Damage evolution of rubble-mound breakwaters based on aerophotogrammetric surveys

Abstract

Due to its extensive coastal zone, Portugal owns many related maritime structures, the most common of which are breakwaters that usually protect man-made harbours. These maritime structures, especially rubble-mound breakwaters, are assumed to be at risk in the design proccess, due to the load they can withstand. Therefore, at some point in the life of the marine structure, repairs will be required, and monitoring programs are deemed of paramount importance in assessing damage evolution of such structures. The use of an UAV (Unmanned Aerial Vehicle), or drone, has enriched ongoing LNEC’s Systematic Observation of Maritime Works program (OSOM+) (Capitão et al., 2018). Since 2018, this methodology has been applied to all breakwaters of the Port of Sines (Fortes et al., 2019), as well as Portimão and Faro-Olhão inlet breakwaters (Lemos et al., 2020). More recently, in early 2022, under the scope of To-SeAlert and BSafe4Sea projects, an aerial survey of the breakwater of Ericeira harbor has been conducted. Using previous aerial surveys of that breakwater, carried out in 2013, 2018 and 2022 it is now possible to make a study on the evolution of this protection structure. The purpose of this paper is to present the results on this evolution and to clarify the additional capabilities of the surveys obtained by drone, in addition to the conventional information of terrestrial visual observations