m 4.11. Assuming a dimesionless hydrograph is applicable, determine the duration of flow if the peak runoff is 8.5 m³/s (300 cfs) and the volume of flow is 100 mm (4 in.) for a 50-year storm from an 85-ha (210 ac) watershed. What are the coordinates for point n on the design hydrograph?

(a) A flood drainage channel has to be designed to carry runoff from 200 km² area. If the flow per square kilometer is 0.5 m³/s/km², determine the flood drainage channel size using (i) the permissible velocity method, and (ii) tractive force method. The material size is 2 mm and S,=0.00002. Provide sufficient justification for assumptions and/or judgement used in your procedure. State clearly the design steps used in the design process. (b) The reservoir level upstream of a 30-m-wide spillway for a flow of 800 m³/s is at El. 250 m and downstream river level channel for this design flow is at El. 150 m. If the stilling basin width is the same as that of the spillway, compute the floor level of the stilling basin so that the jump is formed in the basin. Assume the losses in the spillway are negligible. What would be the basin invert level if one can use an end sill or one row of baffle blocks and an end sill? (c) A mountain creek with a flow rate of 100 ft/s passes through an eight-ft…

You are designing a drainage system for a residential site in Atlanta using a 10-year return period. The site has an area of 1 ha, a flow length of 100 m, an average slop of 1%, a Manning's number of 0.25 and Type B soil. Drainage regulations require that the kinematic wave equation be used to calculate the time of concentration. You are allowed to use either the rational method or TR-55 to calculate the peak runoff rate. It is suggested you used a runoff coefficient of 0.4, which is typical for residential sites. What curve number would be required for both the rational method and the TR-55 method to provide the same peak runoff rate?