Q4 A Figure Q4 Shows Two Catchments A And B That Are Being Facilitated By A Drainage System Which Consist Of Two Inl 1 (29.85 KiB) Viewed 41 times
Q4 A Figure Q4 Shows Two Catchments A And B That Are Being Facilitated By A Drainage System Which Consist Of Two Inl 2 (33.01 KiB) Viewed 41 times
Q4. (a) Figure Q4 shows two catchments, A and B that are being facilitated by a drainage system which consist of two inlets and two pipes. Catchment A has an area of 1 ha and is 50% impervious; catchment B has an area of 2 ha and is 10% impervious. The runoff coefficient, C; length of overland flow, L; average flow velocity, V; are given in Table Q4. Calculate the peak flow to be handled the both pipes based on 10-years IDF equation, In(i) = a + b ln(t) + c (ln(t))² + d (In(t))", where a, b, c, and d are 4.490, 0.997, -0.328 and 0.021, respectively. Table Q4a: Characteristics of the catchment Catchment A B Surface pervious impervious pervious impervious C 0.2 0.9 0.2 0.9 L (m) 80 60 140 65 V (m/s) 0.029 0.091 0.033 0.090
Pipe 1 0 30 60 90 120 150 180 210 240 270 300 Pipe 2 330 360 390 Catchment A Inlet 1 Runoff Time (min) UH (m³/s) 0 1.2 2.8 1.7 Figure Q4: Layout of a drainage system of a catchment. (b) A 30-min unit hydrograph for a 2.25 km² watershed is shown in Table Q4b. Verify that this unit hydrograph corresponds to a 1-cm rainfall excess. Using this unit hydrograph, estimate the direct runoff resulting from the 90-min rainfall shown in Table Q4c. Table Q4b: 30-min unit hydrograph Catchment B 1.4 1.2 1.1 0.91 0.74 0.61 0.50 0.28 0.17 0 Inlet 2 Table Q4c: Hyetograph of a 90-min rainfall Time (min) Excess rainfall (cm) 3.1 2.5 1.7 0-30 30-60 60-90
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