Abstract
Coastal resilience has received significant attention for managing beach erosion issues. We introduced flexible artificial coral reef (ACR) structures to diminish coastal erosion, but planar installation effects should be considered to evaluate the feasibility of coastline maintenance. In this study, we conducted a three-dimensional large-scale experiment to investigate the characteristics of planar installation of ACR, focusing on the wave mitigation performance, wave profile deformation with delay, nearshore current movement, deposition and erosion trends, and beach profile variation. We found that the ACR diminished the wave height by ~50% and the current intensity by ~60% compared with that of a conventional submerged breakwater made of dolos units. Using the dispersion velocity of the dye in a tracer experiment, the dispersion time of the ACR was approximately 1.67-times longer than that of the dolos and the current velocity was reduced, revealing that ACR significantly reduced structural erosion. With dolos, severe erosion of >10 cm occurred behind the structure, whereas there was only slight erosion with the ACR. Moreover, in a vertical beach-profile analysis, the ACR exhibited greater shoreline accretion than that of dolos. These results indicate the potential of ACR in improving coastal resilience.
Highlights
To enhance coastal resilience with ecological components, we focused on the natural coral reef, which is known for its functions in maintaining a stable coastline
A mild water level variation occurred in the artificial coral reef (ACR). These results demonstrate that the advantageous structural properties of ACRs, such as a variable crown depth and large porosity, induce mild wave deformation, which plays a positive role in shoreline protection
With regard to the shoreline change (∆L) on the breakwater open inlet (BO) line, the shoreline retreated 12 cm in the dolos case; the shoreline was stable in the ACR case (Figure 13g,h)
Summary
The main reported reasons for coastal erosion are rising sea levels, abnormal climates due to global warming [3,4], side effects of manmade coastal structures [5,6], and land subsidence [7], all of which threaten coastline stability. To address these erosion issues, numerous studies have been conducted with various analytical approaches, such as hydraulic experiments, numerical modeling, and field monitoring to evaluate coastal prevention methods. Cappietti et al [10] analyzed field wave data to evaluate prior empirical models of transmission and setup and considered their reliability based on root mean square (RMS) error values
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