In what experts call "Flash Flood Alley," the terrain reacts quickly to rainfall steep slopes, rocky ground, and narrow riverbeds leave little time for warning.

Ten teenagers were killed after being swept away by rising floodwaters from the Guadalupe River while evacuating their summer camp in July 1987, according to the National Weather Service. (Credit: NWS

The downpours that swept away a children's summer camp and wreaked deadly havoc on huge areas of Texas caught holidaymakers by surprise. As the death toll passes 90 people, questions are being raised about whether adequate flood warnings were provided and why people weren't evacuated ahead of the deluge.

Officials are being pressed about their response and whether there could have been a better warning system.