Landfill environmental impact study using a combined method of Leopold and RIAM matrices: A case study

The rapid increase in municipal solid waste generation has intensified the need for sustainable landfill management. This study quantitatively evaluated the environmental impacts of open dumping using the RIAM and Leopold methods and investigated the effect of averaging scores on component ranking. The overall environmental scores were −611 (RIAM) and −704 (Leopold), indicating severe negative impacts. In RIAM, the algebraic sum of scores ranked the components from the most to the least negative impact as follows: physico-chemical (−222), cultural-social (−163), biological-ecological (−114), and economic-operational (−112). In the Leopold matrix, the algebraic sum ranked the components as: physico-chemical (−270), economic-operational (−168), biological-ecological (−140), and cultural-social (−126), demonstrating a different ranking pattern between the two methods. After averaging by the number of criteria within each component, the RIAM averages were: physico-chemical −27.8, biological–ecological −38.0, cultural–social −23.3, and economic–operational −37.3, which led to a reordering of the component ranking and produced results that were more consistent with the Leopold outcomes, although the averaging procedures are not strictly equivalent between the two methods (physico-chemical −11.3, biological–ecological −19.0, cultural–social −8.4, economic–operational −14.0). The most significant negative factors included groundwater contamination, increased disease vectors, land-use conflicts, and reduced health indicators. These findings suggest that evaluations based solely on algebraic sums may distort the prioritization of impacts, and normalization or averaging is essential for fair component comparison and method harmonization. To mitigate adverse effects, practical management strategies such as establishing sanitary landfill cells, composting units, leachate treatment systems, and recycling programs are recommended. This study highlights the importance of integrating quantitative assessment methods to support informed decision-making in landfill management and environmental protection. This study introduces an averaging-based normalization within the RIAM method as a novel approach to enhance comparability with the Leopold matrix.