Geospatial data sets for flood-inundation maps in and near Bellville, Ohio

Digital flood-inundation maps for an approximate 2.5-mile (mi) reach of the Clear Fork Mohican River that extends approximately from State Route 97 to the downstream corporate boundary for Bellville, Ohio, were created by the U.S. Geological Survey (USGS) in cooperation with the Muskingum Watershed Conservancy District. The flood-inundation maps show estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Clear Fork Mohican River at Bellville (station number 03131982). The maps can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/. Near-real-time stages at this streamgage can be obtained from the USGS National Water Information System at http://waterdata.usgs.gov/oh/nwis/uv/?site_no=03131982 or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http://water.weather.gov/ahps2/hydrograph.php?wfo=cle&gage=bleo1, which also forecasts flood hydrographs at this site. Flood profiles were computed for the stream reach by means of the one-dimensional step-backwater model HEC-RAS. The model was calibrated by using the current stage-discharge relation at the Clear Fork Mohican River River at Bellville, Ohio, streamgage. The step-backwater model was used to determine 9 flood profiles for flood stages ranging from 9 to 17 feet (ft). The National Weather Service defines the "Major Flood Stage" for this gage as 15.5 ft. The flood profiles were then used in combination with a digital elevation model (DEM), derived from light detection and ranging (lidar) data having a 1.0-ft vertical accuracy and 1.0-ft horizontal resolution, to delineate the area flooded at each stage. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for postflood recovery efforts