Due to their low-lying nature, coral atoll islands are widely acknowledged to be amongst the most vulnerable environments to climate change. Most of them are predicted to be uninhabitable by the mid-21st century because of sea-level rise. However, these forecasts are based on relatively simple hydrodynamic models that consider the islands immobile, whereas, when overwashed during storms, the islands can vertically accrete due to sediment deposition. Repeated overwash can enable atoll islands to keep up with rising sea level. This potentially provides opportunities for island communities to prolong habitability through innovative adaptation strategies, instead of having to construct expensive coastal defences or traumatically relocate to regions with no flood risk. It is generally accepted that overwash is key to atoll island survival, but further research is required to increase our quantitative understanding of overwash processes and transform the enhanced insights into practice by developing management tools. The overarching aim of this project is therefore to 'revolutionise our capability to model the physical impacts of sea-level rise on atoll islands to aid in the formulation, development and implementation of transformative climate-change adaptation strategies for atoll island communities'. We will conduct ground-breaking laboratory experiments in the Delta Flume and unprecedented field measurements in the Maldives and Pacific where we will measure overwash processes and their impacts. We will use these unique data sets to develop, calibrate and validate hydro- and morphodynamic numerical models. An innovative modelling framework will then be used to evaluate the role of the various processes involved in atoll island response to sea-level rise. Finally, the modelling tools will be deployed to enable atoll island communities to implement adaptation strategies that maximise opportunities for continued habitation.

Resilience building requires integrated approaches to disaster risk management (DRM) to identify overlaps and leverage political support for measures that improve early warning systems, encourage adaptations and improve recovery from a range of hazardous events within the context of sustainable development. As our climate changes, accelerating such integration is paramount to improve responses to intensifying and multiple shocks and risks. The need is even more acute for Small Island Developing States, where isolation, limited land availability, a complex range of environmental hazards and limited resource base further intensify their exposure to risk. In this proposal we suggest that 'all hazards' approaches to building resilience are needed and test the thesis that these will be more effective if placed within the particular historical and cultural contexts through which land use patterns were established in individual SIDS, in order to assess how risk is created and disaster risk management responses evolve. We test this on two islands in the Pacific and the Caribbean by focussing particularly on exposure and physical vulnerability to multiple hazards, and analysing historical factors that have shaped tenure and governance processes in order to explore how these may have contributed to increased exposure of populations and physical vulnerability to hazards as well as detrimental political and cultural responses. We are particularly interested in the interactions between differing hazards and the implicit competing pressures on resources and tenure, both on- and offshore. We are taking an 'all-hazards' approach to this analysis, to identify strategies and investments that can relieve these pressures and encourage long-term resilience to multiple land and marine-based hazards. We refer to these measures as DRM investments with 'co-benefits', meaning that one action, originally intended for a particular type of hazard, can be adapted and used to produce joint, multiple and/or simultaneous benefits in terms of reducing risk. We will identify measures that have the potential to reduce risk to multiple hazards through the development of future scenarios and an approach to modelling impacts that tests the benefits (in terms of loss avoidance) of different DRM investments. The two islands selected to trial this holistic approach are exposed to a range of environmental hazards, and have colonial and imperial histories and sets of institutions to address risk with some similarities but also differences. Drawing insights across these settings will allow us to better understand the potential for applying this approach to other SIDS around the world, including in the Indian Ocean. This research will also have implications for implementation of the Sendai Framework for Disaster Risk Reduction 2015-2030 (SFDRR), linking it more closely with resilience targets in the Sustainable Development Goals and the Paris Climate Change Agreement by enhancing knowledge of the links between past and future hazard exposure and development, and identifying options for overcoming resource constraints in SIDS and building resilience to multiple shocks and stresses.