Sediment Dynamics Of Jiaozhou Bay And Adjoining Areas

Sediment transport and deposition patterns of Jiaozhou Bay and adjoining areas, Shandong Peninsula, are investigated in the present study. The approaches adopted are as follows. (1) Grain size trends are identified to delineate sediment transport pathways on the basis of the Gao-Collins model, which are consistent with evidence from natural tracer dispersal patterns. (2) A technique is developed to measure suspended sediment concentrations using ADCP mounted on a moving vessel, based upon contemporary acoustic theory. (3) Rates of sediment accumulation are derived, by 210Pb dating and sediment balance calculations on a temporal scale of 100 years. (4) A formula for the calibration coefficient contained in Bagnold-type bed-load equations is modified and improved, on the basis of re-analysis of original flume experiment data. The data sets used for the study are obtained from analyses of sediment and water samples and turbidity and ADCP measurements, and collation of historical data. The patchy distribution patterns of seabed material, with many sediment types, indicate a multi-source nature of sediment supply and complex hydrodynamic conditions in the study area. Grain size trends show sediment transport towards the central sandbank within the embayment and the seaward end of the deep channel at the entrance. Such patterns are highly consistent with the characteristics of current velocities and geomorphology; they are also in good agreement with heavy mineral movement and spatial distribution patterns of calcareous nannofoss its. The surficial sediment samples are analyzed using a laser particle analyzer and pipette/sieving method to obtain grain size data. It is found that grain size trend patterns derived from the two methods are compatible with each other. The grain size trend model is not only applicable for coastal areas with complex sediment distributions and irregular sediment sampling grids, but also for the use of historical grain size data (which are not obtained with laser techniques), with a potential for studies in the evolution of the embayment. The nearby beaches may supply sediment for the embayment during storm surges, by causing bed-load and suspended-load transport of the beach material towards deeper waters. Suspended sediment concentrations, obtained by field measurements and estimated by a remote sensing algorithm using TM satellite images, are high in the waters of northwestern Jiaozhou Bay and low in its eastern part. Variations in suspended sediment concentrations are significant on annual and seasonal scales; this is associated with local weather, hydrodynamics and river discharges. Strong wind waves during spring and winter result in high concentrations, and the concentration can increase rapidly in response to resuspension during summer storm surges. An equation is derived by theoretical analysis, to establish a relationship between suspended sediment concentrations and ADCP echo intensity output. For the survey at the entrance to Jiaozhou Bay, an ADCP is mounted on a moving vessel; the calibration coefficient in the equation is determined by in situ measurement. Then, a semi-empirical formula is obtained and used to calculate suspended sediment concentration profiles along several cross- II sections. Stratification in terms of the concentration is observed, which is probably in response to sediment settling processes. The current velocities are...