Flash floods in Texas have killed at more than 80 people, many of them children.Heavy rains fell quickly in the predawn hours Friday in the Texas Hill Country, causing the Guadalupe River to rise 26 feet in just 45 minutes.

Hurricane Katrina is the deadliest flood event in the U.S. in the past 25 years. The storm crashed into the Gulf Coast and caused devastating flooding when levees failed in New Orleans, where people had to be rescued by boat and helicopter from rooftops.

After floods left more than 80 dead in Texas, questions are emerging about how to provide better warnings in a region known as “flash flood alley.”