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.

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

Torrential rains triggered flash flooding in central Texas Friday, killing more than 100 people, including dozens of children who were at summer camps along the Guadalupe River. The river rose more than 20 feet in less than two hours.

Meanwhile, Texas authorities have pledged to continue search and rescue operations until every missing person is found.