Improved methods for morphological changes under storm-surge conditions

The Large Wave Flume (GWK) in Hannover

The main objective of WA 4 is to improve the predictions of nearshore morphological changes under storm-surge conditions, which are assumed to lead to significant erosion but still are usually neglected in long-term predictions. The dominant transport direction under storm-surge conditions is cross-shore and sediment is mainly transported in a thin layer above the bottom, the so-called sheet flow.

Existing transport formulas and numerical models usually describe the sediment using a single (mean) grain size. However, natural sediment is widely graded (i.e. consisting of a number of different grain sizes). It has been shown in previous studies that the interaction of grain sizes can lead to transport rates which differ significantly from those of a single grain size. The aim of WA 4 is the development of a transport formula which can represent the behaviour of graded sand. After many months of preparation, a series of large-scale experiments were conducted in the Large Wave Flume (Großer Wellenkanal, GWK) in Hannover in May and June 2018 to provide a solid database for the development and validation of the new formula. The new formulation will eventually be implemented in regional-scale numerical models to improve the prediction of erosion processes during storm events.

Experiments in the Large Wave Flume (GWK) and subsequent development of an improved transport formula for mixed sediment in the sheet-flow layer

Project partner: Forschungszentrum Küste, Hannover