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The construction of landfills is not an alternative option, since a landfill is always a necessary component of the specific waste management system that will be developed. One of the serious and growing potential problems in large urban areas is the shortage of land for waste disposal. In solid waste management programmes, use of geographic information systems (GIS) is a very significant tool because the selection of a suitable site is a very time-consuming process. The analytic hierarchy process in GIS provides objective mathematics to process the subjective preferences of individuals or groups and arrive at a decision. The present paper describes a spatial methodology which comprised several methods, such as multi-criteria analysis, that originate in different scientific fields. The final goal of the methodology was to evaluate the suitability of the studied area (Trabzon, NE Turkey) in order to optimally select a landfill site. Different constraint maps were overlaid with spatial analysis modules to obtain a final suitability map for Trabzon City and five suitable areas were identified. An analytic hierarchy process was applied to select the most suitable solid waste disposal site for municipal waste in the city among these alternative candidate sites. The Düzyurt area was found to be the most suitable solid waste disposal site. However, geotechnical investigations indicated that some remedial measures would be needed before this landfill site could be used.

Ardesen is a settlement area which has been significantly damaged by frequent landslides which are caused by severe rainfalls and result in many casualties. In this study a landslide susceptibility map of Ardesen was prepared using the Analytical Hierarchy Process (AHP) with the help of Geographical Information Systems (GIS) and Digital Photogrametry Techniques (DPT). A landslide inventory, lithology-weathering, slope, aspect, land cover, shear strength, distance to the river, stream density and distance to the road thematics data layers were used to create the map. These layer maps are produced using field, laboratory and office studies, and by the use of GIS and DPT. The landslide inventory map is also required to determine the relationship between these maps and landslides using DPT. In the study field in the Hemsindere Formation there are units that have different weathering classes, and this significantly affects the shear strength of the soil. In this study, shear strength values are calculated in great detail with field and laboratory studies and an additional layer is evaluated with the help of the stability studies used to produce the landslide susceptibility map. Finally, an overlay analysis is carried out by evaluating the layers obtained according to their weight, and the landslide susceptibility map is produced. The study area was classified into five classes of relative landslide susceptibility, namely, very low, low, moderate, high, and very high. Based on this analysis, the area and percentage distribution of landslide susceptibility degrees were calculated and it was found that 28% of the region is under the threat of landslides. Furthermore, the landslide susceptibility map and the landslide inventory map were compared to determine whether the models produced are compatible with the real situation resulting in compatibility rate of 84%. The total numbers of dwellings in the study area were determined one by one using aerial photos and it was found that 30% of the houses, with a total occupancy of approximately 2,300 people, have a high or very high risk of being affected by landslides.

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