عنوان مقاله [English]
One of the major problems that is noticeable in planning and management of most cities in our country today, is the management of increasing solid waste. The last phase in the management of waste is the final disposal, which has always engaged man. There are different ways for urban waste disposal, but their burial is more important and there has not been a perfect alternative to that so far. Choosing a suitable landfill site for waste is the most important step in waste management. It is a complicated matter that requires a vast evaluation process and the environmental, economic, social & tectonic standards should be taken into consideration. With regard to the fact that most of effective factors in determining the suitability of lands for special purposes such as waste burial, are not of the same significance, they must be weighed for more accurate evaluation. The analysis of the layers and numerous factors which are effective in the site location process will only be possible in the framework of multi-criteria decision-making (MCDM) systems and the use of GIS technology. Due to the importance of the subject matter, the present research has sought to locate the landfill site in the city of Ghaleh Ganj in order to take a step towards environmental protection and achieving sustainable development in this city. To achieve this goal, Geographic Information System (GIS) and multi-criteria decision-making systems have been used.
Materials and methods
The present research is an applied one in terms of the goal, and its approach dominating the research space is exploratory with regard to the nature of the subject. To develop the theoretical framework of the research and review the previous researches and extract the indices being used as well, the library method (documentary) was used. Field information was provided through questionnaire and field observations. Analytic Hierarchy Process (AHP) model was used for weighting the indices and its calculations were carried out in Excel software. The Fuzzy method was used for location and zonation that was implemented in GIS environment, which, according to many researchers, is the most accurate and the best method of site location.
The study area of this research is the city of Ghaleh Ganj in the province of Kerman located at 440 km from the capital of the province with a population of 12663 in 3034 families according to the general census of population and housing in the year 1390 (2011).
Results and discussion
AHP model was used to weight the landfill site location indices in the city of Ghaleh Ganj. In this regard, a questionnaire was edited based on Analytic Hierarchy Process (AHP) model and pair-wise comparison matrix, which was completed by 10 experts. The experts ranked the indices from 1 to 9, whose weights were calculated after entering the weights of indexes in Excel software. Then, landfill site location in the city of Ghaleh Ganj was carried out using GIS-Fuzzy model. The stages are as the following:
Preparing the shape files of the layers.
Forming the spatial matrix of the layers (Rasterising the layers).
Fuzzification of the layers by special methods of each layer.
Multiplying fuzzy maps by the weights obtained from AHP model.
Designing fuzzy inference network and integrating the layers to extract the final map.
15 layers were used to locate the landfills of the city of Ghaleh Ganj which are:
Distance from agricultural lands and gardens, land cover, distance from flood zones, distance from floodways, distance from drinking water wells, wind direction, distance from the city of Ghaleh Ganj, distance from rural centers and residential areas, distance from communication lines, distance from industrial park, distance from facilities, distance from the fault, type of soil, slope and finally, the material of bedrock.
After preparing the shape file related to each layer, the layers were grouped into 3 groups, each of which had its own method in rasterisation and fuzzification of the maps. The layers of the first and second groups were programmed using Python programming language and were modeled in GIS environment, and the layers of the third group were fuzzified by the “Raster Calculator” tool. In the next step, the fuzzy maps were multiplied by the weights obtained from the AHP model. Finally, in order to identify the appropriate zones for burying waste materials in the city of Galeh Ganj, the weighted fuzzy maps were combined with each other using “Fuzzy AND” operator, which is a subset of the Fuzzy Overlay tool operators, and the final map was obtained. The obtained map was reclassified and the lands of the city were classified into three classes of very suitable, relatively suitable and unsuitable in terms of waste burial capability. Finally, the land capability map for waste burial in Ghaleh Ganj was presented.
Based on the results of the research, the lands of the city were classified into three groups of very suitable, relatively suitable and unsuitable in terms of waste burial capability. Lands with very suitable capability are 1451.5 Hectares and lands with relatively suitable capability are2425.2 Hectares. The results also showed that the current location of the landfill in the city of Ghaleh Ganj is in the lands with unsuitable capability and it is imperative that the municipality abandon the current location as soon as possible and select a site from the lands with very suitable capability for waste disposal of the city, and if this is not possible, the lands with relatively suitable capability can be used. Finally, the results showed that the application of the AHP-FUZZY method in the GIS environment for locating the uses, including landfill sites, has a high efficiency and the method used in this research can be generalized to different cities of the country.