If one is, gas stations will likely be very busy. If told to evacuate, do so as quickly as possible. Time is of essence. Things to Know About Flash Floods Flash floods can only take several minutes or hours to develop. If you live or are in an area you suspect to be a likely target for a flash flood and it is raining hard, be prepared to evacuate.
Flash floods are typically the result of the hillside runoff of heavy rain.
This situation can be enhanced if the hillsides have been stripped of trees, brush and other watershed by fires or other factors. The force of a flash flood is unlike anything you've ever seen. You don't want to be anywhere near it when it hits. You may have only seconds to escape death or serious injury. If you are forced to evacuate, move to higher ground and away from rivers, streams, creeks and storm drains.