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Hydrology Analysis for Kenya

The document is a rational method calculation sheet for determining peak flow rates for an area called A1. It provides physical characteristics of the catchment area including its size, longest watercourse, and average slope. It also includes calculations of runoff coefficients based on land use and soil factors to determine peak flow rates for return periods of 2, 5, 10, 20, 50, and 100 years. A longsection diagram is also provided showing the slope of the catchment area.

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matshona
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2K views3 pages

Hydrology Analysis for Kenya

The document is a rational method calculation sheet for determining peak flow rates for an area called A1. It provides physical characteristics of the catchment area including its size, longest watercourse, and average slope. It also includes calculations of runoff coefficients based on land use and soil factors to determine peak flow rates for return periods of 2, 5, 10, 20, 50, and 100 years. A longsection diagram is also provided showing the slope of the catchment area.

Uploaded by

matshona
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as XLS, PDF, TXT or read online on Scribd
You are on page 1/ 3

Area A1: 5/9/2014

RATIONAL METHOD CALCULATION SHEET


Project Description:

Project Code:

Kitali

13/1/2014
Calculated by:

Calculation:

Michael
Area A1 (Total catchment area for northern watercourse)
Physical Characteristics
0.0024 km2
0.1 km
0.0209 m/m
0.0%

Area Distribution Factors


Rural

Size of catchment (A):


Longest water course (L):
Average slope (S):
Dolomitic % (D):

a:

Urban

100.0% b:

Lakes

0.0% c:

0.0%

Note: ( + + = 100%)

Runoff Coefficient
Rural
Surface Slope (%)
Vleis & Pans
0.0%
Flat Areas
40.0%
Hilly
60.0%
Steep Areas
0.0%

Urban

Permeability (%)
Very Permeable
0.0%
Permeable
50.0%
Semi-Permeable
50.0%
Impermeable
0.0%

Vegetation (%)
Thick Bush; Plantation
Light Bush; Farmland
Grassland
No vegetation

30.0%
10.0%
60.0%
0.0%

Use (%)
Lawns & Parks
Industrial Areas
City / Residential
Streets

0.0%
0.0%
0.0%
0.0%

Rainfall
Roughness Coefficient
Clean compacted soil, no stones
Paved areas
Sparse grass over fairly rough surface
Medium grass cover
Thick grass cover
Rainfall Station:

Time of concentration
0.0%
0.10
2 Overland Flow
0.0%
0.02
Watercourse
50.0%
0.30
50.0%
0.40 Tc=
0.05 hours
0.0%
0.80
Kenya
Rainfall Intensity (I)
5
10
20
50
100
10.0
20.0
30.0
42.0
50.0
200.2
400.5
600.7
841.0 1001.2
100%
100%
100%
100%
100%
200.2
400.5
600.7
841.0 1001.2
Run-off Factor
5
10
20
50
100
0.30
0.30
0.30
0.30
0.30
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30

Return Period T (years)


Point Rainfall (mm)
Point Intensity (mm/h)
Area Reduction Factor
Average Intensity (mm/h)

5.0
100.1
100%
100.1

Return Period T (years)


Rural C1
Urban C2
Lakes C3
C = aC1 + bC2 + cC3
Cfinal

2
0.30
0.00
0.00
0.30
0.30

Return Period T (years)

Peak Flow Q=C.I.A (m /s)

0.020

0.041

0.081

Saturation Factor Ft
Adjusted Peak Q.Ft

0.64
0.0129

0.69
0.0279

0.74
0.0599

227437588.xls.ms_office

Peak Flow
10
20

50

100

0.122

0.170

0.203

0.80
0.097

0.90
0.153

1.00
0.203

Rainfall Information
MAR:
160.0 mm
Rainfall region:
Summer
Throughout year x
Winter

Max

Notes

Max
0.30
0.00
0.00
0.30
0.30

Notes

Max

Notes

1.00

1 of 3

Area A1: 5/9/2014

RATIONAL METHOD CALCULATION SHEET


Project Description:

Project Code:

Kitali

13/1/2014
Calculated by:

Calculation:

Michael
Area A1 (Total catchment area for northern watercourse)

RUNOFF COEFFICIENT CALCULATIONS


RURAL (C1)
Mean Annual Rainfall (mm)
Runoff Coefficient
Component
Classification
570
630 - 870
930
C
Cx%
Vleis & Pans
0.01
0.03
0.05
0.01
0.00
Surface Slope Flat Areas
0.06
0.08
0.11
0.06
0.02
(Ch)
Hilly
0.12
0.16
0.20
0.12
0.07
Steep Areas
0.22
0.26
0.30
0.22
0.00
Very Permeable
0.03
0.04
0.05
0.03
0.00
Permeability
Permeable
0.06
0.08
0.10
0.06
0.03
(Cd)
Semi-Permeable
0.12
0.16
0.20
0.12
0.06
Impermeable
0.21
0.26
0.30
0.21
0.00
Thick Bush; Plantation
0.03
0.04
0.05
0.03
0.01
Vegetation
Light Bush; Farmland
0.07
0.11
0.15
0.07
0.01
(Cp)
Grassland
0.17
0.21
0.25
0.17
0.10
0.26
0.00
No vegetation
0.26
0.28
0.30
URBAN (C2)
Use
Low Factor High Factor Distribution % Low:
50% % High:
50%
Lawns & Parks
Sandy, flat
0.05
0.10
25.0%
0.08
0.02
Sandy, steep
0.15
0.20
25.0%
0.18
0.04
0.00
Heavy soil, flat
0.13
0.17
25.0%
0.15
0.04
Heavy soil, steep
0.25
0.35
25.0%
0.30
0.08
Industrial Areas
Light industry
0.50
0.80
80.0%
0.65
0.52
0.00
Heavy industry
0.60
0.90
20.0%
0.75
0.15
City / Residential Areas
Houses
0.30
0.50
60.0%
0.40
0.24
Flats
0.50
0.70
10.0%
0.60
0.06
0.00
Suburban Business
0.50
0.70
10.0%
0.60
0.06
City centre
0.70
0.95
20.0%
0.83
0.17
Streets
Streets
0.70
0.95
100.0%
0.83
0.83
0.00
Maximum flood
1.00
1.00
0.0%
1.00
0.00

227437588.xls.ms_office

2 of 3

Area A1: 5/9/2014

RATIONAL METHOD CALCULATION SHEET


Project Description:

Project Code:

Kitali

13/1/2014
Calculated by:

Michael
Area A1 (Total catchment area for northern watercourse)

Calculation:

X (m)
0
343.4
485.8
749.8
927
983.3
1230.3
1429.3
1864.9
2238.78
2740.2
3323.1
3818.3
4653.02
5150.3

Distance (m)
515.03
4377.76

10%
85%

LONGSECTION
10%
85%

Y (m)
1143
1150
1153
1158
1159
1162
1178
1178
1179
1188
1200
1220
1260
1360
1387.25

Notes

1153.55

1327.02

Level (m)
1153.55
1327.02

1085 Slope:
1085 Height:

0.045 m/m
173.47 m

Longsection
1400
1350

Height (m)

1300
Longsection

1250

1085 Slope

1200
1150
1100
0

2000

4000

6000

X (m)

227437588.xls.ms_office

3 of 3

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