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') COLORADO WATER CONSERVATION BOARD J. William McDonald Director MEMORANDUM TO: Larry F. Lang FROM: Brian R. Hyde DATE: December 27, 1983 SUBJECT: Designations for City of Montrose F.r.S. and Montrose County F.I.S. There has been some confusion with regard to floodplain information for certain streams in the City of Montrose and Montrose County and how they should be designated. Some of the confusion results from the fact that, at one time or another, all four members of the Flood Control Section have been involved in the review of and designation of studies for these two communities. Some of the confusion results from the manner in which FEMA and their contractor, MSM, have studied the particular streams in question. ,J The first study to be considered was performed by Hydro-Triad in 1979. They studied Cedar Creek, Montrose Arroyo, and Dry Cedar Creek in detail. On Cedar Creek the only areas of controversy were three road crossings where water backed up and flowed out of the channel. Otherwise water was confined to an incised channel. On Montrose Arroyo there was much more controversy, because there was substantial out-of-bank flow through city streets in Montrose. The scope of work did not include a network analysis, so the profile showed the effect of all of the water staying in the channel although the plan view delineation showed water leaving the channel and water returning to the channel. On Dry Cedar Creek there was no major controversy, because the stream essentially stays in its incised channel. In 1981 Gingery Associates prepared a Flood Control and Drainage Plan for the City of Montrose. Existing 100-year floodplains were delineated for Cedar Creek and Montrose Arroyo, and proposed channel improvements and their effect on the 100-year floodplain were described. The existing floodplain on Cedar Creek remained the same as on the Hydro-Triad study. On Montrose Arroyo, however, major changes were made. A network 524 clmon