Name: Student #:__________________________

University of Toronto

Faculty of Applied Science and Engineering

Department of Civil Engineering

C1V250 - Hydrology and Hydraulics

Final Exam, April 21, 2017

Duration: 2 and V2 hrs

The test is 11 pages and graded out of 70 marks.

Test is closed book, only a non-progranirnable calculator, rulers and a two-sided 8 ½" x 11" aid

sheet is permitted. All work must be neat and legible. Show all your calculations and state any

assumptions. Answers are to be written in exam booklets. Your equation sheet must be

submitted with your exam at the end of the examination period.

F

Page! of 11

TERMS AND CONCEPTS

1. 16 marks] Define and describe 3 of the following (use sketches when appropriate):

Effective Rainfall

Field Capacity

Stage

Lysimeter

CONCEPTUAL QUESTIONS

14 mark] What are the two resistance factors caused by plants that affect evapotranspiration? Describe these two types of resistance factors and how they affect evapotranspiration rates. Use sketches where appropriate.

14 marksl What function do the weirs provide in the Humber River? Many of the weirs along the Humber River have trapezoidal notches removed from the center of the weir. Why was this done? Was this intervention successful? Why or why not?

14

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COMPUTATION QUESTIONS.

4. The stormwater management system of a proposed 1.8 ha commercial development needs

to be designed for a storm with a 25 year return period. The 25-year IDF curve is given

by:

830

- t + 33

Where i is the rainfall intensity in cm/hr and t is the storm duration in minutes. Local

regulations require a minimum time of concentration of 10 minutes. The development has a Manning's n for overland flow of 0.016, an average overland flow length of 90 m and an

average slope of 0.6%.

110 marks] Determine the flow rate that will govern the design of the storm sewer. The

time of concentration can be modelled using the kinematic wave equation.

18 marks] The developer is considering directing the runoff to a reservoir for storage. In order to size the reservoir you need to determine the total volume of runoff that needs

to be stored. Use the NRCS curve number method to estimate the total volume of runoff for a 2 hr design storm, assuming the soil has an average condition at the beginning of the design storm. An infiltration test on the soil shows that the minimum infiltration

rate is 2 mm/hr.

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5. Discharge data was recorded during a 2-hr rain event at the outlet of a 200 km2 watershed.

The data is plotted in Figure 1. The stream outflows into a 50 ha lake.

Hydrograph

900

800

700

600

500

.D 400

300

200

100

0 0 1 2 3 4 5 6 7 8 9 10 11

Time (hrs)

Figure 1 - 2-hr Streamfiow Hydrograph

(i) [15 marks] Create the hydrograph for a 7 hour, 4.5 mm rainfall event. You may draw

on Figure 1 on this page to show your work. Include a sketch that graphically represents your process using the graph paper provided in Figure 2 and label each series. Clearly

show all intermediary steps and calculations for creating this hydro,iraph.

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Figure 2- Graph Paper for Question 5 (i)

[4 marks] The municipality is considering diverting a portion of the river for a micro-

hydroelectric project. They require a 10 m3/s discharge through the diversion channel

for the project to be successful. They have designed a 3 m wide rectangular concrete

lined diversion channel with a slope of 0.1 % to be used to divert the water for this

project. What depth of channel is required to accommodate this discharge?

[2 marks] Will the flow in the channel designed above be sub-critical or supercritical

flow?

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6. A site consists entirely of a sandy loam soil and has 4 mm of depression storage. Assume

the initial moisture content is 0.09. Using the Green and An-pt Method,

[2 marks] Determine if and when ponding begins during the storm. 115 marks] Determine the incremental and cumulative runoff from the site

using the following design storm.

Interval (mm) Average Rainfall (mm/hr)

0-10 20 10-20 40 20-30 60 30-40 110 40-50 60 50-60 20

End of Exam

Page 6 of 11

Flow Wetted Hydraulic Shape Section Area A Perimeter P Radius R

77 (b + zy)y Trapezoidal y y(h+zy) b +2y1+z2 b+v1+z2

ZY Triangular

NI Z 7Y zy 2 2y v1 +

by Rectangular

E _

by b + b 2v

__-

A V

Wide flat I by b y

-b >>y--

bS

sin 0 Circular

(0— sinO ç -

Copynght 32O13 Pearson Education, publishing as Prentice Hall

Page 7ofll

Table 16.5 Rational Runoff Coefficient

Urban Catchments

General Description C Surface C

City 0.7-0.9 Asphalt paving 0.7-0.9

Suburban business 0.5-0.7 Roofs 0.7-0.9

Industrial 0.5-0,9 Lawn heavy soil

>7° slope 0.25-0.35

Residential multiunits 0.6-0.7 2-70 0.18-0.22

Housing estates 0.4-0.6 <2° 0.13-0.17

Bungalows 0.3-0.5 Lawn sandy soil

>71 0.15-0.2

Parks, cemeteries 0.1-0.3 2-70 0.10-0.15

<20 0.05-0.10

Rural Catchments (less than 10 km2)

Ground Cover Basic Factor Corrections: Add or Subtract

Bare surface 0.40 Slope < 5%:-0.05

Grassland 0.35 Slope> 10%: +0.05

Cultivated land 0.30 Recurrence interval <20 yr: -0.05

Timber 0.18 Recurrence interval > SO yr: +0.05 Mean annual precipitation <600 mm: -0.03 Mean annual precipitation> 900 mm: +0.03

Source: Stephenson (1981).

