Problem 7-1

Given the following 2-h unit hydrograph for a certain catchment, find the 3-h unit hydrograph.

Time (h)	Flow (m3/s)
0	0
1	30
2	80
3	100
4	70
5	30
6	10
7	0

Using this unit hydrograph, calculate the 1-h unit hydrograph.

Problem 7-2

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	70
8	50
10	30
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	2.0
4-6	1.5

Calculate the composite hydrograph for the effective storm pattern, assuming a runoff curve number CN = 84.

Problem 7-3

A certain basin has the following 2-h unit hydrograph:

Time (h)	Flow (m3/s)
0	0
1	5
2	20
3	35
4	65
5	90
6	70
7	55
8	40
9	20
10	10
11	0

Calculate the flood hydrograph for the following effective rainfall hyetograph:

Time (h)	Effective Rainfall (cm/h)
0-3	1.3
3-6	2.2

Problem 7-4

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 7-5

Use the computer program EH500 (TR55GRAPH in http://onlinecomp.sdsu.edu) to calculate the peak discharge for a 850-ha catchment with a 100-y 24-h rainfall P = 13 cm, time of concentration t_c = 2.5 h, runoff curve number CN = 81, type I rainfall, and 1% pond and swamp areas.