Caracterización e dinámica dos coídos nas costas de Galicia

Characterization and dynamics of boulder beaches in Galician coast
Coídos are beaches composed of cobbles and boulders that are usually found in association with cliffs and rock platforms, particularly in granite-dominated areas. They consist of accumulations of heterometric, predominantly boulder-sized clasts, often between 1 and 2 m and even with their main axis exceeding 2 m in some areas. The best examples of coídos are found in the area known as Costa da Morte, located north of Cape Vilan (Camariñas, A Coruña); in the Corrubedo area (Ribeira, A Coruña), and along the stretch of coastline located between Cape Silleiro and the Miño river estuary (Baiona, Oia, O Rosal, and A Guarda, in Pontevedra).
According to their shape from top view, five broad types have been defined: longitudinal, double-pointed, arched, corridor-like, and single-pointed. Genetically, four types can also be distinguished: those derived from
granite exhumation processes; those generated by the dislodgement of rock fragments from shore platforms and sea cliffs; those produced by rockslides, and those originated by glacial deposition. Their genesis is often
of multiple origin.
In order to study boulder mobility, a micro-drone was flown at low heights over two coídos, one in Laxe Brava (Ribeira, A Coruña) and the other in Oia (Pontevedra). Flights were carried out in July 2012, May 2013, and
April 2014. These flights yielded ortophotographs and high-resolution digital terrain models (DTM), which were integrated in a GIS and used to monitor thousands of cobbles and boulders for changes in their position.
Maximum storm wave height was greater during winter 2013-2014 than during winter 2012-2013, resulting in an increase in the proportion of moved boulders from 17 % to almost 48 % in Laxe Brava and from 53 % to
almost 88 % in Oia.