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.

The Texas Hill Country has been notorious for flash floods caused by the Guadalupe River. Here's why the area is called "Flash Flood Alley."

This map shows where camps along the Guadalupe River were impacted by the July 4 flood. Meteorologists Pat Cavlin and Kim Castro detail how it all happened.

Follow along for developments on the July Fourth floods along the Guadalupe River in Kerr County and Central Texas.

Also: San Antonio mourned the victims in a Travis Park vigil; UTSA said one of its teachers died in the Guadalupe River flood; Kerrville officials said a privately owned drone collided with a helicopter conducting search and rescue operations.

Along the Guadalupe River, a 60-room inn and nearby homes were quickly filling with water. Confusion, desperation and heroism ensued.

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

Over the last decade, an array of local and state agencies have missed opportunities to fund a flood warning system intended to avert the type of disaster that swept away dozens in Kerr County, Texas.