A faster and economical approach to floodplain mapping using the SSURGO soil database

Abstract:

Floods are the most damaging of all natural disasters, adversely affecting millions of lives and causing financial losses worth billions of dollars every year across the globe. Flood inundation maps play a key role in the assessment and mitigation of potential flood hazards. However, there are several communities in the United States where flood risk maps are not available due to the lack of the resources needed to create such maps through the conventional modeling approach. The objective of this study is to develop and examine an economical alternative approach to floodplain mapping using widely available SSURGO soil data in the United States. By using the state of Indiana as a test case, floodplain maps are developed for the entire state by identifying the flood-prone soil map units based on their attributes recorded in the SSURGO database. For validation, the flood extents obtained from the soil data are compared with the extents predicted by other floodplain maps, including the Federal Emergency Management Agency (FEMA) issued Flood Insurance Rate Maps (FIRM), flood extents observed during past floods, and other flood maps derived using Digital Elevation Models (DEMs). In general, SSURGO based floodplain maps are found to be largely in agreement with flood inundation maps created by FEMA. Comparison between the FEMA maps and the SSURGO derived floodplain maps show an overlap ranging from 65 to 90 percent. Similar results are also found when the SSURGO derived floodplain maps are compared with FEMA maps for recent flood events in other states including Minnesota, Washington and Wisconsin. Although not in perfect conformance with reference flood maps, the SSURGO soil data approach offers an economical and faster alternative to floodplain mapping in areas where detailed flood modeling and mapping has not been conducted.