Overtopping events in breakwaters: comparison of 2D physical experiments and empirical formulae

Abstract

Reliable prediction of wave run-up/overtopping and structure damage is a key task in the design and safety assessment of coastal and harbor structures. Run-up/overtopping and damage must be below acceptable limits, both in extreme and in normal operating conditions, to guarantee the stability of the structure as well as the safety of people and assets on and behind the structure. The mean-sea-level rise caused by climate change and its effects on wave climate may increase run-up/overtopping events and make the existing coastal/harbour structures more vulnerable to damage. Accurate estimates, through physical modelling, of the statistics of overtopping waves for a set of climate change conditions, are needed. Project HYDRALAB+ (H2020-INFRAIA-2014-2015) gathers an advanced network of environmental hydraulic institutes in Europe, which provides access to a suite of environmental hydraulic facilities. They play a vital role in the development of climate change adaptation strategies, by allowing the direct testing of adaptation measures and by providing data for numerical model calibration and validation. The use of physical (scale) models allows the simulation of extreme events as they are now, and as they are projected to be under different climate change scenarios. The experimental work developed at LNEC within HYDRALAB+, TASK 8.2 of RECIPE, entitled “Damage characterization under variable and unsteady test conditions”, considers 2D damage and overtopping tests for a rock armor slope, with four different approaches to represent storms: a standard cumulative storm build-up (with increasing wave heights) with increasing water level; a standard cumulative storm build-up with a constant water level; a constant wave period; and a standard storm build-up, with a constant water level and with rebuilding. This paper presents a comparison of measured (physical model tests) and predicted (empirical formulae) mean overtopping discharges and individual overtopping volumes at a cross-section of a rubble mound breakwater.