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<br />3. Summary <br /> <br /> <br />Preparation of the hydrology for the Flood Insurance Study included the development ofa <br /> <br /> <br />computer model to analyze the rainfall-runoff relationship for the study area. The Geospatial <br /> <br /> <br />Hydrologic Modeling Extension (Geo-HMS) developed by the Corps' Hydrologic Engineering <br /> <br />Center (HEC) was used to process watershed data and subdivide the basin; the Hydrologic <br /> <br />Modeling System (HMS) computer program, also developed by HEC, was used for analysis of <br /> <br />the precipitation-runoff processes 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 />data, were used in the HMS computer model. <br /> <br />The HMS model was tested using the flood event of September 1970 to see if unit <br /> <br />hydro graphs, loss rates, or routing parameters developed in the1976 study needed adjustment. <br /> <br />Hourly streamflow data is only available for the 1970 eveQ.t. Hourly precipitation records for <br /> <br />southwest Colorado climatological stations provided the basis for rainfall distribution during the <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 flows at other locations in the study area. <br /> <br />The Regional Frequency Computation program (REGFQ) was used for the regional analysis <br />(Refererice 4-f). <br /> <br />2 <br /> <br />- <br /> <br />e <br /> <br />e <br />