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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />], Summary <br /> <br />Preparation of the hydrology for the Flood Insurance Study included the development of a <br /> <br />computer model to analyze the rainfall-runolT relationship for the study area. The Gcospatial <br /> <br />Hydrologic Modeling Extension (Geo-IIMS) developed by the Corps' Hydrologic Engineering <br />Center (lIEe) was lIsed to process watershed data and subdivide the basin; the lIydrologic <br /> <br />Modeling System (IIMS) computer program, also developed by BEe. was used for analysis of <br /> <br />the prccipitation-runolTprocesses in the study area (see Reference 4-d and 4-e). Basin hydrologic <br /> <br />characteristics described in the 1976 Corps report (Reference 4-c). as well as available current <br /> <br />dala, were used in the IIMS computer model. <br /> <br />The lIMS model was tested using the flood event of September 1970 to see ifunit <br /> <br />hydrographs. loss rates. or routing parameters developed in the 1976 study needed adjustment. <br /> <br />Hourly streamflow data is only available for the 1970 event. Hourly precipitation records for <br /> <br />southwest Colorado climatological stations provided the basis for rainfatt distribution during the <br /> <br />flood event. <br /> <br />A regional flow frequency analysis was made using available Upper Dolores River <br /> <br />streamflow records to estimate the magnitude of peak nows at other locations in the study area. <br /> <br />The Regional Frequency Computation program (REGFQ) was used for the regional analysis <br /> <br />(Reference 4-t). <br /> <br />2 <br />