Get an overview about the project outputs and related knowledge

D1) Mixed-Size Sediment Morphodynamics

Start: 09/2014
End: 09/2018
Status: Active

Contact details

Victor Chavarrias

Delft University of Technology

Median bed surface grain size in the Pannerdensch Kanaal, c. 5 km downstream from the nourishment place (adapted from Frings, 2007).

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Project output

Insight into the origin and possible solution to the limited predictive capabilities of morphodynamic models that  account for mixed-size sediment.


Rijkswaterstaat has started a large scale nourishment field experiment in the German-Dutch border area, a part of the Rhine River specially relevant for its mixed-sediment properties. The mixed character of the sediment is a property necessary to explain physical phenomena as downstream fining of rivers, the gravel sand transition zone, the formation of bedload sheets, the evolution of bars, or bed surface armoring. When a morphodynamic model accounts for mixed-size sediment it can lose its predictive capabilities. We conduct laboratory experiments aimed at gaining insight into the origin of the problem and in search of a possible solution.

Key goals: Fundamental understanding

Innovative components

In order to predict the evolution of rivers with multiple grain sizes, we use mathematical models in which we impose the conservation of water mass and momentum and the mass of sediment of different size fractions. The conservation of sediment mass of different grain sizes poses a challenge:

  • the model needs to be simple as modelling the behavior of every single particle is de facto impossible;
  • the model needs to be complete enough to be physically realistic.

Our objective is to find the limits where the typical model describing mixed-sediment river morphodynamics is physically realistic (and thus usable). We aim at providing a model that is usable outside these limits.

Form whom and where?

Policy advisors modelling sediment management measures in sand-gravel rivers such as in the Dutch Rhine.

Data-collection methods: Numerical modeling Physical and laboratory experiments

Temporal scale: 10-50 years more than 50 years

Application and findings

  • Mathematical analysis of the typical model for mixed-sediment river morphodynamics.
  • Development of a tool into the software pachake Delft3D to numerically assess the results of simulations and their representation of the natural phenomena.
  • Laboratory experiments to gain insight on the mechanisms that are important under those conditions where the typical model fail to reproduce the natural phenomena.

Status for day-to-day practice

Our results show that the current approach to model river morphodynamics with mixed-sediment is not appropriate over a wide domain. Laboratory experiments are being carried out to assess whether the solutions we propose to improve the modelling approaches is also physically realistic. Eventually, we aim at providing a model that improves the description of the prevailing physics of mixed sediment river morphodynamics.

Spatial scale: River section

Key locations: Abroad Netherlands (NL)

Next steps

This section will be available as soon as possible.

Last modified: 19/05/2019

Explore the contact details to get to know more about the researchers, the supervisory team and the organizations that contribute to this project.

Main researcher

Victor Chavarrias

Delft University of Technology

Supervisory team

dr. ir. Astrid Blom

Delft University of Technology

dr. Ralph Schielen

Rijkswaterstaat Ministry of Infrastructure and Water Management

Prof. dr. ir. Wim Uijttewaal

Delft University of Technology

Contributing partners

As soon as available, explore the storyline to get to know more about the main methods or prototype tools that were developed within this project.

Explore the output details for available publications to get a glance of the innovative components and implications to practice as well as the links to supporting datasets.

Project outputs

Ill-posedness in modeling mixed sediment river morphodynamics

13/02/2018 by Victor Chavarrias et al.

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Contains: Dataset access

Other outputs

Jump to: Conference abstract | Report




  • Chavarrias Borras, V., Stecca, G., Labeur, R. J. & Blom, A. (2017). A strategy to avoid ill-posedness in mixed sediment morphodynamics. RCEM 2017 – Back to Italy: The 10th Symposium on River, Coastal and Estuarine Morphodynamics, Trento-Padova, 15-22 September 2017, Book of Abstracts. Lanzoni, S., Redolfi, M. & Zolezzi, G. (eds.). p. 166.
  • Chavarrias Borras, V., Ottevanger, W., Labeur, R. J. & Blom, A. (2017).  Ill-posedness in modelling 2D river morphodynamics. NCR days 2017: Book of abstracts. Hoitink, A. J. F., de Ruijsscher, T. V., Geertsema, T. J., Makaske, B., Wallinga, J., Candel, J. H. J. & Poelman, J. (eds.). Vol. NCR publication 41-2017p. 74-76.


  • Chavarrias Borras, V., Blom, A. & Stecca, G. (2016). Ill-posedness of the Saint-Venant-Hirano Model. Abstract 90221, 31st IUGG Conference on Mathematical Geophysics, Paris, 6-10 June.
  • Chavarrias Borras, V., Stecca, G., Siviglia, A. & Blom, A. (2016). Ellipticity in modelling mixed-sediment river morphodynamics. Abstract presented at the 9th Symposium of the RCEM, Iquitos, Perú, 30 Aug – 3 Sep.


  • Chavarrias Borras, V., Stecca, G., Siviglia, A., Labeur, R. J. & Blom, A. (2015). Limitations when modelling mixed-sediment river morphodynamics. In: H.J.R. Lenders, F.P.L. Collas, G.W. Geerling, R.S.E.W. Leuven (Eds.). Bridging gaps between river science, governance and management. Book of abstracts NCR-days 2015, NCR Publication 39-2015, 1-2 October 2015, Radboud University, Nijmegen, pp. 97-100.




  • Chavarrias Borras, V. and Ottevanger, W. (2016) Mathematical analysis of the well-posedness of the Hirano active layer concept in 2D models. Tech. Rep. 1230044, Deltares.

Take a look to the dissemination efforts and application experiences which are available in the news items and blogs.


Follow the pretty pebbles

01/06/2017 by Victor Chavarrias

Victor's research aims at predicting how the river will behave if water management authorities consider to add sand to the river.

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The rivers of the future initiative is taken up

30/01/2018 by dr. Ralph Schielen

RiverCare is now well on its course and is delivering great results. Rijkswaterstaat is involved in all user committees and tries to incorporate the...

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Symposium on River, Coastal and Estuarine Morphodynamics 2017 in Padova (Italy)

Seven intrepid researchers took part on one of the most important conferences on the field.

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RiverCare was featured on the DeltaLink edition about rivers

01/10/2016 by dr. ir. Astrid Blom

The Room for the River programme aimed at increasing flood safety by creating space for water. However, when considering integrated management, there are other...

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