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flood on Roan Creek occurred at the end of May 1983. from the melting of an unusually deep snowpack. It resulted 2.4 Flood Protection Measures Levees along the southern bank of the Colorado Ri ver downstream from its confluence with the Gunnison River were constructed by local interests to protect residents in the Connecticut Lakes area. Low dikes were also constructed along the northern bank of the Colorado Ri ver upstream from the Grand Avenue bridge to provide protection to residents of the Riverside Park area. The U.S. Atomic Energy Commission constructed a levee along the eastern bank of the Gunnison River during the 1957 flood to protect its installation near Grand Junction. A floodwater-retarding structure was constructed by the SCS on Indian Wash, approximately 3 miles north of Grand Junction. This structure affords protection to the eastern one-half of the city against lOO-year floodflows. No other flood-control projects afford protection to the areas being studied in Mesa County. Most of the reservoirs in the drainage basins tributary to Mesa County are operated for water conservation and, therefore, provide only incidental flood protection to downstream areas. In the Gunnison River drainage basin, however, regulations for joint conservation-flood control operation of Paonia Reservoir have been prepared by the COE and USBR. The conservation operation of Blue Mesa Reservoir provides substantial flood-control benefits, but formal operating regulations for flood control have not been prepared. Water is diverted from numerous sites in the upper portions of the Colorado River Basin for exportation to the South Platte and Arkansas River basins. However, di versions are often decreased during high runoff periods, making any reduct ion in flood peaks unlikely. Irrigation uses also reduce flows, but not significantly during times of peak flows. Various Federal agencies have been studying water resources development aspects of the Upper Colorado River Basin for many years. A report published in 1971 (Reference 8) contains a reconnaissance-type plan that identifies--for future detailed study--eight potential storage projects that would provide flood-control benefits for Mesa County and three areas for possible future watershed treatment measures. A joint publication of the CWCB and U.S. Department of Agriculture (Reference 9) includes information from a reconnaissance-type study that identifies a number of Roan and Book Cliffs streams that are potentially subject to development of storage projects for flood control. The Horizon Drive Channel has been channelized throughout much of the City of Grand Junction. Long conduits convey minor flows 1 around Mesa Mall and flows up to the SOD-year flood between 252 and 26 Roads. Floodplain regulations have been adopted by Mesa County. Designated floodplains, including low hazard and floodway zones, are incorporated into county zon ing maps. Appl icat ions for new 16