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.

Heavy rain poured over parts of central Texas, dumping more than a month's worth of rain for places like San Angelo.

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.

More than 100 people have been confirmed dead since July 4, when the Guadalupe River in central Texas swelled overnight and triggered flash floods that swept through an area known locally as “Flash Flood Alley.

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.

Texas flooding map, update: Thousands face new flash flood risk Ann-Margret, 84, Makes Rare TV Appearance and Shares 2 Secrets for Her Dance Moves

At least 104 people are dead after heavy rain led to devastating flooding in Texas. Kerr County was hit the hardest, with at least 87 deaths, including 30 children. President Donald Trump signed a disaster declaration for the county and the Federal Emergency Management Agency is on the ground there.

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