The region's rocky topography makes it especially prone to flash flooding, according to the TWRI. The type of clay-rich soil in the region contributes to the flash flooding because clay soils have low infiltration and trigger high water runoff once wet, it said.

Here's what to know about the deadly flooding, the colossal weather system that drove it and ongoing efforts to identify victims.

In Kerr County, home to youth camps in the Texas Hill Country, searchers have found the bodies of 68 people, including 28 children, Sheriff Larry Leitha said Sunday afternoon. Fatalities in nearby counties brought the total number of deaths to 79 as of Sunday evening.