Numerical Analysis on the Effects of Coastline Changes in Jiaozhou Bay on Tidal Prism and Water Exchange

Under the effects of natural processes and human interventions, Jiaozhou Bay (JZB) coastline has been continuously changing. This research used Landsat satellite imagery and Digital Shoreline Analysis System (DSAS) to evaluate coastline change rate from 2000 to 2020, which was found to range from 0.06 to 288.44 meters per year. According to JZB coastline and water depth datasets in different periods, MIKE numerical simulations were performed to compare the tidal prism and water exchange times of JZB across different years. The results showed that net shoreline movement (NSM) and end point rate (EPR) in research area from 2000 to 2020 were 966 meter and 24 meter per year, respectively. It was found that, JZB coastline moved towards the ocean and higher shoreline movement rates resulted in stronger impacts on tidal prism and half-exchange time. The calculated tidal prisms in 2000 and 2020 were 11.5×108 and 11.3×108 m3 , respectively, presenting a decreasing trend with reduction rate of about 2%. Half-exchange time in 2000 was recorded as 785 hours, equivalent to approximately 33 days; but the corresponding value in 2020 was increased to 844 hours (about 36 days), indicating an increasing trend. Furthermore, simulation results also showed that residual current in JZB was small within the bay, but there was a larger residual current at bay mouth, directing outside the bay. Tidal ellipse analyses of M2 and S2 at representative points revealed that M2 and S2 at H1 station were significantly changed.