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Creek Drainage basin. The Horsetooth Reservoir was completcd in the early 19508 and has helped reduce flooding problems by reducing drainage area. Floods occurred in 1975 and 1977, causing flooding in several basemenls, but there are no recorded discharges or damage estimates available (Reference 15). A flood occurred on June 25, 1983, that produced 1.9 inches ofrainfall over 2 hours, The storm sewer that carries Spring Creek under the mobile home park surcharged and water ponded to a depth of several feet. Property damage was estimated in the $5,000 to $10,000 range (Reference 16). The Cooper Slough floodplain is predominantly flat. Channel capacity is limited in places, promoting overbank flows and divided-flow conditions, Channel flow is restricted by relatively small culverts at Vine Drive, the Colorado and Southern Railroad (C&SRR), and SH-14, Due to an undersized culvert at SH-14, a ponded area will form north of the highway, and eventually overtop the highway during storm events, In places, the width of the lOO-year floodplain averages over 1,000 feet, although the depth of flooding is generally less than 3 feet, except in areas where pending occurs, Hydrologic data from stream gages were not available, thus no discharge and recurrence intervals for major floods along Cooper Slough were determined. Floods have been recorded in the Boxelder Creek watershed on \3 occasions since 1900, On August 1, 1961, a storm with a frequency of 50 to 100 years caused an estimated $76,150 in damages in the Wellington vicinity. In May and June 1976, two overtopping 25-year storms caused an estimated $46,100 in damages and took four lives in the Wellington vicinity (Reference 17). Limited information is available regarding past flooding from Dry Creek. In 1904, a flood occurred that resulted in the drowning death of a child when floodwaters overtopped the Eaton Ditch (which intercepts Dry Creek near Willox Road) (Reference 18). Flooding also occurred in 1924 with depths of flows several feet deep. However, it is unclear as to whether the flooding was due to overflow from the Cache La Poudre River (Reference 19), Numerous irrigation canals cross the Dry Creek channel and directly intercept drainage flows. In the past, much of the excess drainage in the lower Dry Creek basin (below Eaton Ditch) was intercepted by irrigation canals. However, the impact of development has increased the magnitude and frequency of drainage flow, and many of the canals no longer have the capacity to intercept the increased drainage flows. Several of the canals, including the Larimer and Weld Canal (Eaton Ditch), Larimer County Canal, Terry Inlet, Poudre Valley Canal, and North Poudre Ditch, have large enough flow capacities to impact flood magnitudes on Dry Creek (Reference 19). 2.4 Flood Protection Measures There are no designated flood-control structures on the Cache La Poudre River in the study area, Two irrigation water-supply storage reservoirs are located on the North Fork of the Cache La Poudre River; however, the effects of the dams on the study reach were considered negligible (Reference 6). The Horsetooth and Dixon Reservoirs are two major reservoirs within the Spring Creek basin. The Dixon Reservoir is located on the western edge of the basin immediately below the hogback that impounds the Horsetooth Reservoir. The Dixon Reservoir 6