7TH INTERNATIONAL CONGRESS ON TECHNOLOGY - ENGINEERING & SCIENCE - Kuala Lumpur - Malaysia (2019-08-08)

A Study on the Hydraulic Phenomenon around Artificial Reefs
An artificial reef is one of the beach erosion countermeasures, and it has a protection function where beach stabilization at the rear side of the shore is induced by dissipating waves at the foreshore. In addition, an artificial reef does not damage landscape as it is installed under the sea surface. The regional income can be expected by providing the habitats of sea creatures such as fish and seaweed. Although the artificial reef has various advantages as mentioned above, it has different effects on the surrounding environment depending on the setup condition. In the case of a low crest artificial reef, the wave attenuation rate is low. So the beach protection function is less efficient. For an artificial reef with a high crest level that is close to the sea surface, a strong return flow occurs depending on the setup condition of the opening width, and this induced fast current velocity causes local scour and the settlement of neighboring sea bed, which results in the malfunction of the artificial reef. The determination of the offshore distance leads to morphological changes by inducing current and sediment transport at the rear side of the artificial reef. Many researchers have conducted experimental research on the aforementioned various phenomena depending on the setup condition, but a clear guideline for the phenomena has not yet been established. In particular, for the current change in the opening based on case studies, there is a difficulty in deriving an accurate conclusion. In this study through the physical model test with an artificial reef consisting of porosity block (Tetrapod), the changes in the wave, current velocity, and current pattern around the artificial reef due to the changes in the opening width, offshore distance, and installation depth were investigated along with the resultant topographical changes. In particular, the wave transmission rate was compared with result of the previous artificial reef research using rubble stone. In addition, the wave data measured at the offshore and rear side of the artificial reef was analyzed based on the case in which an artificial reef had been installed in the field and beach stabilization had been achieved, and the optimum layout for beach stabilization was reviewed through comparison with the field investigation result.
Dr. Kyu-Tae Shim