Erosion and redeposition in tidal flats of the Yellow River delta: Result of tracer stick monitoring

In estimating the sedimentological and morphological evolution of tidal flat, it is essential to know the quantity of redeposition. The knowledge is also helpful to understanding the behavior of tidal flat as the transitional zone for nutrient and harmful substances (e.g., heavy metals). A method “tracer stick method” was applied to collecting data about erosion and accumulation with an accuracy of millimeters. The results show that the annual morphological change in these tidal flats is about one centimeter, but the sediment turnover is almost a magnitude larger. The highest sediment mobility happens in the north tidal flat of the modern Yellow River, because it suffers stronger wave and tidal currents, and it is close to the current river mouth and is affected subsequently by the sediment discharge of the river. The sediment mobility becomes weak during the frozen period between December and March. The south tidal flat also has significant sediment mobility, with the sediment turnover being 5~10cm. A man-made dyke for oil production shelters the east tidal flat and, as a result, the tidal flat has the small sediment mobility.