Missouri StreamStats: Flood and Low-Flow Estimates for Any Stream Site

From a U.S. Geological Survey fact sheet prepared with the Missouri Department of Natural Resources, January 2018.

Missouri StreamStats (https://streamstats.usgs.gov) is a web map application that calculates basin characteristics and selected streamflow statistics for any point a user chooses on a Missouri stream.

The problem it solves

The USGS runs more than 8,200 continuous streamgages across the country, recording water-surface height, streamflow and water quality. From the flow records, scientists and engineers calculate streamflow statistics for each gage, such as:

• the 1-percent annual exceedance probability flood, also called the 100-year flood;
• the mean flow;
• the 7-day, 10-year low flow.

People also need a basin's physical characteristics. Together, these numbers are used for hydraulic design, managing water supply, allocating water use, and mapping floodplains for flood-insurance rates and land-use zoning.

But the USGS updates the published statistics for only some gages at a time, so the latest values are hard to find. And the statistics are most often needed at ungaged sites, where none have been published. The USGS publishes methods for estimating them, but the calculations are complex, often need specialised software, and can give inconsistent results.

StreamStats, built by the USGS with the Missouri Department of Natural Resources, solves both problems: it serves the latest published statistics and basin characteristics for gages, and automatically calculates basin characteristics and estimates streamflow statistics for ungaged sites.

Figure 1. The datasets beneath Missouri StreamStats. USGS.

How it is built

StreamStats combines the National Hydrography Dataset and the Watershed Boundary Dataset, both at 1:24,000 scale, with 10-metre elevation data from the National Elevation Dataset. It has five parts:

• a map interface showing base maps and the stream network, where users pick a point;
• a database, StreamStatsDB, of published streamflow statistics, basin characteristics and information for USGS streamgages;
• a GIS process that automatically draws basin boundaries and measures basin characteristics at ungaged sites;
• a geodatabase holding the base-map data;
• an automated process that feeds those basin characteristics into regression equations to estimate streamflow statistics.

What users can do

The 2018 version lets users:

• move around a base map of roads, streams, political and hydrologic boundaries, zooming by rectangle, coordinates or scale;
• see published statistics, basin characteristics and information for every current and discontinued streamgage, with links to the National Water Information System for historical and real-time data;
• delineate the basin above any point, edit its boundary, and download it as a GIS feature class with its characteristics and statistics attached;
• measure drainage area, longest flow path, main-channel slope, basin shape, impervious area and composite curve number;
• adjust the basin characteristics used in the regression equations;
• estimate low flows, rural flood frequency and urban flood frequency;
• plot land-surface and stream elevation profiles between two points, measure distances, and print the results.

At a gage, StreamStats returns the published values and a link to real-time and historical data. At an ungaged site, it draws the basin upstream, asks the user to confirm it, lets them choose which statistics to estimate, measures the basin characteristics needed, and produces a summary report and a downloadable basin boundary.

A streamgage on a tributary in Fall Hollow, Fort Leonard Wood, Missouri. Larry Buschmann, USGS, 2013.

Statistics for ungaged sites

The USGS has developed regional regression equations that estimate streamflow statistics from the basin characteristics that proved statistically significant at gaged sites. StreamStats measures those characteristics at an ungaged site and plugs them into the equations. For Missouri it can estimate:

Users should understand how the regression equations work, and their limits, before using them; the reports behind them are listed in the fact sheet.

Limitations

• Natural flow is assumed. If human activity upstream changes the timing, amount or duration of flow, users must adjust the estimates.
• Ranges matter. Each equation is valid only for a certain range of basin characteristics. Outside it, StreamStats warns that it is extrapolating, and the results should not be trusted.
• Some rivers are excluded. It works only inside Missouri, and not on the main stems of the Mississippi, Missouri, Chariton, Nodaway and Osage Rivers, whose upstream parts lie outside its data.

Coming next

• Urban areas: storm sewers can make a city's drainage areas differ from what the land surface suggests, so better data are needed. An Urban StreamStats project for St. Louis County, using 3-metre elevation data and detailed infrastructure, is being developed by the USGS with the Metropolitan St. Louis Sewer District.
• Network navigation: users will be able to trace the stream network up- or downstream to find structures that affect water quality or quantity, and follow the path water or a contaminant would take.
• More basin characteristics: many more can be calculated than are offered now, and users can ask the USGS to add the ones they need.

Sources

• U.S. Geological Survey, Missouri StreamStats — A Water-Resources Web Application, Fact Sheet 2018–3003, January 2018, prepared in cooperation with the Missouri Department of Natural Resources. https://doi.org/10.3133/fs20183003 — two figures recovered from the PDF; its screenshots of the application are not reproduced.
• The fact sheet cites Huizinga (2014), Ries and others (2008), Southard (2010, 2013) and Southard and Veilleux (2014) for the regression equations and the application.
• Rewritten in hubnx's own words.