UNIVERSITY OF BOLTON. ENGINEERING, SPORTS and SCIENCES BSC CIVIL ENGINEERING SEMESTER 1 EXAMINATION 2014/2015 WATER ENGINEERING MODULE NO: BLT3023

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1 [TW59] UNIVERSITY OF BOLTON ENGINEERING, SPORTS and SCIENCES BSC CIVIL ENGINEERING SEMESTER 1 EXAMINATION 014/015 WATER ENGINEERING MODULE NO: BLT303 Date: Tuesday, 0 January 015 Time: INSTRUCTIONS TO CANDIDATES: There are FOUR questions. Answer THREE questions. All questions carry equal marks. Marks for parts of questions are shown in brackets. This examination paper carries a total of 75 marks. All working must be shown. A numerical solution to a question obtained by programming an electronic calculator will not be accepted.

2 Page of a) Briefly explain what is meant by the term unit hydrograph and discuss its use in flood prediction. (8 marks) b) Estimate the peak flow during a 15 year flood event for the river Irwell using a synthetic, 10mm 1 hour, unit hydrograph analysis with the data listed below. The base flow in the river is 9m 3 /sec. (17 marks) T B = 6 hours T P = hours Q P = 17m 3 /sec The hourly depths of rainfall, for the chosen 5 hour event, are shown in the table below. Table Q1a is also provided. 1 st hour nd hour 3 rd hour 4 th hour 5 th hour 3.6mm 7.4mm 13.4mm 8.mm 4.1 Table Q1. Total 5 marks. a) Discuss the types of sediment related problems facing the civil engineer and explain the mechanics of sediment transport in rivers. (1 marks) b) A trapezoidal channel is to be constructed in a slightly angular coarse gravel, where d 50 is 50mm, at a gradient of 1 in 900. The channel has a base width of 6.0m and sides which slope at.5h:1v. Using the tractive force method, determine the maximum permissible flow rate in the channel. Table Qa and Fig Qb are provided. (13 marks) Total 5 marks Please turn the page

3 Page 3 of a) Briefly explain the principles behind reservoir flood routing. (8 marks) b) Determine the outflow hydrograph resulting from the probable maximum flood (PMF) at an upland reservoir from the following data: Tables Q3a and Q3b are provided. Reservoir plan area at spillway crest level =.0 km Reservoir plan area m above spillway crest level =.60 km Spillway type = 5m long broad crested weir Discharge preceding occurrence of PMF = 13m 3 /sec Time (h) Inflow m 3 /s (17 marks) Total 5 marks 4. a) Explain, giving two examples of the techniques used, how Sustainable Urban Drainage Systems (SUDS) can help reduce the pollution impact on river systems from CSOs. (7 marks) b) A stilling pond overflow (CSO) chamber, breadth 3.3m, serves a population of 11,00 and receives a peak storm flow of 4.0m 3 /s. A 70mm diameter orifice is used to control the flow passing to the downstream retention sewer. The overflow weir crest height above the centre of the orifice is 1.9m. Using the information given below check the adequacy of the control and determine the peak flow passing to the downstream sewer. (9 marks) G = 40 l/h/d I = 40 l/h/d E = 130,000 l/d Question 4 continued over

4 Page 4 of 10 Question 4 continued c) A stilling basin, utilising a hydraulic jump to dissipate energy, is to be designed for a dam spillway. The maximum flood flow over the spillway is to be 48m 3 /sec, the spillway can be assumed to have a Manning 'n' value of Choose what you consider to be an appropriate width and slope for the spillway and then determine a suitable weir height, above the stilling basin apron, to ensure the formation of a hydraulic jump. (9 marks) END OF QUESTIONS Total 5 marks

5 Page 5 of 10 Formula sheet Formula A = DWF P + E DWF = PG + I + E FTF = 3PG + I + 3E ADF = 1.4 DWF MDF = 0.5 DWF D Min = Q 0.4 Q O = 0.6 A O (gh O ) 1/ Q W = 1.7 B H W 3/ Chamber width =.5 D Min Chamber length = 7 D Min Weir height = 1. D Q = A v Q = A R /3 S O 1/ n R = A P F R v gy y y1 1 8F 1 1 s b sin 1 sin y = b or y = s x S O 9810 x 0.76 x S O Please turn the page

6 Time Period Rainfall (Relative to UH) Unit hydrograph ordinates U 1 = U = U 3 = U 4 = U 5 = Surface r/o + baseflow 1 P 1 = P = 3 P 3 = 4 P 4 = 5 P 5 = Table Q1a To be handed in with answer booklet Student ID No

7 Table Qa

8 Page 8 of 10 Figure Qb

9 Page 9 of 10 h(m) V(m 3 x10 6 ) O(m 3 /s) V/Δt + O m 3 /s Table Q3a To be handed in with answer booklet Student ID No..

10 Page 10 of 10 Time (hours) Inflow (m 3 /s) I t + I t+δt (m 3 /s) V/Δt + O (m 3 /s) (V/Δt + O) - O (m 3 /s) Outflow (m 3 /s) Table Q3b To be handed in with answer booklet Student ID No