Effect of channel deepening on tidal flow and sediment transport—part II: muddy channels

Natural tidal channels often need deepening for navigation purposes (larger vessels). The depth increase may lead to tidal amplification, salt intrusion over longer distances, and increasing sand and mud import. Increasing fine sediment import, in turn, may start a process in which the sediment conc...

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Bibliographic Details
Published in:Ocean dynamics 2018-11, Vol.68 (11), p.1481-1501
Main Authors: van Rijn, Leo, Grasmeijer, Bart
Format: Article
Language:English
Subjects:
Atmospheric Sciences
Bottom trawling
Brackishwater environment
Calibration
Channels
Computer simulation
Debris flow
Dredging
Earth and Environmental Science
Earth Sciences
Ecological effects
Ecological monitoring
Estuaries
Estuarine environments
Evaluation
Fluid- and Aerodynamics
Fluvial sediments
Geophysics/Geodesy
Hydrodynamic models
Hydrodynamics
Imports
Intrusion
Monitoring/Environmental Analysis
Mud
Navigation
Oceanography
Post-production processing
Sediment
Sediment concentration
Sediment transport
Sediments
Three dimensional models
Tidal currents
Tidal flow
Tidal inlets
Transport
Transport processes
Turbidity
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Summary:Natural tidal channels often need deepening for navigation purposes (larger vessels). The depth increase may lead to tidal amplification, salt intrusion over longer distances, and increasing sand and mud import. Increasing fine sediment import, in turn, may start a process in which the sediment concentration progressively increases until the river becomes hyper-turbid, which may lead to increased dredging volumes and to decreased ecological values. These effects can be modeled and studied using detailed 3D models. Reliable simplified models for a first quick engineering evaluation are however lacking. In this paper, we apply both simplified and detailed 3D models to analyze the effects of channel deepening in prismatic and weakly converging tidal channels with saturated mud flow. The objective is to gain quantitative understanding of the effects of channel deepening on mud transport. We developed a simplified tidal mud model describing most relevant processes and effects in saturated mud flows with only minor horizontal transport gradients (quasi uniform conditions). The simplified model is not valid for non-saturated mud flow conditions. This model can either be used in standalone mode or in post-processing mode with computed near-bed velocities from a 3D hydrodynamic model as an input. The standalone model has been compared to various field data sets. Mud transport processes in the mouth region of muddy tidal channels can be realistically represented by the simplified model, if sufficient salinity and sediment data are available for calibration. The simulation of tidal mud transport and the behavior of an estuarine turbidity maximum (ETM) in saturated and non-saturated mud flow conditions cannot be represented by the simplified model and requires the application of a detailed 3D model.
ISSN:1616-7341
1616-7228
DOI:10.1007/s10236-018-1205-1