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.

This week in Texas, estimates put the number of people still missing from the Hill Country floods at 161, a daunting figure atop at least 120 deaths confirmed by authorities. But that missing person tally might not be as precise as it seems.

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

Crews are digging through mountains of debris along the Guadalupe River as they continue their desperate search