Subaerial and subaqueous dynamics of coastal rockfalls

In spite of the hazard represented by rockfalls in coastal areas, few investigators have studied the movement of rocks falling in water. This work describes a model for the propagations of coastal rockfalls, i.e., blocks detaching from a subaerial cliff, propagating initially in air, impacting against the water surface, and finally coming to rest in the water basin. Application of the model to two real cases in Italy shows a satisfactory agreement between the predicted rockfall run-out and the field data. Some scattering observed in the data is explained as the consequence of different heights of the source area. It is shown that largest boulders usually reach a longer distance. However, the schematic shape for blocks adopted in the model likely results in a much more regular behaviour compared to reality.