CIV E 445 - APPLIED HYDROLOGY SPRING 2014 LAB No. 7 The following 2-h unit hydrograph has been developed for a certain catchment: Time (h) Flow (ft3/s) 0 0 2 100 4 200 6 150 8 100 10 50 12 0 A 6-h storm covers the entire catchment and is distributed in time as follows: Time (h) Total rainfall (in/h) 0-2 1.0 2-4 1.5 4-6 0.5 Calculate the composite hydrograph for the effective storm pattern, assuming a runoff curve number CN = 80. Calculate the 25-y peak flow by the TR-55 graphical method for the following watershed data: (1) urban watershed, area A = 9.5 km2; (2) surface flow is shallow concentrated, paved; hydraulic length L = 3,850 m; slope S = 0.01; (3) 42% of watershed is 1/3-ac lots, lawns with 85% grass cover, 34% total impervious, soil group C; (4) 58% of the watershed is 1/3-ac lots, lawns with 95% grass cover, 24% total impervious, 25% of it unconnected, soil group C; (5) Pacific Northwest region, 25-y 24-h rainfall P = 10 cm; 1% ponding.