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<br />2,3 Principal Flood Problems <br /> <br />While slopes are steeper in the upper drainage bisins the dense <br />vegetation in these areas serves to reduce rainfall runoff. A <br />greater percentage of runoff is permitted by the sparse vegetation <br />of the foothills and pasture land at the lower elevations. <br />Consequently. the majority of the flood problems in the study area <br />are caused by rapid snowmelt. This type of fl&oding hiS a long <br />duration runoff which results in a continuous rise in witer level <br />thus producing a high runoff volume, <br /> <br />Flood potential also exists from long and short duration rain <br />storms, Floods from short duration rain storms are characterized <br />by high peaks and small volumes, The potentiil for the most severe <br />flooding is created by the combination of rapid snowmelt with long <br />duration rainfall. <br /> <br />Flooding also occurs during the winter months from ice jamming. <br />This is limited to areas downstream of the corporate limits. <br /> <br />Detailed information on floods before the turn of the century is <br />very limited. Information on past flooding is based on newspaper <br />accounts and interviews with longtime residents of the area. Large <br />floods occurred at Gunnison on the Gunnison River in 1917, 1918, <br />1920, 1921 and 1957. Along Tomichi Creek large floods occurred in <br />1939, 1957, 1970 and 1973. These floods have caused major damage, <br />disrupting highway and railroad traffic and communication services, <br />drowned livestock, destroyed agricultural lands, roads, bridges and <br />buildings. <br /> <br />The flood of June, 1918, is considered the most severe flood known <br />in Gunnison. The Gunnison River reached a record high of 3 feet <br />over the road west of town, which is now US 50, accordinq to the <br />local newspaper (Reference 31. The flood was triggered by high <br />temperatures for an extended period of time and heavy snowfall of <br />the previous winter, The road bed north of town, now Colorado <br />Highway 135, was washed out. Other low-level private bridges and <br />foot bridges were also lost. Peak discharges have been estimated <br />by the USGS at 11,400 cfs for the flood of June, 1918, on the <br />Gunnison River (Reference 51. <br /> <br />Flooding problems within the City of Gunnison are aggravated by the <br />restriction of drainage channels by vegetation growth and <br />accumulated debris. <br /> <br />2.4 Flood Protection Measures <br /> <br />The City of Gunnison adopted the "Floodplain Permit System <br />Ordinance, 1977," which stated regUlations concerning flood <br />plain management and protection measures for new buildings and <br />subdivi sions, <br /> <br />There is very little natural or man made flood protection for the <br />City of Gunnison along either Tomichi Creek or the Gunnison River. <br /> <br />5 <br />