AUTHOR=Sun Hongan , Xu Jishang , Zhang Shaotong , Li Guangxue , Liu Shidong , Qiao Lulu , Yu Yue , Liu Xingmin 

TITLE=Field observations of seabed scour dynamics in front of a seawall during winter gales

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1080578

DOI=10.3389/fmars.2022.1080578

ISSN=2296-7745

ABSTRACT=Seawalls are vital for protecting coastal areas. However, the seabed in front of seawalls may undergo severe scouring. This can result in destabilization of the seawall structure, the underlying mechanisms of which remains unclear. Therefore, an integrated observation system comprising acoustic and optical instruments was deployed in areas with severe seabed scouring. This observation system was used to observe sediment dynamics elements such as waves, currents, tides, turbulence and suspended sediment concentration (SSC) for 31 days in winter. In calm weather conditions, there was no notable increase in SSC, indicating that the tidal dynamics were not sufficient for sediment suspension. During high winds, SSC increased sharply to 12,222 mg/L, and the sediment vertical diffusion flux induced by turbulence was coupled to SSC, indicating that the increased SSC was predominantly attributed to local resuspension. Consistent temporal distribution of turbulence-induced sediment vertical diffusion flux and momentum flux in high wavelet power spectra highlights the important role of turbulence in sediment dynamics. Enhanced longshore currents during high wave conditions intensified sediment transportation. Horizontal net sediment fluxes notably increased to 769 t/m2 per day during winter gales, which plays significant role in seabed erosion. This study reveals key process associated with seabed scouring in front of seawalls during gale events.