Sediment characteristics and sedimentary environment analysis of a sandbar-lagoon system developed at the estuary of Fudu River, China

Abstract

Developed at the estuary of Fudu River, the sandbar-lagoon system there occupies the longest sandy coastline of east coast of Liaodong Bay, China. Over the past several decades, substantial changes are believed to have occurred over the system regarding its sedimentary characteristics and dynamic environment, partly due to the anthropogenic influences. However, few studies have been reported to investigate such evolution. To fill this gap, grain size analysis was conducted with 52 sediment samples to reveal the sediment distribution patterns. In addition, the sedimentary environment and sediment transport trend were studied using the Pejrup M triangular diagram and Gao-Collins grain size trend analysis method. Our results show that the surface sediments are mainly sandy with coarser sediment found over the northern part of the sandbar whereas fine-grained sediments are mainly in the lagoon area. The sedimentary dynamics environment can be divided into the northern area of sandbar and the lagoon area. The relatively larger grain size, low sorting coefficient and positive skewness in the northern part of sandbar indicates a strong and stable hydrodynamic environment dominated by waves and currents. Meanwhile, the small mean size, high sorting coefficient and negative skewness in the lagoon area implies a weak hydrodynamic environment due to significant reduction of hydrodynamic strength. In the lagoon area, the sediments are transported mainly from coastal ocean to the interior of lagoon in suspension. Our study provide basin understanding of the controlling dynamics on sandbar evolution, and can provide guidelines for the preservation of the sandbar-lagoon system.