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