Prioritization of flood risk based on multi-criteria decision-making models (Gray systems theory-ELECTRE-TOPSIS)

In recent years, flood control projects have been more extended in the country. Given the cost of implementation, prioritizing the sub-basins is of most important and making decisions about flood and integrated watershed management being quite necessary.The first and most important step in the runoff flood management projects is prioritizing essential areas to carry out flood control projects. Decision-making methods provide effective tools for dealing with issues involving more than one goal. In this study, Parchin watershed basin was studied. Then, using multi-criteria decision-making methods (ELECTRE, Grey and TOPSIS) the sub-basins were prioritized.The results of Grey method were investigated by gray relational analysis for the score of 9 sub-basins. The sub-basin 7 with the highest score (0.719443) was prioritized in the first and sub-basin 1 with score of (0.466119) in second priority and sub-basin 4 with the least amount of score (.331493) was placed in the last priority.In TOPSIS method rating was done using calculated nearness to ideal solution options, sub-basins 7 with the highest nearness coefficient (0.843721) is in the first rank. The results from rating showed that all three methods were evaluated equally in first priority, in other priories methods gave different results. According to the above-mentioned results the three TOPSIS methods and gray analysis are more similar and more accurate than the electronic method.