Southwest Virginia's Big Laurel Creek - Whitetop Laurel Creek Watershed Study

The data used for this analysis was obtained from the U.S. Geological Survey (USGS) Web Soil Survey (WSS), which “provides soil data and information produced by the National Cooperative Soil Survey. It is operated by the USDA Natural Resources Conservation Service (NRCS) and provides access to the largest natural resource information system in the world” located online at https://websoilsurvey.nrcs.usda.gov/app/ . The USGS Web Soil Survey allows for the delineation and creation of an area of interest (AOI) using a shapefile of watershed boundaries, in this case the Big Laurel Creek – Whitetop Laurel Creek watershed.     The shapefile used to create the AOI is the watershed  shapefile delineated using the USGS’s StreamStats website ( https://streamstats.usgs.gov/ss/ ), which I described in a previous blog post Equipment Research and Useful Modeling Technologies for Watershed Analysis  November 05, 2025 .   To create the AOI, use the “Create AOI from Shapefi...

  The determination of the flood hazard within a watershed is typically defined in the United States as the maximum flooding extant that would be caused by a "100-year design storm”, or an annual exceedance percentage (AEP) of 1 percent (which equals the inverse of the 100-year event, i.e. AEP = 1 / rate of recurrence).   The AEP means that in any given year, there is a 1% chance that the AEP 1% flood will occur. Many people use the Federal Emergency Management Agency’s (FEMA’s) National Flood Hazard Layer (NFHL) as the definitive delineation of the extreme flood hazard to be considered in planning and mitigation of watershed management and improvement projects.  Taken from the webpage FEMA's National Flood Hazard Layer (NFHL) Viewer Based on my experience, relying on the FEMA NFHL alone  is insufficient for design.   A better method to determine the floodplain delineation and flooding hazard is to perform an independent hydrologic and hydraulic (H&...