Revista de Gestão Costeira Integrada
Volume 8, Número 2, Dezembro 2008, Páginas 113-126

DOI: 10.5894/rgci143
* Submissão – 25 Julho 2008; Avaliação – 29 Agosto 2008; Recepção da versão revista –
12 Novembro 2008; Disponibilização on-line - 23 Dezembro 2008

Morfodinâmica de um Canal de Maré Tropical: Estudo de Caso na Costa Norte Rio Grandense, Nordeste do Brasil*

Morphodynamic of a Tropical Tidal Inlet: Case Study on the Rio Grande do Norte Coast, Northeast Brazil

Helenice Vital ^{1, 2}, Francisco dos Santos Neto ²,
José Saraiva Plácido Junior ²

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1 - Autor correspondente: helenice@geologia.ufrn.br
2 - Departamento de Geologia, Laboratório de Geologia e Geofísica Marinha e Monitoramento Ambiental-GGEMMA, Universidade Federal do Rio Grande do Norte, Campus Universitário, Caixa Postal 1596, Natal-RN, 59072-970, Brasil.

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RESUMO
Este artigo trata da morfodinâmica de um canal de maré em barreira costeira tropical, localizado na Reserva de Desenvolvimento Sustentável Ponta do Tubarão-RDSPT, nordeste do Brasil. A região esta sujeita à alta energia sendo classificada como costa mista, dominada por ondas e marés. A influência significativa das marés sobre o sistema barreiras/canais de marés provoca a formação de proeminentes deltas de maré vazante.
A compreensão dos mecanismos de crescimento da barreira costeira e canais associados da Ponta do Tubarão auxiliarão na reconstrução da dinâmica e evolução costeira desta região. Nesta área a barreira costeira tem se modificado de barreira pontal para pontal e ilha barreiras a partir de aberturas de canais de marés no pontal inicial. O primeiro canal aberto naturalmente em 1977, originou a ilha Barreira Ponta do Tubarão, e desde então este canal de maré denominado Barra do Fernandez, tem sido usado como acesso de navegação pelos habitantes das comunidades locais de Barreiras e Diogo Lopes. Entretanto, como a distância entre o canal e Diogo Lopes é maior, persistiram as pressões publicas para abertura de acessos adicionais a navegação. A abertura natural de um novo canal em 2006 proporcionou a oportunidade para acompanhar sistematicamente as mudanças ocorridas em um canal de maré tropical. Desta forma, objetivando uma melhor compreensão dos processos costeiros atuantes na região o segundo canal tem sido monitorado e os dados aqui apresentados incluem a integração de sensoriamento remoto, levantamento batimétrico, sedimentologia, monitoramento da morfodinâmica e forçantes oceanográficas.
As correntes costeiras são responsáveis pelo transporte de sedimentos ao longo da costa, predominantemente para oeste-noroeste da ordem de 1,0m/s. No interior do canal correntes de maré vazante são as mais intensas atingindo até 0,85m/s. O monitoramento morfodinâmico atesta as constantes modificações nos canais de marés. As características geológicas e hidrodinâmicas do Canal da Barra Nova permitem classificá-lo como canal de maré litoral de energia mista dominado por vazante.
O registro de mudanças morfológicas significativas em curto espaço temporal indicam a necessidade do monitoramento continuo dos processos costeiros para entender a evolução de sistemas barreiras-pontal em costas tropicais. Adicionalmente este tipo de dado irá permitir aos tomadores de decisão um manejo racional da zona costeira.

