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CHAPTER 1
INTRODUCTION
1.1
Background
Wide ranges of water-related problems are associated with the urbanization
process: water runoff and flooding, pollution and sedimentation, etc. In the process of
population expansion, people need more land for housing and accommodations. The
growing housing demand in urban areas is typically associated with the increased storm
water runoff and flood (Cai, 2003).
Low-Impact Development (LID) is an approach to land development (or redevelopment) that works with nature to manage stormwater as close to its source as
possible. LID employs principles such as preserving and recreating natural landscape
features, minimizing effective imperviousness to create functional and appealing site
drainage that treat stormwater as a resource rather than a waste product. There are many
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practices that have been used to adhere to these principles such as bioretention facilities,
rain gardens, vegetated rooftops, rain barrels, and permeable pavements (EPA, 2003).
Hence, LID is a comprehensive development approach aims to maintain the predevelopment hydrology system and water quality through small-scale distributed
stormwater controls, in both structural and non-structural ways (Jones, 2004). The
primary objective of LID is to mimic predevelopment site hydrology by using site
design techniques that store, infiltrate, evaporate, and detain runoff.
The use of LID techniques will help reduce off-site runoff and nonpoint resource
pollutant reduction. Pollution washed from the land surface by rainfall is called nonpoint
source pollution. Duda (1993) described nonpoint source pollution including agriculture
activities, urban and industrial runoff, joint sewer overflows and leaks, hazardous waste
dumpsites, septic tank systems, mining and forest harvesting activities, spills,
atmospheric deposition, and hydrologic modification. Pollution from non-point sources
heavily influences water quality in urban creeks and, thus, the urban aquatic
environment.
Nonpoint pollution comes from diverse and hard to identify sources, therefore it
is difficult to estimate. The use of Geographical Information Systems (GIS) provides an
extensive approach to evaluate land use and other mapping characteristics to explain the
spatial distribution of nonpoint source contamination.
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1.2
Problem Statement
In recent years, the contribution that nonpoint sources make to pollution in the
earth’s surface waters has come under closer consideration. Nonpoint source, or diffuse,
pollution can be defined as pollution that is not associated with a specific location, pipe
effluent discharge, or “point”.
On the other hand, recent developing decreases the pervious surface in the cities
and developed area. The consequence of this new impervious area is increasing the
stormwater runoff and flood. Finding new approaches like LID to manage the
stormwater runoff in cities is still on progress.
GIS is widely used for a broad variety of landuse planning purpose. For nonpoint
source pollution control planning, it has been shown to be very effective in targeting and
prioritizing nonpoint source pollution control resources. In this study, GIS analysis is
discussed in order to find the suitability of locations for LID components (birotention
cells) and determine the amount of NPS pollution that can be reduced by LID practice.
Most of LID projects were done already; ignore site selection and location efficiency to
install LID. By using GIS and deriving a fuzzy GIS based model, the suitability of
places for LID projects was determined. On the other side, calculating run off and non
point source pollution loading to compare before and after LID practice are the other
challenging issues of this project.
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1.3
Aim
The aim of this study is to assess the effects of LID on the amount of runoff and
its nonpoint source pollution in a specific area by using GIS. The reason of choosing
GIS lies in its ability to effectively represent spatial distribution of a variety of system
parameters such as hydrologic and geographic.
1.4
Objective
There are three primary objectives for this study:
i.
To identify criteria and design geospatial analysis for determining LID site
suitability.
ii.
To compare the result of GIS analysis with SWMM and evaluate the outcome
accuracy.
iii.
To assess the LID effects on quantity and quality of runoff.
1.5
Scope of Study
The scope of this study explains the flowing subsections: Study area, data and
software used for analysis.
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1.5.1
Study Area
The study area is part of Taman Wangsa Melawati which is located in the state of
Selangor with an area of 7.14 hectares. It is located on the upstream catchment of Klang
River and surrounded by housing estates that are Taman Melawati and Taman Permata.
This area is chosen because of its location reflects the development of urban area which
can impact directly and indirectly to surface water runoff. Figure 1.1 shows the location
of study areas along rivers in the vicinity.
Figure 1.1: Location of Study Area
Source: Google Earth
This residential area consists of two storey terrace houses, shop houses, mosque,
parks and playgrounds, and childcare centre. Table 1.1 shows the details of landuse
while Figure 1.2 depicts landuse categories in the study area.
