The second most deadly flash flood in the nation's history occurred along a creek, not even a river. Water came down multiple canyons and built up behind something--per wikipedia, a steam laundry that had been built across the creek. When the blockage failed, the water barreled into town with the force of a large river. About 250 people died in a community of roughly a thousand. Riders on horseback managed to warn the citizens of the next two communities down the creek and save the people in those towns. (Though some people there later died of typhoid due to unsanitary water conditions caused by the flooding).
In the 60s & 70s, multiple flood-control studies were done; and a concrete dam was built in the early 80s to prevent a similar event along that creek.
