The response of morphplogy and sediment characteristics to human modification in an Estuarine tidal flat

The estuarine tidal flats are always under the influences of both river inputs and tidal currents. The morphological statuses of estuarine tidal flats are always being dynamic due to both human impacts and natural variations. The human modifications particularly show a strong influence on the short-term morphological changes and sediment characteristics in estuarine tidal flats. A huge embankment was construct in the eastern Chongming tidal flats in the Changjiang River Estuary from 2013 to 2014. Based on Terrestrial Laser Scanner system, non-ground points fitering method, sediment samples and laboratory analyses, this study aim to explore the response of morphplogy and sediment characteristics to human modification in an estuarine tidal flat. The results show that:(1) significant erosion occurs in the southern part while even though light deposition appears in the northern part, the entire tidal flat still experiences significant erosion after the completion of the embankment, with a average decrease of 4 cm in elevation; (2) the median particle size of the sediments increases from 29 µm to 38 µm after the construction; (3) after the completion of the embankment, sediment particle size in the southern part and the flat front increases while decreases in the northern part. The results indicate that human modifications would lead to severe erosion and surficial sediment coarsening, but the response of morphological changes and sediment characteristics still varies in different zones of tidal flats. This study also finds that even though it is riverine sediment input that plays a dominantly role in long-term evolution of estuarine tidal flats, human modifications could change short-term tidal flat morphodynamic processes remarkably.