Inundation risk assessment based on G-DEMATEL-AHP and its application to Zhengzhou flooding disaster

This study proposed an integrated approach to investigate the flooding risk in urban areas of mega-cities. The new method integrated the grey decision-making trial and evaluation laboratory (Grey-DEMATEL) into analytical hierarchical process (AHP) (simplified as G-DEMATEL-AHP). The risk distribution was mapped using geographic information system (GIS). A nine-score questionnaire was adopted in Grey-DEMATEL to analyse the inundation risk. Zhengzhou was selected as a case study with different rainfall scenarios, including flooding disaster induced by heavy storm on July 20, 2021 (i.e., “7.20 Storm”) and average rainfall of five years (i.e., “5-Yr Average”). The results showed that the proposed method can assess the flood risk distribution effectively in Zhengzhou. Comparison between the results from different scenarios showed that the impact of the “7.20 Storm” was much stronger than that of the “5-Yr Average” scenario. Moreover, an existing method, fuzzy AHP (FAHP), was also used to assess the same scenario. The results indicated that the G-DEMATEL-AHP method could more effectively identify the most critical risk areas when compared to the FAHP.