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The Ca Mau Peninsula plays a critical role in the agricultural and aquacultural productivity of the Vietnam Mekong Delta (VMD), central to regional food security and the population's economic and social welfare. Unfortunately, this region has also historically been a hotspot for natural disasters, particularly from flooding, which is initiated by seasonal river flux upstream and heightened sea levels downstream, but also exacerbated by global climate change (e.g., increased rainfall and sea-level rise, tropical storm surges) and human activities (e.g. river bed lowering, land subsidence). The potential risks associated with rising inundation levels is important information for the future sustainability of the region and its ability to adapt to both current and forthcoming changes. The research around the influence of such drivers on future flood risk, in the Ca Mau Peninsula, is incomplete, primarily due to the absence of a quantitative coastal inundation map corresponding to future compounded scenarios. In this study, we therefore evaluate flooding dynamics in the Ca Mau peninsula using a fully calibrated 1D model, to represent a range of anthropogenic and climate change compound scenarios. Our findings indicate that factors such as increased high-flows upstream, alterations in the riverbed of the main Mekong channel, and occurrences of storm surges effecting the mainstream Mekong River, are unlikely to significantly affect inundation dynamics in this region. However, land subsidence, rising sea levels, and their combined effects emerge as the primary drivers behind the escalation of inundation events in the Ca Mau peninsula, both in terms of their extent and intensity, in the foreseeable future. These results serve as vital groundwork for strategic development and investment as well as for emergency decision-making and flood management planning, providing essential insights for shaping development policies and devising investment strategies related to infrastructure systems in an area which is rapidly developing. [ABSTRACT FROM AUTHOR]

Coastal floods, driven by extreme sea levels, are one of the most dangerous natural hazards. The people at highest risk are those living in low-lying coastal areas exposed to tropical-cyclone-forced storm surges. Here we apply a novel modelling framework to estimate past and/or present and future storm-surge-level and extreme-sea-level probabilities along the coastlines of southern China, Vietnam, Cambodia, Thailand, and Malaysia. A regional hydrodynamic model is configured to simulate 10 000 years of synthetic tropical cyclone activity, representative of a past/present (1980–2017) and high-emission-scenario future (2015–2050) period. Results show that extreme storm surges, and therefore total water levels, will increase substantially in the coming decades, driven by an increase in the frequency of intense tropical cyclones. Storm surges along the southern Chinese and northern and southern Vietnamese coastlines increase by up to 1 m, significantly larger than expected changes in mean sea-level rise over the same period. The length of coastline that is presently exposed to storm surge levels of 2.5 m or greater will more than double by 2050. Sections of Cambodian, Thai, and Malaysian coastlines are projected to experience storm surges (at higher return periods) in the future, not previously seen, due to a southward shift in tropical cyclone tracks. Given these findings, coastal flood management and adaptation in these areas should be reviewed for their resilience against future extreme sea levels. [ABSTRACT FROM AUTHOR]

It is vital to robustly estimate the risks posed by extreme sea levels, especially in tropical regions where cyclones can generate large storm surges and observations are too limited in time and space to deliver reliable analyses. To address this limitation for the South China Sea region, we force a hydrodynamic model with a new synthetic database representing 10,000 years of past/present and future tropical cyclone activity, to investigate climate change impacts on extreme sea levels forced by storm surges (± tides). We show that, as stronger and more numerous tropical cyclones likely pass through this region over the next 30 years, both the spatial extent and severity of storm surge hazard increases. While extreme storm surge events in this location become generally a more frequent occurrence in the future, larger storm surges around Vietnam and China coastlines are projected to regionally amplify this hazard. This threatens low-lying, densely-populated areas such as the Red and Mekong River deltas, while sections of the Cambodian and Thai coastline face previously unseen storm surge hazards. These future hazards strongly signal that coastal flood management and adaptation in these areas should be reviewed for their resilience against future extreme sea levels. [ABSTRACT FROM AUTHOR]