Inundation layers for the Brazos River for the August and September 2017 flood event in Texas

Hurricane Harvey made landfall near Rockport, Texas on August 25 as a category 4 hurricane with wind gusts exceeding 150 miles per hour. As Harvey moved inland the forward motion of the storm slowed down and produced tremendous rainfall amounts to southeastern Texas and southwestern Louisiana. Historic flooding occurred in Texas and Louisiana as a result of the widespread, heavy rainfall over an 8-day period in Louisiana in August and September 2017. Following the storm event, U.S. Geological Survey (USGS) hydrographers recovered and documented 2,123 high-water marks in Texas, noting location and height of the water above land surface. Many of these high-water marks were used to create flood-inundation maps for selected communities of Texas that experienced flooding in August and September, 2017. The mapped area boundary, flood inundation extents, and depth rasters were created to provide an estimated extent of flood inundation along the Brazos River. The mapped area of the Brazos Basin was separated into two sections due to the availability and location of high-water marks; upper and lower. The upper-reach inundation map includes 99-miles of the main stem of the Brazos River from Burleigh, Texas downstream to Thompsons, Texas. The upper-reach inundation map also includes a 43-mile reach of Bessies Creek beginning upstream from Pattison, Texas to the confluence with the Brazos River near Fulshear, Texas, and a 9-mile reach of Mill Creek from USGS streamflow-gaging station 08111700 Mill Creek near Bellville, Texas to the confluence with the Brazos River. Communities along the upper reach include San Felipe, Wallis, Brazos Country, Simonton, Weston Lakes, Rosenberg, Richmond, Sugar Land, and Booth, Texas, covering parts of Waller, Austin, and Fort Bend counties. The lower reach inundation map is for a 20-mile reach of the main stem of the Brazos River from Holiday Lakes, Texas to just upstream from Lake Jackson, Texas. Communities along the lower reach include the following communities in Brazoria County: West Columbia, East Columbia, Bailey’s Prairie, Brazoria, and Lake Jackson, Texas. These geospatial data include the following items: 1. bnd_brazos_upper and bnd_brazos_lower; shapefiles containing the polygon showing the mapped area boundary for the upper and lower Brazos River flood maps, 2. hwm_brazos_upper and hwm_ brazos lower; shapefiles containing high-water mark points used for inundation maps, 3. polygon brazos_upper and polygon_ brazos _lower; shapefiles containing mapped extent of flood inundation for the upper and lower mapped sections of the Brazos River, derived from the water-surface elevation surveyed at high-water marks, and 4. depth_upper and depth_lower; raster files for the flood depths derived from the water-surface elevation surveyed at high-water marks. The upstream and downstream mapped area extent is limited to the upstream-most and downstream-most high-water mark locations. In areas of uncertainty of flood extent, the mapped area boundary is lined up with the flood inundation polygon extent. The mapped area boundary polygon was used to extract the final flood inundation polygon and depth raster from the water-surface elevation raster file. Depth raster files were created using the "Topo to Raster" tool in ArcMap (ESRI, 2012).