Rogério Portantiolo Manzolli

IMPACTOS NO SISTEMA DE DUNAS: DINÂMICA NATURAL VERSUS INTERFERÊNCIA ANTRÓPICA

A orla de Capao da Canoa, RS, intercala areas de alta densidade ocupacional com areas nao urbanizadas que preservam suas caracteristicas naturais. Neste trabalho, buscou-se analisar o indice de vulnerabilidade das dunas frontais, a partir de levantamentos de campo realizados no inverno e verao, utilizando-se uma lista de parâmetros. A partir da taxacao destes, atribuiu-se um indice de vulnerabilidade para cada perfil. Os valores mais altos coincidiram com as areas mais urbanizadas do municipio, devido a posicao da urbanizacao que reduz a largura dos cordoes de dunas frontais. A superioridade dos valores do indice de vulnerabilidade de inverno ao de verao altera o consenso sobre a interferencia humana como principal vetor de vulnerabilidade. Os fatores que mais contribuiram para a degradacao das dunas frontais foram: a condicao de praia, no inverno, e a pressao de uso, no verao, indicando a alta fragilidade de alguns perfis ao longo da orla.

Geological and Stratigraphic Characteristics of a Holocene Regressive Barrier in Southern Brazil: GIS and GPR Applied for Evolution Analysis

ABSTRACT Leal, R.A.; Barboza, E.G., Bitencourt, V. Jr. Biancini da Silva, A. and Manzolli, R.P., 2016. Geological and Stratigraphic Characteristics of a Holocene Regressive Barrier in Southern Brazil: GIS and GPR Applied for Evolution Analysis. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 750–754. Coconut Creek (Florida), ISSN 0749-0208. The observation of geological and geomorphological factors in coastal barriers to allows interpret the processes involved and the temporal trends over time. During the Holocene, the Balneário Torneiro barrier, located in the southern coast of Santa Catarina, prograded approximately 1.3 km, preserving the records of Urussanga rivers system dynamics in surface and subsurface paleochannels. The presence of such features close to the boundary with the Pleistocene deposits up to the present coastline indicates that the evolutionary behavior of the barrier is progradational. The identification of superficial morphological features interpreted on the barrier such as transgressive dune sheets and beach ridges corroborates this interpretation. In subsurface, three main radar facies (RF-1, RF-2, RF-3), a surface radar (erosive surface) and a subsurface feature (SF) were identified in the Ground Penetrating Radar (GPR) profiles. Continuous to discontinuous reflectors, sub parallel with high amplitude, were interpreted as corresponding to the beach/shallow marine environment (RF-1) formed by the barrier progradation. An erosive surface in concave form truncating these reflectors, with onlap and downlap reflectors in the concave face, and truncation in the convex base, was interpreted as the base of a paleochannel. The others radar facies (RF-2 and RF-3) are related to the filling of the channel. The integrated interpretation of GIS and GPR data have allowed to interpret evolutionary characteristics at different time scales of the studied barrier sector.

Dune System Restoration in Osório Municipality (Rio Grande do Sul, Brazil): Good Practices Based on Coastal Management Legislation

Dune Management Plans are useful tools to integrate coastal development, dune conservation and even dune restoration. The environmental legislation of Rio Grande do Sul (South of Brasil) establishes a Permanent Preservation Area of 60-m minimum width that should be protected in the coastal dune systems. This study shows the implementation of a coastal management plan in Osorio Municipality (N of Rio Grande do Sul) for the restoration of the foredune. The analysis of previous evolution (1997–2010) of the dune field showed widths lower than the legal requirement and decreasing in the last years. Then, a dune restoration plan was designed and implemented in 2011. The measures included the planned retreat of the road located back the foredune, channelization of the northern whashout’s mouth with a structure under the foredune, installation of sand fences and control of the pedestrian accesses to the beach by both a pathway and a footbridge. Finally, efficiency of the management plan was assessed by monitoring (2011–2016) the foredune evolution, which permitted to conclude a satisfactory result. Only the foredune sector close to the washout’ mouth did not achieve the expected minimum width, but it can be considered acceptable considering its higher sedimentary dynamics, the inherent difficulties of these structures and the short monitoring period from the implementation of the plan.

Sediment Bypassing from the New Human-Induced Lobe to the Ancient Lobe of the Turbo Delta (Gulf of Urabá, Southern Caribbean Sea)

ABSTRACT Alcántara-Carrió, J.; Caicedo, A.; Hernández, J.C.; Jaramillo-Vélez, A., and Manzolli, R.P., 2019. Sediment bypassing from the new human-induced lobe to the ancient lobe of the Turbo Delta (Gulf of Urabá, Southern Caribbean Sea). Journal of Coastal Research, 35(1), 196–209. Coconut Creek (Florida), ISSN 0749-0208. Artificial river diversions cause intense and unpredictable changes in the geomorphological evolution and sedimentary dynamics of deltas. This study analyzes the effects of the 1958 course diversion of the Turbo River delta, Gulf of Urabá, southern Caribbean Sea. Recent satellite images were analyzed and beach topography was monitored to obtain the shoreline migration and sediment budget; surface sediments were seasonally sampled, and their grain size parameters were determined; and seasonal sediment transport directions were deduced according to grain size trends. It was concluded that the bimodal wave regime controls the seasonal sedimentary patterns associated with southward longshore transport during both the dry and rainy seasons, and the northward longshore transport occurs in the midsummer drought. Beach morphodynamics of Yarumal Point, close to the present-day river mouth, show that this is the most exposed sector to waves, whereas fluvial sediment inputs are evidenced by a decrease in mean grain size and by poorly sorted sediments in the rainy season. A new spit is forming in Yarumal Point, with an intense increase in area and a westward progradation related to high fluvial sediment inputs from the La Niña event of 2010–12 and low erosion from the El Niño events of 2009–10 and 2015–16. In the central sector, longshore drift has formed the Yarumal barrier spit with a southeastward progradation that recently closed the interdistributary El Uno Bay. Consequently, a humaninduced sand barrier–lagoon system resulted with a stable or slightly regressive shoreline. Moreover, the Yarumal barrier spit has generated a new sediment bypass to Barajas Beach in the northern limit of the Las Vacas spit (i.e. the ancient delta lobe). Therefore, there is an unusual accretion of the abandoned delta lobe by sediment supply from the new lobe.