Floods in Utah, magnitude and frequency

This report presents a procedure for estimating the magnitude and frequency of floods, within the range of the base data, for any site, gaged or ungaged. From the relation of annual floods to the mean annual flood, a composite frequency curve was derived for recurrence intervals of 1.1 to 50 years. For regions of similar hydrologic characteristics, curves were developed by multiple correlation to express the relation of mean annual flood to drainage area and mean altitude. The records of gaging stations having 5 or more years of record were used as base data when the natural conditions of streamflow are not affected by works of man. For major rivers where the flow is affected by diversion or regulation, separate analyses were made for each stream. The results may be applied to any area in Utah, except the Great Salt Lake Desert and a small area of the State in the Snake River basin.