1 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 2 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. 3 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. 4 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. 5 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. 6 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 7 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 8 9 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. 10 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 11 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. 12 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.