Development of scour in non-cohesive sediments under a poorly erodible top layer (poster)

This study deals with the development of deep scour holes in the river bed of the Dutch Rhine delta in the Netherlands. Assessment of multi-beam surveys, laboratory-flume experiments, and 3D numerical modelling, shows how fast this type of scour holes grows in depth and width and which are the relevant processes.

Design and modeling of reservoir operation strategies for sediment management

Appropriate operation strategies that allow for sediment flushing and sluicing (sediment routing) can reduce rapid storage losses of (hydropower and water-supply) reservoirs. In this study we have shown, using field observations and computational models, that the efficiency of these operations increases when utilizing dynamics of flow and...

Development of scour in non-cohesive sediments under a poorly erodible top layer

This study deals with the development of deep scour holes in the river bed of the Dutch Rhine delta in the Netherlands. Assessment of multi-beam surveys, laboratory-flume experiments, and 3D numerical modelling, shows how fast this type of scour holes grows in depth and width. These typical scour holes are found in the tidal deltaic rivers that...

Detailed simulation of morphodynamics: 3. Ripples and dunes

We present a 3-D physics-based high-resolution modeling approach to the dynamics of underwater ripples and dunes. The flow is modeled by large eddy simulation on a Cartesian grid with local refinements. The sediment transport is modeled by computing pickup, transport over the bed, transport in the water column, and deposition of rigid spherical...

Detailed simulation of morphodynamics: 2. Sediment pickup, transport, and deposition

The paper describes a numerical model for simulating sediment transport with eddy-resolving 3-D models. This sediment model consists of four submodels: pickup, transport over the bed, transport in the water column and deposition, all based on a turbulent flow model using large-eddy simulation. The sediment is considered as uniform rigid...

Optimising long-term morphodynamic simulations of the Rhine-Meuse Delta (abstract)

Computational effort still poses serious limitations to practical use of 2D and 3D models for long-term largescale morphological modelling. To deal with long-term issues related to sea-level rise and long-term planning in the Dutch Rhine delta, we have adapted the computational approach for more efficient and fast modelling while including all...

Numerical nonlinear analysis of alternate-bar formation and overdeepening under superresonant conditions (abstract)

Numerical nonlinear analysis of alternate-bar formation and overdeepening under superresonant conditions (poster)

Local geometrical perturbations in alluvial channels can generate a pattern of alternate bars called ‘overdeepening’. Previous linear analyses and laboratory experiments showed that these bars arise downstream of perturbations in the relatively narrow and deep channels corresponding to subresonant conditions, but both upstream and downstream of...

Multireservoir operations for flood management in Tanshui River basin, Taiwan

Detailed simulation of morphodynamics: 1. Hydrodynamic model

We present a three-dimensional high-resolution hydrodynamic model for unsteady incompressible flow over an evolving bed topography. This is achieved by using a multilevel Cartesian grid technique that allows the grid to be refined in high-gradient regions and in the vicinity of the river bed. The grid can be locally refined and adapted to the...

Understanding and managing the morphology of Rhine Delta branches incising into sand-clay deposits

In the Rhine-Meuse delta in the south-western part of the Netherlands, the morphology of the river branches is highly dependent on the erodibility of the subsoil. Erosion processes that were initiated after closure of the Haringvliet estuary branch by a dam (in 1970), caused a strong incision of several connecting branches. Due to the geological...

Numerical simulations of upstream and downstream overdeepening

Local geometrical perturbations of alluvial channels can generate a pattern of non-migrating bars and pools. This phenomenon is known as “overdeepening”, because the pools locally enhance the scour in river bends. Overdeepening occurs only downstream of a perturbation if the channel is in the subresonant and subcritically damped regime, which...

DVR toolbox for sediment management in the Rhine delta

The DVR Toolbox is a modeling system developed to be used as an operational model for long-term morphological assessment of the Rhine branches in the Netherlands (10 to 50 years). The Toolbox consists of a 2D computational core (containing the Delft3D modeling system), a shell that controls input- and output, and a system for time/simulation...

Bifurcation dynamics and avulsion duration in meandering rivers by one-dimensional and three-dimensional models

At river bifurcations, water and sediment are divided over two branches. The dynamics of the bifurcation determine the long-term evolution (centuries) of the downstream branches, potentially leading to avulsion, but the dynamics are poorly understood. The long-term evolution can only be studied by one-dimensional models because of computational...

On the morphology of rivers on volcano slopes

The rivers on the slopes of the Kelud volcano in Indonesia are marked by steep slopes and fine sediment. Therefore often supercritical flow and large sediment transports occur. In this exploratory study a mathematical model has been developed for this type of rivers. The properties of this model are examined with an analysis of the...