A retired nurse, her son and a family friend say they were lucky to survive last week's flash floods in Texas that killed more than 100 people, including many summer campers.

The Texas Hill Country has been notorious for flash floods caused by the Guadalupe River. Here's why the area is called "Flash Flood Alley."

Virginia Hollis is one of the girls missing from Camp Mystic, according to a social media post from Bregman. She was staying in Cabin Twins 2 when floodwaters from the Guadalupe rushed through the campgrounds. Ellen is a missing Camp Mystic camper, according to her family.

Flash floods last week in Texas caused the Guadalupe River to rise dramatically, reaching three stories high in just two hours.

Flash floods surged through in the middle of the night, but many local officials appeared unaware of the unfolding catastrophe, initially leaving people near the river on their own.

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.

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.

Officials in Texas are facing mounting 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 more than 100 people, including at least 27 children and counselors at an all-girls Christian camp.