Closure dams in estuaries and tidal areas have a strong impact on their hydrodynamics and morphology. Among other reasons, this impact can be due to tidal reflection. In the Guadalquivir estuary (SW Spain), data measured allowed to identify a partially standing motion along the upper third of the estuary. We estimate the frequency-dependent complex reflection coefficients at the head dam, and analyze the effect of the combined action of the incident and reflected tidal waves on the residual currents. Erosion-deposition patterns induced by the tidal reflection were identified. The most energetic tidal constituent, the semidiurnal M2, favors sedimentation near the entrance of the Port of Seville, where the most intense dredging works take place. Finally, we briefly discuss the potential consequences of reflection on the turbidity spatial distribution.

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Tidal wave reflection from the closure dam in the guadalquivir estuary (sw spain)

In aquatic ecosystems, tributaries play an important role in maintaining the populations and diversity of aquatic organisms throughout the drainage basin, but because of their small catchments, these ecosystems are often more susceptible to the effect of land-use changes and flow-regime alterations. Here, we examined anthropogenic effects on benthic macroinvertebrate diversity in the tributary lagoons, collectively called “Naiko,” surrounding Lake Biwa. We sampled macroinvertebrates and determined the environmental characteristics of 20 tributary lagoons. We identified the environmental factors determining the diversity of macroinvertebrates and found that turbidity significantly diminished species diversity. We assessed the anthropogenic stressors that contributed to the increase in turbidity and found that human population density and the proportion of paddy fields in the watershed area were positively correlated with turbidity, most likely caused by erosion of terrigenous organic matter from the paddy fields and urban areas. In addition, the presence of sluice gates and the lengths of channels connecting to the main lake were positively correlated with turbidity, suggesting that these factors lowered hydrologic connectivity and retained organic matter. We concluded that changes to the landscape and decreased hydrologic connectivity caused by human activity increased turbidity, which in turn decreased macroinvertebrate diversity. The identification of these factors in tributaries is vital for developing a strategy for habitat restoration to conserve the entire ecosystem of the Lake Biwa basin.

The effect of human activities on benthic macroinvertebrate diversity in tributary lagoons surrounding Lake Biwa

Disentangle the sediment mixing from geochemical proxies and detrital zircon geochronology

Law and Early Warning of Vertical Sluice Cluster Displacements in Soft Coastal Soil

In order to resist tides and salt intrusion, there have been more than 300 tidal gates built at many river estuaries in China since 1960s. However, the serious deposition occurred at a lot of gates due to the changes of hydrodynamic and sediment conditions and lack of discharge from the rivers. At present, the research is mainly to analyze the reasons for siltation downstream gates and the measures of dredging. It is not enough for study on distribution simulation of deposition downstream sluice. Studies have shown that 2D numerical model cannot reflect the distribution of sediment siltation downstream gates. Therefore, it needs to develop 3D sediment numerical model for deposition prediction. In this paper, combined the feasibility study of a tidal gate at Mulanxi River, a physical model and 3D numerical model of sediment siltation downstream gate are conducted.

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Numerical simulation study on deposition downstream estuarine sluice

For the channel regulation in tidal rivers, groins are often used as typical hydraulic structures. Precisely predicting the local scour depth at the groin head is the key for the project of river regulation. The local scour of groins for tidal rivers is significantly different from that for the undirectional steady flow of general rivers. In the present paper, a three-dimendional (3D) mathematical model for turbulence and sediment transport are establishmented. The local scour near the groin under the actions of tidal current and steady flow are simulated by established 3D turbulence and sediment transport numerical model.The differences of the scour development and the scour pattern near the groin under these two actions are compared.

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Xiangming Wang

Papers

Numerical simulation study on deposition downstream estuarine sluice

Local scour characteristics of groins at tidal waterways and their simulation