FLOOD09087 - Laserfiche WebLink

Home Browse Search

and woodland. Except for a narrow fringe of Rocky Mountain juniper, Ponderosa pine makes up the bulk of the woodland cover. The wood- lands are very picturesque, and most of the area is used for grazing and homesites, with both year-around and summer homes. Average annual precipitation is approximately 18.5 inches and the normal mean temperature is 5l.80F. Extremes of annual precipitation have varied from a maximum of 29.09 inches in 1938 to a minimum of 10.91 inches in 1954. The mean maximum and minimum temperatures in July are 85.30F and 59.0oF, respectively. 2.3 Principal Flood Problems Storms producing floods occur during May through September. During this period, warm, moist air masses from the Gulf of Mexico combine with cold and comparatively dry air from the polar regions, causing thunderstorms. These are usually characterized by high rai.nfall intensities of short duration, producing high peak flows and moder- ate water volumes. Frequently, thunderstorms are severe and occur over rather limited areas. Floods are especially severe if the thunderstorms follow a period of high snowmelt or prolonged rainy weather. Historical documentation of flood damage is meager. This is probably due to the small stream size and lack of extensive urbanization. Major flood damages in the watershed are to roads, bridges, irriga- tion structures, and agricultural land. Duration of flooding is brief, due to steep slopes and small drainage area. In general, peak flows last from 1 to 4 hours during a flooding period of from 6 to 24 hours. The following floods have been reported: The floods of 1876; 1891; June 3, 1921; and May 26, 1935 w~re caused by rapid snowmelt in the mountains and heavy rainfall in the area of Lafayette. A flood occurred in June 1896 which was reported as the maximum of record in the part of the valley near Louisville. The flood of September 2, 1938, was caused by cloudbursts in the mountains and foothills, resulting in a flood slightly higher than that of 1935. Using slope-area measurements, the u.s. Army Corps of Engineers estimated the flood discharges on Coal Creek near Erie to be 13,200, 7,800, and 3,500 cubic feet per second (cfs) in 1876, 1921, and 1938, respectively (Reference 2). The 1876 flood is the largest recorded at the Town of Erie and approximates the 100-year recurrence interval, as determined by the U.S. Soil Conservation Service (Reference 2), using synthetic methods for flood routing. The most recent floods in the watershed occurred on June 9, '1949; May 9, 1957; and May 1969. The fallowing are recorded accounts of flood damage on Coal Creek and Rock Creek: 4 ~: .