The need for the law came from the lack of storm sewers in the deserts of the Southwestern United States and heavy rainfall in the desert, usually associated with the summer season. This lack of adequate drainage leads to short term flooding. Many desert cities and towns don't use culverts to channel minor washes (also known by the Spanish name arroyos) beneath the roadway. Only major washes and floodplains have bridges over them. Storm drains are spaced quite far apart when they are present at all. Consequently, during rain storms, storm runoff flows over the roadway. During hard, strong rain storms, the washes, underpasses, and areas around large storm drains can flow fast and deep enough to pick up an automobile and carry it downstream. During particularly strong floods, one might see a motorist stuck in the middle of a wash, sitting on the roof of a dead car submerged to the windows.