This paper presents a new set of physical model tests on wave propagation over complex coastal bathymetry and wave overtopping. These relate to a coastal defence with a steep front wall and a setback wall. The experimental measurements are reproduced numerically using the SWASH model. Experimental measurements are also compared to state-of-the-art numerical and analytical methods of predicting wave overtopping (Artificial Neural Networks, EurOtop equations). Considerable discrepancies between experiments and predictions are observed. These are resolved using a newly proposed method, which adapts theoretical predictions to measurements. Finally, this method is verified against additional experimental data and is shown to provide an effective way to define
adaptations to existing infrastructure to satisfy engineering design criteria.