EROSIVE EVIDENCES IN “SANTA CATARINA” ISLAND BEACHES
Transcrição
EROSIVE EVIDENCES IN “SANTA CATARINA” ISLAND BEACHES
Proceedings of the 12th Biennial Coastal Zone Conference Cleveland, OH July 15-19, 2001 EROSIVE EVIDENCES IN “SANTA CATARINA” ISLAND BEACHES, SC, BRAZIL Norberto Olmiro Horn Filho, Universidade Federal de Santa Catarina* Paulo Cesar Leal, Universidade Federal de Santa Catarina* João Sérgio de Oliveira, Universidade Federal de Santa Catarina* Fernando Luis Diehl, Universidade do Vale do Itajaí* Keywords: Coastal erosion, beach, “Santa Catarina” island, Brazil INTRODUCTION Beaches constitute representative geomorphologic feature of the coastal environment. Several works have been accomplished in beaches along of world shorelines, focalizing different geological aspects related to morphology, sedimentology and morphodynamic, objectifing to study the processes, causes and consequences of the coastal erosion. Coastal erosion is associated to several causes and processes, compreeending: oceanographic influence of coastal hydrodynamics (waves, currents, tides, winds); relative sea- level changes; climactic oscillations during the Quaternary; anthropic interference along the coast and decreasing of sediments originated of continental areas. These factors produce relative shortage of sediments along of coastlines. Erosive evidences are usual in brazilian beaches, associated to natural or anthropic origin, resulting in most of the situations in consequent desestabilization of the fragile balance of theses ecosystems. The beaches have been studied by brazilian researchers aiming elucidate the coastal erosive processes, identifying their causes and consequences. In “Santa Catarina” island, the studies are still recent, detacching the results obtained from Santos (1995), Abreu de Castilhos (1995), Diehl (1997), Nunes (1997), Leal et al. (1998), Faraco (1998), Horn Filho et al. (1999b) and Torronteguy and Horn Filho (2000), which indicate erosive evidences in “Armação, Barra da Lagoa, Campeche, Canasvieiras, Daniela, Forte, Ingleses, Joaquina and Moçambique” beaches. LOCALIZATION OF THE STUDIED AREA The “Santa Catarina” island is located between 27º22’45” and 27º50’10” south latitudes and 48º21’37” and 48º34’49” west longitudes, littoral Central of the “Santa Catarina” state at southeast brazilian coast. Presents along of 174.3km of total perimeter 117 sandy beaches. Its littoral is compartmented according geomorphologic and sedimentologic aspects in six coasts: Northwest, North, Northeast, Southeast, South and Southwest (Horn Filho et al., 1999a): 1 Proceedings of the 12th Biennial Coastal Zone Conference Cleveland, OH July 15-19, 2001 COASTAL EROSION IN “SANTA CATARINA” ISLAND Along of perimeter of the island, are evidenced several erosion focus, originated from natural and anthropic processes. According to their localization, granulometry, shape, morphology, occupation, energy level and oceanographical parameters, the beaches generate different answers in their profiles and sectors. The areas where the erosion points are more perma nent or temporary, are associated to beaches exposed to higher energy, mainly in coasts faced to Atlantic ocean and represented predominantely by North, Northeast and Southeast coasts. Have been pointed out erosion evidences in “Daniela, Forte, Canasvieiras, Ponta das Canas, Ingleses, Brava, Moçambique, Barra da Lagoa, Galheta, Mole, Joaquina, Campeche and Armação” beaches. The beaches of North coast (“Canasvieiras, Ingleses, Forte and Ponta das Canas”), present the erosion allied dominately to disordered occupation above backshore, decreasing consequentely the sediment volume resulting sedimentar deficit in beach profiles. Relationed to beaches of Northeast and Southeast coasts, exposed to higher energy, the dominant erosive agents are associated to natural causes, observed