Texas StreamStats
StreamStats for Texas was developed in cooperation with the Texas Department of Transportation.
StreamStats for Texas can be used to estimate the magnitude of peak flows for Texas under natural streamflow conditions at the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2- percent annual exceedance probabilities. The report below presents the equations used to estimate the flow statistics, describe the uncertainty associated with the estimates, and describe the methods used to develop the equations and to measure the basin characteristics used in the equations. Users should familiarize themselves with the reports before using StreamStats to obtain estimates of streamflow statistics for ungaged sites.
Click below to view foundational layers and metadata for the Texas application, as well as specific sources and computation methods for basin characteristics:
- Garvin, K.M., Schultz, A.R., Lamberts, A.P., and Labriola, L.G., 2026, Basin characteristics rasters for Texas StreamStats: U.S. Geological Survey, https://doi.org/10.5066/P13MLQOI.
- Garvin, K.M., Schultz, A.R., Lamberts, A.P., Villa, J., Null, M.L., and Labriola, L.G., 2026, Texas StreamStats digital elevation, flow direction, and flow accumulation GIS data: U.S. Geological Survey, https://doi.org/10.5066/P13WCF2B.
The equations are applicable for all areas of Texas except tidal areas along the Gulf coast and the Rio Grande River. Estimates obtained from the equations assume natural flow conditions at the site.
IMPORTANT INFORMATION CONCERNING ESTIMATED PEAK FLOWS
StreamStats outputs for ungaged sites provide estimates of peak flows.
Users are cautioned against using the equations outside of the ranges of values of the independent variables used to develop the equations, as potential errors are unknown in these cases. For the peak-flow equations (Asquith and Roussel, 2009), the range in drainage area is from 0.1 to 9,329 square miles. The dimensionless main-channel slope times 100 for streamgages used to develop the equations range from 0.023 to 7.03. The range of mean annual precipitation used in the equations is from 8 inches to 57 inches. Table 1 in Asquith and Roussel (2009), provides the summary statistics of the watershed characteristics for the 638 U.S. Geological Survey streamflow-gaging stations used to develop regional equations for estimation of peak-streamflow frequency.
The Texas StreamStats application was developed from the best continuous elevation data available within Texas at the start of the project in 2024, Fathom DEM — Global Terrain Data (Fathom, 2023). Light Detection and Ranging (LiDAR) derived digital elevation models (DEMs) at 3-meter post spacing were used as the basis for basin delineation, streamlines, flow direction, and flow accumulation. The high-resolution elevation data provides an opportunity to provide the most accurate results from StreamStats for a variety of scientific applications. For portions of the study area outside Texas where Fathom data were unavailable, including Louisiana, Arkansas, Oklahoma, New Mexico, Colorado, and Mexico, National Hydrography Dataset Plus High Resolution (NHDPlus HR) 1/3rd arc-second (or 1 arc-second where needed) tiles were used to supplement coverage.
The StreamStats application interfaces with the DEMs and the current regional streamflow regression equations and datasets of landscape characteristics. Basin characteristics, such as rainfall data, topographic variables (such as slope, drainage area, U.S. Environmental Protection Agency Level III Ecological Regions, and OmegaEM), soil permeability from SSURGO, and 2023 National Land-Cover Datasets (NLCD) also are incorporated in the Texas StreamStats application.
Click on this link to obtain general information on the Texas application, as well as specific sources and computation methods for basin characteristics.