Preparation of Design Guides for Erosion and Sediment Control in Malaysia

Researchers:

Prof. Dr. Aminuddin Ab. Ghani <This email address is being protected from spambots. You need JavaScript enabled to view it.>

Prof Dr. Nor Azazi Zakaria <This email address is being protected from spambots. You need JavaScript enabled to view it.>

Zorkeflee Abu Hasan

Dr. H. Md. Azamathulla

Dr. Lai Sai Hin

Mohd Fazly Yusof <This email address is being protected from spambots. You need JavaScript enabled to view it.>

Leow Cheng Siang <This email address is being protected from spambots. You need JavaScript enabled to view it.>

Chang Chun Kiat <This email address is being protected from spambots. You need JavaScript enabled to view it.>

Project Report:

The project consists of two volumes as stated below:

Guideline for Erosion and Sediment Control in Malaysia
Final Report

Executive Summary:

River Engineering and Urban Drainage Research Centre (REDAC), under USAINS Holding Sdn. Bhd. has been appointed by Department of Irrigation and Drainage (DID), Malaysia to carry out a study on “Preparation of Design Guides for Erosion and Sediment Control in Malaysia”.

The content of this report are as follow:

Chapter 1 - Introduction

Chapter 2 - Estimation of Soil Loss and Sediment Yield

Chapter 3 - Determination of Rainfall Erosivity, R Factor

Chapter 4 - Determination of Soil Erodibility, K Factor

Chapter 5 - Determination of Slope Length and Slope Steepness, LS Factor

Chapter 6 - Determination of Crop Management, and Erosion Control Practice, CC and P Factors

Chapter 7 - Determination of Curve Number (CN) and Direct Runoff

Chapter 8 - Revised Erosion & Sediment Control Guideline

Chapter 1 outlines the background of this study and contents of this report.

Chapter 2 provides a description on the Universal Soil Loss Equation (USLE/RUSLE) and the Modified Universal Soil Loss Equation (MUSLE), which are the most widely used methods for calculation of soil loss and sediment yield. Among the parameters required for these equations are the rainfall erosivity (R factor), soil erodibility (K factor), slope length and slope steepness (LS factor), crop management (C factor), erosion control practice (P factor) and SCS curve number (CN values). The concept of Sediment Delivery Ratio (SDR) is also introduced in this chapter to estimate the amount of sediment yield from the site/ area involves at a location further downstream.

Chapter 3 provides a detail literature review on rainfall erosivity (R factor), following by a description of methodology, and results of R factor calculated from 10 years Rainfall records (10-minute interval) at 241 stations in Peninsular Malaysia. The results are presented in the forms of tables, and isoerodent maps. Also included is a table with adjustment factors for the estimation of soil loss in a certain period within a year (partial year). The adjustment factor is divided into 4 regions (Northern, Central, Eastern and Southern) based on rainfall distribution in Peninsular Malaysia.

Chapter 4 Chapter provides a detail literature review on soil erodibility (K factor), and a description of methodology for the calculation of K factor. The soil survey data for 74 soil series has been collected. These soil data which include the soil profile description, the content of sand, silt, clay, and organic matter are useful for the determination of varies properties of all the soil series such as soil structure, soil permeability, soil texture and hydrologic soil group. The K factors for different soil layers (Surface soil, Subsoil, Substratum) are calculated using Tew Equation. These values are organized in a table for future usage.

Chapter 5 provides a detail description on the slope length and slope steepness (LS factor) which include a literature review on previous studies, methodology used for the calculation of LS factor, and the results obtained. Two methods have been used in the calculation of LS factor in this study. These methods are as suggested in AH537 (Renard et.al., 1997) and MSMA (DID, 2000). Different slope length and slope steepness are used in each case. The values obtained show that the differences between LS values using MSMA and AH537 are not very apparent, and therefore the MSMA method has been suggested for future usage. However, caution need to be taken for site slope steeper than 15%.

Chapter 6 deals with the crop management (C factor) and erosion control practice (P factor). A thorough literature review on C and P factors has been carried out, and most of the common C and P values related to Malaysian conditions have been obtained. These values are further analyzed to provide a list of suggested C and P values for future usage. The C factors have been categorized into different groups based on surface condition, e.g. C factor for forested and undisturbed lands; C factor for agricultural and urbanized areas; and C factor for BMPs at Construction sites. Similarly, the suggested P factors have also been categorized into different groups to show the effects of erosion control BMPs to sediment transport; and effects of mechanical actions on the ground.

Chapter 7 is particularly useful for sediment yield estimation using MUSLE equation, in which useful information to determine runoff volume (V) and peak discharge Q_p are presented in this chapter. For runoff volume, the required CN values for most common land use in Malaysia are obtained from literature review and presented in various table. A runoff chart has also been produced for determination of runoff volume from CN value representing the area. For peak discharge estimation, a number of widely used methods such as Rational Method and Time Area Method as mentioned MSMA (DID, 2000) are recommended.

Chapter 8 provides a summary of the revised ESC guideline for Malaysia, submitted separately from this report. A case study with BMPs for erosion and sediment control, detail drawing and calculation is also provided.

Background:

Soil can be eroded from its present state by the action of water, and wind. Soil erosion by water, is the process of soil particles detachment by the impact of rainfall and runoff, and its transport down the slope by flowing water. Erosion from mountainous areas and agricultural lands are the major source of sediment transported by streams and deposited in reservoirs, flood plains, and deltas. Sediment load is also generated by erosion of the beds and banks of streams, by the mass movements of sediment such as landslides, rockslides and mud flows, and by construction activity of roads, buildings and dams.

Malaysia cannot avoid from having erosion and sedimentation problems (Figures 1.1 and 1.2) as many parts of the country are experiencing rapid development, e.g. land clearing for urban developmet, logging, and agriculture. While these activities are necessary for the development of the country, regulatory efforts to minimize erosion and sedimentation problems should not stifle economic development planned for attaining a developed country status by year 2020. Therefore, an erosion and sediment control procedure/guideline similar to that available for users United States of America is needed for estimating general erosion rates and sediment yields specific to any particular site in the country. In principle, the procedure to be developed should be based on generally accepted equations for soil loss i.e. USLE, MUSLE, RUSLE etc. in which the variables involved are obtained through standardized charts and tables (e.g. erosivity chart based on rainfall characteristics, tables of erodibility based on local soil characteristics, tables of slope length and gradient, tables of land use practices or ‘C’ factor, tables of management practices or ‘P’ factor, and etc.) for ease of use in the country.

Study Objectives:

The objectives of this study are as follows:

to enable engineers and planners to have access to a single standard procedure to calculate erosion and sedimentation rates at any site in the country, primarily for the purpose of controlling erosion and sedimentation during the earthworks stage of construction.
to enable engineers to have expertise in designing control structures like sediment traps and basins using available historical records of rainfall for Peninsular Malaysia and soil series/type data.

Scope of Works:

Review existing US methodology as laid out in the CPESC (Certified Professional in Erosion and Sediment Control) manual.
Rainfall, soil and landuse data collection and collation.
Production of isoerodent, ie. Erosivity map for Malaysia.
Production of slope length, erodibility, P factor (management practice), and C factor (crop cover) tables.
Production of hydrologic soil group tables, runoff curve number tables for various categories of landuse, and runoff curve number graph.
Production of soil erodibility tables for various soil textures and layers, and soil erodibility nomograph.
Incorporation of work examples and photographs to illustrate estimates.
Incorporation of the use of BMPs to control earthworks in typical Erosion and Sediment Plans (ESCP).
Producing relevant isopleths using GIS for further modeling application.
Hands-on training for JPS staff.