The Mekong River Basin is a region with many rivers and human communities facing the evolving threat of tropical cyclones. Understanding how tropical cyclone hazards intersect with human exposure in a spatiotemporal context is crucial to climate change and population growth. Our study examines how flood risk changes over time and space by combining numerical modeling with historical observations and future projections of tropical cyclone tracks.

Changing risk patterns 

Our study shows that flood risk from tropical cyclones is not static. The results show that tropical cyclones have historically increased flood risk in 14% while decreasing flood risk in 7% of the basin. Looking ahead to future climate change scenarios, tropical cyclones may increase flood risk in about 7% and decrease flood risk in ~18% of the basin. As the population has grown, flood risk has increased in 3% of the basin. This is set to increase in 1% of the basin in the future. Regarding where the flood risk is, we're seeing a significant shift. It's moving away from the densely populated Mekong Delta and towards the eastern part of the Lower Mekong Basin. This shift is mainly due to the interaction of cyclone-induced extreme rainfall and changes in the spatial distribution of population exposure. This shows that tropical cyclone flooding in the Mekong Basin is a regional issue.

While natural hazards are the primary drivers of flood risk, human factors also play an important role. The spatial distribution of population exposure in our study highlights the important role of population migration in reshaping flood risk. As the population becomes more concentrated due to urbanization, population exposure may decrease in the regions where people move out. However, it will increase population exposure to natural hazards, especially in the Mekong Delta, which is prone to flooding from tropical cyclones.

Why it matters

The Mekong River Basin is home to millions of people who depend on the environment there to make a living, have access to food, and keep their traditions alive. However, our findings show that this stability is being threatened by complex and changing risk patterns. Traditional views of flood hazards that focus only on climate don't give the full picture. Instead, we need to look at the big picture and see how human factors fit in. It's important to understand that socioeconomic factors and climate activities are connected.

Shaping a Resilient Future

Our research suggests that improving resilience goes beyond preparing for more frequent or intense tropical cyclones and requires understanding how the interplay of natural hazards and socioeconomics will reshape the lives of Mekong Basin residents. Therefore, disaster response requires some rapid and flexible policy adjustments that consider these changing risk factors to reduce the impact of natural disasters.