Dune stochastics in river morphodynamics


Astrid Blom

Gary Parker (USA)


University of Twente




1 April 2004 – 1 January 2008


In a densely populated and lowland country as the Netherlands, there is an increasing need for adequate tools that predict water levels in rivers during flood events. One of the main factors influencing water levels is the bed roughness, which is mainly determined by bed-form dimensions and the composition of the riverbed surface.

Dr. Blom has introduced a new way of modelling the vertical sorting of river bed material and thus the composition of the river bed surface during his PhD research. The upper active part of the river bed is no longer represented by a discrete layer, but by a probability density function of active bed elevations. Accounting for the stochastic of river bed deformations, this new sediment continuity model is the first to describe the complex interaction among dune dimensions, sediment transport, vertical sorting, and river morphodynamics.


The project further extends the sediment continuity model and makes it applicable to realistic situations with free evolution of the mean bed level. This extension is required to make the model suitable for predictive river studies, such as the prediction of the effects of the river measures proposed by De Maaswerken for the river Meuse. The study involves new flume experiments to be conducted at the US National Center for Earth-surface Dynamics in order to provide data for model validation. As a field case-study, the model will be applied to the 1993 and 1995 floods in the river Waal.

The model’s stochastic approach will enable proper modelling of the complex interaction between vertical sorting and river morphodynamics. As such, the study will improve existing tools for predicting morphological changes and water levels in rivers during flood events.