Practical sea-level and wave climate information for small-island states

Small-island states (SIS) are at risk of coastal erosion and flooding from extreme water levels and waves. The effects of climate change are causing sea level rise and an increased incidence of extreme water levels from storm surge and waves from hurricanes. The cost of inaction in on climate change in the Caribbean is projected to amount to over 22 billion USD annually by 2050 (10% of the current size of the Caribbean economy) [1]. SIS therefore have a need for information on climate change impacts, but a lack of local observational data. Government departments in small countries often do not have the technical and scientific resources required to research these impacts, or design appropriate adaptation strategies.

We will present example wave and sea-level advice, generated for Saint Vincent and the Grenadines. Through collaboration with local planners and other coastal stakeholders we have identified particular areas at risk from changing water level and wave conditions. By using results from the numerical wave model WaveWatch III with global and regional coverage, we can provide local information on changing risk from rising mean sea-levels and episodic storm events. We then use the SWAN wave model for dynamic downscaling to capture nearshore wave processes and wave setup. These methods draw-out bespoke, island-scale information and projections of risk from waves and rising-sea level, on which to base practical decision making and planning. Our wave model is able to accurately capture wave conditions in the Caribbean Sea observed during past hurricane events, and synthetic storms to investigate worst-case scenarios.

Lessons learnt from this work apply to other SIS, either in the path of direct tropical cyclone impact, or those threatened by swell waves from remote storms. The challenge of generalising these results to other small island and archipelago settings is two-fold, as it depends on the geographic character of the island, and exposure to storms and their character.

[1] Global Development Institute (2008)