Reconstructing the Texas Flood of 1938

City of Brady in Texas
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Published November 9, 2010
Location Texas
Categories Agriculture, Infrastructure Management, Technology Commercialization, Water Resources
Author Jude Kastens
License Attribution Non-Commercial Share Alike - Creative Commons License

Description

During July 1938, intense rainfall across several counties in central Texas produced record flooding along the San Saba River and Brady Creek, in addition to other waterways. The floodwaters had a devastating impact on many local communities, including the cities of Brady (McCulloch County), San Saba (San Saba County), and Menard (Menard County).

The Kansas Biological Survey’s FLDPLN (“Floodplain”) model and U.S. Geological Survey’s 1/3 arc second (10-m) NED elevation data (downloaded in March 2010) were used to simulate flood depth and flood extent associated with this 1938 flood event for approximately 111 miles of San Saba River reach and approximately 33 miles of Brady Creek reach. The FLDPLN model was calibrated using landmark-referenced high water mark data collected by the U.S. Army Corps of Engineers at the time of the event and provided to KBS by the Texas Natural Resources Information System (TNRIS), part of the Texas Water Development Board. These results were developed as a demonstration of FLDPLN model capabilities, at the request of TNRIS. Communities in the study area will be able to use the resulting flood maps for developmental planning guidance and for flood emergency preparedness.

Equivalent analyses were also performed using alternative elevation data. First, LiDAR elevation data (provided by TNRIS in May 2010) covering a polygon interior to the study area were downsampled to the 10-m NED grid and substituted into the NED data. The LiDAR data have partial coverage of the stream reach under study. Second, Intermap elevation data (provided by Intermap in October 2010) covering a polygon enveloping the study reach floodplain were downsampled to the 10-m NED grid and substituted into the NED data. Thus there were three analyses in total, one using NED data, one using combined LiDAR-NED data, and one using primarily Intermap data.

This web mapping application and web mapping service display vector and raster data, including the high water mark points that were used for model calibration, the DEM-derived stream reaches to which the model was applied, and the resulting modeled flood depth grids, which show the estimated extents of inundation and flood depths. These data layers were generated by the Kansas Remote Sensing Program (KARS) at the Kansas Biological Survey located at the University of Kansas, in collaboration with TNRIS. For more information, contact Jude Kastens (jkastens@ku.edu).

Results from the study were presented at the 2010 Texas GIS Forum in Austin, TX, on October 28, 2010 (download presentation).

The FLDPLN model was originally developed at KBS for river valley identification and “depth to flood” mapping. In addition to flood event simulation, the FLDPLN model is currently used by KBS scientists for emergency response applications, wetland identification and analysis, river valley morphology assessment, lake extent mapping, and as a guide for floodplain geometry specification in hydraulic analyses.

Web Maps

Web Mapping Application

http://kars.ku.edu/texasflood1938

Web Service (ESRI)

http://kars.ku.edu/ArcGIS/rest/services/Texas_Flood_1938/MapServer