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Hydroloqy The hydrology for this study area involves three streams; 1) Plateau Creek, 2)Buzzard Creek, 3)Grove Creek. These are mountain streams that can flood in response to snowmelt in the spring and rainfall in the summer. The technique for developing flood-frequency values for streams of this nature is to analyze a population of historical flood events from snowmelt and a seperate population for rainfal I events, and then combine the data statistically. The refrences used herein followed this process. There are three main refrences avai lable pertaining to the hydro logy for the Co II bran area; l>Hydro logy Report - Flood Insurance Studies for Unincorporated Areas of Delta and Montrose Counties, Town of Collbran, Cederedge, Orchard City, Paonia and Naturita, Colorado, Apr~ 1979, by Meurer, Serafini and Meurer Inc., 2)Flood Insurance Study - Town of Collbran, Colorado, Oct. 1981, by Federal Emergency Management Agency, 3)Hydrology Report for Town of Rangley, City of Rifle, and Garfield County Flood Insurance Studies, by Simons, Li & Associates Inc. It was decided in meetings at the beginning of this study to use as much data from the 1981 Flood Insurance Study (Ref 2) as possible since it has already been designated and approved by the CWCB. Therefore, this study makes use of the peak discharge - frequency values which appear below; Stream Discharge-Frequency Values 10yr 50yr 100yr 500yr Plateau Cr at 2880 4000 4850 6900 West Town Limit Plateau Cr at 1325 1800 2100 2920 East Town Limit Buzzard Cr at 1180 1940 2300 3080 Collbran Grove Cr at 415 590 775 1200 Co I I bran Discharge-frequency data is not abai lable for Buzzard Creek in the 1981 Flood Insurance Report. However, the Simons, Li & Associates, Inc. Hydrology Report (Ref 3) shows data for Buzzard Creek which is included herein. 10