How Tides and Waves Enhance Aeolian Sediment Transport at The Sand Motor

Bas Hoonhout1, Nicholas Cohn2, Sierd de Vries1, Jan Adriaan Roelvink3, Peter Ruggiero2, Reuben Biel4, Orencio Duran Vinent5 and Evan B Goldstein4, (1)TU Delft, Delft, Netherlands, (2)Oregon State University, Corvallis, OR, United States, (3)UNESCO-IHE Institute for Water Education, Delft, Netherlands, (4)University of North Carolina at Chapel Hill, Geological Sciences, Chapel Hill, NC, United States, (5)Marum, Bremen
Abstract:
The Sand Motor is an artificial sandy peninsula extruding from the Dutch coast about 1 kilometer into the North Sea (Stive et al., 2013). It is virtually permanently exposed to tides, waves and wind and is consequently highly dynamic. In order to understand the complex morphological behavior of the Sand Motor, it is vital to take both subtidal and subaerial processes into account.

About 70% of the Sand Motor area is located above 2m+MSL and is therefore uniquely shaped by subaerial processes. These dry areas are hardly eroded due to the presence of a coarse sand armor layer that was naturally established over time. However, significant aeolian transport is observed originating from the intertidal beaches surrounding the Sand Motor. Due to periodic flooding no armor layer can be established in the intertidal zone. Consequently, subtidal processes significantly influence the subaerial morphology.

An international collaboration initiated the development of the open-source Windsurf modeling framework that enables us to simulate multi-fraction sediment transport due to subtidal and subaerial processes simultaneously. The Windsurf framework couples separate model cores for subtidal (XBeach; Roelvink, 2006) and subaerial morphodynamics (Coastal Dune Model; Duran and Moore, 2013) and multi-fraction aeolian sediment supply (AeoLiS; based on work by de Vries, 2015). Preliminary model results from a one-year one-dimensional simulation show a concentration of aeolian sediment supply from the intertidal beach area during calm conditions and an elevated aeolian activity shortly after a strong wind or surge event. The period of elevated transport may last for over a week resulting in the immediate initiation of recovery after a surge.

Here we will present an application of the Windsurf modeling framework on the Sand Motor and a detailed description on how the interaction between subtidal and subaerial processes explain its complex morphological development.

Back to: Sediment Dynamics in Coastal Settings: Observations and Modeling of Sediment Transport, Morphology, and Change on Event to Decadal Timescales III