The heterogeneity of mudflat erodibility
| Autor: | Peng Yao, Zheng Bing Wang, T. Daggers, B.C. van Prooijen, Q. Zhu, D.C. Maan, Shilun Yang |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
010504 meteorology & atmospheric sciences
Lead (sea ice) Sediment Intertidal zone Storm Soil science Forcing (mathematics) 010502 geochemistry & geophysics 01 natural sciences Waves and shallow water Critical resolved shear stress Erosion Bacillariophyceae [Featherlike diatoms] Geology 0105 earth and related environmental sciences Earth-Surface Processes |
| Popis: | The prediction of the erosion of mudflats is hampered by inaccurate estimates of the erodibility distribution of the sediment bed. To investigate how erodibility varies in space and what the vertical distribution over the sediment depth is, comprehensive observations of the sediment properties, hydrodynamics and bed-level changes were conducted on an intertidal flat in the Western Scheldt Estuary, the Netherlands. The erosion potential on a mudflat is determined by the critical shear stress for erosion (τe), erosion rate coefficient (M) and local hydrodynamic conditions. A clear difference in hydrodynamic forcing was observed, leading to significant bed level variations at the low water line, where erosion often occurs during very shallow water condition, and a nearly constant bed level at the upper part. The erosion parameters τe and M could be determined over a sediment bed of 12 cm at the low water line. The erosion coefficient M can be considered constant with depth, although there is a large spreading. A clear vertical variation of τe was found: τe increased significantly downward from 0.10 Pa at the sediment surface to 1.13 Pa at 12 cm below the surface. Additionally, there was a strong indication that the presence of diatoms enhanced τe in the upper 2 mm of sediment by five times of the abiotic τe (from 0.09 Pa to 0.46 Pa). These findings lead to the following improvement for predicting morphological changes of tidal mudflats: (1) very shallow conditions should be better simulated, (2) the vertical distribution of τe should be considered. Otherwise, erosion rates can be overestimated, especially during extreme events, because exposure of the deeper well-consolidated layer likely occurs; and (3) an appropriate description of the effect of diatoms should be considered as part of the bottom boundary condition. |
| Databáze: | OpenAIRE |
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