Flash Flood Alley Segements

South Central Texas October, 1998

Storm Summary
& Rescue Efforts
Property Damage
& Relief Efforts
Success Stories
Regional Flood
& Publications
Known Hazards
in Central Texas
Flood Clean Up after 30 inches
October 1998

South Central Texas October, 1998
Max. Precipitation: 30 inches
Deaths: 32
Damage: 1.5 Billion (approx.)

Floods in the Guadalupe and San Antonio River Basins in Texas, October 1998

Severe flooding in parts of south-central Texas resulted from a major storm during October 17-18, 1998. The flooding occurred in parts of the major streams and tributaries of the San Jacinto, San Benard, Colorado, Lavaca, Guadalupe, and San Antonio River Basins. Peak gage height, peak streamflow, and documentation of the significance of the peaks were compiled for the streamflow-gaging stations where the storm caused substantial flooding. This information is available on the U.S. Geological Survey (USGS) world-wide web site at http://tx.usgs.gov/alert/oct_floods_98.html.

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Flood Map


Staying Safe During a Flood

GBRA " Staying Safe"
Publication on '98 Floo

The majority of the water fell in the upper river basin (as opposed to the lower basin deluge of '98). This brought Canyon Dam into its most important role since it was built in 1932? At the flood peak, the dam held back 70, 000 cfs - though 70,000 more escaped over the spillway as it was designed to do.

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Texas Storm Map

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The San Antonio River Tunnels proved their value to that city as they diverted water safely underneath downtown. Construction on these tunnels was finished by the San Antonio River Authority just months before the massive storm hit.



River Tunnel

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Storm Description (from USGS storm summaries)

October 17 to 18, 1998

Up to 30 in. of rainfall occurred in a 2-day period--about 5,000 square miles in parts of 19 counties received at least 8 in. of rain. Thirteen streamflow-gaging stations in the Guadalupe and San Antonio River Basins recorded peak discharges equal to or greater than the 100-year peak and record-breaking peak discharges were recorded at 11 of the stations. read more...

Deaths and Damage:   Thirty-two lives were lost and property damage was estimated to be approximately one billion dollars.

Max. Precipitation:   30.00 in. (Hays Co.) 22.00 in. (Comal Co.)

Severity:   Catastrophic

Storm Center(s):   Hays Co., San Marcos Comal Co.

References:   Slade and Persky, 1999


The storms produced large volumes of runoff and as many as four flood peaks at each of many streamflow-gaging stations in the Brazos, Colorado, and Guadalupe River Basins. Record flood stages occurred at sites on the Medina River, San Antonio River, Sabinal River, and Nueces River. For the first time since it filled in 1968, Canyon Lake (northeast of San Antonio) poured over its spillway, adding to the flooding in the Guadalupe River. Emergency managers also were concerned about the 90-year-old dam at Medina Lake (west of San Antonio). Medina Lake topped its spillway and rose to within 18 inches of the top of the dam. Areas downstream from the dam were evacuated as a precaution to the fear of dam failure.