Central Texas Flooding and Fatalities

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Episode released on October 30, 2025 
Episode recorded on September 3, 2025

Hatim SharifHatim Sharif discusses recent central Texas flooding in Kerr County and San Antonio and flood fatalities.

 Hatim Sharif is a Professor in the Department of Civil and Environmental Engineering at the University of Texas in San Antonio (UTSA). His research focuses on hydrometeorology, flooding, flood fatalities, and traffic safety. In addition to his engineering degrees, he has a Master’s degree in Public Health. 

 Highlights  |  Transcript

  • July 4th Kerr County Flooding (Fig. 1): key factors that led to the severe impact of this storm:
    • Large uncertainty with storm location of storms in flood forecasting which is critical when assessing watershed response
    • High intensity rainfall (~ 10 inches in 3 hr) along the South Fork Guadalupe River, with 100 – 500 yr return period events (Fig. 2) (Halff Engineering Report).
    • Severe flood peak occurred ~ 5 10 am on July 4th at the USGS Hunt gage (>37.52 ft) (Fig. 3a, 3b). Corresponding peak discharge at Hunt was 297,000 cfs (Fig. 3c).
    • The storm occurred at night with rain beginning shortly after midnight on July 4th.
    • NWS: warning potential heavy rains, July 1, flash flood warning into central Kerr County (1 am, Jul 4), flash flooding likely occurred (2.28 pm), flash flood emergency (4.20 am).
    • A total of 119 deaths attributed to the flooding in Kerr County area, including 27 girls and counselors from Camp Mystic (link).
    • US Coast Guard saved 165 people at Camp Mystic using helicopter rescues (link).
    • Camp Mystic, many buildings within the 100 yr flood plain, received exemptions from FEMA (link).
    • Previous flood peaks recorded at Hunt gage station (Fig. 4), including July 16, 1987 (28.4 ft).
    • Precipitation data estimated by data for 3h and 24h accumulation (link).
    • David Maidment in collaboration with USGS has been involved with installing radar gages on bridges in Texas that is funded by Texas Dept. of Transportation (Maidment link). The gage at Comfort, downstream of Hunt, showed velocity spike at ~ 8 am on July 4th, preceding the stage ht peak by about an hr, providing additional warning.
    • Storm direction is also important as storms moving downstream amplify flooding.
  • San Antonio flood, June 11-12, 2025 (NWS Storymap)
    • Fluvial flash flood associated with river channel, e.g., River Creek Channel and not pluvial (related to rainfall runoff)
    • A total of 13 people lost their lives during the flood, 11 people within a 1.5 mile stretch where Beitel Creek intersected service road (Loop 410) in San Antonio. Cars with people in them were swept away (Fig. 5, Han and Sharif, 2020).
    • Flooding linked to intense rain over short period (~ 3 hr). San Antonio Intl. Airport gage recorded 3.98 inches between 2.51 am and 3.51 am CDT June 12.  Nearly 6 inches fell within hours, ranking as San Antonio’s 10th wettest day on record.
    • Up to 7.2 inches fell between 2.00 and 6.00 am in upstream watershed, ≥100 yr, 3 hr storm event.
  • Wimberley floods in 2015
    • May 23, 24 along the Blanco River Basin, adjacent to the Guadalupe River Basin (Figs. 6, 7).
    • Rapidly moving floodwave resulted in 11 fatalities in the town of Wimberley (Furl et al., 2018).
    • Drivers of the flood include heavy storm cells over headwaters and slow movement downstream with very moist antecedent soil moisture conditions prior to flood onset.
  • Flash Flood Alley:
    • Texas Hill Country is known as Flash Flood Alley on the edge of the Balcones Escarpment  (Hatim Sharif, The Conversation, 2025).
    • its steep slopes, thin soils, and terrain carved by a dense network of small streams. These streams quickly funnel rainfall over the limestone bedrock into larger channels and rivers, leaving little time for absorption or warning. The result is rapid, high-velocity runoff that can transform normally dry creeks into dangerous torrents within hours (Fig. 8).
    • Also, the Balcones Escarpment plays a key role in enhancing rainfall across Central Texas. As moist air from the Gulf of Mexico moves inland, it is forced upward when it encounters the escarpment’s steep rise. This lifting cools the air, promotes condensation, and increases the likelihood of heavy precipitation. Combined with storm systems that can stall along the escarpment, the topography helps explain why this region is so prone to intense downpours and flash flooding.
  • Sources of flood information (Halff Engineering Report)
    • TexasFLOOD (https://texasflood.org/) includes
    • TxGIO Flood Viewer (link) displays lake levels, river heights. You can set up notifications for alerts when water is rising near your house.
    • TWDB TexMesonet (link) displays real time and seasonal data from weather stations across the state including precipitation, soil moisture, and other measurements.
