Flash floods happen when heavy rains unleash more water than the ground can absorb, causing that water to pile up and flow to low-lying areas

Flash flood alley is a curved-shaped region about 300 miles long and 50 miles wide in central/south-central Texas, extending from north of Dallas to southwest of San Antonio. Its location, weather patterns, and geology often combine to create devastating floods.

At least 82 people are dead and at least 41 more are missing after devastating flash floods slammed Texas Hill Country, with water rescues taking place along the Guadalupe River, which rose rapidly early Friday morning to the height of a two-story building.