Study on the evolution of the tidal morphodynamic processes in south-western Laizhou Bay based on numerical simulation in the past 50 years

Using the two-dimensional shallow water equations,the paper simulated the tidal field of Laizhou bay based on three charts surveyed in 1958,1984 and 2002 respectively. The models were used to study the evolution rule and to reveal the effect on the tidal dynamics by the Yellow River Sandspit formation and evolution over the past 50 years. Results show that,the high-velocity zones have developed outside of the sandspit,and on the periphery of the high-velocity zones,there are the tidal shear fronts which can be divided into inner-ebb-outer-flood type（IEOF) and the inner-flood-outer-ebb type（IFOE). Acompannied with the sandspit extension toward the the Laizhou bay constantly,distribution of the tide field have converted to the rayonnant model with the sandspit as the center,the arc high-velocity zone moved to the open seas with the increases of range and velocity,the tidal shear fronts lasted longer,spaced shorter,and its length from north to south had clear growth too. But the high-velocity zones and tidal shear fronts are always in the north of the Qingtuizi. Under the combined action of the arc high-velocity zone and tidal shear front,compared with the results of the coastal geomorphology evolution in the same period,a majority of the Yellow River sediment migrated and settled in the north sea area of the Qingtuozi merely. It is the main driving factors that lead to the different geomorphical evolution between the south and west coast.