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Agenda Item 4a,b,c,d May 12, 1995 Page Two . (3) (4) FPR No. 95-403 - Floodnlain Information Renort. Gunnison River from Delta to the Confluence with the Colorado River. Volume llI, dated March 1995. FPR No. 95-404 - Floodnlain Information Renort. Colorado River Mainstem from Rifle to the Utab Stateline. Volume IV, dated March 1995. DISCUSSION Geol!ranhic Scone of Studv In planning for the recovery effort for the four species of endangered fish the U.S. Fish and Wildlife Service defined critical habitat for those species in the Upper Colorado River watershed. The chief criterion for determining whether a specific area fell within the critical habitat was whether it was within the 100-year floodplain of one of the stream reaches in question. The reaches in Colorado are: Yampa River (from Dinosaur National Monument upstream to Craig), e White River (from the Utah stateline upstream to Rio Blanco Reservoir), Gunnison River (from its confluence with the Colorado River upstream to Delta), and Colorado River mainstem (from the Utah stateline upstream to Rifle). For portions of these stream reaches there was existing approximate or detailed floodplain information, but many steam miles had not previously been studied. CWCB staff used the existing information when it was available and was found to be technically valid. When it was not, staff conducted new hydrologic analyses, topographic surveys, approximate hydraulic analyses and floodplain delineations. When the work was finished, a four-volume report was produced with approximate floodplain information for the four streams listed above: Vol.! Vol. 2 Vol. 3 Vol. 4 Yampa River White River Gunnison River Colorado River mainstem (57 miles) (52.5 miles) (43.5 miles) (93 miles) Desil!nation bv Board Initiative Rule No. 9.D.2 allows designation and approval action to be taken unilaterally by . the Board, provided that "the Board shall notifY the affected communities in writing at least 45-