Kara M. Watson Toby L. Welborn Victoria G. Stengel David S. Wallace Jeremy S. McDowell 2018 vector digital data Denver, CO U.S. Geological Survey https://doi.org/10.5066/F7VH5N3N Kara M. Watson Glenn R. Harwell David S. Wallace Toby L. Welborn Victoria G. Stengel Jeremy S. McDowell 2018 Digital Document Reston, VA U.S. Geological Survey https://doi.org/10.3133/sir20185070 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, depth rasters, and coastal surge layer were created to provide an estimated extent of flood inundation in Coastal basins including East and West Matagorda Bay Subbasins, East and West San Antonio Bay Subbasins, and Aransas Bay Subbasin, Texas. The mapped area of the Coastal basins were separated into three sections based on the availability and location of high-water marks. The maps of the eastern part of the East Matagorda Bay Subbasin include a 17-mi reach of Peyton Creek and a 16-mi reach of Big Boggy Creek, and flood-inundation map for 6-mi reach of Little Boggy Creek in Matagorda County. The maps of the western part of East Matagorda Bay Subbasin include a 13.5-mi reach of West Carancahua Creek, 14.5-mi reach of East Carancahua Creek, and 9.6-mi reach of Keller Creek within Matagorda, Jackson, and Calhoun Counties. The maps of the middle part of the East Matagorda Bay Subbasin are for a 21-mi reach of the Tres Palacios River within Matagorda County. These geospatial data include the following items: 1. bnd_emb1, bnd_emb2, and bnd_tres_palacios; shapefiles containing the polygon showing the mapped area boundary for the Coastal basins flood maps, 2. hwm_emb_1, hwm_emb2, and hwm_tres_palacios; shapefiles containing high-water mark points used for inundation maps, 3. polygon_emb1, polygon_emb_2, and polygon_tres_palacios; shapefiles containing mapped extent of flood inundation for the Coastal basins, derived from the water-surface elevation surveyed at high-water marks, 4. depth_emb1, depth_emb2, and depth_tres; raster files for the flood depths derived from the water-surface elevation surveyed at high-water marks, and 5. coastal_surge.lyr; a layer file generated from the depth raster depicting water height above ground recorded at the 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). The HWM elevation data from the USGS Short-tern Network (STN) was used to create the flood water-surface raster file (U.S. Geological Survey [USGS], 2018, Short-Term Network Data Portal: USGS flood information web page, accessed February 13, 2018, at https://water.usgs.gov/floods/FEV.). The water-surface raster was the basis for the creation of the final flood inundation polygon and depth layer to support the development of flood inundation map for the Federal Emergency Management Agency's (FEMA) response and recovery operations. Flood documentation maps were created using GIS to show the extent of inundation along impacted river reaches in Texas following the August and September, 2017 Hurricane Harvey flood event. Flood-inundation maps are intended to estimate the areal extent and depth of flooding that correspond to the HWMs identified and surveyed by USGS hydrographers following the flood event. The mapped area boundary, flood inundation extents, and depth rasters were created to support the development of flood inundation maps for the Federal Emergency Management Agency's (FEMA) response and recovery operations following the August and September, 2017 flood event in Texas. 20170825 20170901 ground condition Complete None planned -96.496420999999 -96.272892999996 28.907735 28.615936 USGS Thesaurus flood extent high-water marks depth flood inundation mapping USGS Metadata Identifier USGS:5aa023fae4b0b1c392e6888a Geographic Names Information System (GNIS) Matagorda County Calhoun County Jackson County Texas West Carancahua Creek East Carancahua Creek Keller Creek None August 25- September 1, 2017 none Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The U.S. Geological Survey provides these maps "as-is" for a quick reference, emergency planning tool but assumes no legal liability or responsibility resulting from the use of this information. TXWSC Public Information Officer USGS, Texas Water Science Center, Southwest Region PIO - Public Information Office mailing and physical

