Flood Inundation Mapping

Science Center Objects

Flood inundation maps are a sequence of maps which show where flooding may occur at different stream levels. These maps can help communities prepare for, understand, and mitigate flood risks in their area.

Flood inundation maps (FIMs) help communities in Nebraska prepare for floods by creating a valuable resource for visualizing which areas may be impacted by flood waters. FIMs are created in a six-step process: selecting a USGS streamgage, hydraulic modeling, geospatial processing, and FIM library production. Once a FIM library is created, it is included in the USGS Flood Inundation Mapper which an online tool that shows potential flooding at different river levels on a map.

Here's how the FIMs work:

National Weather Service graph showing flood stage and the corresponding flood inundation maps
Example of a National Weather Service flood forecast graph visualized in the Flood Inundation Mapper.
  1. We develop FIM libraries that show the extent and depth of flooding at specific water-level (stream stage) intervals along a section of a stream or river using hydraulic modeling which allows users to visualize a much wider range of flood scenarios. 
  2. We operate streamgages throughout Nebraska that provide real-time data about the level (or height) of water in a stream or river. Our real-time data is collected, checked, and stored in the USGS National Water Information System (NWIS) and is available to the public through NWISweb
  3. The National Weather Service provides flood forecasts at roughly half of all USGS streamgages: A flood forecast is an estimation of how high flood waters may rise. Flood forecasts are developed with local hydrologic models and typically provide forecasts up to several days before the flood impacts the area. 
  4. Once a flood has been forecasted, local officials and the public can interact with the FIM for their location through the USGS Flood Inundation Mapper. The Flood Inundation Mapper is an interactive, online mapping application that shows the estimated extent of flood waters on a map at various water levels. The Flood Inundation Mapper can be used by local agencies and communities to visualize potential flood scenarios, identify which areas may be at risk, and improve local response during floods.

We have created two flood inundation map libraries for communities in Nebraska: one for the Big Papillion Creek at Omaha, NE, and one for the North Platte River at Scottsbluff, NE.

Big Papillion Creek at Omaha, NE

The Papillion Creek watershed is one of the most flood-prone areas in Nebraska as well as being one of the most heavily populated areas.  A devastating flood in 1964 caused 95 trailer homes to be washed downstream and seven lives were lost. However, the severity and occurrence of flooding may be increasing due to the development and urbanization of the western part of the watershed which has caused a dramatic increase in the amount of stormwater runoff.

Several resources have been available to emergency responders, local officials, and the public including the Federal Emergency Management Agency flood insurance study for Douglas County, the USGS streamgage records for Big Papillion Creek at Fort Street at Omaha, Nebr., and the National Weather Service Advanced Hydrologic Prediction Service flood forecasts. While these resources are all valuable, combining the information from them before, during, or after a flood was difficult. To help address these difficulties, we worked with the Papio-Missouri River Natural Resources District to develop a FIM library for a 12.5-mile reach of the Big Papillion Creek from 0.6 mile upstream from the State Street Bridge to the 72nd Street Bridge in Omaha, Nebr.

The FIM library was published as USGS Scientific Investigations Report 2015-5052 and is also part of the USGS Flood Inundation Mapper.

North Platte River at Scottsbluff, NE

North Platte River at Scottsbluff, NE in May 2015
North Platte River at Scottsbluff, NE, May 2015. 

The city of Scottsbluff along with numerous smaller communities located along the North Platte River in the Nebraska panhandle, experienced flooding in 2011 and again in 2013. Current floodplain maps in these areas rely solely on National Flood Insurance Program products that were developed without LiDAR data or the use of reservoir regulation modeling in the 1970s; therefore, they do not accurately identify those areas considered at-risk for flooding. By developing a FIM for the North Platte River at Scottsbluff, the community will have the information needed to make informed decisions regarding future development and land use along the river.

We are working on the FIM library for Scottsbluff which includes the reach of the North Platte River from several miles upstream of the Nebraska Department of Natural Resources North Platte River at Mitchell, NE (station number 06679500) stream gage, to several miles downstream of the Nebraska Department of Natural Resources North Platte River near Minatare (station number 06682000) stream gage.