Flood Inundation Mapping to Aid Emergency Management Planning in the Cities of Hattiesburg and Petal

Author(s): Storm, J.

Many cities throughout Mississippi are located on or near major rivers or streams. As a result, residential, commercial, and industrial areas, as well as transportation structures can be at risk when flooding occurs. The cities of Hattiesburg and Petal are located along the Leaf River and have experienced flooding in the past including major events in 1961, 1974, and 1983. The largest recorded flood event occurred on April 15, 1974 and affected approximately 6,000 people and caused damages in excess of $8.3 million (1974 value unadjusted for inflation). The U.S. Geological Survey (USGS), in cooperation with the Cities of Hattiesburg and Petal, Forrest County, Mississippi Emergency Management Agency, Mississippi Department of Homeland Security, and the Emergency Management District, has developed a series of flood inundation maps at 1-foot increments ranging in stage from bank-full (22.0 ft) to approximately the peak of record flood (34.0 ft) for a 6.8 mile reach of the Leaf River through the cities. A one-dimensional steady-flow model was calibrated with the stage/discharge relationship at the USGS stream gaging station 02473000 Leaf River at Hattiesburg, MS (http://waterdata.usgs.gov/ms/nwis/uv/?site_no=02473000&PARAmeter_cd=00065,00060), and flood profile information obtained following the 1974 event. The model results were coupled with land surface elevation data from Light Detection and Ranging (LiDAR) surveys and GIS to produce inundation maps depicting the areal extent of flooding in Hattiesburg and Petal at pre-defined river stages. The inundation maps are available to the public through a web based interactive mapper that allows the user to select the river stage and then display the corresponding inundation map. Estimated water depths are shown by clicking anywhere within the inundated area on the map. Emergency management personnel will be able to use the inundation maps to manage and plan a course of action for future floods by pre-determining affected residences, businesses, municipalities, and roadways at forecasted National Weather Service (NWS) flood levels. Citizens will be able to visually determine what affect there may be to their property or business and take appropriate action ahead of time. The maps are available to the public through the USGS and from the NWS at the following links: http://wim.usgs.gov/FIMI/ http://water.weather.gov/ahps/inundation.php

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