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Table 1.1: Landuse of Taman Wangsa Melawati
Land Use
Number
Extent (m2)
Percentage (%)
Two-storey Terrace Houses
242
31,504
43.9
Two-storey Shophouse
10
1,505
2.1
Field
1
12,484
17.4
Mosque
1
1,414
1.97
Playgrounds
1
312
0.43
Road
1
23,515
32.7
Childcare Centre
1
1,509
1.48
71,793
100
Total
Figure 1.2: Landuse Map
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Overall, the topographic conditions in the catchment area are within the
horizontal height of 67.8 meters in the upstream, up to 57.8 meters at the point of
expression (outlet downstream). The catchment area includes Persiaran Wangsa
Melawati in North, Jalan Melawati 4 in the south, Jalan Wangsa Melawati Wangsa Road
in the east and the west, Siaga 1.
The existing drainage system at Taman Wangsa Melawati is a conventional
system with water runoff from a roof will flow directly into the drain through the gutter
and perimeter drain. Water runoff from residential will be combined with water runoff
from roads and will eventually flow to the outlet. Type of drain consists of a fully
enclosed concrete drain. Figure 1.3 and 1.4 show the appearance of topography.
Figure1.3: DEM of Study Area
Figure1.4: 3D Elevation Map of Study Area
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1.5.2 Data
A contour map of study area with 0.1 meter intervals was exploited to make
DEM in order to train editing and eliciting the drainage network and catchment points.
Landuse map was utilized to bring out the imperviousness. To calculate the runoff, a 120
minutes stormwater design data with 10 years return was used.
1.5.3 Software
Two software were used to accomplish the studies are ArcGIS 9.3 and
XPSWMM. ArcGIS is an integrated collection of GIS software produces that provides a
standard-based platform for spatial analysis, data management, and mapping.
XPSWMM is a comprehensive software package for modeling stormwater, sanitary and
river systems. XPSWMM is used by scientists, engineers and managers to develop linknode (1D) and spatially distributed hydraulic models (2D). It simulates natural rainfallrunoff processes and the performance of engineered systems that manage our water
resources.
1.6
Methodology
Generally, there are 4 phases to complete this study. Figure 1.5 depicts these
phases.
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IDENTIFY THE CRITERIA
1.
2.
3.
4.
Slope
Distance From Building
Distance From Drainage Network
Distance From Catchment Points
CONVERT MAPS TO FUZZY MEMBERSHIP MAPS
COMBINE THE FUZZY MEMBERSHIP MAPS TO
DETERMINE THE SUITIBILITY LOCATION FOR LID
EXPLOIT THE XPSWMM TO EVALUATE THE FUZZY GIS
BASED MODEL ACCURACY
NO
CRITERIA AND WEIGHTS ARE
ACCEPTABLE
YES
AS
ASSESS THE LID EFFECTS OF RUNOFF
Figure1.5: The Flow Chart of Methodology
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1.7
Significance of Study
This study carried out to find suitable location for LID components in a small
developed area and assess the LID effects on Runoff. Previous LID works mostly
focused on LID site design and LID construction materials. In this study, a fuzzy GIS
based model was exploited to determine the suitability of areas for LID to increase their
efficiency in removing pollution and runoff. Besides LID site suitability model,
additional analyses were developed to calculate the volume of LID components
(bioretention cells) according to their corresponding catchment in order to increase cost
effective. The study was extended to find LID (which was located in suitable area with
different volumes) effects on runoff.
1.8
Chapter Organization
This research covers 5 chapters which are introduction, literature review,
methodology, analysis and conclusion.
Chapter1: This chapter includes the introduction of research, the problem statement, the
aim of study, the objectives, scope of study, general methodology and
significant of study.
Chapter2: In this chapter, literature related to study were reviewed. These literature
covers stormwater management, LID Component and Fuzzy GIS based
model. The early findings in this chapter are important to provide a useful
guideline to plan and accomplish the flowing chapter.
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Chapter3: This chapter describes the details methodology to achieve the aims and
objectives which were shown in chapter1. All the explained phases are
including LID site suitability, LID hydrologic analysis components and LID
effects on none point source pollutant loading.
Chapter4: All the analysis carried out to find the LID effects on runoff in the study area
is completely depicted in this chapter. The result of the analyses is display
and discuss.
Chapter5: In this chapter, it concluded the entire research with the achievement. In
addition, some recommendation is proposed to the reader.
1.9
Summary
This chapter highlights the purpose of the proposed study. Aims, objectives and
metrologies are identified and explained. This provides a general framework of the
entire execution of the study area.