CIV E 530 - OPEN-CHANNEL HYDRAULICS FALL 2005 HOMEWORK No. 14 Calculate the average annual soil loss by the Universal Soil Loss Equation for a 300-ac watershed near Lexington, Kentucky, with the following conditions: (1) cropland, 250 ac, contoured, soil is Keen silt loam, slopes are 7% and 150 ft long, C = 0.15; (2) pasture, 50 acres, 75% canopy cover, 60% ground cover with grass, soil is Ida silt loam, slopes are 10% and 200 ft long. Using the Dendy and Bolton formula (Eq. 15-13), calculate the sediment yield for a 25.9 km2 watershed with 5 cm of mean annual runoff. Given the following flow characteristics: flow depth 5 ft, mean velocity 3 fps, median bed material size 0.3 mm, mean channel width 225 ft, water temperature 70o, wash load concentration 300 ppm. Calculate the discharge of sands by the Colby 1964 method. A reservoir is to be built with a total storage capacity of 50 million cubic meters. The contributing drainage basin is 800 km2, and the mean annual runoff at the site is 200 mm. Assume well graded sediment deposits with specific weight of 1400 kg/m3. (a) How long will it take for the reservoir to lose 20% of its storage volume? (b) How long will it take for the reservoir to lose 100% of its storage volume? Estimate sediment yield by the Dendy and Bolton formula (Eq. 15-13).