ProblemSet_4_2011 - C&EE 250A Surface Water Hydrology...

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1 C&EE 250A – Surface Water Hydrology UCLA, Fall 2011 Problem Set #4 – due Monday, November 28 th , 2pm 1. Below is a 30-minute unit hydrograph for a 2.1 km 2 urban catchment (runoff resulting from 30-minute precipitation event). Time (min) 0 30 60 90 120 150 180 210 Runoff (m 3 /s) 0 1.4 3.2 1.5 1.2 1.1 1.0 0.66 Time (min) 240 270 300 330 360 390 Runoff (m 3 /s) 0.49 0.36 0.28 0.25 0.17 0 a) Verify that the unit hydrograph is consistent with 1-cm of rainfall excess (i.e. contains 1 unit of runoff). b) Estimate the runoff hydrograph for a 30-minute event with a rainfall excess of 2.8 cm. c) Create a 120-minute unit hydrograph using S-curve convolution. d) Estimate the runoff from the following storm using the new unit hydrograph. Assume a constnant infiltration rate of 0.3 cm per each 30 minute period. Time (min) 0-30 30-60 60-90 90-120 Rainfall (cm) 2.3 4.5 2.1 0.8 2. Develop the SCS triangular unit hydrograph for a 520-acre watershed that has been commercially developed. The flow length is 3000 feet, the slope is 5.1%, and the soil group is type B. 3. Estimate hydrograph and response parameters for your watershed: a) Select a single storm for your watershed that is isolated from other events and where you have a distinct hyetograph (precipitation) and hydrograph (storm response). Put your values in a table. b) Plot the hydrograph and precipitation hyetograph together on a single figure. c) Estimate the runoff ratio for this single storm event. c) Following the examples in Dingman, estimate the response descriptors discussed in class and in your text: Precipitation centroid (T WC ), discharge centroid (T QC ), lag to peak (T LP ), time of rise (T R ), centroid lag (T LC ), centroid lag-to-peak (T LPC ), time of concentration (T C ) and time base (T B ). Report your answers relative to the storm time below (which is in military time). 4. Route the following inflow through a downstream channel reach using the Muskingum method (calculate outflow, Q, at each time step). Assume initial outflow at 6am is 100 cfs.
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This note was uploaded on 02/02/2012 for the course CEE 250 taught by Professor Terrihogue during the Fall '11 term at UCLA.

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ProblemSet_4_2011 - C&EE 250A Surface Water Hydrology...

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