Click to view larger image. Arizona has both local and regional floods. Local floods occur most frequently. Local floods occur primarily in basins of less than about 100 mi 2 because the area affected by an individual thunderstorm is small. Cumulative damage from local floods can be substantial, even though a single flood rarely causes much damage.
Local floods cause several drownings annually in Arizona.
Eight people were killed. These larger peaks were not noticed by the public and caused no damage because no one had been at risk on the canyon streambed when the peaks occurred. Regional floods generally occur between September and March in drainage basins larger than 200 mi 2 . The areal extent and severity of five regional floods, as determined from streamflow data and other sources, are shown in Figure 1 . These floods are caused by several days of intense regional rainfall, sometimes combined with snowmelt.