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.

At least 24 people are dead after heavy rain lashed Texas, leading to "catastrophic" flooding. Texas Gov. Greg Abbott said emergency responders remained in a search and rescue posture, hours after the flooding along the Guadalupe River inundated nearby areas.

US President Donald Trump was set to visit Texas on Friday as questions mounted over the response to flash floods that have left at least 120 people dead, including dozens of children. FEMA began its response to the Texas flash floods over the weekend after Trump signed a major disaster declaration to release federal resources.

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

A retired nurse, her son and a family friend say they were lucky to survive last week's flash floods in Texas that killed more than 100 people, including many summer campers.

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.