Traffic and Highway Engineering
5th Edition
ISBN: 9781305156241
Author: Garber, Nicholas J.
Publisher: Cengage Learning
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Chapter 16, Problem 9P
To determine
The runoff rate for a storm of
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Q2) Annual rainfall and runoff values of a catchment for a period of 10 years are given below.
Analyze the data to (a) develop a non-linear correlation equation to estimate annual runoff volume
for a given annual rainfall value, (b) Estimate r values for the equation, (c) Estimate the runoff depth
when the rainfall depth is (i) 350 mm (ii) 600 mm.
2010 2011
2017 2018 2019
Year
Annual
2012 2013
2014 2015 2016
Rainfall
361
408
217
324
510
488
275
392
296
420
(mm)
Annual
Runoff
(mm)
145
160
90
130
205
195
110
157
120
165
A certain watershed in Region VIII with an area of 60 ha flat heavy soil is to be converted
into a mixed subdivision consisting of:
40% apartment dwelling areas
20% business neighborhood areas
20% playgrounds and parks
20% light industrial areas
Using the rational method, estimate the percent change in peak runoff flow rates before
and after the development.
Refer to the table below for the values of runoff coefficients.
Values of Runoff coefficients, C (Chow, 1962)
Runoff
coefficient, C
Runoff
coefficient, C
Type of drainage area
Type of drainage area
Lawns:
Sandy soil, flat, 2%
Sandy soil, average, 2–7%
Sandy soil, steep, 7%
Heavy soil, flat, 2%
Heavy soil, average, 2–7%
Heavy soil, steep, 7%
Industrial
0.05–0.10
0.10-0.15
0.15-0.20
0.13-0.17
0.18-0.22
0.25-0.35
0.50–0.80
0.60–0.90
0. 10-0.25
0.20-0.35
Light areas
Heavy areas
Parks, cemeteries
Playgrounds
Railroad yard areas
Unimproved areas
Streets:
Asphaltic
Concrete
0.20-0.40
Business:
Downtown areas
Neighborhood areas
0.10-0.30…
The streamflow data given in the table was produced by a storm of 1-hour duration
considered to have uniform intensiry over the catchment. If the catchment area is 5 km',
calculate the equivalent runoff depth for the catclument.
Q. Total
(n/s)
flow Q.
(n/s)
Time
Baseflow
(hr)
2.80
2.80
2.78
2.60
3
6.23
2.60
14.50
2.60
16.57
2.60
13.03
2.60
7.
9.35
2.60
5.95
2.60
4.25
2.60
10
2.97
2.60
2.12
2.12
12
1.70
1.70
13
1.53
1.53
14
1.53
1.53
Chapter 16 Solutions
Traffic and Highway Engineering
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Similar questions
- Problem 1. The following are the ordinates of the hydrograph flow from a catchment area of 770 km2 due to a 6-hr rainfall. a. Derive the ordinates of the 6-hr unit hydrograph. Assume that the graph of the baseflow is linear with respect to time. b. Plot the direct runoff hydrograph. c. Determine the rainfall excess in terms of (i) volume in m3 and (2) depth in cm. d. Plot the unit hydrograph. Time from the beginning of the storm (hr) 0 6 12 18 24 30 36 42 48 54 60 66 72 Discharge (cumecs) 40 65 215 360 400 350 270 205 145 100 70 50 42arrow_forwardA catchment has a runoff coefficient of 0.20, area = 1.5 km² with a general slope of 0.001 and maximum length of travel of overland flow of 1.25 km. Information on the storm of 50 years return period is given as follows: Duration (min) 15 30 45 60 80 Rainfall (mm) 40 60 75 100 120 Estimate the peak flow to be drained by a culvert for a 50 year stormarrow_forwardCalculate the runoff depth for the 100 year storm event over a catchment basin using the SCS Runoff Method. The design rainfall for 100 year storm event is 6 inches. NOTE: Round off your weighted CN to the nearest WHOLE NUMBER. SOIL GROUP C D C D LAND USE 20% 15% 40% 25% HINT: Determine first the weighted CN by weighted CN CN to determine the runoff depth. Σ(%land use CURVE NUMBER 94 93 83 80 X CN) then use the weightedarrow_forward
