Understanding Compound Flooding in the Past, Present and Future for North Atlantic Coastlines (CHANCE)
US Principal Investigator:
Thomas Wahl (PI), University of Central Florida Project Period: July 2019 – June 2022
Total Project Funding: $1,000,000 |
UK Collaborators:
Ivan Haigh (PI), University of Southampton Gustavo Adolfo De Almeida (Co-PI), University of Southampton Stephen Darby (Co-PI), University of Southampton Robert James Nicholls (Co-PI), University of East Anglia |
Project Description.
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. This project addresses the topic of compound flooding, where multiple flood drivers occur concurrently or in close succession. Compound flooding is especially impactful along coastlines, where storm surges, waves, river flooding, and direct runoff can combine to exacerbate potential flooding situations. The research team, including personnel from the UK and US, plan to conduct a variety of analyses, including dependence analyses, state-of-the-art weather typing approaches, multivariate extreme value analysis, and advanced ensemble hydrodynamic modelling to determine where and why compound flood events occur. The specific goals of the project are to: 1) Determine relevant variables that can lead to compound events along coastlines on both sides of the North Atlantic and assess the spatial footprints of the individual drivers; 2) Assess which large-scale weather types and other conditions led to the identified compound events in the past and determine if and how the frequency of compound events has changed in the past and may change in the future; 3) Quantify the likelihood of the occurrence of compound events along different stretches of coastline including relevant variables and spatial footprints; and 4) Integrate the results to quantify the extent to which compounding effects from multiple flood sources exacerbate impacts to coastal communities. |
Funding Agency: This project is jointly funded by the National Science Foundation's Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK).
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All Rights Reserved.
Website developed and maintained by Javed Ali.