1505 Ferguson Lane

Austin TX 78754 United States 512-927-5300 gs-w-txpublic-info@usgs.gov During large, short-term events, the USGS collects additional data (high-water marks, additional sensor deployments) to aid in documenting high-water events. This short-term event data is uploaded to the USGS Short-Term Network (STN) for long-term archival. The USGS Flood Event Viewer provides convenient, map-based and data table access to storm-surge and high-water mark event-based data collected within the USGS STN. Attributes for the high-water marks were input from surveyed values obtained at the recorded high-water mark. Surveys were conducted and recorded by USGS staff. High-water mark attributes went through quality assurance check before input into USGS Short-Term Network (STN). U.S. Geological Survey, 2017, Short-Term Network Data Portal, accessed on November 29, 2017, at ttp://water.usgs.gov/floods/FEV/ All values of depth are positive values. Data was checked for unattached polygons, which were deleted. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. Used GPS equipment to record locational data for high-water mark, NAD83 datum. Used cross-section data points from surveyed high-water mark data, accurate to the datum of the survey. No formal positional accuracy tests were conducted The first step in the generation of the flood-inundation maps was the creation of a flood-elevation raster surface. Flood extent and depth surfaces were created independently for each community, using the HWM elevations and the “Topo to Raster” interpolation/geoprocessing technique to create a water-surface elevation layer. A geographic limit was placed on the extent of the generated surface based on the distribution of HWMs and an understanding of the natural hydrologic flow in the area of each community. The ArcGIS Spatial Analyst Tool used to create the water-surface elevation raster was the “Topo to Raster” tool with the cross sections interpolation procedure (http://pro.arcgis. com/en/pro-app/tool-reference/3d-analyst/how-topo-to-rasterworks.htm, accessed March 2017). A cross section was drawn through the location of the HWM and was run perpendicular to the direction of the flood flow. If there were multiple HWMs in an area with the same or similar elevations, one cross section was drawn that either passed through the HWMs or through the center of a group of HWMs. The elevation of the HWM was assigned to the water-surface elevation of the cross section. This method was used when flooding was a result of overtopped banks of rivers or streams. An inundated area was depicted where the flood-elevation surface was higher than the DEM land surface. The depth of flooding was determined as the difference between the flood-elevation surface and the DEM land surface. Because of the large number of bridges involved in the flood-inundation mapping, the inundation surfaces were not clipped to show any bridges that were not inundated. 20180201 The digital elevation models (lidar dem) that were used for spatial processing are a 1.4-meter resolution dataset. Texas Natural Resources Information System, 2006, FEMA 2006 140cm Lidar: Federal Emergency Management Agency, accessed December 5, 2017, at https://tnris.org/data-catalog/entry/fema-2006-140cm/. 201802 Geographic Names Index System (GNIS) place names, search West Carancahua Creek, East Carancahua Creek, and Keller Creek, Texas, search Matagorda, Jackson, and Calhoun Counties Vector Albers Conical Equal Area 27.5 35.0 100.0 18.0 1500000.0 6000000.0 coordinate pair 4.145639387331813E-9 4.145639387331813E-9 SURVEY_FEET NAD_1983_Texas_Centric_Mapping_System_Albers Geodetic Reference System 1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.001 feet Attribute values Entity and attribute information are provided with each dataset to describes the tabular data associated with the data. The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. ScienceBase U.S. Geological Survey - ScienceBase mailing and physical

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. Inundated areas shown should not be used for navigation, regulatory, permitting, or other legal purposes. The U.S. Geological Survey provides these maps "as-is" for a quick reference, emergency planning tool but assumes no legal liability or responsibility resulting from the use of this information. These maps are only depicting the August and September, 2017 flood event and may not be representative of other flooding conditions. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20200827 Kara M. Watson U.S. Geological Survey, New Jersey Water Science Center Hydrologist mailing and physical

3450 Princeton Pike, Suite 110

Lawrenceville NJ 08648 United States 609-414-6115 kmwatson@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998