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.

Local officials have faced angry questions about whether they could have warned people of dangerous flash floods in Texas Hill Country sooner. Rescue teams from neighboring states and Mexico have joined local efforts to search for survivors,