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Table 4.6 Green-Ampt Infiltration Parameters

Wetting front soil Effective hydraulic

Soil texture class Porosity, 9 suction head, S1, cm conductivity, K, cm/h

Sand 0,437 4,95 11.78

(0.374-0.500) (0.97-25.36)

Loamy sand 0,437 6.13 2.99

(0.363-0.506) (1.35-27.94)

Sandy loam 0.453 11.01 1.09

(0.351-0.555) (2.67-45.47)

Loam 0.463 8.89 0.66

(0.375-0.551) (1.33-59.38)

Silt loam 0,501 16,68 0,34

(0.420-0.582) (2.92-95.39)

Sandy clay loam 0,398 21.85 0.15

(0.332-0.464) (4.42-108.0)

Clay loam 0.464 20.88 0.10

(0.409-0.519) (4.79-91.10)

Silty clay loam 0.471 27.30 0.10

(0.418-0.524) (5.67-131.50)

Sandy clay 0,430 23.90 0.06

(0.370-0.490) (4.08-140.2)

Silty clay 0,479 29.22 0.05

(0.425-0.533) (6.13-139.4)

Clay 0.475 31,63 0.03

(0.427-0,523) (6.39-156.5)

Source: Rawls and 8rakensiek (1983).

Table 4.10 Hydrologic Soil Groups

Minimum

Infiltration Rate

Group Range (rnm.hr) Texture'

A 7.62 11.43 Sand, loamy sand, or sandy loam

3.81 7.62 Silt loam or loam

C 1.27 3.81 Sandy clay loam

D 0 1.27 Clay loam, silty clay Foam, sandy clay, silty clay, or clay

a Reproduced from U.S..Soil Conservation Service (1986.

Page 9 of It

Table 2-1 Runoff Curve Numbers for Selected Agricultural, Suburban, and Urban Land Use (Antecedent Moisture

Condition II; 0.25)

Land Use Description A

Hydrologic Soil

Group

B C D

Cultivated land' Without conservation treatment 72 81 88 91

With conservation treatment 62 71 78 81

Pasture or range land

Poor condition 68 79 86 89

Good condition 39 61 74 80

Meadow

Good condition 30 58 71 78

Wood or forest land

Thin stand, poor cover, no mulch 45 66 77 83

Good cover2 25 55 70 77

Open spaces, lawns, parks, golf courses, cemeteries, etc.

Good condition: grass cover on 75% or more of the area 39 61 74 80

Fair condition: grass cover on 50%-75% of the areai 49 69 79 84

Commercial and business areas (85% impervious) 89 92 94 95

Industrial districts (72% impervious) 81 88 91 93

Residential3

Average lot size Average % impervious4

1/8 ac or less 65 77 85 90 92

114 ac 38 61 75 83 87

1/3 ac 30 57 72 81 86

1/2 ac 25 54 70 80 85

lac 20 51 68 79 84

Paved parking lots, roofs, driveways, etc.5 98 98 98 98

Streets and roads

Paved with curbs and storm sewers5 98 98 98 98

Gravel 76 85 89 91

Dirt 72 82 87 89

Factor to convert runoff volume to depth

Unit of Runoff Ordinate

Unit of Time Base

Unit of Volume

Unit of Area

Unit of depth

K

m3/s day m3/s*day km2 mm 86.4 m3/s hour m2/s*-hr km2 mm 3.6

Conversions:

1 ha = 10,000 m2

1 nun = 0.039 in

Page 10 of 11

Table 14.4 Values of Manning's Roughness Coefficient'

Material Manning n

Closed conduit or built-up channel

1.1 Metal

Brass 0.01

Copper 0.011

Steel—welded 0.012

Steel—riveted 0.016

Cast iron—coated 0.013

Wrought iron—galvanized 0.016

Corrugated metal (storm drain) 0.024

1.2 Nonmetal

Glass 0.01

Cement 0.011

Cement mortar 0.013

Concrete culvert 0.013

Concrete lined channel/pipe 0.015

Wood 0.012

Clay 0.013

Brickwork 0,013

Brickwork with cement mortar 0.015

Masonry/ rubble masonry 0.025

Sanitary sewer coated with slime 0.013

Asphalt 0.013

Plastic 0.013

PVC 0.009-0,011

Polyethylene 0009-0.015

Excavated or Dredged Channel

Straight and clean 0.022

Winding and sluggish 0.025

Dredged 0.028

Rock cut/stony 0.035

Earth bottom, rubble sides 0.03

Unmaintained/uncut brush 0.08

Natural streams

On plain, clean, straight, no pools 0.03

On plain, clean, winding, some pools 0.04

On plain, sluggish, weedy, deep pools 0.07

On mountain, few boulders 0,04

On mountain, large boulders 0.05

a For overland flow roughness coefficient see Table 16.7.

Note: Judgment must be used to determine n for channel characteristics that fall in between these cate- gories. See Chow (1959) for a detailed reference.

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