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 = 10.5 km²; (2) surface flow is shallow concentrated, paved; hydraulic length L = 2800 m; slope S = 0.02; (3) 40% of watershed is 1/3-ac lots, lawns with 65% grass cover, 40% total impervious, soil group C; (4) 60% of the watershed is 1/3-ac lots, lawns with 65% grass cover, 20% total impervious, 25% of it unconnected, soil group C; (5) San Diego County, 50-y 24-h rainfall P = 12.5 cm; 0.0% ponding.

Problem 7-2

Use ONLINE TR-55 to calculate the peak discharge for a 10.5 km² catchment with a 50-y 24-h rainfall P = 12.5 cm, runoff curve number CN = 84, time of concentration t_c = 0.88 h, 0% pond and swamp areas, and Type I rainfall.