest 

within the stream network of a selected site can be 

obtained by using the StreamStats stream-network 

navigation tool. The StreamStats map shown in 

figure 5 illustrates the results of an upstream trace 

for a selected location on a stream in the Flat River 

basin in the Piedmont Physiographic Province. 

The primary benefit of the trace functionality is to 

understand how the flow at a particular site can be 

affected by upstream activities or how downstream 

flow can be affected by current or proposed activities at the selected site. The U.S. Environmental 

Protection Agency and many State and local 

agencies have supported the indexing of waterrelated data to the NHD, and many similar efforts 

are underway (Ries and others, 2008). Currently 

(2012), streamgages are the only layer indexed 

to the local-resolution stream network in the NC 

StreamStats application, but the expectation is that 

layers will be added in the future.

Summary

StreamStats automates and provides 

consistent processing for many important components necessary for the management of water 

resources in North Carolina. Functions such as 

automated basin delineation and calculation of 

basin characteristics, calculation of streamflow 

statistics at gaged and ungaged sites, and streamnetwork navigation were formerly very time 

intensive and often were not reproducible. The 

Web-based application incorporates important 

local data sets developed by the State as well as 

established national data sets in a framework that 

allows future updates to be made. Applications as 

diverse as planning for bridge and road construction, managing water-resources quality and quantity, characterizing watersheds, or examining the 

effects of urbanization on streamflow can be easily 

implemented with the StreamStats application. 

Figure 4. Example of a summary table containing peak-flow frequency 

statistics for the watershed of a user-defined steam site in StreamStats.

The USGS has developed equations to estimate peak-flow frequency 

statistics, such as the 1-percent exceedance level flood, for ungaged rural 

sites in North Carolina. As an example, the equation for estimating the 

1-percent exceedance level flood for ungaged rural sites in Hydrologic 

Region 1 (Piedmont) in North Carolina, South Carolina, and Georgia is:

 Q1% = 776 DA0.594

where

Q1% is the peak flow with a 1-percent exceedance level (1-percent chance 

of being equaled or exceeded in any year, formerly termed the 

100-year recurrence interval flood), in cubic feet per second;

DA is the drainage area, in square miles
Figure 5. Example results of an upstream stream-network navigation from a 

user-defined point in StreamStats where the drainage area is shaded magenta 

and upstream network is light blue.

Selected References

NC Center for Geographic Information and 

Analysis, 2012, NC Stream Mapping 

Program, accessed June 28, 2012 at 

http://www.ncstreams.org/.

North Carolina Floodplain Mapping 

Program, 2003, LIDAR and digital 

elevation data, accessed July 2, 2012, at 

http://www.ncfloodmaps.com/pubdocs/

lidar_final_jan03.pdf.

Ries, K.G., III, Guthrie, J.G., 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.; also available at 

http://pubs.usgs.gov/fs/2008/3067/.

Robbins, J.C., and Pope, B.F., 1996, 

Estimation of flood frequency characteristics of small urban streams in 

North Carolina: U.S. Geological Survey 

Water-Resources Investigations Report 

96–4084, 21 p.; also available at http://

pubs.er.usgs.gov/publication/wri964084/.

U.S. Geological Survey, 2012, National 

Hydrography Dataset, accessed 

July 2, 2012, at http://nhd.usgs.gov/.

For additional information regarding this 

publication, contact:

John Curtis Weaver, Hydrologist

USGS North Carolina Water Science Center

3916 Sunset Ridge Road

Raleigh, NC 27607

email: jcweaver@usgs.gov

Or visit the North Carolina Water Science 

Center website at:

http://nc.water.usgs.gov/

Wagner, C.R., Tighe, K.C., and Terziotti, 

Silvia, 2009, Use of StreamStats in the 

upper French Broad River basin, North 

Carolina–A pilot water-resources Web 

application: U.S. Geological Survey Fact 

Sheet 2009–3088, 4 p.; also available at 

http://pubs.usgs.gov/fs/2009/3088/.

Weaver, J.C., Feaster, T.D., and Gotvald, 

A.J., 2009, Magnitude and frequency of 

rural floods in the Southeastern United 

States, through 2006: Volume 2, North 

Carolina: U.S. Geological Survey Scientific Investigations Report 2009–5158, 

111 p.; also available at http://pubs.usgs.

gov/sir/2009/5158/.

By J. Curtis Weaver, Silvia Terziotti, 

Katharine R. Kolb, and Chad R. Wagner

1

 The use of trade, product, or firm names in this report is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Highlights of the NC StreamStats 

include

Potential future directions for 

NC StreamStats

• Web-map interface providing

 detailed spatial data, including

 aerial imagery, roads, land

 cover, soils, elevation, 

 precipitation, and stream data

• Automated, consistent methods 

 for computing streamflow

 statistics for ungaged sites

 anywhere along a stream

 network in North Carolina

• Watershed delineation upstream

 from any point on a stream

• Calculation of up to 47 basin

 characteristics upstream from

 any point

• Stream-network navigation up

 or downstream

• Downloadable shapefiles of

 basin delineations with basin

 characteristics for use in other

 applications

• Quick and easy access to 

 calculated results of streamflow

 statistics and basin

 characteristic to apply to a 

 variety of planning and 

 watershed-management 

 objectives

Incorporate additional important

streamflow statistics, including:

• revised urban peak-flow

 frequency equations,

• updated low-flow statistics,

• water-use withdrawal and

 discharge amounts along a

 stream, and 

• estimates of perennial flow

Index additional data sets to stream

reaches for upstream and downstream

network analysis, including

• water-quality monitoring sites, 

• bridge locations,

• dams, and

• recreational and stream-access

 points

Addition of Web-map interface services, 

such as population projections by census

block and real-time NEXRAD

precipitation maps. 

Extend the local-resolution stream

network into other parts of the State.