Longshore transport of coarse-grained material

Abstract

The consortium Projectorganisatie Uitbreiding Maasvlakte (PUMA), consisting out of Van Oord and Boskalis, constructed a hard sea defence for the protection of Maasvlakte 2, which is the expansion of the Port of Rotterdam. This hard sea defence consists of a Dynamic Rock Slope (DRS) with a Block Dam (BD) situated in front of it. The BD is build up out of large concrete blocks which were recycled from Maasvlakte 1. The DRS behind it protects the hinterland through an approximate three to four meter thick layer of quarry rock. When waves travel obliquely through this Block Dam and interact with the DRS, stones are transported in alongshore direction. This process is called Longshore Transport (LT) and will have erosion and accretion of stones to effect along the DRS. In order to maintain the layer thickness of this stone layer, PUMA made a prognosis on LT for the coming 50 years after construction. From this prognosis a nourishment campaign was set-up, consisting of volumes of stone PUMA expected to nourish every 2.5 years. After a maintenance period of five years it was concluded by PUMA that the nourishment volumes were lower than expected. Therefore this thesis assessed where differences in the prognosis of PUMA on LT and the observed LT rates over the period 2013 to 2018 come from. Within their prognosis, PUMA made use of a dimensional LT relation. As this specifically calibrated Longshore Transport relation is only applicable for the computation of LT rates at a structure containing the characteristics of the DRS at Maasvlakte 2, this research looked into the possibilities of using a non-dimensional Longshore Transport relation for the computation of Longshore Transport rates at the DRS of Maasvlakte 2.