Shoreface migration Dutch coast decreases after nourishments
At the end of November, David Barmentloo successfully completed his MSc thesis at the University of Twente. David graduated on an assignment from the Building with Nature project. The subject of his thesis is pre- and post-nourishment morphological behavior along the Dutch and Danish North Sea coast.
Migration along the Dutch coast is decreasing
Results from David's research show that before the implementation of nourishments along the coast of the Netherlands, nearshore sandbanks migrated offshore, with the most seaworthy bar dying off offshore while forming a new bar near the coastline. This resulted in bar cycle return periods of 15 and 3-4 years respectively north and south of the harbor moles of IJmuiden. After the use of shoreface nourishments, this offshore migration decreased or stagnated for 1 to 13 years.
Migration along the Danish coast is not affected
Along the Danish Midtjylland coast, generally offshore migrating shore-oblique sandbars were observed. The sandbanks have a length of about 6-10 km and are attached to the coast in the north and extend seawards in the south. The observed bar migration prior to the implementation of nourishments forms a noisier and more irregular pattern than observed along the coast of the Netherlands. No consistent influence of sand nourishment on the bar migration has been found for the Danish site.
Dutch and Danish coast analysed
For the Msc thesis, David researched a large dataset with annual cross-country profile measurements. He did this to improve understanding of nearshore morphological behavior and to gain insight into the differences within the North Sea region. He also assessed the effect of coastal nutritional supplements on nearshore morphology, including sandbar migration. In this study, the Dutch and Danish west coast were analysed over a period of more than 50 years. The dataset used came about in collaboration with Belgian, Dutch, German and Danish coastal authorities in the Building with Nature project.
Photo credits: https://beeldbank.rws.nl/, Rijkswaterstaat