ABSTRACT
This paper examines the tidal inlet morphodynamics on a tropical sandy coast, located on the “Reserva de Desenvolvimento Sustentável Ponta do Tubarão-RDSPT”, northeastern Brazil. . The region experiences high-energy been classified as a mixed coast, tide and wave dominated. The significant tidal influence to the barrier/inlet system causes formation of a substantial ebb-tidal delta. The mechanisms of growth and elongation of the coastal spit and tidal inlets from Ponta do Tubarão are underway to reconstruct the historical evolution and dynamics. The barrier on this area was completely joined to the mainland as a spit; around 1977 an inlet was naturally created and the barrier island was called Ponta do Tubarão. Since then this inlet, called Barra do Fernandez, is used as navigational access to lagoon by the habitants from Barreiras and Diogo Lopes villages. The distance between this inlet and Diogo Lopes is quite large, creating public pressure for additional navigation access. A new tidal inlet opened in 2006 give the oportunity to monitoring the changes in a tidal inlet. This way, we discuss the type of data that are being collected and analyzed to understand the environmental forcing affecting the inlet’s morphology. In a novel approach the integrated data set presented here includes remote sensing, bathymetric, althymetric, oceanographic, and sedimentologic data. The longshore currents flow toward west-northwest (oblique to the coast). They are by far the dominant contributor to the net sediment transport along the coast of Rio Grande do Norte. Currents measured inside a new inlet show maximum speed of 0.85m/s during ebb phase, while nearshore it can reaches 1.0m/s. The littoral environments of sedimentation are influenced by tidal, waves and wave-generated (longshore) currents. Aeolian deposits are also observed to migrate from the shoreline landward over tidal flat and lagoon sediments. A composite vertical sedimentary sequence in this region is composed of barrier spit/beach and aeolian dune sediments, over tidal inlet and shoreface units. The Reserva de Desenvolvimento Sustentável Ponta do Tubarão coast has nowadays two active inlets, naturally occurring. The net drift is to the West-Northwest along this coast. Natural inlets were created by overwash processes during more energetic periods. Our results indicated that, Barra Nova can be classified as a littoral origin, mixed energy, ebb-dominated tidal inlet.
If the hydrodynamic conditions persist, to maintain navigational interests, the Barra Nova inlet needs to be stabilized. This requires that this barrier spit coast be viewed as a system of structural features and transient morphology that interact with the environmental forcing at the inlet to attain an ever changing “dynamic equilibrium”. The imperative for sustainability at this area is managing the inlet in terms of extended time-space scales as defined by natural sediment processes, which means continuous monitoring. This data set is important to develop a detailed understanding of this kind of barrier-spit system evolution, to provide good architectural analogues for the nearby subsurface reservoir, and will enable planners to make the right decisions for a rational management of the coastal zone.

 

Araujo, M., Vital, H., Amaro, V.E., Silva, M.A. & Frazão, E.P. (2004) - Caracterização das forçantes hidrodinâmicas - Correntes, ondas e marés - na região costeira de Guamaré - RN. III Workshop Técnico-Científico do Projeto PETRORISCO, Anais (CD-ROM). Belém,  PA, Brasil.

Ashley, G.M. (1990) - Classification of large-scale subaqueous bedforms: a new look at an old problem. Journal of Sedimentary Petrology., 60:160-172.

Baptista, P., Bastos, L., Cunha, T., Bernardes, C. & Dias, J.A. (2008) – Aplicações de metodologias de monitorização GPS em litorais arenosos. Geração de modelos de elevação do terreno. Revista de Gestão Costeira Integrada, 8(1):9-23. (http://www.aprh.pt/rgci/pdf/
revista8f1_1.pdf)

Bezerra, F.H.R., Barreto, A.M.F. & Suguio, K. (2003) - Holocene sea-level history on the Rio Grande do Norte State coast, Brazil. Marine Geology., 196(1-2):73-89. (doi: 10.1016/S0025-3227(03)00044-6).

Boon, J.D. & Birne, R.J. (1981) – On basin hypsometry and morphodynamic response of coastal inlet systems. Marine Geology, 40(1-2):27-48. (doi: 10.1016/0025-3227(81)90041-4).

Bruun, P. & Gerritsen, F. (1960) – Stability of coastal inlets. 123 p., North-Holland Publishing Company, Amsterdam, Netherlands. (ISBN-13: 978-0720416015).

Caldas, L.H.O., Stattegger, K. & Vital, H. (2006) - Holocene sea-level history: Evidence from coastal sediments of the northern Rio Grande do Norte coast, NE Brazil. Marine Geology, 228(1-4):39-53.
(doi: 10.1016/j.margeo.2005.12.008).

Chaves, M.S., Vital, H. & Silveira, I.M. (2006) - Beach morphodynamics of the Serra oil field, northeastern Brazil. Journal of Coastal Research, SI39:594-597.

Davis Jr., R.A. (ed.) (1994) - Geology of Holocene Barrier Island Systems. 646p., Springer–Verlag, Berlin, Germany. (ISBN-13: 9783540569640).

Dean, R.G. & Dalrymple, R. A. (2002) - Coastal Processes with Engineering Applications. Cambridge University Press, Cambridge, UK. (ISBN: 0521495350).

Dingler, J.R. & Clifton, H.E. (1994) - Barrier Systems of California. Oregon, and Washington. In: Davis Jr., R.A. (ed), Geology of Holocene Barrier Island Systems, pp. 115-165, Springer–Verlag, Berlin, Germany. (ISBN-13: 9783540569640).

ECOPLAM - Empresa de Consultoria e Planejamento Ambiental (2001) - Relatório de Avaliação Ambiental. Plataforma PUB-1, Bacia Potiguar RN – Campo de Ubarana para PETROBRAS. Natal, RN, Brasil. (não publicado).

