scholarly journals Where river and tide meet: The morphodynamic equilibrium of alluvial estuaries

2015 ◽  
Vol 120 (1) ◽  
pp. 75-94 ◽  
Author(s):  
Michele Bolla Pittaluga ◽  
Nicoletta Tambroni ◽  
Alberto Canestrelli ◽  
Rudy Slingerland ◽  
Stefano Lanzoni ◽  
...  
Keyword(s):  
Morphodynamic Equilibrium ◽  
Alluvial Estuaries

scholarly journals Supplemental Material: Morphodynamic equilibrium of lowland river systems during autoretreat

2020 ◽  
Author(s):  
Chenliang Wu ◽  
et al.
Keyword(s):  
Numerical Model ◽  
Lowland River ◽  
River Systems ◽  
Model Code ◽  
Morphodynamic Equilibrium

Additional details on the numerical model, code availability, and data from natural examples.<br>

scholarly journals SUSPENDED PARTICLE DYNAMICS IN A WELL-MIXED ESTUARY: DEVIATIONS FROM MORPHODYNAMIC EQUILIBRIUM

2014 ◽  
Vol 1 (34) ◽  
pp. 78 ◽  
Author(s):  
Manuel Díez-Minguito ◽  
Miguel Ortega-Sánchez ◽  
Asunción Baquerizo ◽  
Huib E. De Swart ◽  
Miguel A. Losada
Keyword(s):  
Suspended Particle ◽  
Particle Dynamics ◽  
Morphodynamic Equilibrium

Modeling the morphodynamic equilibrium of an intermediate reach of the Po River (Italy)

2015 ◽  
Vol 81 ◽  
pp. 95-102 ◽  
Author(s):  
Stefano Lanzoni ◽  
Rossella Luchi ◽  
Michele Bolla Pittaluga
Keyword(s):  
Po River ◽  
Morphodynamic Equilibrium

scholarly journals Salt intrusion in multi-channel estuaries: a case study in the Mekong Delta, Vietnam

2006 ◽  
Vol 10 (5) ◽  
pp. 743-754 ◽  
Author(s):  
A. D. Nguyen ◽  
H. H. Savenije
Keyword(s):  
River Discharge ◽  
Single Channel ◽  
Mekong Delta ◽  
Salt Intrusion ◽  
Predictive Equations ◽  
Alluvial Estuaries ◽  
Tidal Characteristics ◽  
Mixing Behaviour ◽  
Sloping Bottom

Abstract. There is a well-tested theory for the computation of salt intrusion in alluvial estuaries that is fully analytical and predictive. The theory uses analytical equations to predict the mixing behaviour of the estuary based on measurable quantities, such as channel topography, river discharge and tidal characteristics. It applies to single-channel topographies and estuaries that demonstrate moderate tidal damping. The Mekong delta is a multi-channel estuary where the tide is damped due to a relatively strong river discharge (in the order of 2000 m3/s), even during the dry season. As a result the Mekong is a strongly riverine estuary. This paper aims to test if the theory can be applied to such a riverine multi-channel estuary, and to see if possible adjustments or generalisations need to be made. The paper presents salt intrusion measurements that were done by moving boat in 2005, to which the salt intrusion model was calibrated. The theory has been expanded to cater for tidal damping. Subsequently the model has been validated with observations made at fixed locations over the years 1998 and 1999. Finally it has been tested whether the Mekong calibration fits the overall predictive equations derived in other estuaries. The test has been successful and led to a slight adjustment of the predictive equation to cater for estuaries that experience a sloping bottom.

scholarly journals Maximum power of saline and fresh water mixing in estuaries

2019 ◽  
Vol 10 (4) ◽  
pp. 667-684
Author(s):  
Zhilin Zhang ◽  
Hubert Savenije
Keyword(s):  
Fresh Water ◽  
Dispersion Coefficient ◽  
Saline Water ◽  
Maximum Power ◽  
Estuarine System ◽  
Natural Systems ◽  
Gravitational Circulation ◽  
Advection Dispersion ◽  
Physically Based ◽  
Alluvial Estuaries

