GIS as Decision Support Tool for Landfills Siting

GIS as Decision Support Tool for Landfills Siting

Steps 4 and 5, as demonstrated in this particular research, involve some degree of public participation whereby the proponent was given the opportunity to express their wishes on the location criteria. The working group consists of several government departments, private 5 individuals and representatives from non-governmental originations. Some of the government departments involved in this project is the owners of specific data.

Steps 6, 7 and 8 are the intelligent part where GIS operations take place. Step 9 provides the final result of this study, which is potential search area for landfill for Sandakan District. It is pertinent to note at this point that step 4 which is the input criteria plays a very important role because it can influence the result of the GIS operation. Therefore, this particular research made use of the existing mechanism where the author presented the process and example of how the methodology works with the Sandakan Spatial Planning Working Group. The purpose here was to make the working group understand the process and requirement.

Case Study
The case study focused on Sandakan District which covers approximately 218,200 hectares; one of the 23 districts in Sabah and located on the East Coast with the population of 347,334 (Census 2000). The Sandakan Municipal Council administrative area covers 18,500 hectares and according to year 2000 census, there are 70,192 living quarters for Sandakan district. The majority of the housing estates are located within 13km radius from the town centre.

The daily average waste collection for Sandakan Municipal Council was about 165,000 kilograms or about 0.468 kilograms per persons per day in the year 2000 and expected to double in year 2005 (MPS 2002). The current landfills site is located at Jalan Sin Fook Kim, about 13 kilometres from the town centre but under the current planning exercise, Sandakan Municipal Council (SMC) is planning to relocate the present landfill. At about the same time, SMC also received a directive from the Ministry of Local Government and Housing, Sabah (KKTP.100 44/25 dated 24th April 2002) to plan its landfill operation up to year 2030.

Input Data
Data for this study comes from seven (7) different agencies, which include Town & Regional Planning Department, Department of Environmental Conservation, Department of Forestry, Lands and Survey Department, Department of Drainage and Irrigation, Department of Public works and Department of Agriculture.

GIS Spatial Operation
The spatial operations for constraint mapping began by identifying the criteria or conditions for constraint mapping and after that the criteria was then converted into GIS layers. From the GIS layers the spatial operation was performed. The spatial operation is normally performed in conjunction with GIS functionality found in most GIS software. Figure 2 summarizes the workflow for the spatial operation.

This particular study used the quarry functionality to a create buffer surrounding the theme such as river, road and others. In particular, spatial operation to produce the buffer was conducted for the following 5 themes:

Create 100 metres buffer from surface water and water sources,
Create 100 metres buffer from transportation routes,
Create 3,000 metres buffer from environmentally sensitive or protected areas,
Create population density map based on enumeration blocks of 1991 and 2000 census,
Create 3,000 metres buffer from rural settlements areas.

Figure 2: Workflow for the Spatial Operation
For the 4 remaining criteria, the spatial operation was performed by identifying the layer not suitable for landfill site, for examples, under the Landform and Soil Type, there were 9 different layers of Landform and Soil Type identified. These are the mangrove swamps (43,019 ha), sandy beach strips (5,072 ha), flood plain (6,298 ha), freshwater (peat), swamps (part of flood plain) (4,562 ha), raised (old) alluvial terraces (2,884 ha), undulating to gently rolling, low to very low hills, and valley floors slopes 0-15 degrees, relief amplitudes 15 to 30 meters (93,139 ha), strongly rolling to moderately steep, moderately high hills, slopes 10-20 degrees, relief amplitudes 60-150 meters (35,528 ha), steep to very steep high hills and ridges; slopes steeper than 25 degrees relief amplitudes 150 to 300 meters (14,980 ha) and finally the very steep, very high hills and mountains at 6,779 ha.

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