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.

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.

During Texas's second-worst flood, Matthew Crowder ignored dispatch warnings to save a family. Now the community rallies to help survivors.