A Study On Modern Sedimentary Environment In Southwestern Laizhou Bay

The gulf has been important for human survival and development, and LaizhouBay especially its southwestern part is an important economic belt in ShandongProvince and has rich natural resources. Although there are many previous studies onthe Laizhou Bay, it mainly focused on research of the coast, suspended sediment andso on. Therefore, studies on modern sedimentary environment in SouthwesternLaizhou Bay, which stands on the point of sediment analysis, are few and lesssystematic.Based on “China’s coastal marine environment, a comprehensive surveyand evaluation” and numerical model of MIKE21, this paper makes detailed analysisof sediment in the study area and carry out numerical simulation of hydrodynamicenvironment, erosion and deposition. By comprehensive research on hydrodynamics,sediment distribution, source of sediment, this paper seeks to ascertain modernsedimentary environment in southwestern Laizhou Bay and its controlling factors, tohave a better understanding of the development of Laizhou Bay, the basic conclusionsare drawn four aspects:(1) Relying on comprehensive analysis on sediment grain size and clusteranalysis method, the study area is divided into four partitions including silty sandsedimentary area, sandy silt sedimentary area, clayey silt sedimentary area andXiaoqing River coarse-grained sedimentary area.(2) According to the numerical simulation of tide, sediment partition and thetopography of the study area, the tidal current field is divided into four areas. Thevelocity and trends of flow have a good relationship with sediment partition.(3)According to the position of surf zone in numerical simulation, topographyof the study area and sediment partition, it is divided into surf zone and the rest.(4)Based on the numerical simulation of erosion and deposition and sedimentpartition, it is divided into four regions: the coastal accumulation zone, the offshore low-rate accumulation zone, high-rate fine deposition zone and estuarine erosion-deposition zone.With cluster partition of surface sediments as the basis, the trend, waves, erosionand deposition environment for the secondary partition, and with support of sedimentsource analysis, this paper draws a comprehensive modern sedimentary partition inthe study area, the major conclusions are as follows:(1)Modern sedimentary environments in the study area can be divided into fourzones namely Xiaoqing River estuary coarse-grain sandy sedimentary area, silty sandsedimentary area, sandy silt sedimentary area in the centr of the study area andfine-grain clayey silt sedimentary area in the north of the study area. Hydrodynamicenvironment shows that the wave action in turn weakens and the tide graduallybecome important, the source of the sediment changes from river and coastal erosionto the sediment from Yellow River.(2)The construction of port and beach culture and so on made a difference on thehydrodynamic conditions in the study area and the source and transport of coastalsediment, therefore human activities has gradually become one of the majorcontrolling factors of modern sedimentary environment in the southwest of LaizhouBay.