Wind, Water, Wadden Sea

A study regarding the influence of wind direction and wind speed on water levels in the Dutch Wadden Sea

Sjoerd Schouten Faculty of Science Future Planet Studies / Earth Sciences Student ID: 5984831 Supervisor: prof.dr.ir. W. (Willem) Bouten Amsterdam, 10th of August 2011

Abstract

The aim of this research is to asses the influence of wind direction and wind speed on water levels in the Dutch Wadden Sea. The research is executed using the Delft3D-FlOW model with a working 2D Wadden Sea module, provided by research institute Deltares, showing the distribution of water at different wind scenarios for the entire Wadden Sea. Displaying which areas are most responsive to wind factors, as well as variations in water level for two specific locations. Herman et al (2007, 2009) already proved that there is a significant correlation between wind factors and water levels; however this study was not yet applied to the Dutch Wadden Sea. Several wind scenarios are developed and run by the model. The output is analysed through two different methods; an analysis using map data, and a location based analysis, as well as statistically tested. The map analysis shows the influence of wind directions at two different wind speeds for the entire Dutch Wadden Sea at low and high tide. This method shows the distribution of water with the corresponding wind variables, compared to a no wind scenario. The scenarios used, contain a constant wind direction and wind speed. The second method is location based, showing water level variations for a period of one month for two locations, namely Vlieland and Harlingen. The scenarios used in this method contain variable wind directions and wind speeds. Again a no wind scenario is used as a reference. Both methods show a significant influence considering wind direction and wind speed on water levels in the Dutch Wadden Sea. Differences up to 1.7 meter compared to the no wind scenario, were simulated. The distribution of water depends on the wind direction, where westerly originated winds result in overall higher water levels and easterly winds result in overall lower water levels in the Wadden Sea. Wind speed defines the amount of this difference, where higher wind speeds result in higher differences in water levels compared to the no wind scenario. Astonishing is the effect of (local) bathymetry which, depending on wind direction and especially during low tide, could have great influence on the distribution of water.