Backward erosion piping (BEP) is a common failure mechanism of dikes. Dikes are currently assessed on this mechanism with the Sellmeijer 2011 rule, a method based on experiments with homogeneous deposits. However, the presence of tidal fines positively influences the cohesive strength of soils and the embedding of the soil grains in the soil matrix. For analytical assessment of BEP, a strength factor of 1.4 [-] is currently used in Dutch regulations to incorporate the extra strength due to tidal deposits. Tidal deposits also correlate with anisotropy in hydraulic conductivity due to the layering of tidal deposits. This influences flow patterns in the aquifer, thereby affecting the BEP process...