Plans to develop a flood monitoring system in the Texas county hit hardest by deadly floods were scheduled to begin only a few weeks later.

Over just two hours, the Guadalupe River at Comfort, Texas, rose from hip-height to three stories tall, sending water weighing as much as the Empire State building downstream roughly every minute it remained at its crest. The force of floodwater is often more powerful and surprising than people imagine.

The deadly Texas floods have brought the state's approach to land approvals, especially in flood-prone areas, under more scrutiny.

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.

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

Follow for live updates in the Texas flooding as the death toll rises to 120, as rescue operations start to shift to recovery phase

Four North Texas families say their daughters were among those who did not survive the flash flooding at Camp Mystic Friday in the Hill Country.