Rainall intensity-duration-frequency relations for the Wasatch Mountains of northern Utah


  • Eugene E. Farmer,

  • Joel E. Fletcher


The results of data analyses for 25 precipitation intensity stations in central and north central Utah at altitudes of 4350–10,150 feet are presented. All data were collected from May 1 to October 31. Each station has 10 or more years of record; one station has 30 years of record. Analyses were made of (1) record consistency, (2) definition of local precipitation zones, (3) intensity-duration-frequency characteristics, (4) 24-hour depths, (5) monthly depths and number of storms, (6) storm occurrence by hour of the day, and (7) storm occurrence by storm duration. The precipitation zone at 6500–8000 feet altitude is expected to receive the greatest rainfall intensities. There is a trend toward reduced intensities with increasing elevation, but the trend is not uniform. However, those precipitation zones receiving the greatest intensity of rainfall do not coincide with those zones receiving the greatest depth of rainfall. Rainfall depth generally increases with altitude, but on one study area the zone of greatest depth was not the highest zone. There is a marked difference between the two study areas with respect to the distribution of storm occurrence by hour. This difference is attributed to differences in storm type and in the principal source of summer moisture. Average storm length varies inversely with altitude.