Wave Run-Up on a Rubble Mound Breakwater: prototype measurements versus scale model tests

Physical processes such as wave run-up and wave overtopping are very important with regard to the design of sloping coastal structures. However, these are not yet fully understood. Preliminary prototype measuring campaigns (1993-1996) indicated clearly higher wave run-up values than the values found by laboratory testing and reported in literature. The design of the crest height of a breakwater is mainly based on wave run-up values obtained by small scale model tests. Prototype measurements are seen as the big challenge to be addressed to verify small scale model test results. Therefore, a rubble mound breakwater protecting the outer harbour of Zeebrugge (Belgium) and armoured with 25 ton grooved cubes is fully instrumented to measure sea state, wave run-up and wave overtopping. Wave run-up is measured by two different measuring devices. Extensive laboratory testing is carried out on two t-o dimensional models (1:30) and on one thr-e dimensional scale model (1:40). For a better determination of wave run-up on the scale models, a novel step gauge is developed. Still, differences between results of prototype measurement and small scale model test results and between the various laboratory results are noticed.