1. Role Of Catchment Drain For Earth Slope Stability
Surface Drainage
Built lined to the earth slope contour
Built to stabilize the earth slopes
Role Of Catchment Drain For Earth Slope Stability
Mohd Dzulkarnain Bin Mohd Jame

2. Water penetration deep below drain
Problem Statement
Water penetration deep below drain
Rainfall
Surface runoff
Erosion,land sliding still happens
Most surface water penetrates into the soil
Catchment drain not operating on it’s full capacity

3. Water penetration is controlled
Rainfall
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.

4. Site Study Location 106.4 km from Kota Kinabalu,Sabah
Slope at km 106.4

5. Field Test
T Bar & Measuring tape
Penetration test
The site study

6. Data Analysis Start - Soil moisture content (%)
- Catchment drain distance (m)
- Wetted soil depth (mm)
Site Data
Change Q Values
Initial Q = 0.4 l/s
- Surface runoff (mm)
- Inflow time (minutes)
Refer to SCS Design Chart
Determine Runoff/hr equivalent & Rainfall equivalent type NO
- Rainfall intensity (mm/hr)
- Duration (minutes)
Refer to rainfall IDF curve
to determine rain type
Is rain application on slope ≈ runoff values?
SCS formula
Calculations
-Actual rain application on slope (mm)
-Intake into soil (mm)
-Wetted soil depth (mm)
-Surface runoff (mm)
YES
Catchment drains interval height comparison to JKR requirement.

7. Cumulative Wetted Soil Depth Comparison

8. Recommendation Conclusion
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
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 .