Flood hydrology near Flagstaff, Arizona

Peak discharges measured at 11 crest-stage gages near Flagstaff were used to determine discharges that have recurrence intervals of 2, 5, 10, and 25 years. The discharges were related to drainage area and urban development in order to provide equations for design of hydraulic structure in the Flagstaff area. Peak discharges in various parts of the city differ considerably. The differences are due to combinations of several drainage-basin characteristics. Coefficients for the rational formula were computed for drainages of less than 10 sq mi. Coefficients for undeveloped rural basins are less than 0.1; coefficients for urban development range from 0.05 to 0.39. This range in values indicates that, with some limitations, coefficients found in general engineering handbooks for urban types of land use are applicable for design in Flagstaff. (USGS)