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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 />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />the basin model can be exported to HEC-HMS, The first of these steps include Terrain <br />Preprocessing and HMS Project Setup. <br /> <br />Another problem that was encountered with HEC-GeoHMS was that a Segmentation Violation <br />was generated when trying to generate the HMS Project, In order to remedy this problem, James <br />Doan, the developer of the extension was contacted for assistance, The data was then sent to him <br />for troubleshooting, He did not encountered the violation, however, he did select a different <br />outlet point. At that point, the upstream limit to the study was selected as the outlet point and a <br />HMS Project was successfully generated, Any point selected lower than this point, however, did <br />produce the Segmentation Violation, The source of this error was never determined, Using the <br />HMS Project generated for the upstream study limit, the remaining HEC-GeoHMS steps, Basin <br />Processing, determining Basin Characteristics, and generating HMS export files, were <br />completed, For more information refer to the HEC-GeoHMS User's Manual, <br /> <br />Once the basin model has been created using HEC-GeoHMS it can be imported into HEC-HMS <br />as either lumped or distributed, A lumped basin model was used since precipitation and the <br />basin characteristics were assumed to be uniform across the watershed. HEC-HMS supports <br />many different methods for computing the flow that must be selected by the user. The user must <br />indicate the methods to compute the loss rate, transform, and any baseflow as well as supply any <br />other parameters these operations require, <br /> <br />The SCS Curve number approach was selected for the loss rate analysis with a 20,75 mm initial <br />loss, 0% imperviousness, and a curve number of 71, The General Soil Map for Delta County <br />indicated that the soil was of Mesa-Orchard association (SCS), both of which belong in the B <br />soil class, Chapter 2 of the Soil Conservation Service Engineering Field Manual then indicated <br />that for herbaceous ground cover in fair hydrologic condition in an arid or semiarid rangeland a <br />runoff curve number of 71 was appropriate. The same manual also gave the following two <br />equations: <br /> <br />19 <br />