With more than 170 still missing, communities must reconcile how to pick up the pieces around a waterway that remains both a wellspring and a looming menace.

The Guadalupe River has a history of deadly flooding. Here is a look over the decades. (AP video Marshall Ritzel/Albee Zhang)

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.

Two days before flash floods on the Guadalupe River in Texas killed dozens of campers at a Christian girls summer camp, a state inspector approved operations, noting there was a written plan for responding to natural disasters.

Texas inspectors approved Camp Mystic’s emergency plan just two days before devastating floods killed over 27 people, mostly children, at the Texas summer camp

Camp Mystic was overrun by flash flooding that started on Independence Day. Rapidly rising waters ripped through the century-old all-girls Christian summer camp, killing at least 27 people. Others are still missing.

Over 100 people have died after heavy rain pounded Kerr County, Texas, early Friday, leading to "catastrophic" flooding, the sheriff said.

The flash flood was the deadliest from inland flooding in the U.S. since Colorado’s Big Thompson Canyon flood on July 31, 1976, killed 144 people, said Bob Henson, a meteorologist with Yale Climate Connections. That flood surged through a narrow canyon packed with people on a holiday weekend marking Colorado’s centennial.