This work presents a model which allows considering the interaction between rockfill dams and the water. The fluid behaviour is analyzed on an Eulerian fixed mesh. A level set technique is employed to tack the evolution of the free surface. An edge based approach is used to solve efficiently the modified form of the Navier‐Stokes equations. The dam response is evaluated on a Lagrangian moving mesh using PFEM. A visco‐rigid constitutive model is used to describe the structural behaviour and collapse of rockfill under fluid dynamic forces. Mohr‐Coulomb is the failure criteria adopted in the calculation. Finally a nodal projection algorithm allows the transferring of information through non matching meshes.