Mohd Dzulkarnain Bin Mohd Jame

Role Of Catchment Drain For Earth Slope Stability

Catchment Drain

• Surface Drainage

• Built lined to the earth slope contour

• Built to stabilize the earth slopes

Problem Statement

• Erosion,land sliding still happens

• Most surface water penetrates into the soil

• Catchment drain not operating on it’s full capacity

Water penetration deep below drain

Rai

nfal

l

Surface runoff

Objective

• To determine the optimum spacings requirement for lateral storm water catchments drain on hill slopes that can reduce soil moisture content and depth of soil water penetration into the ground from heavy rainfall downpours.Water penetration is controlled

Rai

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Surface runoff

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Site Study Location

• 106.4 km from Kota

Kinabalu,Sabah

Slope at km 106.4

Field Test

T Bar & Measuring

tapePenetration

test

The site study

Start

Data Analysis

Site Data

Refer to SCS Design Chart

Determine Runoff/hr equivalent & Rainfall equivalent type

Refer to rainfall IDF curveto determine rain type

SCS formulaCalculations

Catchment drains interval height comparison to JKR requirement.

Is rain application on slope ≈ runoff values?

Change Q Values

NO

YES

- Soil moisture content (%)- Catchment drain distance (m)- Wetted soil depth (mm)

Initial Q = 0.4 l/s- Surface runoff (mm)- Inflow time (minutes)

- Rainfall intensity (mm/hr)- Duration (minutes)

-Actual rain application on slope (mm)-Intake into soil (mm)-Wetted soil depth (mm)-Surface runoff (mm)

Cumulative Wetted Soil Depth Comparison

Cumulative Wetted Soil Depth Comparison

R2 = 0.9967

R2 = 0.9712

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

7000.00

8000.00

9000.00

Slope A A A B B B C C C D D D C C C D D D D E E E E F F F F F F F G G G G G G G G G G H H H H H

Sec. 6 7 8 6 7 8 6 7 8 6 7 8 9 10 11 9 10 11 12 9 10 11 12 10 11 12 13 5 6 7 9 10 11 12 13 4 5 6 7 8 4 5 6 7 8

Location

Dep

th (

mm

)

Cumulative (SCS) Cumulative (Measured) Linear (Cumulative (SCS)) Linear (Cumulative (Measured))

Conclusion

• Depth of soil water penetration into the ground from heavy downpour and soil moisture content can be reduced by minimizing the wetted soil depth on the hill slope .

• Equation method shows a potential to be used as a design method for earth slope drainage .

• This study has been successfully shows that the SCS charts

and equations can give a close resemblance to the actual

measured wetted soil depth .

Recommendation

• Conservation Service (USDA, 1974) design of

gradient furrows equation should need some

calibration to be used in Malaysia

• A localized design chart for slope rain water flow

similar to the SCS design chart should be developed