Meteorological Analysis for the Las Vegas, Nevada, Flood of 3 July 1975

Abstract

Meteorological data are analysed to determine the location and intensity of the rainstorms that led to flash flooding in the Las Vegas Valley and resulted in approximately $4.5 million in damages on 3 July 1975. The effective precipitation contributing to the flood was found to cover an area of 550 km2. Within this area two centers of heavy rainfall were found, one situated approximately 14 km southwest of the central business district and the other about 13 km north-northwest. Maximum rainfall amounts are estimated to be of the order of 3.0 inch. A maximum rainfall rate of 1.0 inch per hour was detected in a weighing-bucket raingage. Hail and surface wind gusts of about 50 kt were observed in the northwestern portion of the city. Furthermore, the area of heavy rainfall is shown to have developed over the Las Vegas Valley and not over the surrounding mountains. Integration of an isohyetal analysis shows that, at least, 2.3?107 m3 (1.9?104 acre ft) of water was available before infiltration. This amount of detail in the documentation of southwestern desert rainstorms is rarely available.