Research project

Comp-Flood: Compound flooding in coastal Viet Nam

Project overview

Floods are among the most dangerous and costly natural hazards. Since 1980, floods have accounted for more than 200,000 fatalities globally and resulted in at least $1 trillion in economic losses. More than 50% of these deaths and a large proportion of the losses have occurred in densely populated low-lying deltas. Water related disasters are a major concern in deltas because they are located between the sea and major rivers, and hence are subject to flooding from the coastal zone and from rivers. Furthermore, deltas occupy large low-lying areas that are densely populated.

In deltas, flooding arises from three main sources: (i) storm tides (storm surges plus tides); but also, from heavy precipitation, either through (ii) increased river discharge (fluvial) and/or (iii) direct surface runoff (pluvial). To date the majority of flood risk assessments in deltas (and other environments) have considered these main causes of flooding separately, because of the lack of information on their inter-dependence, and because of the perceived difficulty in handling the necessary underpinning statistics (known as joint probability analysis methods). However, the adverse consequences of a flood in a delta can be greatly increased when the coastal, fluvial and surface flood sources occur concurrently, or in close succession, resulting in a disproportionately extreme event referred to as 'compound flooding'. Despite their high impact potential, compound events remain poorly understood. This is why the World Climate Research Program has identified compound flood events as an international research priority.

This project will bring together UK and Vietnamese expertise 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. Exposed to heavy monsoon rains that can cause both fluvial and pluvial flooding, and tropical cyclones that cause coastal flooding, the Mekong is one of the three most vulnerable deltas in the world. Our hypothesis is that previous flood assessments have underestimated the source drivers and hence the likelihood of flooding and associated risk, as compound events have not previously been considered.

We propose a new integrated approach, to make a step change in our understanding and prediction of the source mechanisms driving compound flood events in delta regions. We will assess the large-scale drivers of variability in storms and monsoon rainfall that impact Viet Nam and develop novel (for both the past/present and future) meteorological datasets needed to drive the coupled flood models of the Mekong delta and its catchment. This involves use of next-generation climate models, which can simulate both intense monsoon events and tropical cyclones, providing datasets that are sufficiently large for our statistical analysis of flood risk.

We will calculate the past/present and future likelihood of coastal and fluvial flooding across the delta, quantifying the occurrence of compound flooding events. For key hot spot areas, we will estimate areas of land inundated, numbers of people affected and how infrastructure and agriculture might be impacted, now and in the future. In particular we will examine low probability, high impact, events and quantify how compounding flood effects from multiple flood sources exacerbate impacts to coastal communities. Working in close partnership with our national, regional and provincial governmental project partners, we will consider management and planning options and provide guidance that will increase preparedness and resilience to future flood events.

Our new methods will enable us, for the first time, to fully assess and predict all the source variables associated with compound events in the Mekong delta (at present and in the future) and will result in a major advance in the way compound flooding is understood, quantified and managed.


Lead researcher

Professor Ivan Haigh


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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Professor Robert Marsh

Professor of Oceanography and Climate
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Collaborating research institutes, centres and groups

Research outputs

Nadia Bloemendaal, Hans De Moel, Sanne Muis, Ivan D. Haigh & Jeroen C. J. H. Aerts, 2020, Scientific Data, 7(1)
Type: article
Nadia Bloemendaal, Ivan Haigh, Hans de Moel, Sanne Muis, Reindert J. Haarsma & Jeroen C. J. H. Aerts, 2020, Scientific Data, 7(1)
Type: article