SCALE EFFECTS RELATED TO SMALL SCALE PHYSICAL MODELLING OF OVERTOPPING OF RUBBLE MOUND BREAKWATERS

By comparison of overtopping discharges recorded in prototype and small scale physical models it was demonstrated in the EU-CLASH project that small scale tests significantly underestimate smaller discharges. Deviations in overtopping are due to model and scale effects. These effects are discussed in the paper and it is explained why it is impossible quantitatively to identify model and scale effects by comparison of the performance of prototype and small scale models. For such identification are needed special dedicated tests. The paper presents such a test which identify the scale effect in the rubble armour on the upper part of the slope. This effect is believed to be the main reason for the found deviations between overtopping in prototype and small scale tests.