Laserfiche WebLink
<br />STORM OF MAY 5-6, 1973, IN THE DENVER METRO AREA: <br /> <br />FREQUENCY AND EFFECT <br /> <br />By G. Louis Ducret, Jr., and Wallace R. Hansen <br /> <br />INTRODUCTION <br /> <br />A light drizzle that began to fall on parts of the Denver metropolitan <br />area (fig. 1) late Saturday evening, May 5, 1973, was the forerunner of a <br />general long-duration rainstorm which, by daylight Sunday, had saturated the <br />soils of the area and sent creeks and gullies swelling with runoff. Rainstorm <br />total precipitation ranged from 2.06 to 4.38 inches at U.S. Geological Survey <br />rainfall-runoff stations in the Denver area. A typical small stream hydro- <br />graph for May 5-6, 1973 (fig. 2) shows that the runoff increased gradually as <br />the soil reached saturation and the ground became less capable of absorbing <br />steady precipitation. Figures 3 and 4 are hydrographs from major drainage <br />basins and represent typical responses of large drainages within the storm <br />area. Irrigation canals that crisscross the Denver area began to intercept <br />the increasing overland runoff. The water levels in many reservoirs and <br />lakes began rising towards capacity. <br /> <br />By midday on Sunday the small streams had reached their peak discharge; <br />many canal banks, weakened by capacity flows, broke (fig. 5); reservoirs were <br />spilling; and lakes were flooding adjacent areas. Meanwhile, the South Platte <br />River and major tributaries within the storm area were rising toward peak dis- <br />charges late Sunday night and early Monday morning. <br /> <br />Purpose and Scope <br /> <br />The U.S. Geological Survey, in cooperation with the Urban Drainage and <br />Flood Control District, was operating 27 rainfall-runoff data collection <br />stations in the Denver metropolitan area at the time of the subject storm. <br />Because of the widespread interest in the May 5-6, 1973, rainstorm and <br />resulting runoff, this report is designed to provide a preliminary evaluation <br />relative to the frequencies of storm precipitation and runoff. Pertinent <br />discharge data from the South Platte River and major gaged tributaries in <br />the Denver metropolitan area are included. The locations of all stations <br />and miscellaneous peak flow sites as referenced in this report are showe <br />in figure 1. Appendix 1 provides location data for these stations. <br /> <br />1 <br />