The seasonal variations of erosion processes off the modern abandoned Yellow River delta lobe

JI Jinlong; WANG Baoduo; WANG Shixiong; WU Xiao; WANG Houjie; BI Naishuang

doi:10.13984/j.cnki.cn37-1141.2024.05.006

Abstract：Based on the continuous observation and tripod observation data of key stations in the aban-doned Diaokou(DK)and Shanxiangou(SXG)delta lobe in August 2017 and in March 2018,the seasonal variations of erosion processes off the modern abandoned yellow river delta lobe were studied.The ero-sion process in the abandoned delta lobe of the Yellow River had significant seasonal characteristics.Under calm sea conditions in summer,the delta slope was strongly mixed and the delta front was strat-ified significantly.The average suspended sediment concentration(SSC)of the delta slope was about 25-55 mg/L,which was 1.5-3 times of SSC of the delta front.The erosion flux of the delta slope was about 2 times of that of the delta front.The suspended sediments were mainly transported to Bohai bay,the suspended sediment flux of the delta slope was about twice of that of the front area.The SSC in winter was 5-7 times of that in summer,and the average sediment concentration in the delta slope could reach 175-280 mg/L.The SSC increased significantly during storms and it could be 1-2 orders of magnitude higher than that in summer.Meanwhile,remarkable sediment liquefaction and cross-slope transport might occur during winter storm.Sediment trap records showed that the near bottom deposi-tion flux under storm conditions was much higher than that under calm conditions,up to more than 20 kg/m2/d,which was about 30-50 times of that under calm sea conditions.A storm process could make the seabed sediments change in centimeter scale.The continuous action of tidal current was an important reason for the rapid erosion of the delta lobe in the study area,and the short time scale wave action under extreme weather was also considerable.