Impacts of reservoir operation and urbanization on flood inundation in the Vu Gia Thu Bon Basin, Vietnam

This study examines the effects of upstream reservoir operation and urbanization on flood inundation in the Vu Gia Thu Bon river basin. The alternative reservoir operation strategies corresponding to the flood storage capacity (Vpl) of 10, 20, and 30% of the active storage capacity (Vhi) are evaluated and compared with the prevailing inter-reservoir operation procedure in terms of inundation effects. The results reveal that increasing the Vpl from 10% to 30% of the Vhi reduces the flooded area by 11.8% and lowers the water level at downstream stations from 6% to 30%. The government's procedure is considered safe to supply water, but the inundation duration is longer, resulting in more damage than the scenario of Vpl=20%Vhi. Regarding urbanization, the expansion of newly urbanized areas has resulted in increased flooding in their surrounding areas, with an increase in flood depth of more than 3 m. Moreover, the new roads have reduced the capacity of flood drainage and caused severe flooding. The water level difference between the two sides of the road can be as high as 2 m. This research will assist managers in developing and implementing appropriate downstream flood control measures.