How a confluence of extreme weather, geography and timing created Texas' flood disaster

Texas leads the country in flood deaths. Steep hills, shallow soils and a fault zone have made Hill Country, also called "flash flood alley," one of the state's most dangerous regions.

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Gagne reviewed the modeling tools available to NWS forecasters. The most urgent warnings went out, he said, when the two NOAA tools showed rainfall rates beginning to spike.

That gave people just a few hours to flee, assuming they received the warnings through cellphone alerts, weather radio broadcasts or by other means. Some residents likely didn't get the alert and Kerr County does not have a siren.

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During the six-decade period of study, the National Weather Service's San Antonio/Austin area forecasting office counted the second-highest number of flooding-related deaths in the country. Many of those took place in the Hill Country, which some call "flash flood alley."

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Sharif said steep hills, narrow canyons carved out of limestone, rapidly funnel water from smaller creeks into larger ones and then into swollen rivers. In many areas, there's only a few inches of shallow soil on top of bedrock. Narrow creeks are etched into bedrock.

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