Flood vulnerability assessment and mapping: A case of Ben Hai-Thach Han River basin in Vietnam

Abstract

This study evaluates the extent of flood vulnerability in the Ben Hai-Thach Han river basin, specifically Quang Tri province in the central area of Vietnam, where floods annually occur from September to November. A vulnerability assessment framework is used to calculate the flood vulnerability indexes (FVIs) under socio-economic, environmental, and physical aspects. We first analysed socio-economic data to examine the provincial socio-economic development from 2004 to 2019. We interviewed 573 residents and 111 officials during 2017 and 2018 in 111 communes of 9 districts to add detailed socio-economic and physical data, which were then classified, processed, and standardized based on 34 indicators for the FVIs calculations. All calculated indexes were then mapped for visual assessments. Results show that 29 communes are at high vulnerability levels (FVIs = 0.4–0.6). Notably, Gio Linh, Dong Ha, and Vinh Linh districts present the highest vulnerability, with five vulnerable communes. These communes present moderate probabilities of flood occurrence due to their low–lying terrain and agricultural production dominance. Our calculations also reveal that 81 communes (73.8% of the communes in Quang Tri province) were indexed with low vulnerability levels (FVIs = 0.2–0.4); of which Gio Linh has 17 out of 22 communes (77%), and Vinh Linh has 16 out of 21 communes (76%). Our findings suggest that the local government considers effective floodwater management strategies for the region, especially those with high vulnerability indexes and adaptation measures to mitigate flood damages.