Investigation on deterioration mechanisms of the basalts employed in the Di̇yarbakır city walls

The primary objective of this thesis is to identify suitable locations for subsurface dam construction in the Diyarbakır Plain by integrating the Analytic Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) within a Geographic Information System (GIS) framework. Increasing population, climate change, and agricultural water demand have highlighted the need for alternative water storage solutions, especially in semi-arid regions. Subsurface dams offer a sustainable alternative by minimizing evaporation and environmental impact. In this study, eleven parameters—groundwater level, slope, soil texture, geology, proximity to surface water bodies, land use, precipitation, distance to active faults, hydraulic conductivity–storage coefficient, aquifer condition, and alluvial deposit presence—were transferred into the GIS environment as raster layers and normalized using a 3–6–9 scale. Pairwise comparisons using AHP produced relative weights with a consistency ratio (CR) below 10%. Weighted raster data were then analyzed using the TOPSIS method to calculate suitability scores for each grid cell. Scores between 0.70 and 1.00 were classified as "highly suitable," 0.50–0.70 as "moderately suitable," and below 0.50 as "unsuitable." The results show that areas with dense alluvial deposits, low slopes, and proximity to surface water bodies exhibit the highest suitability scores. This study demonstrates the effectiveness of GIS-based multi-criteria decision-making approaches for sustainable water resource planning and provides guidance for subsurface dam site selection.