Master Thesis presented by Eduardo Loureiro, 2000

Abstract
The knowledge about the dynamics and evolution of shingle beaches is still limited, despite the fact that are very important areas of coastal zones around the world.
This dissertation intends to contribute to a better understanding of short and medium-term evolutionary processes which are fundamental in each area, as well as their rythm.
The study focusses on an area of Esposende coastline (Belinho), in the North-west of Portugal, because today it represents a different reality when comparing with others shingle beaches located north of Viana do Castelo.
During the past year, the sandy beaches of Esposende have being gradually replaced by shingle beaches. Their presence is now almost permanent in this sector of the coast. The beach of Belinho (Esposende) was chosen as a representative area and monitored during the past year. It lies about 5 km north of the Cávado river mouth, and has an extension of about 3 km, almost up to the Neiva river mouth.
The morphology of the beach changes in relation to the wave climate, particularly to the incidence of edge-waves associated to the plunging breaker wave type. Three main types of morphology were observed: 1) beach ridges associated with ridge-and-runnel systems; 2) beach ridges, beach cusps, and ridge-and-runnel systems; 3) multiple systems of beach cusps of different wavelength. In all situations pebbles and cobbles are largely dominant over the sand.
Apart from the changing morphology, the net trend of the beach is erosive. Its undercutting now shows several, formerly inexistent rocky outcrops at low tide, and a strong recession of the sandy cliff at the backshore. After storms, pebbles and cobbles can be observed against the sandy bluff and the beach presents a very steep gradient. During the period just after a storm, the beach frequently displays a sandy cover that results from the recession of the bluff. This sandy cover disappears sooner or later, leading to the shingle beach situation.
The mainly quartzite pebbles and cobbles have different origins. Some of them are derived from emerged outcrops, but others have no equivalent on land, being probably derived from submerged outcrops on the shelf.
Taking the sedimentation model of Bluck (1967) as a base, a comparison is made with the Belinho beach, and analogies and differences are pointed out.
Concerning Environmental Education issues, several activities explaining the main morphodynamic changes occurring in this coastal zone, were organised for local groups like secondary school and Comunity, APPLE (Área de Paisagem Protegida do Litoral de Esposende) and Environmental Assotiations. Part of this dissertation was used as a chapter for the book "Ecology and Geomorphology of Coastal Shingle" edited by Packham, Randale, Barnes and Neal, European Union for Coastal Conservation (EUCC), to be published in 2000.