A smart approach to sand and mud in the Wadden Sea
During the next few months, the Wadden Sea between the Friesian coast and Ameland will be the subject of a project undertaken by researchers from TU Delft and Utrecht University. Measuring equipment in the channels and on the mudflats will help explain the interaction of water, sand, and mud. How can we keep the valuable sand and mud in the Wadden Sea, but at the same time keep the navigation channels open?
The researchers are keen to gain a better understanding of how the channels and mudflats are formed. This is because there is too much sand and mud in the navigation channels in the Wadden Sea. Accessibility through the channels for ferries and other vessels is made possible by dredging. Nonetheless, there is much to be said for taking care of this sand and mud, as it is needed to accompany the rise in sea levels; it also provides a unique and valuable intertidal zone.
Smart dredging
In the coming months, Roy van Weerdenburg, Coastal Engineering PhD candidate at TU Delft, will be monitoring the movements of sand and mud in the Wadden Sea. “Sand and mud can be found on the mudflats and in the channels, but actually, there are still many aspects about their interaction that we do not yet fully understand. We would like to use that knowledge, for example, to identify locations where dredged mud stays where it is or moves elsewhere in the Wadden Sea. What we are hoping for is a decrease in the amount of mud that ends up more or less straight away in the channels used by sailing vessels.” Rijkswaterstaat is following the research with great interest and is hoping to gain fresh insights into how to keep the channels navigable in a sustainable manner.
Sticky layer
Van Weerdenburg is particularly curious about the effect of quiet storm-free periods. Mud that has been on the mudflats all summer is often much stronger, partly because of a sticky layer of algal mats. “If we can learn more about this sticky layer, then we can factor it in when dredging and disposing mud, to enable it to remain more reliably on the mudflats during the stormy winter months.”
Mobile lab
To answer these questions, frames will be installed in the next two months in the channel and on the mudflats that will measure, among other things, the flow velocity and the concentrations of sand and mud in the water. Van Weerdenburg will also be taking samples from the sea bed of the mudflats for erosion tests. With the greatest of care, he will be taking them to TU Delft’s mobile lab, for this research project temporarily installed on the pier in Holwerd. In a controlled environment, he will test how the sediment moves under the influence of flowing water.
Eventually, the data will be incorporated into models, so that various future scenarios can be investigated in more detail.
This measuring campaign is part of the Dutch Research Council’s WadSED Perspectief Programme, under the leadership of Utrecht University. The project sees various knowledge institutes, businesses, nature organisations, and government bodies working in partnership to gain a smarter understanding of sand and mud.