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<br />5.0 IIIo'TERPRETATION OF THIS REPORT
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<br />5.1
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<br />Hyd.rololl:ic Findinl!s
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<br />The results of the hydrologic analysis for the Colorado River mainstem are considered accurate.
<br />They are based principally on exisling approved data prepared by federal agencies. The
<br />availability of detailed information for almost 70% of the study reach provided accurate
<br />relationships with the unstudied reach fIndings.
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<br />5.2 Hvdraulic Findini!S
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<br />The hydraulic methods used for this study are similar to those used in more detailed studies.
<br />They are much more detailed than the methods used in typical approximate studies. The 100-
<br />year flood depths for the previously unstudied reaches range from 19,2 feet in a medium reach
<br />of the river to 26.5 feet near the downstream limil of the study (where the drainage area
<br />essentially doubles at the Gunnison River confluence). The majority of the flood depths are
<br />genera\ly consistern throughout the previously unstudied ponions of the study reach with
<br />differences of only a few feet (18.2-26.5 feet for the loo-year flow depths). The variation
<br />between the 50-year and lOll-year flood depths isgeoerally less than one fool. To find flood
<br />depths for the reaches where there has already been a detailed study. interested parties are
<br />directed 10 the flood profIies in those detailed srudies.
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<br />5,3
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<br />Floodulain Delineations
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<br />The primary difficulty in presenting precise delineations of the 50-year and lOO-year floodplains
<br />for the previously unstudied reaches was the limited quality of the available base mapping for
<br />the ;.;nstudied r(:ache. 0f t,'lC COl0radO Rivcr. Using USGS wpographie quadrangle map. at
<br />C\'Intour intervals 0f 20 or 40 feet to ponrny flood line.' in unsurveyed area. provid<."s limIted
<br />information, The margin for interpretation is very great, especially in medium to wide reaches
<br />of the river where contours are widely spaced. Morc detailed topographic information will be
<br />needed in areas of specific interest.
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<br />This study can be uti1il,cd to prepare more detailed floodplain delineations in such areas of
<br />specific interest. Thosc who are interested in greater detail have three choices for using this
<br />study:
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<br />1)
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<br />They can consult the extsung detalled strn:lIes, if they pert.'un to theIr slIe. 10 better
<br />ascenain the flood SlaIDS of the site in question;
<br />They can rely on the hydrologic determinations in this report and use other topographk
<br />information ;!.!1Q hydraulic models; Of
<br />They can use the depth infonnation in this repon with more detailed topographic
<br />infonnation to modify the floodplain ddinealion.
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<br />3)
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<br />6.0 REFERE1',CES
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<br />14,
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<br />15.
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<br />Federal Emerl!encv MaruJl!ement Al!enn'; Flood Insurance Study and Flood Insurance
<br />Rate Map date<llanuary, 1986; Town of Rifle. Colorado.
<br />
<br />Federal Emeri!encv Manaflement Afencv; Flood Insurance Study and Flood lnsurancc
<br />Rate Map dated lanuary. 1986; unincorporaled Garfield County.
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<br />Federal Emeri!encv Manai!emenf Aflencv; Flood Insurance Study and Flood Insurance
<br />Rate Map dated April, 1989; Town of DeBeque, Colorado,
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<br />Federal Emereencv Manaflement Al?encv; Flood Insurance Study and Flood Insurancc
<br />Rate Map dated September, 1991; Town of Parachute, Colorado.
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<br />Federal Emeruncv MaruJl!emerlt AUr/(Y; Flood Insurance Study and Flood Insurance
<br />Rate Map dated July, 1992; Town of Palisade, Colorado.
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<br />Federal Emeri!encv Manaflement Avencv; Flood Insurance Study and Flood Illsurance
<br />Rate Map dated July, 1992; City of Grarnl Junction, Colorado.
<br />
<br />Federal Emerflencv Manal!ement Averlcv; Flood Insurance Study and Flood Insurance
<br />Rate Map dated luly, 1992; Town of Fruita, Colorado.
<br />
<br />Federal Emereency MaruJeement Aeencv; Flood Insurance Studies and Flood In,urance
<br />Rate Map dated July, 1992; unincorporated M<:,a County.
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<br />J.E. , flfzvford &: Associates: Floodplain Information Repon. Parachute Cn.:ek, Colorado
<br />River, TO'w'jJ of P;:;raehmc, C'..o]orado dalcd OclOhcr. 1989.
<br />
<br />J.P. Saw and Associates. ['Ie.: Hydrology Report, Flood Insurance Studies in Mesa
<br />County Colorado, dated May, 1989 and work maps from Rille 10 DeBcque Canyon dated
<br />October 1988.
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<br />U,S. Annv COrDS of Enl!ineers. Sacramento Disln'ct: Unpublished Hydrology Report
<br />dated 1985.
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<br />United States Geolollical Sun-e...: Water-Data Repon, Water Resources Data. Colorado,
<br />Water Year 1993,
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<br />CUrl-'efir PrO!!ram: A public domain computer program, version 1.0 b)' T. S. Cor..
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<br />Chow, Ve.l1.h,: Open Channel Hydraulics, 1959.
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<br />Q1JYr; An in-house hydraulics computer program (not for public domain)
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