Amid its diverse landscapes and cultures, Southeast Asian countries share a pressing environmental challenge - floods. Research by the ASEAN Risk Monitor and Disaster Management Review in 2020 showed that flooding is the most common disaster event in the region, with 13 percent of the ASEAN population exposed and USD 926 billion in capital stock at risk of damage. Vietnam (26 million), Indonesia (20 million) and Thailand (13 million) rank highest based on the number of lives at stake, while Singapore, which has the lowest multi-hazard exposure, remains in a vulnerable position with 93 percent of its population exposed to flooding.

As climate change threatens to increase the frequency and intensity of these disastrous events through higher rainfall and sea levels, all Southeast Asian nations must be equipped with the tools and insights to mitigate and manage this looming crisis. Fiona Williamson, Associate Professor of Environmental History, explains, “Even developed countries with good flood mitigation, like Singapore, will need to step up in the face of these combined hazards. It may not be enough to build higher walls but to re-design cities to allow them to live with water.”

The need for anticipatory action

While sea walls, land reclamation and barrages are some flood mitigation measures commonly implemented within the region, engineering alone cannot eliminate the impact and risks caused by larger floods. Here, flood monitoring can play a critical role in reducing the mortality rates and economic burden caused by such catastrophic events.

Assoc Prof Williamson explains, “Flood monitoring does not necessarily prevent a flood, but it helps cities anticipate a flood emergency and speeds up response times for evacuation and emergency services. It also allows response services to pinpoint the worst hit areas.”

Forecasting future floods

With the help of predictive models, Flood Frequency Analysis (FFA) is used to predict (through probability) the magnitude, location and extent of future flooding events. Past data is central to the process, with information taken from scientific instruments such as stream gauges which monitor peak water flow over extended periods.

However, the limited availability and size of such data meant that most FFA efforts fall short of their possibilities. Assoc Prof Fiona says, “In some places, there is stream gauge data extant, for perhaps 30-90 years. However, developing countries often have a dearth of this information – either not going back long enough to really inform a predictive model or only for some areas and not others.”
Therefore, she argues that more emphasis should be given to using and adapting other forms of historical source material in FFA. In her paper, Assoc Prof Williamson and her co-authors highlight the role palaeo-historical information can play in improving flood estimates, reducing uncertainty and allowing for better flood risk estimates.

What can palaeo-historical information reveal?

Palaeohydrological information refers to physical evidence left in the landscape by floods, an example being sedimentary archives in lakes and resources. Natural proxies like tree rings and ice cores can also be used to provide clues about the frequency and magnitude of flooding in ancient times.

Meanwhile, historical documents such as newspapers, correspondence, photographs, oral histories and ancient texts offer unique contextual insights into the socio-economic conditions of specific ancient civilisations during periods of flooding. When combined, this palaeo-historical information can provide a holistic view of the drivers and contributing factors that cause and worsen the effects of flooding in the area. 

Assoc Prof Fiona explains, “Historical information plays an important role, not just in improving long-term predictive models, but also by looking at the factors that traditionally make communities more vulnerable”. By assessing past floods’ physical and socio-economic contexts and impacts, countries can generate better insights for guiding and improving their flood hazard management practices.

Under-utilised data with life-saving potential

While palaeo-historical data has been used in FFA in countries like Europe and the United States, these approaches are rarely utilised in Southeast Asia, a deficiency that Assoc Prof Williamson and her co-authors believe needs to be addressed. As such, they argue for the collection and incorporation of more palaeo-historical information together with modern gauged data to improve FFA in the region.

These additions would allow for more robust flood predictions, enabling policymakers to make well-informed decisions when designing flood risk reduction policies and actions. Overall, this leads to increased resilience to changing flood risks due to uncontrolled urbanisation, unpredictable tropical storms and the influence of climate change.

Taking a holistic approach to flood resilience

Given the high costs to build and maintain flood defence infrastructures, many Southeast Asian countries face significant barriers in reaching the level of flood resilience needed. However, Assoc Prof Williamson reminds governments that effective flood mitigation involves more than FFA, flood defence infrastructures and Disaster Risk Reduction (DDR) strategies.

“We need a joined-up approach that does not just take into account predictive or engineered solutions, but wider socio-economic ones,” she shares. “To truly create a flood-proof society, communities must improve housing, move people out of flood-prone areas, re-design cities, promote community awareness and responsiveness, and move people out of poverty.” 

She points out: “Historical information can help to improve long-term predictive models by looking at the factors that traditionally make communities more vulnerable and by assessing the impacts of past floods and studying the contexts in which flood disasters are created.”

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“While the instigator of a disaster might be natural, the scale of the disaster is relative to levels of preparedness, vulnerability and resilience in the society that the disaster affects. This might include technological and infrastructural preparedness, policy, and social resilience,” she explains.

Building a collaborative and resilient Southeast Asia

Despite these gloomy prospects, there are signs of hope for Southeast Asia, with collaborative efforts being made to enhance the region’s preparedness and response to disasters such as floods. One such initiative is the ASEAN Framework on Anticipatory Action in Disaster Management that ASEAN leaders adopted in November 2021. The framework provides a common understanding of anticipatory action and sets out several key targets for ASEAN Member States (AMS) to achieve over a four-year period  (2021 - 2025). One of the initiative’s key objectives is to promote cooperation and coordination among AMS to amplify their individual efforts.

Assoc Prof Williamson says, "(As each Southeast Asian country takes a step towards building their flood resilience,) I hope to see better joined-up solutions that address socio-economic circumstances alongside engineered solutions to enable communities to become disaster resilient. Learning from the past is a huge part of how we manage our present.”