Exploration and estimation: connecting hydrodynamic responses and hazard potential to coral reef characteristics

Coastal areas are one of the most vulnerable regions being subjected to multiple hazards while sheltering people, diverse ecosystems, key infrastructure and other assets. Climate change will produce expected changes to the drivers affecting these hazardous events which when coupled with the uncertainty of the degree of the adverse impacts, place vulnerable coastal communities in intractable circumstances. In regions with limited access to human and financial resources, like in Caribbean Small Island Developing States (SIDS), there must be a focus on practical solutions and tools that can support optimal decision-making in coastal areas. The adoption of nature-based approaches is but one solution to mitigating these potentially deleterious effects, reducing vulnerability and enhancing coastal resilience. Through physical modelling, this study explores how the changes to selected characteristics of synthesized offshore coral reefs affect the hydrodynamics in the nearshore zone and seeks to formulate quantitative relationships for practical applications. These quantitative relationships can serve to support the assessment of present-day levels of protection offered by coral reefs and provide an insight into how future changes of these coastal ecosystems and offshore conditions, whether caused by man or natural influences, can affect the nearshore hydrodynamics. Assessment of the potential future levels of protection under different scenarios allow for a holistic optimization of proposed coastal solutions. The outputs of this study demonstrated a good correlation between the wave height after the reef and the above reef velocities with the incident wave conditions, the reef width and the water depths on the reef. The experimental results also support the trends observed from other studies in terms of wave attenuation, albeit to a smaller extent. The relationships between assessed experimental parameters generally corroborated with anticipated patterns although the wave reflection in the flume appeared to skew some output. The expressions produced from this study, though limited given the experimental scope, demonstrate a methodology which can be readily augmented to improve the assessment of existing and future levels of protection offered by coral reefs in order to implement hazard mitigation strategies that not only reduce the risk to assets in coastal areas, but incorporate natural systems in a meaningful way to support valuable co-benefits to these coastal communities.