Sample/practice exam 2014, questions and answers - final exam PDF

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Final Exam - Final Exam merged files: 2004ENG - SAMPLE Final(1).pdf - 2004ENG - SAMPLE Final - SOLUTIONS.pdf...

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2004ENG Hydrology SAMPLE EXAM Section A – Multiple Choice Questions A.1.

The continuity equation implies that: (a) (b) (c) (d) (e)

A.2.

Rainfall excess of 150 mm over a 1 km2 catchment is equivalent to a runoff volume of: (a) (b) (c) (d)

A.3.

Input must equal to the sum of the change in storage and output. The change in storage is equal to the difference between input and output. Output is the difference between the input and change in storage. All of the above. None of the above.

150 ML 150 m3 1500 L 1500 mL

An El Niño climate event generally results in: (a) (b) (c) (d)

wetter than normal conditions in eastern Australia and a suppression of oceanic upwelling along the Pacific coast of South America drier than normal conditions in eastern Australia and a suppression of oceanic upwelling along the Pacific coast of South America drier than normal conditions in eastern Australia and an increase in oceanic upwelling along the Pacific coast of South America wetter than normal conditions in eastern Australia and an increase in oceanic upwelling along the Pacific coast of South America

A.4. Estimate when runoff will begin on a soil with hydraulic conductivity Ks = 1.5cm/hr is subject to a rainfall intensity of 12mm/hr. The effective matrix potential of the soil is 10 mm. (a) (b) (c) (d)

0.12 hr 4.17 hrs This problem is unsolvable Runoff will not occur

A.5. Consider a design rainfall intensity for a one in 2 year storm of 4 hour duration, 2I4 hour = 10mm/hr. How much rain will fall in a pulse that contributes 40% of the total rainfall in the storm? (a) (b) (c) (d)

1.5 mm 16 mm 6 mm 20 mm

A.6. If the notation for a one in Y-year, t-hour duration rainfall intensity is YIt hour, which of the following sequences is ordered from highest to lowest rainfall intensity? (a) 2I1 hour; 2I12 hour; 50I1 hour (b) 50 I1 hour; 2 I1 hour ; 2I12 hour (c) 2I12 hour; 50I 1 hour; 2I1 hour (d) 2I12 hour; 2I12 hour ; 50I1 hour A.7. What is the time of concentration for a 20km2 catchment with the main channel profile shown below?

(a) (b) (c) (d)

136 minutes 135611 minutes 540 minutes 62 minutes

A.8. If the design life of a river crossing causeway is 50 years, what is the average recurrence interval of the design flood such that the design hydrologic risk is 30% (a) (b) (c) (d) A.9.

100 years 120 years 140 years 160 years

The probability of a one in 5-year flood to occur exactly three times in 5 years is: (a) (b) (c) (d)

5% 10% 15% 20%

A.10. Compared to the average stream particle velocity, a kinematic flood wave moves (a) (b) (c) (d)

faster. at the same speed. slower. any of the above.

Section B – Written Response Type Questions B.1.

The graphs below show inflow (solid line) to and outflow (dashed line) from a storage device, e.g. a lake or reservoir. Which of these graphs are likely to be realistic and correct? Why? Which ones are likely to be unrealistic and wrong? Why? Pay particular attention to where the hydrographs begin, where they end, and where the peak flows occur.

B.2. You are asked to design a simple sand column filtration system for a community water supply. The filter needs to be at least 3.5 m long to adequately trap particulates in the water and the sand has a conductivity K = 5.1 m/day. The system will be driven by gravity with the top and bottom of the (vertically oriented) cylindrical filter is exposed to the atmosphere. The required daily water supply is 18.8m3. (a) Draw a sketch of the filter clearly labelling all parameters including both the elevation and pressure heads. (b) What diameter filter is required to treat the 18.8 m3 of water per day? (c) If the filter diameter has to be fixed at 1.25m, evaluate and quantify the following design alternatives to treat the 18.8m3/day. Be sure to provide evidence to support and justify your evaluation. i. Lengthen the sand filter (how long?) ii. Raise the hydraulic head at the inflow (how high?) iii. Use several filters (how many, what size?)

B.3.

Suppose that a structure can withstand a flood with a peak discharge no greater than 1,350 m3/s and that it was designed to have an economic life span of 100 years. Determine the risk of failure assuming the Extreme Value Distribution if the mean and standard deviation of the annual flood series are 242m3/s and 190m3/s respectively. During recent flooding in south-east Queensland, rainfall intensities in excess of 180 mm/h were recorded in some areas. In one particular catchment with an area of 32 km2, the runoff coefficient for the 3 hour storm event in the context of the rational method was 0.92. Determine whether the structure mentioned in part (a) would have failed during the flood event.

B.4. Table 1 below provides the rainfall runoff data for a 5.3km2 catchment. Table 1. Rainfall-runoff data from a 5.3km2 catchment. Time (hours) 1 2 3 4 5 6 7

Streamflow (m3/s) 0.9 4.2 17.1 13.3 5.8 3.9 0.9

Rain (mm) in preceding hour 10 39 7 0 0 0 0

(a) Determine the direct runoff depth in mm from the catchment assuming a constant baseflow of 0.9 m3 s-1. (b) Assuming a constant loss rate, confirm that the direct runoff was produced from a single 1-hour period of rainfall excess. Be sure to provide quantitative evidence to support this. (c) Derive a 1-hour unit hydrograph for the catchment. (d) If a 50-year flood results from a 2-hour storm having 48 mm of rainfall excess for the first hour and 21 mm of rainfall excess for the second hour, determine the peak streamflow discharge in m3/s using the unit hydrograph derived for the catchment. B.5. You are approached to design an artificial wetland within a 5.1 km2 catchment area in southeast Queensland in order to filter effluent rich in nutrients. A sketch of the catchment and the proposed wetland site is shown below. The entire catchment is low-lying with clayey sub-soil low in permeability.

Some relevant information on this catchment is: Mean annual rainfall = 1100 mm Mean annual potential evaporation = 1350 mm Volumetric runoff coefficient = 0.2

Area = ? The required natural drainage from the catchment outlet for environmental flow will need to be at least 155 ML/year, and effluent will be discharged into the proposed wetland area at a rate of 80 ML/year. Your task is to determine the maximum wetland area that is hydrologically sustainable in the long term. (Hint: This is essentially a water balance problem.) FOR ADDITIONAL EXAMPLE QUESTIONS REFER TO HOMEWORK PROBLEMS...