Morphodynamic modeling the impact of large-scale embankment on the large bar in a convergent estuary

Xie, Dongfeng; Wang, Zhengbing; van der Wegen, Mick; Huang, Junbao

doi:10.1016/j.margeo.2021.106638

Morphodynamic modeling the impact of large-scale embankment on the large bar in a convergent estuary

Title

Morphodynamic modeling the impact of large-scale embankment on the large bar in a convergent estuary

Author

Xie, Dongfeng (Zhejiang Institute of Hydraulics and Estuary)
Wang, Zhengbing (TU Delft Coastal Engineering; Deltares)
van der Wegen, Mick (IHE Delft Institute for Water Education; Deltares)
Huang, Junbao (Zhejiang Institute of Hydraulics and Estuary)

Date

2021

Abstract

Many alluvial estuaries worldwide include an inside bar system, a large sediment deposit deeply stretched into the estuary. A good example of such a system is the large sediment deposit in the Qiantang Estuary, China. Its length and height reach 130 km and 10 m, respectively. Bathymetrical comparison reveals that the large bar has moved seaward by around 15 km over the last decades, probably related to the large-scale coastal embankment project. This motivated a quantitative investigation of the impact of estuarine planform on the inside bar development. The bar morphology is reproduced by means of an idealized 1-D morphodynamic model. Model results suggest that the bar movement is related to a decreasing tidal prism, increasing flood dominance in the lower reach and enhanced ebb currents in the upper reach, in response to the embankment. The timescale of the morphological response is only several years. The rapid response is related to the strong tidal currents and large sediment fluxes within the estuary. Sensitivity experiments show that the location and dimensions of the bar are related to the convergence length of the estuary. A decrease of the convergence length causes seaward movement and shortening and lowering of the bar. The bar dimensions also depend on the ratio between river and tidal discharges. When the ratio increases, the bar apex moves seaward and the elevation decreases. The bar movement has significantly influenced the tidal bore in the Qiantang Estuary.

Subject

Morphodynamic modeling
Inside bar dimensions
Coastal embankment
Tidal bore
Qiantang Estuary
Coastal management

To reference this document use:

http://resolver.tudelft.nl/uuid:4a4c833a-48aa-4554-b3ec-a06b47566097

DOI

https://doi.org/10.1016/j.margeo.2021.106638

Embargo date

2023-09-24

ISSN

0025-3227

Source

Marine Geology, 442