Increasing flood risks in the Vietnamese Ca river basin: a challenge for reservoir-based flood management

As global warming is expected to intensify extreme rainfall over Vietnam, an increase in flooding is also anticipated. To study this issue for the Ca river basin, we conducted an assessment of future flood changes under various global warming levels by integrating extreme rainfall projections from climate models with
hydrological and hydraulic modeling. Results show large increases in flood flow over the basin, especially in the main Ca River and Hieu River. Flooding in the downstream area would be more severe, with for instance an increase in the number of inundated communes for a typical flood event from 119 currently to 125 at 3°C of global warming compared to preindustrial levels. The findings further suggest that the flood regulation capacity of major reservoirs, such as Ban Ve reservoir, would be exceeded.