Comparison of the New Digital Flood Insurance Map (DFIRM) with the Existing FIRM, Wilson, North Carolina

The 100-yr floodplain on new Digital Flood Insurance Rate Maps (DFIRMs) for the city of Wilson, North Carolina, were compared with the floodplain defined by the existing Flood Insurance Rate Maps (FIRMs) and validated against two recent flood events. Of the 16,776 ha in the study area, 16% and 79% were delineated as areas within and outside of the 100-yr floodplain on both flood maps, respectively. In the remaining 5% of the study area, areas located within the 100-yr floodplain (based on the DFIRMs) increased by 2.8%. The 100-yr floodplain on both flood maps was also compared to the September 1999 and August 2002 flood events. For the 1999 flood, only 67% and 62% of the flooded parcels were within the 100-yr floodplain on the DFIRMs and FIRMs, respectively. Of the 29 street intersections flooded during the 2002 flood, 52% were identi- fied by the DFIRMs, and 38% by the FIRMs. Although the 100-yr floodplain on the DFIRMs performed a better overall job of delineating the flooded parcels and intersections, it did miss a portion of the flooded areas.