FitzgGerald, D.M. (1982) – Sediment bypassing at mixed energy inlets. Proceedings of the 18th Coastal Engineering Conference, pp. 1094-1118, ASCE (American Society of Civil Engineers), New York, NY, USA.

FitzgGerald, D.M. (1988) - Shoreline erosional-depositional processes associated with tidal inlets. In: Aubrey, D.G. & Weishar, L. (eds.), Hydrodynamics and Sediment Dynamics of Tidal Inlets , pp. 186-224, Springer-Verlag, Heidelberg, Germany. (ISBN: 0387968881).

FitzgGerald, D.M. (1996) – Geomorphic variability and morphologic and sedimentologic controls on tidal inlets. Journal of Coastal Research, SI23:47-71.

FitzgGerald, D.M. & Nummedal, D. (1983) – Response characteristics of an ebb-dominated tidal inlet channel. Journal of Sedimentary Petrology, 53(3):833-845.

Hayes, M.O. (1975) - Morphology of sand accumulation in estuaries. In: Cronin, L.E. (ed.), “Estuarine Research”, v.2 (Geology and Engineering): 3-22, Academic Press, New York, USA. (ISBN: 0121975010).

Hayes, M.O. (1979) - Barrier island morphology as a function of tidal and wave regime. In: S.P. Leatherman (ed.), Barrier islands from the Gulf of St. Lawrence to the Gulf of Mexico, pp. 1-27,.Academic Press, New York, USA.. (ISBN: 9780124402607).

Hesp, P.A. & Short, A.D. (1999) - Barrier morphodynamics. In: Short, A.D. (ed.), Handbook of Beach and Shoreface Morphodynamic, pp. 307-333, John Wiley & Sons, New York, USA.

Hughes, S.A. & Kraus, N.C. (2006) – Frequently-Asked questions (FAQs) about coastal inlets and U.S. Army Corps of Engineers, Coastal Inlets Research Program (CIRP), Coastal and Hydraulic Laboratory Engineering Technical Note ERDC/CHL CETN-IV-67, U.S. Army Corps of Engineer Research and Development Center, Vicksburg, MS, USA.

Komar, P.D. (1996) – Tidal-inlet processes and morphology related to the transport of sediments. Journal of Coastal Research, SI23:23-45.

Lima, Z.M.C., Alves, A.L., Amaro, V.E. & Vital, H. (2001) - Evolução da linha de costa do Esporão de Galinhos (NE Brasil) utilizando fotografias aéreas e Imagens LandsatTM. (Coastline evolution of the Galinhos Spit (NE Brazil) using air photography and landsatTM images). Revista Pesquisas em Geociências., 28(2):497-507. Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.

Lima, Z.M.C., Vital, H., Xavier Neto, P., Medeiros, W.E. & Andrade, P.R.O. (2002) - Sand spits from NE Brazil: high resolution Quaternary analogous for reservoir model. AAPG (American Association of Petroleum Geologist) Annual Meeting, Extended Abstracts, Houston, Texas, USA. CD-ROOM. (http://www.searchanddiscovery.net/documents/
abstracts/annual2002/DATA/2002/13ANNUAL/EXTENDED/43911.pdf).

Martin, L., Dominguez, J.M.L. & Bittencourt, A.C.S.P. (2003) - Fluctuating Holocene sea-levels in eastern and southeastern Brazil: Evidence from multiple fossil and geometric indicators. Journal of Coastal Research, 19:101-124.

Masselink, G. & Short, A.D. (1993) – The effect of tide range on beach morphodynamics, A conceptual beach model. Journal of Coastal Research, 9:785-800.

Masselink, G. & Turner, I.L. (1999): The effect of tides on beach morphodynamics. In: Short, A.D. (ed.), Handbook of Beach and Shoreface Morphodynamics, pp.204-229, John Wiley and Sons, Chichester, U.K. (ISBN-13: 9780471965701).

Mehta, A.J. (1996) – A perspective on processes related research needs for sandy inlets. Journal of Coastal Research, 23:3-21.

Neto, L.X.C. (2008) – Caracterização Geomorfológica e Física do Sistema Pisa Sal, Galinhos-RN, litoral norte do Rio Grande do Norte. Dissertação de Doutorado, 280 p., Universidade Federal do Rio Grande do Norte, Natal, RN, Brasil.

Neto, P.X., Lima, Z.M.C., Andrade, P.R.O., Oliveira Jr., J.G., Medeiros, W.E. & Vital, H. (2001) - GPR images of the Galinhos Península, NE Brazil: the register of a geologic evolution from paleochannel to a sand spit ?. Proceedings of the I Symposium about GPR in sediments: applications and interpretation, Geological Society and UCL. London, UK. CD ROOM.