- The observed rainfall and discharge of a catchment is given the table. The catchment area is 0.23Km^2. Time (h) 1 2 3 4 5 6 7 8 00 9 10 11 12 13 Rainfall (mm) 0 0 2 6 10 8 2 0 0 0 0 0 0 1. Estimate the base flow. 2. Estimate the surface runoff. 3. Estimate the initial loss 4. Estimate the continuous loss using phi method. Discharge (M3/s) 20 20 20 20 30 50 40 35 25 21 20 20 20arrow_forwardUsing the rational method, determine the peak water discharge rate, Q, in ft3/s at a culvert inlet for a drainage basin with the following characteristics: • Drainage Area is 125 acres Short grassy pasture/meadow 2% average overland slope Distance from farthest point in drainage basin to the culvert inlet = 0.5 mi 50-year design storm frequency Be sure to state all assumptions in your calculationsarrow_forward5. From the 1mm 6 hour unity hydrograph given below, derive the 2 hour unit hydrograph. Time 12 18 24 30 (hrs) UH 15 8 3.6 0.6 0.0 (cumecs) What would be the peak surface runoff resulting from 3mm of rainfall falling in the space of two hours?arrow_forward
- You have been given a 1-hour unit hydrograph (1 unit = 1 cm) and have been asked to use it to derive the surface runoff hydrograph for a 2-hour storm for which the total depth of rainfall excess was X cm and the intensity was constant. To derive it, you can: Multiply the ordinates of the 1-hour unit hydrograph by X/2 Find the 2-hour unit hydrograph and then multiply its ordinates X/2 Consider the storm as having two 1-hour periods of depth X/2 , multiply each 1-hour UH by X/2, lag them by 1 hour, and then add their ordinates. Multiply the ordinates of the 1-hour unit hydrograph by 2Xarrow_forwardThe following table shows the observed annual rainfall and the corresponding annual runoff for a small catchment. Develop the rainfall-runoff correlation equation for this catchment and find the correlation coefficient. What annual runoff can be expected from this catchment for an annual rainfall of 100 cm? Year Annual Rainfall (cm) Annual Runoff (cm) Year Annual Rainfall (cm) Annual Runoff (cm) 1964 90.5 30.1 1970 147.6 64.7 1965 1966 1967 1968 1969 111.0 38.7 129.5 145.5 99.8 50.2 5.3 61.5 74.8 39.9 1971 1972 1973 1974 1975 90.3 65.2 75.9 36.2 24.6 20.0 50.9 120.2 6.5 46.1arrow_forward1. A 160-acre drainage basin has the following characteristics: Land Use Residential, flat, 60% impervious Residential, flat, 30% impervious Concrete or sheet asphalt pavement Turf Meadows Forested Area * for a range of values, the runoff coefficient can be calculated as an average value. Rainfall Intensity (in/hr) Find the peak runoff from the drainage area for a 20-minute duration storm with a return frequency of 25-years? 20 18 16 14 2 0 0 Frequency (years) 100 50 25 10 10 Area % 20 30 5 25 20 20 30 Duration (min) Coefficient (C)* 0.55 0.40 0.85 0.25 0.2 40 50 60arrow_forward
- In the table below data for precipitation and runoff both in depths of cm are given for June during ten years from 2010 to 2018. Develop a linear equation relating precipitation and runoff.arrow_forward3. The figure below shows 5 different isohyets in a watershed. Find the average rainfall using the isohyetal method Given: The left-most side area (Zone A) can be assumed to receive a rainfall of 1 cm. The area between the isohyets are given in the following table: A Zone A B C D E F B 1 cm D E 1.5 cm 4 cm Area (km²) 80 75 95 82 68 5 2.5 cm 3.5 cmarrow_forwardThe flowrate at the outlet of a watershed for 2-hr rain event is given in the table. Base flow is 20 cfs and the runoff depth is 2 inches. Determine 2-hr UH. Must use table format to show details of your solutions. time, hr Q, cfs 20 26 30 3 34 4 28 5 24 6 22 7 20 1. 2.arrow_forward
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