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ground cover. Increased precipitation supports dense pine and aspen forests above this el evation to timberl ine. Rock outcrops and tundra grasses predominate on the high mountain peaks where cl imatic conditions are too severe for forest growth. A number of irrigation ditches; such as the North Fork Ditch, Cameron Ditch, and the Missouri Park Ditch, convey water across natural drainage boundaries into adjacent basins. The Larkspur Ditch conveys water frcrn the headwaters of Tcrnichi Creek in the Colorado River Basin across the Continental Divide at Marshall Pass and into the Poncha Creek Basin. 2.3 Principal Flood Problems While slopes are steeper in the upper drainage basins, the dense vegeta ti on in these areas serves to reduce ra i nfa 11 runoff. A greater percentage of runoff is permitted by the sparse vegetation of the foothills and pasture land at the lower elevations. Conse- quently, the majority of the flood problems in the study area are caused by rapid snowmelt. This type of flooding has a long duration runoff which results in a continuous rise in water level thus producing a high runoff volume. Flood potential also exists from long and short duration rain storms. These types of floods are characteri zed by high peaks, small vol urnes and short dura ti on. The potenti a 1 for the most severe fl oodi ng is created by the combination of rapid snowmelt with long duration rainfall. Detailed information on floods before the turn of the century is very limited. Information on past flooding is based on newspaper accounts and intervi ews with longtime resi dents of the area. Large fl oods occurred at Salida in 1901, 1923, 1924, 1947, 1948, 1957 and 1973. These floods have caused major damage, disrupting highway and railroad traffic and communication services, drowned livestock, destroyed agricultural lands, roads, bridges and buildings. The flood of June, 1957, is considered the most severe flood known in Sal ida. The South Arkansas River reached a record high of 8.1 feet (Reference 3). The flood was triggered by high temperatures over an extended period of time and melted the heavy snowpack of the previous winter. Diversion ditches frcrn the South Arkansas River carried almost twice as much water as compared with other years. A farm bridge on the Hutchinson Ranch was lost and County Road 125 bridge was threatened. Other low-level private bridges and foot bridges were al so lost. Peak discharges have been estimated by correlation to other gaging stations since the gaging station on the South Arkansas River near Sal ida was not in use from 1940 to 1971. The peak discharge was estimated at 1841 cfs (Reference 1). This discharge represents a recurrence interval of approximately 50 years. 5