Stakeholder perceptions in flood risk assessment: A hybrid fuzzy AHP-TOPSIS approach for Istanbul, Turkey

As an initial exploration, preliminary studies which are conducted for the identification of key points to be addressed in flood risk management (FRM) processes are crucial to mitigate potential impacts of floods. Generating the flood risk maps with the participation of diverse stakeholders at each level of administration is essential to develop effective FRM strategies. Hence, the objectives of this study are twofold: i) to produce district-based vulnerability, hazard, and flood risk maps for Istanbul with a hybrid fuzzy AHP-TOPSIS model, ii) to generate these maps by considering the perceptions of different stakeholders separately, which is an initial attempt in the literature, ensuring the comparative analysis of stakeholder perceptions in FRM. Local and metropolitan municipalities, disaster management and coordination centres, water and sewerage administrations, and universities were considered as the leading stakeholders since they are chiefly responsible decision-making bodies in FRM practices in Istanbul. Pearson's correlation coefficient and Spearman's rank correlation coefficient tests were used to obtain a more accurate understanding of the agreement levels between stakeholders. The results revealed the need for the involvement of various stakeholders to generate flood risk maps since significantly different perspectives were observed; and the need for changing the generated flood risk maps. The findings of this study are critical because generated maps show distinct differences according to the mentality of the organizations and experts, which inevitably change the most flood-prone areas and possible mitigation investments.