Novel particle method for modelling the episodic collapse of soft coastal bluffs

This paper presents a new, novel, particle-based Bluff Morphology Model (BMM), and with it investigates the stability, collapse, and equilibrium position of soft coastal bluffs (cliffs). This model combines a multiple wedge displacement method with an adapted Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. At first, the wedge method is applied to compute the stability of the bluff. Once the critical failure mechanism of the bluff slope has been identified, and if the factor of safety for the mechanism is less than 1, the adapted WCSPH method is used to predict the failure movement and residual shape of the slope. The model is validated against benchmark test cases of bluff stability for purely frictional, purely cohesive, and mixed strength bluff materials including 2D static water tables. The model predictions give a good correlation with the expected values, with medium resolution models producing errors of typically less than 2.0%. In addition, the prediction of lateral movement of a surveyed cliff and the dynamic collapse of a vertical bluff are computed, and compare well with published literature.