Analyzing natural bed-level dynamics to mitigate the morphological impact of river interventions

Local river interventions, such as channel narrowing or side channels, are often necessary to maintain safety, ecology, or navigation. Such interventions have different effects on the river's bed morphology during periods of high- and low-discharge events. Mapping the bed-level variations for different discharge levels and understanding these...

Bank erosion in regulated navigable rivers

Banks constitute important areas for the river ecology since they provide a multitude of favourable conditions for flora and fauna. The hydromorphological diversity typical of these transitional zones between water and land, and the associated processes of erosion and accretion, make riverbanks vital for many aquatic and riparian plants and...

Assessment of the functional performance of lowland river systems subjected to climate change and large-scale morphological trends

Worldwide, rivers provide important socio-economic and environmental functions and are essential to human well-being. The growing demand of user-functions and the change in river conditions due to large-scale morphology and climate change, increase the pressure on lowland river systems (e.g. Rhine, Meuse, Danube and Mississippi). To ensure a...

The Quasi-Equilibrium Longitudinal Profile in Backwater Reaches of the Engineered Alluvial River: A Space-Marching Method

An engineered alluvial river (i.e., a fixed-width channel) has constrained planform but is free to adjust channel slope and bed surface texture. These features are subject to controls: the hydrograph, sediment flux, and downstream base level. If the controls are sustained (or change slowly relative to the timescale of channel response), the...

Morphological Adaptation of River Channels to Vegetation Establishment: A Laboratory Study

While the scientific community has long recognized that alluvial rivers are the product of interactions between flowing water and bed material transport, it is increasingly evident that vegetation mediates these interactions and influences the stream channel characteristics. In a novel set of mobile bed laboratory experiments with variable...

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...

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...

Computational modelling of small-scale river morphodynamics

Alluvial open channel beds often exhibit statistically periodic irregularities, known as dunes. Dunes have considerable effects on sediment transport and flow resistance. When growing during a flood, the dunes create more resistance and flood levels may rise significantly. Accurate prediction of dune properties therefore contributes to effective...

Effects of riparian and floodplain vegetation on river patterns and flow dynamics

Flume experiments and field observations demonstrating the effects of vegetation on river planforms are reported in literature, but numerical studies of these effects at the river scale are lacking. We investigated the effects of vegetation in a 2D morphodynamic model using submodels for flow resistance and colonisation of newly formed deposits....

Different approaches to handling vertical and streamwise sorting in modeling river morphodynamics

This paper presents an assessment of the strengths and weaknesses of four sediment continuity models for nonuniform sediment by applying these models to an aggradational flume experiment that is dominated by nonuniform sediment and dunes. The author makes simulations of the flume experiment using four numerical morphodynamic model systems to...

Effects of smoothing and regridding in numerical meander migration models

Meander migration models include an as yet poorly investigated source of numerical errors related to the computation of the channel curvature, which are amplified by the procedure of adding and deleting grid points as the river planform evolves. The methods adopted to reduce these errors may influence size, form, and migration rate of the...