Browsing by Author "Ferreira, Mónica Patrícia Pereira Raposo"
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- Coastal risk assessment associated with cliff evolution and management proposals between Galé and AlbufeiraPublication . Ferreira, Mónica Patrícia Pereira Raposo; Ferreira, Óscar; Loureiro, CarlosCoastal areas are densely occupied and inhabited, being susceptible to suffer consequences of extreme events (storms, sea level rising, etc.). The combination of hazard (event) and exposure (occupancy) creates a significant, relevant and, in some cases, threatening potential risk. These events can cause serious implications at all levels (social, economic and environmental). The Algarve region, in Portugal, is often considered as one of the most appealing regions for tourism in the country, contributing to increase the pressure on coastal areas and, consequently, increasing the coastal risk. This dissertation presents an assessment of coastal risk associated with the evolution and development of rocky cliffs, as well as the analysis and definition of management procedures and proposals for the coastal sector between Galé and Albufeira. Throughout the dissertation, different risk factors were assessed, which may endanger the existing population and buildings in a particular area of the coast – cliff top section - in respect to a specific hazard – slope mass movements in cliffs. To accomplish this, the methods presented here combined two complementary analyzes: (i) Coastal Index calculation, based on the detailed mapping of the cliff top line, the areas associated to different hazard degrees according to mass movements return periods and existing variability in occupancy; (ii) analysis of coastal risk management procedures along with definition of mitigation proposals, based on the analysis of the hotspots present on the study area. In order to complement the analysis, an assessment of the existing management measures was carried out, evaluating its agreement with the present risk and new measures to reduced it were proposed. The results obtained indicate that very low and low risk were dominant along the study area. The hazard index, for a return period of 100 years, until extends to 67 m landward of the cliff top, but the exposure index along the area is generally low, notably for the transport and infrastructure components. In the areas where the risk was medium and high, eighteen different properties/structures were highlighted and considered as hotspots and further subjected to detailed analysis and proposal of management measures. These measures should be adjusted according with the relevance of each structure, and include relocation of hotels, residences and the restaurants (under a high risk) to areas outside the protection area defined by Planos de Ordenamento da Orla Costeira, designed by POOC (the recent Planos da Orla Costeira – POC). The other restaurants, parking areas, roads and small gardens should be relocated to the area between the 48 and 67 m landward of the cliff top. Since relocation measures face difficult social acceptance, relocation and removal of properties from the protection area should be phased, as licenses are due to come to an end, not allowing residences and other properties to be resold. It is also essential the creation of a policy to promote a devaluation of property within the risk zone and incentive the removal out of protection area. Additionally, in order to improve the information to the public about the coastal risk, the number of signs that warn to the rockfall hazard should be increased alongside the adjustment of the existing information posters on the beach entrance to highlight the hazard zoning on the cliff top upper area. In future research, in order to improve the proposed methodology for risk assessment, other components can be included on the coastal index calculation, such as the incorporation of the economic value and vulnerability associated to structures and residents on the coastal index, as well as the wave exposure and cliff lithology on the hazard index.