US national wide gSSURGO based floodplain maps are developed by using Gridded Soil Survey Geographic (gSSURGO) database. Specifically, the SSURGO map units are joined to certain key attributes in the muaggatt and component tables. After joining the spatial data to ‘muaggatt’ and ‘component’ tables, map unit polygons are selected by the following two queries: (1) "geomdesc" LIKE '%flood%' AND "comppct_r" >= 85) OR "taxsubgrp" LIKE '%fluv%'; (2) “muname" ='Water' OR "flodfreqdcd" in ('Rare', 'Occasional', 'Frequent', 'Very Frequent')". The result from this query, which is a polygon feature class or shapefile, is then dissolved to remove any area less than 15000 square meters are removed. More details about this approach can be found in the following publication: Sangwan, Nikhil, and V. Merwade, A faster and economical approach to floodplain mapping by using soil information, Journal of American Water Resources Association, 51(5): 1286-1304. (2015)
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This floodplain map was created with Esri ArcGIS 10.3.1, and revised in March 2016. It is in GCS North American 1983 coordinate system.