A new USGS report on peak discharge in New Mexico and surrounding areas, actually covers the Colorado Plateau, including a large part of Arizona. Area 9, covering the Plateau south of the Colorado River, mostly in Arizona, has the 3rd lowest envelope curve comparing maximum observed peak discharge to drainage area, of the whole region.
Ref: "Analysis of the Magnitude and Frequency of Peak Discharge and Maximum Observed Peak Discharge in New Mexico and Surrounding Areas," USGS Scientific Investigations Report 2008–5119