Resumo

CARMO, José Simão Antunes do. Recovery experience of a dune system and complementary instruments proposal of protection, attraction, and environmental enhancement. RGCI [online]. 2013, vol.13, n.3, pp.317-328. ISSN 1646-8872.  https://doi.org/10.5894/rgci394.

The serious problems in most countries with extensive coastal zones are in some way, directly or indirectly linked to the progressive urban occupation of these areas, resulting in a strong degradation of many natural protection structures that exist. Simultaneously, it is also clear that activities and interventions of anthropogenic origin (such as the construction of dams, holding of inerts in rivers and dredging operations in ports) have contributed to strongly disturb these systems, notably through a significant reduction of sediment supply. Accordingly, these actions threaten the ability of the coastal areas to adapt to the increasing frequency and intensity of storm events, as a result of global climate change and the expected increase in the average sea level, which will inevitably lead to a pronounced erosion and to the consequent retreat of the shorelines. Knowing that banning the uses of coastal zones is not a solution to the serious constraints that exist, it is then necessary to recover them with the necessary infrastructures in order to guarantee that their intensive uses are not necessarily synonymous of degradation. The Leirosa sand dune system, located at south of Figueira da Foz, has been the scene of three major dune rehabilitation interventions in the past twelve years. The first involved the reconstruction of the sand dunes followed by revegetation using native marram grass. The effectiveness of this rehabilitation technique could not be confirmed, since the ocean side of the dune system was destroyed at the end of the winter of 2000-2001. In the other two interventions, two different applications of geotextiles were used. The first technique consisted in constructing several layers of sand enclosed in geotextiles, a so-called wrap-around technique, which stabilizes the sand and is quickly installed. The second technique was employed to protect the toe of the constructed barrier, which entailed the use of geotextile tube technology. The lessons learned with the methodology used for the rehabilitation and protection of the Leirosa sand dunes allowed to address new protection concepts, incorporating multi-functionality and environmental enhancing. It is in this context that we propose the implementation of multifunctional artificial reefs as alternative or complementary technique to traditional heavy protections. Examples of success are known, but there are not yet sufficiently detailed and systematic studies so that this kind of constructions could be generalized along the coastal zones, particularly with the dual aim of protecting them and improving the characteristics of many of their bathing spaces. Therefore, the main focus of this paper is to present a short description of the works carried out in Leirosa, and to propose a complementary protection using the same material, but in submerged conditions and with a suitable geometry, in order to take advantage of the changes occurring in a wave when propagating from deep water conditions to shallow waters.

Palavras-chave : Dune system of Leirosa; Multifunctional artificial reefs; Surfing; Diving; Fishing; Environmental enhancement.

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