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.

The data also highlights critical risks in other areas along the Guadalupe River in Kerr County, revealing more than twice as many Americans live in flood prone areas than FEMA's maps show.

Texas records show Camp Mystic had an emergency plan before floods killed at least 27 campers and counselors, but details of its storm response are still unclear.