Seabed erosion mechanism and maximum scour depth in front of the Gudong seawall

SUN Jian; XU Jishang; LI Guangxue

doi:10.13984/j.cnki.cn37-1141.2024.03.004

Abstract：Seawalls play an important role in preventing coastal areas from storm surges,but the seabed in front of seawalls usually suffers serious erosion after their construction,which would threaten the safety of seawalls.To analysis the scour problem in Gudong Seawall,we recovered the scouring process according to the water depth during the past 20 years,discussed the scour mechanism and cal-culated the maximum scouring depth.The results showed that:(1)Gudong seawall was under the ero-sion background in the abandoned sub-lobes of the underwater delta of the Yellow River Delta,and the seabed within 500 m offshore suffered more severe erosion,which was called background scouring and toe scouring respectively in this manuscript.The background water depth had deepened from 2-3 m in 2000 to the present depth of 6 m,and the maximum water depth at the toe of the seawall had exceeded 7 m.(2)Background scouring was mainly caused by the diversion of the river course and the reduction of sediment into the sea.Waves were the main driving factor for seabed scouring.Seawall toe scouring was caused by complex hydrodynamic processes in front of the Gudong Seawall,such as wave reflec-tions,wave breaking,turbulence,coastal current,offshore current,etc.(3)It was predicted that the maximum scouring depth for background erosion in the Gudong Sea area was 7 m,whilst for toe scou-ring was 1.7-2.5 m,so the maximum water depth in front of the Gudong seawall was 8.7-9.5 m.