Runoff Activity-1

Civil and Environmental Engineering Runoff and Erosion Activity Names: __________________, ______________________ Objective: To practice runoff and soil erosion calculations Task: A map of part NCSSM Campus is shown below. A cistern is planned at the location designated by red oval. If the collected water is all runoff from the area outlined in blue, how much water could we collect each month? How much nitrogen and phosphorus is in the runoff? Data: Elevation at highest point: 412 feet Elevation near cistern: 398 feet Length of catchment area: 370 feet Width of catchment area: 110 feet

Formula and Tables: I a = 0.2 S • Q is runoff (in) • P is rainfall (in) • S is the potential maximum soil moisture retention after runoff begins (storage) (in) • I a is the initial abstraction (in), or the amount of water before runoff, such as infiltration, or rainfall interception by vegetation Curve Number Cover description Curve numbers for hydrologic soil group A High Infiltration Porous B C D Very low Infiltration, mostly clay Open space (lawns, parks, golf courses, etc.) Poor condition (grass cover <50%) 68 79 86 89 Fair condition (grass cover 50 to 75%) 49 69 79 84 Good condition (grass cover >75%) 39 61 74 80 Impervious areas: Paved parking lots, roofs, driveways, etc. (excluding right of way) 98 98 98 98 Streets and roads: Paved; curbs and storm sewers (excluding right-of-way) 98 98 98 98 Paved; open ditches (including right-of-way) 83 89 92 93 Gravel (including right of way) 76 85 89 91 Dirt (including right-of-way) 72 82 87 89 Nutrients Phosporus Nitrogen Land Use Dissolved Sediment Dissolved Sediment Category (mg/l) Attached (mg/kg) (mg/l) Attached (mg/kg) Cropland 0.300 308.0 1.80 1200.00 Pasture 0.250 308.0 3.00 1200.00 Pasture-manure 3.000 800.0 11.90 1900.00 Forest 0.009 308.0 0.06 900.00 Urban/Built-up 0.33 900.0 2.18 900.0 Wetlands 0.000 1.0 0.00 0.00 Barren Land 0.045 200.0 0.74 800.00