Morphological monitoring of a nourishment at Mariakerke

The monitoring of the pilot nourishment executed at Mariakerke coastal area for comparing the morphological response to a combined beach and shoreface nourishment and to a beach nourishment took place from the start of the pilot nourishment in 2013 until 2018. Comprehensive data sets containing topographical (LIDAR and beach profiles) and bathymetrical (single and multibeam) measurements carried out at the study zone area have been analysed in order to evaluate the efficiency of the nourishments. Large part of the deployed sand is still in the area three years after the nourishment was carried out. The morphological trends show erosion in the intertidal beach, accumulation on the dry beach and re-organization of the shoreface nourishment into one or two submerged sand bar. Numerical modelling proved that this sand bar attenuates the wave height during stormy events both at low and high tide. The large space created south-west from the Ostend port through its extension in 2011 accommodates much of the sand eroding from the two coastal areas of the pilot site. The shoreline advanced towards the sea immediately after the nourishments and it maintains similar position after three years. The dominant process for the beach evolution was the cross-shore transport immediately after execution, but alongshore transport became dominant on the medium and long term and it was calculated to have a net rate of 150 000 to 200 000 m3 in the north-east direction.

Topobathymetrische evolutie

The digital elevation model comparisons: a) difference between 2014 and 2013; b) difference between 2017 and 2013; c) difference between 2017 and 2014.