FLOOD03420 - Laserfiche WebLink

Home Browse Search

area resulted in unusually high snowmelt floods. Flood losses can include damage to grazing lands; irrigation systems; fences; residential and commerc.ial buildings; parks and other recrea- tional facilities; roads; bridges; and public utilities. Stream channels may be subject to severe erosion. 2.4 Flood Protection Measures There are several small lakes and reservoirs in Pitkin County, mostly located within the upper watersheds of the Roaring Fork River. The Twin Lakes diversion reservoir controls flows from only a lS-square-mile drainage area and is intended to provide storage for irrigation and water supply. The above measures are insufficient for flood protection. A few temporary or localized flood protection works, including berms, levees, and bank protection works, are scattered near deve~oped areas. The Fryingpan and Roaring Fork Rivers exist in deep channels. No authorized flood-control structures are in the local study area, and none are under investigation. The only substantial structure that affects the flow of the Frying- pan River is the Ruedi Dam, looated approximately 17 miles east of Basalt. The Ruedi Dam is part of the Fryingpan-Arkansas Project to divert water from the Colorado River basin to the Arkansas River basin. The dam was designed for an inflow design flood of 17,500 cfs at a lS-day volume of 110,000 acre-feet. The probable maximum discharge is 5,540 cfs from the spillway and 1,810 cfs from the outlet structure. The total p~obable maximum discharge from the outlet structure and spillway is 7,350 cfs, approximating the 500- year flood in the Town of Basalt (Reference 8). A SOO-foot reach of the Roaring Fork River, located approximately 800 feet upstream of North Mill Street in Aspen, was widened in December 1984. Current regulations in Pitkin County limit construction in flood- prone areas, thus contributing.to reduction in future flood potential. No other flood plain management measures are in effect in Pitkin County. 3.0 ENGINEERING METHODS For the flooding sources studied in detail in the community, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Flood events of a magnitude which are expected to be equaled or exceeded once on the average during any 10-, 50-, 100-, or SOO-year period (~ecurrence interval) have been select- ed as having special significance fo~ flood plain management and for 8