Cataract Creek and Supai Flood - Aug 15-17, 2008
On the afternoons of August 15th-17th thunderstorms dropped heavy rain over the area between the city of Williams and the Grand Canyon, resulting in significant flooding on Cataract Creek and the Havasupai Reservation (village of Supai). Total rainfall for the period from Friday the 15th through Sunday the 17th was generally light in the Supai area, but as high as 4 to 6 inches within the Cataract Creek Drainage 20 to 40 miles southeast of Supai on the Coconino Plateau (as estimated by National Weather Service Doppler radar). As this water collected in the Cataract Creek drainage, it lead to significant flooding and the destruction of bridges and a campground in Supai Canyon, three homes destroyed near Supai Village, a small dam (Redlands Dam) breach on upper Cataract Creek, and hundreds of tourists and residents stranded in the Supai area. Multiple public safety agencies worked together to evacuate residents and tourists from the Supai area on Sunday and Monday (Aug 17th and 18th).
In the remote region of Coconino County from which Cataract Creek originates, accurate rain gauge data were unavailable. Radar estimated that scattered areas in the Cataract Creek watershed received 1 to 2.5 inches of rain on Friday, setting the stage for moderate to heavy flows on Cataract Creek. On Saturday, 1 to 3.5 inches of additional rain fell over the upper reaches of Cataract Creek. Another round of thunderstorms rolled through the area Sunday afternoon (well after the flood event began in the Supai area), producing additional (smaller) regions of 1 to 3 inch rainfalls on the drainage. Due to the localized and highly variable nature of rain associated with thunderstorms, the peak precipitation fell in slightly different locations of this drainage basin each of the three days, however a total of around 6 inches of rain fell at a few locations over the 3 day period, and many areas saw in excess of 3 inches over the period (three inches of rain represents more than a normal month's worth of precipitation in this area). See the image below which illustrates the location of the heaviest rain areas on each of these three days.
Runoff from Saturday's storms began to significantly impact Supai Village late on Saturday night (5 to 9 hours after the rain fell upstream on the Coconino Plateau). By early Sunday morning, severe flooding was occuring in the Supai area. Redlands Dam, a small holding pond (about 45 to 50 river miles upstream from Supai Village) failed at approximately 6:00 AM on Sunday morning, but likely added little to the enhanced flows on the stream.
On Sunday afternoon and evening additional thunderstorms moved through the upper Cataract Creek watershed, dropping up to 3 inches of additional precipitation. This rainfall washed out another road west of Valle, and kept the flood waters high in the Supai area through Monday, August 18.
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