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• 2.4 Land Use Condition (LUC) <br />LUC values influence the rate of runoff from a site. They are consistently applied as follows (reference <br />SEDCAD+ guide): <br />For undisturbed portiotu of the watershed, overland flow: 3 (short grass pasture). <br />For reclaimed portions of the watershed, overland flow: 4 (cultivated, straight row). <br />For initial concentrated flows: 7 (small upland gullies). <br />For consolidated concentrated flows: 8 (large gullies). <br />2.5 Areas <br />Areas (acres) were measured (map) as follows: <br />Location SEDCAD+ Identifier Acres <br />Undisturbed 1-1-1- l 71.30 <br />Reclaimed 1-1-1-2 26.70 <br />Pond surface 2-1.1-1 2.25 <br />2.6 Curve Number (CN) <br />• Curve numbers reflect the runoff potential of an area (a value of 100 represents an impervious area where <br />100% of the water would run oft), and is a function of soil type (a "D" used in this analysis) and the land use. <br />For this analysis, a CN value of 84 was selected (reference the SEDCAD+ guide, fair grassland cover) as <br />representative of the land areas (a conservative value as a higher CN might be used for undisturbed areas). <br />A CN of 98 was selected for the pond surface areas (indicating no loss). <br />2.7 Hydrograph Response Shape and Overland Flow Lengths <br />Hydrograph response shapes reflex the rapidity with which water runs off a watershed, rated in SEDCAD+ <br />as fast, medium, or slow. A slow response shape would correspond to a forested area or an area with a lot <br />of obstructions, while a fast response shape would correspond to an unvegetated or poorly protected area. <br />A medium response shape was selected for the watersheds in this analysis. A fast response shape was selected <br />aaoss the surface of the pond. These ratings are for overland flow. <br />Lengths of overland flow (sheet and rill drainage) are direct input parameters in SEDCAD+ for hydrologic <br />(time of concentration) and sedimentology (erosion phase) analyses, and relate to other parameters, such as <br />LUC. In this analysis, overland flow was limited to 200 feet in undisturbed areas, and 300 feet in reclaimed <br />areas. <br />2.8 Control Practice Factor <br />The SEDCAD+ Model considers the sediment loss from an area with a given cover and conservation practice, <br />• as compared to that of a field in continuous fallow, by introduction of a Control Practice (CP) Factor. This <br />(Canadian Strip Mioe, Pond 1 Riprap Review, 27 Dec 94, Page 3 of 5) <br />