Nimer, E. (1989) - Climatologia do Brasil. 2ed., IBGE (Instituto Brasileiro de Geografia e Estatística) – SUPREN (Superintendência de Recursos Naturais e Meio Ambiente), Rio de Janeiro, RJ, Brasil.

Oertel, G.F. (1985) - The barrier island system. Marine Geology, 63(1-4):1-18. (doi:10.1016/0025-3227(85)90077-5).

Pendleton, E.A. & FitzGerald, D.M. (2005) - Comparison of the hydrodynamic character of three tidal inlet systems. In: FitzGerald, D.M & Knight, J. (eds.), “High-Resolution Investigations of the Morphodynamics and Sedimentary Evolution of Estuaries”, pp. 83-100, Series: Coastal Systems and Continental Margins, Vol. 8, Springer, Dordrecht, Netherlands. (ISBN: 9781402032950).

Postma, H. (1967) – Sediment transport and sedimentation in the estuarine environment. In: Lauff. G.H. (ed.), Estuaries, vol. 83, pp. 158–179, American Association for the Advancement of Science, Washington, DC, USA.

Roy, P.S., Cowell, P.J., Ferland, M.A. & Thom, B.G. (1994): Wave dominated coasts. In: Carter, R.W.G. & Woodroffe, C.D. (eds.), Coastal Evolution, Late Quaternary Shoreline Morphodynamics, pp. 121-186, Cambridge University Press, Cambridge, UK. (ISBN: 052159890).

Santos, D.A.S., Vital, H., Silveira, I.M., Chaves, M.S., Lima, Z.M.C. & Tabosa, W.F. (2003) - Caracterização Hidrodinâmica em áreas sob Influência da Industria Petrolífera. 2º Congresso Brasileiro de P & D em Petróleo e Gás (CD-ROOM), Rio de Janeiro, RJ, Brasil.

Silva, C.G. (1991) - Holocene Stratigraphy and Evolution of the Açu River Delta, Rio Grande do Norte State, Northeastern Brazil. PhD thesis, 400p., Duke University, Durham, NC, USA.

Silveira, I.M., Vital, H., Amaro, V.E. & Chaves, M.S. (2006) - The Evolutionary Study of Environmental Conditions of the Guamaré Coast (Northeastern Brazil). Journal of Coastal Research, SI39:237-241.

Souto, M.V.S., Castro, A.F., Grigio, A.M., Amaro, V.E. & Vital, H. (2002) - Multitemporal Analysis of Geoenvironmental Elements of the Coastal Dynamics of the Region of the Ponta do Tubarão, City of Macau/RN, on the Basis of Remote Sensing Products and Integration in GIS. Journal of Coastal Research, SI39:1618-1621.

Stattegger, K., Caldas, L.H.O. & Vital, H. (2006) - Holocene coastal evolution of the Northern Rio Grande do Norte Coast, Brazil. Journal of Coastal Research, SI39:151-156.

Van der Spek, A.J.F & Beets, D.J. (1992) – Mid-Holocene evolution of a tidal basin in the western Netherlands: a model for future changes in the northern Netherlands under conditions of accelerated sea-level rise?. Sedimentary Geology, 80(3-4):185-197. (doi: 10.1016/0037-0738(92)90040-X).

Vital, H. (2009) - The mesotidal barrier of Rio Grande do Norte. In: Dillemburg, S. & Hesp, P. (eds.), Geology and Geomorphology of Holocene Coastal Barriers of Brazil, pp. 289-324, Springer-Verlag, Berlin, Germany. (ISBN: 9783540250081).

Vital, H., Chaves, M.S., Souto, M.V.S. & Amaro, V.E. (2006b) - The Macau-Serra coastal erosion hotspot. 4th Latin American Congress of Sedimentology together with the XI Argentinian Meeting of Sedimentology, Bariloche, (CD-ROOM), San Carlos de Bariloche, Argentina.

Vital, H., Lima, Z.M.C., Silveira, I.M., Amaro, V.E. & Souto, M.V.S. (2003) - Barrier-Spit System From The Northern Rio Grande do Norte State Coast, NE Brazil: A Tectonic Control?. Proceedings of the 3th Latin-American Congress on Sedimentology, 113-115. Belém,  PA, Brasil.

Vital, H.; Amaro, V.E. & Silveira (2006a) – Coastal erosion on the Rio Grande do Norte State (Northeastern Brazil): Causes and factor versus effects associated processes. Journal of Coastal Research, SI39:1307-1310.

 

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