Process-based modeling of sediment transport under waves in the sheet-flow regime


Type

PhD-research


Persons involved:

Ir. W.M. Kranenburg (PhD student)

dr.ir. J.S. Ribberink

dr.ir. R.E. Uittenbogaard (Deltares

prof. dr S.J.M.H. Hulscher (promoter)


Funding

Partly from the European Union projects SANDS and SANTOSS and partly by the University of Twente.


Duration

2008 – 2012


Summary

Under high waves sand in the surf-zone is transported by sheet-flow. The main characteristic of this phenomenon is that the motion of sediment extends down to several grain diameters below the initial bed level. The moving layer with high concentrations of sediment is held responsible for the larger part of the sediment transport. Knowledge on sediment transport is of major importance to predict the development of coastal systems and to assess the influence of human intervention. In the last two decades measurements in wave tunnels and flumes and modeling activities on increasing level of detail have been carried out to study the sheet-flow phenomenon.


The main objective of this Ph.D.-project is to develop a numeric process-based model that predicts sediment transport under waves in the sheet-flow regime by solving velocity and concentration profiles down to the stationary bed. A second objective is to assess the effects and relative importance of various processes for sediment transport by application of the model as a research tool on cases with various hydrodynamic and morphological conditions. An important question is e.g. how the hydrodynamic differences between wave tunnels and wave flumes influence the sediment transport, because formulae presently used in morphodynamic models are mainly based on experimental results from tunnels, while the flumes form a more realistic representation of reality. A third objective is to provide morphodynamic models on engineering length and time-scales with the newly obtained insight in transport mechanisms and rates.