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.

Walston drove from his home to the Center Point Bridge on FM 480 near Highway 27, where he shot video of the river below. He recorded nearly 38 minutes of surging water as it rose over 20 feet, carrying massive cypress trees, debris and even a house.

Officials in Texas are facing questions about whether they did enough to get people out of harm's way before a flash flood swept down the Guadalupe River and killed at least 120 people, including more than two dozen children and counselors at an all-girls Christian camp.

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.

Two 8-year-old sisters from Dallas who had just completed 2nd grade. A beloved soccer coach and teacher. An Alabama elementary school student away from home.

Flash flooding is common enough around the crescent-shaped region from Dallas through the Hill Country, the area earned the nickname "Flash Flood Alley."

Teens at the Pot O’ Gold Christian Camp near Comfort, Texas, were swamped by a wall of water as they tried to escape.

The region of Texas where flash flooding killed more than 90 people -- including dozens of campers -- is known for its tendency to experience flood emergencies.

The older brother of former San Francisco Giants pitcher Tyler Walker is missing after Texas flooding, along with his wife and their son.