AN INTERACTIVE FLOOD-INUNDATION MAPPING APPLICATION FOR THE SUNCOOK RIVER IN NH

Digital flood-inundation maps for a 16.5-mile reach of the Suncook River in Epsom, Pembroke, Allenstown, and Chichester, N.H., from the confluence with the Merrimack River to U.S. Geological Survey (USGS) Suncook River streamgage 01089500 at Depot Road in North Chichester, N.H., were created by the USGS in cooperation with the New Hampshire Department of Safety, Division of Homeland Security and Emergency Management. The inundation maps depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage at Suncook River at North Chichester, N.H. (station 01089500).

The National Weather Service forecasts flood hydrographs at many places that are often collocated with USGS streamgages. Forecasted peak-stage information is available on the Internet at the National Weather Service (NWS) Advanced Hydrologic Prediction Service (AHPS) flood-warning system site and may be used in conjunction with the maps developed in this study to show predicted areas of flood inundation.

Flood-inundation maps were created in a GIS by combining modeled water surface profiles and digital-elevation model (DEM) data. The DEM data were derived from LiDAR and aerial photogrammetry data. These maps along with real-time stream stage data from the USGS Suncook River streamgage (station 01089500) and forecasted stream stage from the NWS were created to provide emergency management personnel and residents with information that is critical for flood-response activities, such as evacuations, road closures, disaster declarations, and post-flood recovery. The maps, along with current stream-stage data from the USGS Suncook River streamgage and forecasted stream-stage data from the NWS, can be accessed at the interactive USGS Flood Inundation Mapping Science Web site.