HYDRAULIC CHARACTERISTICS OF BIMODAL ARTIFICIAL REEF AT KINEICHO ON NIIGATA COAST

Abstract

 Hydraulic characteristics of a bimodal artificial reef were evaluated by using field observation data. The wave transmission coefficient was less than 0.5 for offshore wave height greater than 4m. The wave setup was less than conventional artificial reefs. It was confirmed that the bimodal artificial reef have the necessary protection performance. Current patterns behind the artificial reef varies with the incident wave height. Undertow velocity is generated by surface rollers of breaking waves when incident waves are high. Also, it was presumed that suspended sediments increase with wave height from backscatter intensities of ADCP. The scouring that occurred during artificial reef construction is thought to have been caused by suspended sediment transport due to undertow through an unbuilt section during high wave periods.