The risk of the catastrophic flooding that struck Texas Hill Country as people slept on July 4 and left at least 120 dead was potentially underestimated by federal authorities, according to an ABC News analysis of Federal Emergency Management Agency data, satellite imagery and risk modeling.

At least 27 campers and counselors at Camp Mystic perished in Friday's floods, with the total death toll in the floods now surpassing 100.

When too much rain falls for the ground to absorb, it runs downhill, pulled by gravity into streams, creeks and rivers.