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Associations have moderate infiltration rates, while the soils of the Fluvaquents-Fluvents Association have moderate to low infiltration rates (Reference 10), The Cooper Slough study reach is approximately 1.5 miles long, The tributary area for the Cooper Slough basin is approximately 10,2 square miles (Reference 2). The basin is approximately 6 miles long and 1,75 miles wide, and is fairly flat, with poorly defined drainage patterns. Cooper Slough flows in a southerly direction and joins Boxelder Creek in the vicinity of Prospect Street and 1-25, east of the City of Fort Collins. The Dry Creek study reach is approximately 1.9 miles long. The stream is a tributary of the Cache La Poudre River, which flows from the northwest in a southeasterly direction to its confluence with the Cache La Pondre River on the eastern corporate limits of the City of Fort Collins. Over 500 structures are located within the base floodplain in the City of Fort Collins, The total number of structures throughout the Dry Creek floodplain for both County and City areas was estimated as over 800 structures in 1995 (Reference 11). The channel is approximately 3 to 4 feet deep and 10 to 15 feet wide from the downstream limit to Andersonville. after which the channel is basically nonexistent to the upstream limit of the study. The stream channel gradienl within the study reach is approximately 18 feet per mile, The soils within the Dry Creek basin floodplain are of the Fluvaquents-Fluvents and Otero-Nelson Associations (Reference 10). Boxelder Creek flows in a southerly direction through Larimer County and the City of Fort Collins. The Boxelder Creek watershed, approximately 32 miles long with an average width of 8 miles. flows from an altitude of 7,720 feet at its headwaters in Wyoming to 4,860 feet at its confluence with the Cache La Poudre River. Geological formations exposed within the watershed consist of rocks and sediment ranging from Precambrian to Quaternary in age. and the soils in the basin are of the Fluvaquents- Fluvents and Arguistolls-HapluslOlls Associations (Reference 12). 2.3 Principal Flood Problems Floods in the City of Fort Collins area usually result from general rain and cloudburst storms from May through September. Floods resulting from heavy rainfall over the watershed are characterized by high peak flow of moderate volume and duration, The cloudburst storm is a high-intensity, short-duration rainstorm that produces a flood with a high peak flow, short duration, and relatively small volume of runoff. Peak runoff will usually occur within a few hours after a single storm. Flooding can also occur as a resul1 of rapid spring snowmelt. Snowmel1-caused floods are characteristically oflong duration, Notable floods occurred on the Cache La Poudre River in 1844, 1864, 1884, 1891, 1904, 1923, and 1930 (Reference 13), The three largest floods occurred in 1864, 1891, and 1904. with flood peaks of approximately 21,000 cubic feet per second (cfs). The 1904 flood probably did the greatest financial damage. During this flood, approximately 150 houses were swept away and aU bridges, with the exception of one, were destroyed. The snowmelt runoff from 1983 produced a peak of 7,000 cfs, This was the highest peak in 53 years, Extensive channel damage occurred because of prolonged duration of the runoff (Reference 14), Floods occurred on Spring Creek in 1902, 1904, 1938, 1949, and 1951, prior to the completion of the Horsetooth Reservoir, which cuts off the upper portion of the Spring 5