Yes, flash flooding is terrifying and very dangerous. The water moves with such force that nothing, including boulders, vehicles, trees, etc. can withstand it. Normally this occurs when it is raining hard further up in the mountains. I lived for a time between the twin canyons sacred to the Apache between the Rio Grande and the Rio Conchos. It was very graphically revealed to me where the saying "God willing and the creek don't rise." came from. A calm rain falling then and there did not cause more than a slight swelling of the canyons output and smelled delicious. In the desert, any rain is welcome, at least in the first several minutes. The natives of the area always refered to the hardpacked hardpan, white crusted clay-based soil as caliche. I always understood it to refer to the soil, anyway.
