For the development of the Dangote Oil Refinery near Lagos/Lekki, Nigeria, a land fill of about 30 million m3 is required. The fill material consists of sand that is being dredged offshore and pumped ashore by means of hydraulic transport. The dredging and land fill activities are executed by Jan de Nul Dredging and started early October 2015. Shortly after the start of the works, erosion of the coastline was reported on the east side of the landfall of the sinker lines. In the vicinity of the sinker lines accretion was observed. Jan de Nul requested CDR, with partner Svašek, to assess the causes of the erosion and to propose remedial measures. They have assessed the causes of the erosion and proposed remedial measures. A site visit was undertaken, followed by a desk and numerical model study.