Abstract. According to Kleidon (2016), natural systems evolve towards a state of maximum power, leading to higher levels of entropy production by different mechanisms, including gravitational circulation in alluvial estuaries. Gravitational circulation is driven by the potential energy of fresh water. Due to the density difference between seawater and river water, the water level on the riverside is higher. The hydrostatic forces on both sides are equal but have different lines of action. This triggers an angular moment, providing rotational kinetic energy to the system, part of which drives mixing by gravitational circulation, lifting up heavier saline water from the bottom and pushing down relatively fresh water from the surface against gravity; the remainder is dissipated by friction while mixing. With a constant freshwater discharge over a tidal cycle, it is assumed that the gravitational circulation in the estuarine system performs work at maximum power. This rotational flow causes the spread of salinity inland, which is mathematically represented by the dispersion coefficient. In this paper, a new equation is derived for the dispersion coefficient related to density-driven mixing, also called gravitational circulation. Together with the steady-state advection–dispersion equation, this results in a new analytical model for density-driven salinity intrusion. The simulated longitudinal salinity profiles have been confronted with observations in a myriad of estuaries worldwide. It shows that the performance is promising in 18 out of 23 estuaries that have relatively large convergence length. Finally, a predictive equation is presented to estimate the dispersion coefficient at the downstream boundary. Overall, the maximum power concept has provided a new physically based alternative for existing empirical descriptions of the dispersion coefficient for gravitational circulation in alluvial estuaries.

scholarly journals Supplemental Material: Morphodynamic equilibrium of lowland river systems during autoretreat

2020 ◽  
Author(s):  
Chenliang Wu ◽  
et al.
Keyword(s):  
Numerical Model ◽  
Lowland River ◽  
River Systems ◽  
Model Code ◽  
Morphodynamic Equilibrium

Additional details on the numerical model, code availability, and data from natural examples.<br>

scholarly journals Numerical groyne layout optimisation for restoration projects in large rivers: An adaptive approach towards a desired morphodynamic equilibrium

2018 ◽  
Vol 40 ◽  
pp. 02002
Author(s):  
Martin Glas ◽  
Michael Tritthart ◽  
Marcel Liedermann ◽  
Sebastian Pessenlehner ◽  
Helmut Habersack
Keyword(s):  
Transport Model ◽  
Numerical Models ◽  
Cost Effective ◽  
Pilot Project ◽  
Large Rivers ◽  
Sediment Transport Model ◽  
River Bed ◽  
Morphodynamic Equilibrium ◽  
3D Numerical Model ◽  
Restoration Measures

Integrative restoration measures at large rivers target the improvement of morphological and ecological conditions, under consideration of economic demands, specifically navigational ones. Alternative groyne layouts with e.g. reduced groyne spacing and lowered crest elevation reduce ecological deficits and have the potential to cease frequently encountered river bed incision of heavily modified rivers. On the other hand, the induced change in the morphodynamic equilibrium may interfere with navigation by reducing the water depth in the fairway. In 2009, a pilot project was realised on the Austrian Danube, including an alternative groyne layout. As a consequence the desired aggradations in the fairway became too large, leading to an increased dredging effort. In 2014, a numerical groyne optimisation, specifically a 3D numerical model in combination with a sediment transport model, was applied. In 2015, after implementing the optimised groyne layout in the field, morphodynamic equilibrium was reached reducing the need of extensive dredging. This equilibrium could be shown by analysing subsequently observed bathymetries until 2017. Moreover, the morphodynamic changes due to the groyne optimisation in 2015 were reproduced successfully with the numerical models. Thus they represent a cost effective tool for planning and optimising future restoration measures in large and heavily modified rivers.

scholarly journals Thermodynamics of saline and fresh water mixing in estuaries

2018 ◽  
Vol 9 (1) ◽  
pp. 241-247 ◽  
Author(s):  
Zhilin Zhang ◽  
Hubert H. G. Savenije
Keyword(s):  
Potential Energy ◽  
Fresh Water ◽  
River Flow ◽  
Maximum Power ◽  
Gradual Transition ◽  
Mixing Processes ◽  
Advection Dispersion ◽  
Alluvial Estuaries ◽  
New Equation ◽  
A Minor

Abstract. The mixing of saline and fresh water is a process of energy dissipation. The freshwater flow that enters an estuary from the river contains potential energy with respect to the saline ocean water. This potential energy is able to perform work. Looking from the ocean to the river, there is a gradual transition from saline to fresh water and an associated rise in the water level in accordance with the increase in potential energy. Alluvial estuaries are systems that are free to adjust dissipation processes to the energy sources that drive them, primarily the kinetic energy of the tide and the potential energy of the river flow and to a minor extent the energy in wind and waves. Mixing is the process that dissipates the potential energy of the fresh water. The maximum power (MP) concept assumes that this dissipation takes place at maximum power, whereby the different mixing mechanisms of the estuary jointly perform the work. In this paper, the power is maximized with respect to the dispersion coefficient that reflects the combined mixing processes. The resulting equation is an additional differential equation that can be solved in combination with the advection–dispersion equation, requiring only two boundary conditions for the salinity and the dispersion. The new equation has been confronted with 52 salinity distributions observed in 23 estuaries in different parts of the world and performs very well.

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