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La Plata County, Colo....do FPMS Flood Plain Delineation Study Watershed above Bayfield, Colorado (approximately 70 square miles) Regional Equations: USGS 86-4101 USGS 96-4112 Region 2 - Northwest Plateau Region 70.0S sq mi Region 2 - Northwest Plateau Region 70.0S sq mi Area of basin above Bayfield = Q(2-yr) = Q(5-yr) = Q(10-yr) = Q(25-yr) = Q(SO-yr) = Q( 1 OO-yr) = USGS 93-419> 2-Feb-99 Gl Area of basin above Bayfield = 732 cfs 1510 cfs 2179 cfs 3255 cfs 4211 cfs 5251 cfs Q(2-yr) = Q(5-yr) = Q(10-yr) = Q(25-yr) = Q(50-yr) = Q(100-yr) = Q(SOo-yr)= Area of basin~bc)veBayfield = Mean Basin ElE!vation = 70~OS sq mi 8013 NGVD I I USGS 93419'; , I , I , I , I I I , I , I , I I I I I I 624 cfs 1391 cfs 2161 cfs 3289 cfs 4426 cfs 5773 cfs 9813 cfs Region 8-Four Coffi'ns~egioll Region1- Higbetevatlon ~egio.. Q(2-yr) = Q(5-yr) == ' Q(1();'yr) == Q(25-yr) "I' Q(So-yr)..; , Q(100-yr) = USGS 93-419 Area;Ofbasil1abo~f!la~;o ,70.05 sq mi Mean Annual PreCipitation": #l; " 17 inches ,602 cfs , , 1230 cfs 1154 cfs '2620 cfs 3404 cfs 4227 cfs Q(2:..yr) = , Q($.yr) :: " Q(1o.::yrl= ' Q(2&;yr)= Q(5Q-yr)::: Q(1 oo.;yrt:: ' 26$:d$ , 483~' fot,d1f. 801 ct&, ,947 cfs 1089 cfs USGS 85-4086 (Western Colorado) Weighted flood.freq~"~V;""I~tiOhS (e~uation7 ,p21) ElevationofConc;el)ttation;Point'(Bayfield) = 6877 Q(2-yr) = Q(5-yr) = Q(10-yr) = Q(25-yr) = Q(So-yr) = Q(100-yr) = Area of basin above Bayfield = 70.0S sq mi Mean Basin Elev minus 5000 ft per 1000 ft = 3.013 ,,' S65cfs 1146cfs 1628 cfs 2420cfs 3134 cfs 3882cfs Q(2-yr) = Q(5-yr) = Q(10-yr) = Q(25-yr) = Q(So-yr) = Q(100-yr) = Q(200-yr)= Q(50o-yr)= 449cfs 994 cfs 1275 cfs 1659 cfs 1977 cfs 2302 cfs 2668 cfs 3178 cfs San Juan River Basin eweB Guidelines for Determinina 100-vr Flood Flows. Draft. Januarv 1999 Q( 1 OO-yr) = Area of basin above Bayfield = 5189 cfs 70.0S sq mi . Obtained from Vallecito Dam and Reservior Operations Manual, Plate 4-4, September 1998 (USACOE)