Analysis of the incident sea-waves and of the consequent run-up in the RODBreak experiment

Abstract

In 2017, the RODBreak experiment was conducted. The experiment aimed at characterizing wave run-up, overtopping and damage in rubble-mound breakwaters. The reason for these experiments was the huge impact that climate can have on maritime structures, particularly in rubble mound breakwaters. In fact, the forecast sea level rise associated with more frequent and severe storms will have consequences either on the increase of wave runup, wave overtopping or on damage on existent structures since they were not design for those extreme values. However, for those climate change scenarios, little is known about the actual failure probability of such structures. Within this framework, a stretch of a rubble-mound breakwater was built in a wave basin. Under extreme wave conditions, with different incident wave angles (from 40° to 90°), a total of 49 tests were performed. Each test had different testing parameters, such as significant wave height (Hs), peak period (Tp) and wave direction. Also, for each test, different types of measurements were considered. Incident sea waves were measured with 3 arrays of 6 acoustic wave probes each as well as with isolated acoustic wave probes and 5 Acoustic Doppler Velocimeters (ADV’s). For the run-up measurements five capacitive wave probes 0,87 m long, were placed along the model slope, 3 at the breakwater trunk and 2 at the breakwater roundhead. The analysis of the data from acoustic wave probes, as well as ADV’s was carried out with two different methodologies: the first one uses the SAM package (Capitão 2001), whereas the second uses a MATLAB script (Pinheiro, 2019) with the DIWASP (DIrectional WAve SPectra) plugin (Johnson, 2002). To convert the capacitive wave probes measurements into run-up data, simple geometrical relationships were taken into consideration. This paper focuses on the methodology for incident wave characterization since there is little experience at LNEC with the short-crested sea states as the ones used in this experiment. The evaluation of the impact on wave runup by considering different wave attack is also made.