资源环境科技发展态势分析平台

We use the results of a one-dimensional morphodynamic model and the basis of the Lagrangian equilibrium state (Maan et al., 2015, ) to derive a quantitative relationship between the progradation speed of tidal flats and the suspended sediment concentration in their adjacent waters and show that the speed increases more than linearly with the concentration. We also show that horizontally prograding flats rise vertically with sea level rise at the expense of their horizontal speed via a linear relationship. If accretion rates are insufficient to keep up with sea level rise, however, the intertidal flat submerges and retreats landward at the same time. We apply the obtained relationships to the Yangtze Estuary to estimate the critical sediment concentration level below which a shift from progradation to retreat can be expected.

Plain Language Summary The combination of sea level rise, decreasing sediment availability, and human fixation of the coastline results in large stresses on coastal areas worldwide. Extremely sensitive are the intertidal wetlands, lying in-between the low and the high water line. Loss of coastal wetlands increases the coastal vulnerability to extreme events and sea level rise and undermines the coastal defense. We need a better understanding of the complex dynamics of the seabed to effectively interfere and stimulate its rise. System theory can be used to express system variables in terms of external system drivers. In this paper, the basis of the Lagrangian equilibrium state (Maan et al., 2015, ) is used to derive quantitative relationships between the expansion rate of intertidal flats and three external drivers: the suspended sediment concentration in their adjacent waters (i.e., in the tidal channels), the wave-induced erosion, and the rate of sea level rise. Wave-induced erosion and sea level rise lead to the existence of a critical sediment concentration level below which the intertidal system shifts from expansion to retreat. We apply the obtained relationships on the expanding flats in the Yangtze Estuary to estimate the critical shrinkage factor for the suspended sediment concentration in the estuary.