    • First Street’s Flood Factor (link) national model used to assess potential flood risk from rain (pluvial flooding), streamflow (riverine), sea level rise, tide, and storm surge (coastal) for any location. It provides probabilistic flood risk maps based on elevation, climate, proximity to water bodies, and adaptation measures. The selected probabilities include 50%, 20%, 10%, 1% (100 yr return period), and 0.2% (500 yr return period).
    • Interagency Flood Risk Management (InFRM) Flood Decision Support Toolbox: shows estimated water depths corresponding to hypothetical flooding scenarios to address questions, such as “Will my house flood if a flood event causes the Colorado River to rise 10ft?”. Can access library of inundations related to river stages modeled by the USGS.
    • NOAA National Weather Prediction Center
    • USGS WaterWatch
    • NOAA Advanced Hydrologic Prediction Services (AHPS)
    • West Gulf River Forecast Service
  • Flood Fatalities:
    • Texas ranks number 1 for flood fatalities in the US (Table 1, Fig. 9).
    • Fatalities evaluated from 1959 – 2019 (61 yr period) (Han and Sharif, Water, 2021).
      • Flash flooding primary cause of fatalities
      • Purposely driving into floods accounts for ~ 70% of fatalities and walking into floodwaters another 16% of fatalities.
    • Texas has ~ 9,000 low water crossings in the State (State Flood Plan, 2024).
    • Almost 900,000 buildings in Texas are mapped within the 100 yr flood plain and 1.7 million within the 500 yr flood plain (link).
    • Men are more vulnerable than women to flood fatalities  (Han and Sharif, Water, 2021).
  • Communication is important: “Turn around, don’t drown”, Keri Stephens (UT Austin) developed new messages, such as “Keep Your Car High and Dry” that better resonates with young adults (link).
    • Most table-top exercises and drills generally only involve first responders and rarely entire communities (link).
    • Communicating flood risk needs to include information to advise people on what to do, such as stay home etc.
    • Norfolk (VA) uses a Waze program, in partnership with FloodMapp and RISE Resilience Innovations, to provide real time flood alerts for flooded streets. The system includes pluvial (rainfall), riverine, and coastal (tidal) flooding. Feedback from drivers improves the accuracy of the models.
Figure 1. Map of Kerr County showing Guadalupe River, including South Fork and North Fork tributaries and important sites relative to July 4th flooding.
Figure 1. Map of Kerr County showing Guadalupe River, including South Fork and North Fork tributaries and important sites relative to July 4th flooding.
Figure 2. Extreme rainfall frequencies in Upper Guadalupe watershed over 3-hr duration
Figure 2. Extreme rainfall frequencies in Upper Guadalupe watershed over 3-hr duration (Halff Engineering report).
Figure 3a. Map showing location of USGS Hunt gage and related upstream watershed
Figure 3a. Map showing location of USGS Hunt gage and related upstream watershed (link).
Figure 3b. Streamflow measurements at Hunt gage showing peak at 37.52 ft at 5.10 am
Figure 3b. Streamflow measurements at Hunt gage showing peak at 37.52 ft at 5.10 am (link).
Figure 3c. Stream discharge at Hunt, Texas with peak at 31,400 cfw at 05.10 am July 4, 2025
Figure 3c. Stream discharge at Hunt, Texas with peak at 31,400 cfw at 05.10 am July 4, 2025 (link).
Figure 4. Previous flood peaks at Hunt gage station, Texas
Figure 4. Previous flood peaks at Hunt gage station, Texas (link). The corresponding discharges include 314,000 cfs (July 4, 2025), 206,000 cfs (Jul 1, 1932), 108,000 cfs (Jul 16, 1987).
Figure 5. River stage and discharge at San Antonio River at Loop 410 with stage reaching 25.1 ft at discharge ~ 36,000 cfs (Link).
Figure 5. River stage and discharge at San Antonio River at Loop 410 with stage reaching 25.1 ft at discharge ~ 36,000 cfs (Link).
Figure 5b. 14 vehicles swept off access road near Beitel Creek.
Figure 5b. 14 vehicles swept off access road near Beitel Creek.
Figure 6. The Blanco River watershed and relevant tributaries related to the Wimberley flood in 2015 (Furl et al., JoH, 2018).
Figure 6. The Blanco River watershed and relevant tributaries related to the Wimberley flood in 2015 (Furl et al., JoH, 2018).
Figure 7. Streamflow (left) and stage (right) during Wimberley floods.
Figure 7. Streamflow (left) and stage (right) during Wimberley floods. Gage locations are shown in Fig. 6 (Furl et al., JoH, 2018).
Figure 8. Flash Flood Alley is represented by the light green crescent.
Figure 8. Flash Flood Alley is represented by the light green crescent. The background colors show the slope of the land, with red the sharpest rise. Zhongyu Han and Hatim Sharif, GIS Application: Flood Risk Management, 2020
Table 1. Flood fatalities in the US and their ranks based on data from 1959 – 2019 (Han and Sharif, Water, 2021).
Table 1. Flood fatalities in the US and their ranks based on data from 1959 – 2019 (Han and Sharif, Water, 2021).
Flood fatalities in the CONUS (1959 – 2019) by state (Han and Sharif, Water, 2021).
Figure 9. Flood fatalities in the CONUS (1959 – 2019) by state (Han and Sharif, Water, 2021).

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