Problem 7-1

Calculate the 50-y peak flow by the TR-55 graphical method for the following watershed data: (1) urban watershed, area A = 8.5 km²; (2) surface flow is shallow concentrated, paved; hydraulic length L = 3350 m; slope S = 0.01; (3) 48% of watershed is 1/3-ac lots, lawns with 85% grass cover, 34% total impervious, soil group C; (4) 52% 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, 50-y 24-h rainfall P = 12 cm; 0.2% ponding.

Problem 7-2

Use ONLINE TR-55 to calculate the peak discharge for a 850-ha catchment with a 100-y 24-h rainfall P = 13 cm, runoff curve number CN = 81, time of concentration t_c = 2.5 h, 1% pond and swamp areas, and Type I rainfall.