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each structure. A curve number was assigned to each district hydrologic <br /> region of the watershed, using the values in Table 2. An overall curve <br /> number for the subwatershed was derived by calculating a subwatershed <br /> weighted average based on the relative acreage of each distinct <br /> hydrologic region. The runoff was then routed into the sediment <br /> structure (See Table 1). <br /> Precipitation and Storm Type <br /> Precipitation depts for the 10-year, and 25-year storms were developed <br /> using procedures and data published in the Soil Conservation Service <br /> publication "Procedures for Determining Peak Flows in Colorado". A <br /> standard SCS Type II storm was utilized for each analysis. <br /> Unit Hydrograph and Surface Condition <br /> The SEDIMOT II computer program provides three unity hydrograph shapes <br /> to choose from in determining the runoff characteristics of a <br /> subwatershed. In general , the agricultural hydrograph (No. 2) was used <br /> for agricultural and undisturbed areas. The disturbed hydrograph (No. <br /> 1) was used for disturbed and reclaimed areas. <br /> Travel Time <br /> The travel times for subwatershed to structure were determined utilizing <br /> the Manning Equation. In using this method, the flow velocity is <br /> determined by flow rate and channel characteristics. The travel time <br /> will be the result of dividing the channel length by the velocity. <br /> Time of Concentration <br /> The time of concentration for each subwatershed was determined using the <br /> SCS Upland Method. In using this method, the longest flow path in each <br /> subwatershed is divided into segments to uniform flow characteristics. <br /> Within each segment, the travel time is estimated by dividing the flow <br /> length by the velocity. The time of concentration is the some of these <br /> travel times. <br /> 5 <br />