"Hazardous violent free surface flows are regularly observed at coasts in connection with storm surges or tsunami and inland in connection with embankment / dam failure. At these instances, the motion of the water results in the pick up of (artificial) debris either directly from the ground or after destroying man-made infrastructure which lies in the pathway of propagation. That debris is advected by the flow over significant distances. In this regard it is unknown how single debris objects are picked up and how they eventually distribute spatiotemporally within the front of such a bore that is propagating over dry or wetted ground. It is equally unknown how large the forces of multiple debris are that exert to man-made structures with respect to the actual debris-burden in the bore front. Few guidelines exist to incorporate floating or submerged debris into design and no evidence is given for multi-object impact. Therefore, the stated questions will be studied by experimental and numerical means. Experiments will be based on dam-break and very long waves which may reproduce natural flows in a laboratory. Distribution of debris and the pick up process will be measured by means of innovative techniques (accelerations/inclinations and radio waves) in conjunction with a SME. Measurement of forces will allow for correlation of multi-object impact and structural loading. In addition, the meshless numerical tool ""smoothed particle hydrodynamics"" will be applied to reproduce laboratory conditions for validation. The tool will be enhanced in order to account for the pick up of debris objects from the ground. This will enable the simulation of additional impact/load combinations. Eventually, it is hoped for the development of engineering design formula to predict appropriate structural loadings in order to contribute to the safety and stability of buildings as well as to help mitigating natural hazard effects."