Research project

CHANCE - Understanding compound flooding in the past, present and future for North Atlantic coastlines

Project overview

Floods are the most dangerous and costly of all natural hazards. From 1980 to 2013, floods accounted for more than $1 trillion in losses and resulted in at least 220,000 fatalities globally. More than 50% of these deaths, and a large proportion of the losses, occurred in densely populated low-lying coastal regions, especially those at the coastal-river interface. Continuing to advance our understanding of flooding is therefore of utmost importance.

In coastal regions, floods are often caused by multiple factors. Floods can arise through the joint occurrence of factors such as (1) storm surges plus astronomical tides (storm-tides) and/or (2) local or remotely (swell) generated waves; but also from heavy precipitation, either through (3) increased river discharge (fluvial) and/or (4) direct runoff (pluvial). Most flood risk assessments to date have considered these four main drivers of flooding separately. However, the adverse consequences of a flood in coastal regions can be greatly exacerbated when the oceanographic (storm-tides and waves), fluvial, and/or pluvial sources of flooding occur concurrently or in close succession, a condition known as 'compound flooding', which can result in disproportionately extreme events. Despite their high impact potential, compound events remain poorly understood, in large part because of the lack of information on the inter-dependence of the driving factors, which varies considerably from place to place, and the perceived difficulty of the joint probability analysis methods required to analyse these interdepencies. This is why the World Climate Research Program Grand Challenge on Extremes has identified climatic compound events as an international research priority.

A recent example of a compound event is that associated with Hurricane Harvey in 2017. Record breaking rainfall, river discharge and runoff, combined with a moderate but long-lasting storm surge, resulted in disastrous flooding in Houston. It was the second costliest natural disaster in US history. Moreover, it is recognised that, by not considering compound flooding, the risk to Houston and elsewhere had been, and still is, greatly underestimated.

In CHANCE we will deliver a new integrated approach, incorporating all the spatial and temporal dependencies between the four main source drivers of flooding in coastal regions. This will allow us to make a step change in our understanding and prediction of the source mechanisms driving compound flood events in coastal areas around the North Atlantic basin. We will address the following key questions:

1. Where do (and where don't) compound events occur and which combinations of source-variables are most important in different regions?

2. Which weather types favour the occurrence of compound events and will the frequency of compound events increase/decrease in the future as weather patterns change?

3. What is the likelihood and spatial extent of compound events in different regions?

4. How do compounding effects from multiple flood sources exacerbate impacts to coastal communities?

We will do this through a series of methodological innovations (e.g., novel dependence analyses and state-of-the art weather typing approaches, along with inventive multivariate extreme value analysis techniques and advanced ensemble hydrodynamic modelling) that not only have relevance to the serious issue of compound flooding, but which will also be transferable to other cascading hazards in the earth and environmental sciences, such as: heat waves, drought and bush fires; extreme rainfall, landslides and cliff falls; earthquake and tsunami; and river discharge and turbidity currents. Our new methods will enable us to fully assess and predict all the source variables associated with compound flood events and their spatial extents in coastal regions (past, present and future) and will result in a major advance in the way compound flooding is understood, quantified and managed.

Staff

Lead researchers

Professor Ivan Haigh

Professor

Research interests

  • I currently have 8 active research grants (4 as principle investigator (PI)) worth £4.8M. 
  • I am the PI on two international grants that started in 2019, both looking at compound flooding. Compound flooding (when the combination, or successive occurrence of, two or more hazard events leads to an extreme impact e.g., coastal and fluvial flooding), can greatly exacerbate the adverse consequences associated with flooding in coastal regions and yet it remains under-appreciated and poorly understood. In the £788k NERC- and NSF- (US National Science Foundation) funded CHANCE project, I am leading a team (working alongside researchers from the University of Central Florida), to deliver a new integrated approach to make a step-change in our understanding, and prediction of, the source mechanisms driving compound flood events in coastal areas around the North Atlantic basin. In the £575k NERC- and NAFOSTED- (Vietnam’s National Foundation for Science and Technology Development) funded project, I am leading a team that is working with colleagues in Vietnam to map and characterise present, and predict future, flood risk from coastal, fluvial, and surface sources and, uniquely, to assess the risk of compound flooding across the Mekong delta; one of the three most vulnerable deltas in the world. I am also the PI on a grant, which started in 2021. In this 41k project, funded by the Dutch Ministry of Infrastructure and Water Management (Rijkswaterstaat), we are assessing past and future closures of the six storm surge barriers in the Netherlands.
  • In 2021, I was awarded a 3-year (50% of my time) prestigious Knowledge Exchange Fellowship funded by NERC (UK’s Natural Environmental Research Council) and worth £154k. This fellowship builds strongly on my prior research and the overall goal is to provide guidance and tools that will help storm surge barrier operators better prepare for the impacts of climate change across every area of their operation now and into the future. Within the fellowship I am working primary with the UK Environment Agency (EA) and the Dutch Ministry of Infrastructure and Water Management (Rijkswaterstaat). However, to ensure the work undertaken can benefit all the existing (and planned) surge barriers around the world, I am also working closely with I-STORM. I-STORM is an international knowledge sharing network for professionals relating to the management, operation and maintenance of storm surge barriers, and has representation from all the surge barriers worldwide.
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Other researchers

Professor Steve Darby

Associate Dean Research

Research interests

  • River and coastal flooding - relationships between geomorphology and flooding in rivers and deltas
  • Biogeomorphology - interactions between river processes and life
  • River bank erosion processes
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Dr Gustavo De Almeida

Associate Professor
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Collaborating research institutes, centres and groups

Research outputs

Alistair Hendry, Ivan Haigh, Robert Nicholls, Hugo Winter, Robert Neal, Thomas Wahl, Amelie Joly-Laugel & Stephen Darby, 2019, Hydrology and Earth System Sciences, 23, 3117-3139
Type: article