The Spatial Analysis to Choose a Location to be Designated as a Landfill Site

Pekanbaru city has a landfill site (TPA). The local government estimated that it could only accommodate disposal for the next 2 years and a half. The aims of this research are: to identify a location suitable to be designated as a landfill site and considering to the land use change. The methods it employed were the overlay technique in Geographic Information System and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) as non-spatial analysis. Research findings found 4 feasible locations using GIS, i.e: Palas Sub-district and Rumbai Bukit Subdistrict in Rumbai; Tebing Okura Sub-district in Rumbai Pesisir; Sail Subdistrict in Tenayan Raya; and Labuh Baru Sub-district in Payung Sekaki District. From the TOPSIS, a number of locations with a specific rank were found such as: Rumbai, Rumbai Pesisir, Tenayan Raya & Tampan District. This research have one recommendation namely that Rumbai is the most suitable district to be designated as a landfill site.


Introduction
The TPA has been established since 1987 situated in Muara Fajar. It produces 1.816 m 3 of waste per day from 12 districts and has over capacity. There are 18.062 residents who working in agriculture sector [3] , and product i.e: paddy, maizena flour, cassava, crops, chili and fruits. According to Borges, Fragoso, et al: land use is the key for human activity that drives socio-economic development in rural regions [4] . Therefore, the agriculture area in the urban fringe need protection to guarantee a sustainable agriculture land management. That is to determine the best position to establish lasting monuments and other valuable place [5]. This study fills this gap and was conducted with the objective to determine a location suitable to be designated as a landfill site. It will make an alternative method in landfill site selection & geomorphic study in planning [1] .  There are no flood hazards. The probability of flood is more than 25 years. The probability of flood is less than 25 years.  The ideal slope for a landfill ranges from 0 to 20%. There are two colors, the pink zone refers to the area which is not suitable to be designated as a landfill which cover the following districts: some areas in Rumbai, Rumbai Pesisir & Tenayan Raya.

Protected Area
In the map, there are two zones, namely the green zone, which is located within the protected areas, and the yellow zone, which is located outside the protected area.

The Overlay of the Regional Feasibility and Filter Feasibility Map
Based on the overlay result, Rumbai District especially in Palas and Rumbai Bukit Subdistrict, is considered a zone suitable to be designated as a landfill site. Palas & Rumbai Bukit Sub-district have a slope ranging from 2 to 15% which falls into the slightly sloping category. The potential location 3 (Tebing Okura) has a slope ranging from 2 to 8%.

3.2.The Non-Spatial Analysis for Landfill Site Selection
To support the results of spatial analysis, TOPSIS method that classifies districts on the ranking basis was performed as alternative landfill locations, also to strengthen the basis for decision making as well. There are weights and criteria set to determine the selected alternative as alternative landfill locations. Each category has a criterion weight between 1 and 5 namely the categories very bad (1), bad (2), fairly good (3), good (4), excellent (5).

Developing the Decision Matrix
The matrix column states that the attributes are comprised of the existing criteria, whereas the matrix row states that the alternative is the assessment data on the zones suitable to be used as a landfill to be compared.

Developing the normalized decision matrix
Once the decision matrix has been developed, the next step was to develop the normalized decision matrix R, in which the elements are determined using: where i = 1, 2, 3,.... m; and j = 1, 2, 3,..., n An example of the normalized matrix calculation (matrix R) for K1 in Bukit Raya:

Developing the weighted normalized decision matrix
With the weight wj = (w1, w2,… wn), where wj is the weight of the j th criterion and ∑ = = n 1 j 1 j w , thus the weight normalisation of the matrix V is: Vij = Wij*rij V1,1 = Criterion Weight * R1,1 = 5 * 0.311 = 1.555 (this calculation for Criterion-1 in Bukit Raya District)

Determining the positive and negative ideal solution matrices
The positive ideal solution is denoted by the symbol A+, while the negative ideal solution is denoted by the symbol A-.

Calculating Separation
D + is the alternative distance (in the Euclidean perspective) from the positive ideal solutions , with j = 1,2,3....,n (3) Dis the alternative distance from the negative ideal solution. It is described as: , with j = 1, 2, 3,...., n vij = element of the weighted normalized decision matrix V v1 + = element of the positive ideal solution v1 -= element of the negative ideal solution An example of the distance calculation for positive (D + ) and negative (D -).
the alternative distance from the negative ideal solution, which is defined:

Calculating the relative proximity to the ideal positive solution
Vi + is the relative proximity from the I th alternative to the positive ideal solution. V1 = 2.153 = 0,578 2.153+1.570 Table 4. Ranking of the Alternatives

Recapitulation of the Potential Locations
Based on the recapitulation results of the spatial analysis (GIS) and TOPSIS, there are 3 districts with the same score, namely Rumbai, Rumbai Pesisir and Tenayan Raya.