LITE Flood: Simple GIS-Based Mapping Approach for Real-Time Redelineation of Multifrequency Floods

Flood zones with 1 and 0.02% of annual flooding chance are projected in FEMA's digital flood insurance rate maps (DFIRMs) and are suited for identifying flood risk at the largest impacts. However, less severe floods, which are not mapped in DFIRMs, still cause significant damage and occur on a more frequent basis. This article uses a simplified rapid geographic information system (GIS)-based solution for on-the-fly inundation mapping of small flood events. The linear interpolation technique (LITE Flood) was developed to approximate the prone flood zones based on river stage without performing additional hydraulic simulations. The approach was evaluated by comparing the results to the corresponding storm scenarios simulated in a standard river hydraulics simulator. The case study is a portion of Wolf River and its two main tributaries in Shelby County, which is located in the southwest corner of Tennessee. The stream channelization of the lower portion of Wolf River has mitigated large flood events, while causing frequent flooding from less severe storms. LITE Flood produced results with good to acceptable accuracy. LITE Flood can be used for rapid, cost-effective, and real-time mapping of multifrequency floods at a large scale, thereby aiding local community emergency response agencies who often do not have the expertise to perform more sophisticated hydraulic modeling but do have a GIS capacity.