Longshore sediment transport in the surf zone plays a considerable role in the long-term morphological behaviour of the Belgian coast. Based on previous efforts (Zimmermann et al., 2013b; Zimmermann et al., 2013), this report firstly presents a 2D numerical model which covers almost the entire Belgian coast from Nieuwpoort to the Zwin. With the MorMerge online-parallel approach the time horizon for modelling long term morphology in the surf zone was successfully increased to 10 years. Compared with the measurement data, most major morphological changes in the surf zone are well captured qualitatively by the 2D numerical model with an exception of the sedimentation in the Baai van Heist. The modelled sedimentation/erosion is further quantitatively compared with beach accretion/erosion trends of the last 25 years reported in Houthuys (2012). This model still shows a reasonable agreement and its quality is discussed. The sedimentation in the Baai van Heist is specially investigated by an updated 2D and later a new 3D model. For a further validation of the model used in this study, another 3 models OKNO, Zeebrugge and MU-HEIST are introduced and their results are compared with that of the model used in this study. After a series of sensitivity tests a roughness map is employed to update the 2D model, but the updated 2D model seems to be still unable to reproduce the sedimentation in the Baai van Heist properly, especially from the quantitative point of view. To avoid the Gallapatti time scale, a new 3D model is built up, and driven by boundary condition of full spring-neap tides rather than representative ones imposed in the 2D model. With the technique of time-varying MorFac and multiple sediment fractions, the 3D model shows a quite good potential to reproduce the sedimentation in the Baai van Heist. Based on the promising result produced by the 3D model, additional work is proposed for further investigation and research in the future.