Over just two hours, the Guadalupe River at Comfort, Texas, rose from hip-height to three stories tall, sending water weighing as much as the Empire State building downstream roughly every minute it remained at its crest. The force of floodwater is often more powerful and surprising than people imagine.

Texas Hill Country, where much of the flooding took place this time, is often referred to as “flash flood alley.” It's home to steep terrain and a lack of vegetation that creates a perfect storm for waters to rise quickly.