Regulation structures

Morphological modelling for rivers with non-uniform flow

In Chapter I a derivation of the equations and an extension of the mathematical model will be carried out. The sediment-mixture is separated in a number of fractions - each with a representative grain size - and the equations describing the sediment-movement are split up for every fraction separately. In order to get some insight in the new...

A theoretical model for suspended sediment transport in river bends

A two dimensional depth-averaged model for the concentration field of suspended sediment in river bend flow is formulated. Transport of suspended sediment in horizontal and vertical directions is modelled. Convection by the main and secondary flow and turbulent diffusion are incorporated. The model is capable of computing the exchange of...

Theoretical investigation on discharge-induced river-bank erosion

Bank erosion is incorporated in one-dimensional and two-dimensional horizontal models for river morphology. The banks are assumed to consist of a fraction of cohesive material, which becomes washload after being eroded, and a fraction of granular material, with the same properties as the material of the bed. The banks are taken to be eroded by...

Simulation of meandering river processes

A simple mathematical model for the simulation of river meandering processes is presented and analysed. The model is schematized as follows: computation of steady-state flow field and riverbed topography; and computation of bank erosion rate as a function of the near-bank hydraulic and morphological properties. The model is linear for the...

Modelling of river morphology with non-orthogonal horizontal curvilinear coordinates

A numerical two-dimensional model for river morphology is extended with bank erosion. The model is formulated in curvilinear coordinates. This allows the use of a boundary-fitted computational grid, suited for rivers with a curved centre-line and a non-uni form width. Dealing with non-homogeneous bank erodibility is shown to require a non...

Use of models for river problems

In Chapter 2 of this report an overview is given on fluvial processes involved in the modelling discussed. Chapter 3 is concerned with scale models, whilst Chapter 4 deals with numerical models. The main problems treated are, firstly, modelling of the water movement, followed by sediment transport and morphology. Attention is also given to the...

Hydraulics and morphology of mountain rivers; literature survey

Present knowledge on fluvial processes in mountain rivers should be expanded to enable the development of projects dealing with mountain rivers or mountain-river catchment areas. This study reviews research on hydraulic and morphological features of mountain rivers. A major characteristic of mountain rivers is the variability of the hydraulic...

Notes on the mathematical modelling of alluvial mountain rivers

The ability of describing and predicting hydraulic and morphological phenomena in mountain rivers is limited, partially due to the limits of deterministic approaches where stochastic effects in sediment supply and water inflow are extremely significant, and partially due to the very specific conditions that can be observed in mountain rivers,...

Analysis of the transport of a pollution cloud in the Upper-Rhine River between Lake of Constance

In the one-dimensional 'Rhine Alarm Model' differences between the actual travel time of a pollution cloud, originating from an instantaneous release of an accidental spill, and the travel time, based on the flow velocity is represented by a lag coefficient. In the model this lag coefficient is defined by the relative difference between these...

A study on one-dimensional and discontinuous river flows with mobile beds

This report focusses on discontinuous behaviour of hydraulics and morphology in rivers. The varying widths, slopes and bed levels that can be observed in mountain rivers can induce rapid, or discontinuous changes at a short lengthscale. When present, these discontinuities have a major impact on changes in water and bed levels during floods. In...

Advection models of longitudinal dispersion in rivers

A derivation is presented of a general cross-section averaged model of longitudinal dispersion, which is based on the notion of the advection of tracer particles. Particle displacement length and particle travel time are conceived as stochastic variables, and a joint probability density function is introduced to arrive at an integral advection...

One-dimensional models for mountain-river morphology

In this report, some classical and new simplifications in mathematical and numerical models for river morphology are compared for conditions representing rivers in mountainous areas (high values of Froude numbers and relatively large values of sediment transport rates). Options for simplification are summarized based on time scale of hydrographs...

The effect of groynes on rivers: Literature review

Groynes are structures constructed at an angle to the flow in order to deflect the flowing water away from critical zones. They are made of stone, gravel, rock, earth, or piles, beginning at the riverbank with a root and ending at the regulation line with a head. They serve to maintain a desirable channel for the purpose of flood control,...

Environmental flow requirements for rivers: An integrated approach for river and coastal zone management

Sediment exchange between the main channel and the groyne fields of a river

Report on a physical scale model test in the Fluid Mechanics lab on the effect of groynes on the bed and sediment transport in rivers.