Towards better informed decisions on flood defence programs

Sea level rise due to climate change and melting ice sheets on the north and south poles is one of tomorrow’s biggest challenges. With latest projections pointing up to 3.2 °C of surface warming by 2100, hundreds of millions of people living in coastal areas face an uncertain future. Some countries, like Japan, have reached a turning point where the threat of climate change-induced flooding is already very much a reality. As a response, the island has invested over 100 billion euros in dikes reinforcements over the past 5 years, and they are not the only ones massively investing in flood defence programs. At the same time, government budgets for infrastructure management are under pressure. Recognising the great societal significance of a thorough understanding of the costs vs. benefits of flood defence systems, Dr. Jeremy Bricker is leading a research project called the INtegrated Flood Risk Assessment (INFRA). In a Joint Research Initiative with AXA, he aims to develop a tool to evaluate the costs vs. benefits of proposed coastal flood defences. The ultimate objective is to enable governments, as well as private entities, to take better and more informed decisions about flood defence programs, and potentially save costs. 

There already exist costs vs. benefits analysis tools for storm surge defense measures, but current methods fail to encompass one important aspect: the assessment of loss due to failure of flood defenses. The INFRA project’s main innovation is to add this capability to the methodology of existing models that have demonstrated success in the past. «INFRA is the first project to incorporate the fragility of flood defenses themselves into a risk assessment tool, allowing potential failure of flood defenses to be taken into account in evaluating the fragility and risk of protected areas, and in the cost/benefit analyses of the defenses themselves», Dr. Jeremy Bricker explains. Another way INFRA generates added value for society and for science «is by taking into account more than just maximum water depth when evaluating the fragility of buildings and non-building structures», Dr Bricker further details. «It will clarify the relative contribution to damage of hydrodynamic and wave parameters including flow speed, inundation duration, wave height, wave breaker type, etc. Such fragility relations are essential to the accurate evaluation of vulnerability and thus risk ». 

Simulating reality as accurately as possible with the help of AXA

To reach both these objectives, fragility functions – a measure of the probability of damage to facility components given the force, deformation, to which each is subjected –, will be developed based on storm surge model output from historical storms. That’s where the AXA teams come in. The historical events chosen for this are the Xynthia storm in France and Typhoon Hato in Hong Kong, for which AXA has collected large amounts of water and hazard data. « Using this data will enable us to make sure our numerical model simulates reality accurately, both in terms of the physics of how the storm surge moves onto shore, as well as regarding the movement of the water over the land itself ». Collaboration with AXA will also complement the flood and risk modeling capabilities of the research team’s institutions, TU Delft’s and IHE-Delft’s. For instance, «the meteorological modeling conducted by AXA will allow more realistic wind and pressure fields to be generated». To give the project the best possible odds, Dr. Jeremy Bricker is also working with two renowned co-investigators, Prof. S.N. (Bas) Jonkman and Prof. Roshanka Ranasinghe, who act as consultants for the project on risk analysis and the effects of climate change, respectively. 

Now more than ever, climate change calls for stakeholders not only to act fast, but also to do it right. By putting various expert heads together, the present project will provide precious 'state-of-the-art' insight into the actual benefits to be expected from flood defence programs. «AXA’s contact with real-world end users will give the research societal relevance and help steer efforts toward the development of a generically applicable and practical tool», Dr. Bricker puts forward, adding that cost vs. benefit is but one application of this collaborative research project. « We are also looking into the development of a probabilistic framework that will help determine the damages a given hypothetical storm would cause ». Another precious tool in the face of global warming.