An Integrated Approach to Coastal Hazard Protection

An integrated approach that combines coastal hazard protection and coral reef resilience is vital for adaptive coastal communities in the face of changing climate
Published in Sustainability
An Integrated Approach to Coastal Hazard Protection
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Evaluating the feasibility and advantage of a multi-purpose submerged breakwater for harbor protection and benthic habitat enhancement at Kahului Commercial Harbor, Hawai‘i: case study - SN Applied Sciences

Construction of breakwaters provides an engineering solution for coastal protection. However, little effort has been made toward understanding the ecological impact on local coral reef ecosystems and developing engineering structures that would enhance the coral reef environment. A submerged breakwater proposed for Kahului Commercial Harbor, Hawai‘i, provided an opportunity to design a multi-purpose ‘reef structure’ to mitigate wave impacts while providing new coral reef habitat. This design involved ecological and environmental considerations alongside engineering principles, serving as a model for environmentally sound harbor development. This field study evaluated environmental conditions and reef community composition at the proposed site in a gradient extending outward from the harbor, using in situ data with multivariate analyses. Benthic and topographic features in the area were assessed using a towed drop camera system to relate to biological factors. Results that support breakwater topography should follow the natural spur and groove and depth of the adjacent reef and orient with wave direction. A deep area characterized by unconsolidated substrata and low coral cover would be replaced with the shallow, sloping hard bottom of the breakwater, and provide an exemplary area for corals to flourish while protecting the harbor from large ocean swells. Surfaces on shallow sloping hard bottoms receive higher levels of irradiance that benefits coral growth. Optimal levels of water motion facilitate sediment removal and promote coral recruitment and growth. The design of the Kahului Harbor submerged multi-purpose structure serves as a model for design of shoreline modification that enhances, rather than degrades, the local coral reef environment.

The construction of coastal defence structures to keep people’s feet dry can have severe consequences on the coastal ecosystem if the project is not well designed. The construction of breakwaters for coastal protection requires a better understanding of the ecological impact on local coral reefs. 

 In an interesting study published in SN Applied Sciences, Stender et al. indicated that though breakwaters are suitable for coastal protection, very little effort has been made to understand the ecological impact of their constructions on the local coral reefs in Hawai’i. The authors revealed that the design of the commercial harbour in Hawai’i, which takes into consideration ecological and environmental factors as well as engineering principles, could serve as a model for environmentally friendly harbour development.

 The researchers employed different methodologies to evaluate environmental conditions and reef community composition at the proposed site. The features of the lower ecological zone were assessed using a towed drop camera system to relate to biological factors. In addition, detailed visual surveys were carried out at the existing breakwater, the proposed site, the unaltered surrounding habitat, and within and outside the shipping channel. Finally, water quality at the different sites was measured to derive information about prevailing environmental conditions.

 The authors show that the breakwater topography should follow the natural spur and groove and depth of the adjacent reef and orient with wave direction. Their results also indicate that a deep area characterized by unconsolidated sublayers and low coral cover would be replaced with the shallow, sloping hard bottom of the breakwater, and provide an ideal environment for coral to flourish while at the same time protecting the harbour from large ocean waves. They also found that surfaces on shallow sloping hard bottoms receive higher levels of sunlight that benefits coral growths and that optimal movement of water facilitates sediment removal and enhances coral recruitment and growth.

 It is clear from this study that an integrated approach that combines coastal hazard protection and coral reef resilience is vital for adaptive coastal communities in the face of changing climate and its associated impact. By combining ecological, environmental, and engineering aspects of coastal defence structure this interdisciplinary project can be used by policymakers as guidelines for harbour development and shoreline modification throughout the tropics. 

 Stender, Y., Foley, M., Rodgers, K. et al. Evaluating the feasibility and advantage of a multi-purpose submerged breakwater for harbor protection and benthic habitat enhancement at Kahului Commercial Harbor, Hawai‘i: case study. SN Appl. Sci. 3, 167 (2021). https://doi.org/10.1007/s42452-020-04072-4

 

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Applied Life Sciences (General)

The Applied Life Sciences section of SN Applied Sciences aims to publish relevant articles that focus on modern applications of life sciences research in Biological Sciences, Chemistry, Health Sciences, Physics, Engineering and Environmental Sciences. We are particularly interested in applied research that makes significant scientific and societal contributions across the broad spectrum of life sciences.

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The Earth and Environmental Sciences section of SN Applied Sciences aims to publish relevant articles and case studies within Earth and Environmental System Sciences. We welcome disciplinary papers from the fields of Physical Geography, Geology, Climate, Oceanography and Natural Hazards, as well as those with strong interdisciplinary connections from the fields of Geophysics, Environmental Chemistry, Geochemistry and Environmental Engineering. We welcome contributions which demonstrate linkages between natural and anthropogenic processes, human-environmental interactions and environmental processes.

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