in “Moçambique, Mole, Joaquina, Campeche and Armação” beaches. These causes are allied to cold front passages, decreasing of sediments, incident swell, longshore currents and batymetry of the foreshore and inner continental shelf. The anthropic causes are also considered like secondary factor, mainly in beach extremities, e.g., “Barra da Lagoa, Joaquina and Armação” beaches. The human influence is related to predatorious occupation of the coastal environment, taking up the sectors of backshore, foredune and coastal plain, shaping several edification types like residences, resorts, hotels, public eating houses and engineering structures, which do harm to the beaches. During winter and fall storm conditions, the natural processes are aggravated mainly under syzygy tide, lifting the tide level and consequentely reaching highest sectors of the beach profile. This situation is common along “Santa Catarina” island littoral during may to september months. Integrated studies are primordial to the monitoring of the observed focus, attempting possibly the recuperation and recognition of new hazard areas. REFERENCES ABREU DE CASTILHOS, J. 1995. Estudo evolutivo-sedimentológico e morfodinâmico da praia da Armação, ilha de Santa Catarina- SC. Florianópolis. 179p. Dissertação de Mestrado. Curso de Pós-Graduação em Geociências, Universidade Federal de Santa Catarina. DIEHL, L. F. 1997. Aspectos geoevolutivos, morfodinâmicos e ambientais do pontal da Daniela, ilha de Santa Catarina, Brasil. Florianópolis.132p. Dissertação de 2 Proceedings of the 12th Biennial Coastal Zone Conference Cleveland, OH July 15-19, 2001 Mestrado, Programa de Pós-Graduação em Geografia, Universidade Federal de Santa Catarina. FARACO, K. R. 1998. Estudo morfodinâmico e granulométrico da praia dos Ingleses, ilha de Santa Catarina, SC. Florianópolis. 68p. Monografia de Conclusão de Curso. Curso de Bacharelado em Geografia. Universidade Federal de Santa Catarina. HORN FILHO, N. O.; OLIVEIRA, J. S. de; LEAL, P. C. 1999a. Mapping the Santa Catarina island’s coast, Santa Catarina, southeastern, Brazil. In: COASTAL ZONE 99. San Diego, 1999. Abstracts: pp.401-403. HORN FILHO, N. O.; OLIVEIRA, J. S. de; & LEAL, P. C. 1999b. Evidências erosivas na praia de Canasvieiras, ilha de Santa Catarina, SC, Brasil. In: SEMANA NACIONAL DE OCEANOGRAFIA, 12., Rio de Janeiro, 1999. Resumos Expandidos...Rio de Janeiro: AOCEANO. pp. 56-59. LEAL, P. C.; HORN FILHO, N. O. & OLIVEIRA, J. S. de. 1998. Evidências erosivas do setor Centro-Norte da praia de Moçambique, ilha de Santa Catarina, Santa Catarina, Brasil. In: SIMPÓSIO NACIONAL DE GEOMORFOLOGIA, 2., Florianópolis, 1998. Resumos Expandidos. Florianópolis: UGB/UFSC. Geosul, 27:229-231. NUNES, M. G. 1997. Estudo evolutivo, sedimentológico e morfodinâmico da praia do Forte – ilha de Santa Catarina. Florianópolis. 72p. Monografia de Conclusão de Curso, Curso de Bacharelado em Geografia, Departamento de Geociências, Universidade Federal de Santa Catarina. SANTOS, C. R. dos 1995. Inter-relação entre a dinâmica da vegetação pioneira e os padrões morfo-sedimentológicos sazonais da praia da Joaquina, ilha de Santa Catarina, Brasil. 207p. Dissertação de Mestrado. Curso de Pós-Graduação em Geociências, Universidade Federal de Santa Catarina. TORRONTEGUY, M.de C. & HORN FILHO, N.O. 2000. Influência da ilha do Campeche no comportamento morfodinâmico do arco praial Joaquina - Morro das Pedras, ilha de Santa Catarina, SC, Brasil. In: SEMANA NACIONAL DE OCEANOGRAFIA, 13., Itajaí, 2000. Anais.. Itajaí. p.90-92. * Institutions of the Brazilian Marine Geology and Geophysics Program - PGGM Norberto Olmiro Horn Filho Departamento de Geociências Universidade Federal de Santa Catarina - UFSC PO Box 476 Florianópolis, Santa Catarina, Brasil 88040-900 (48) 331-9664 [email protected] 3
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