Banca de DEFESA: FILIPE EZEQUIEL DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : FILIPE EZEQUIEL DA SILVA
DATA : 23/08/2019
HORA: 14:30
LOCAL: Auditório do LGGP I
TÍTULO:

Morphodynamic of Barrier Island Systems, Northeast Brazil

PALAVRAS-CHAVES:

barrier islands, sandy spits, morphodynamics, coastal erosion, equatorial coast

PÁGINAS: 95
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

The northern littoral of Rio Grande do Norte State (RN) is a tropical mixed energy coast where geological conditioning favors the maintenance of barrier island systems. These systems include barrier islands, sandy spits, ebb tidal deltas, mangrove forests, tidal inlets and plains. Coastal dynamics in these systems is intense, which causes large shoreline retreat, sandy spits growth, as well opening and closure of tidal inlets in a short time. This dynamic directly affects onshore oil exploration, and for this reason, several studies have been conducted in the region in recent decades, in order to better understand its morphodynamic aspects. However, much remains to be understood, especially when considering the extension of these systems. This work aimed to evaluate the morphodynamics of the barrier islands systems of the northern coast of RN through quantitative data obtained from multitemporal analysis of orbital images of Landsat 5 TM and Landsat 8 OLI sensors, and associated knowledge of coastal processes as well. The analysis were carried in a period of 33 years (1984 to 2016), with 4-year sampling intervals for the low frequency analysis, and 1 year for the high frequency analysis. The results indicate a great influence of the sampling interval on the interpretation of the evolutionary behavior of these barrier islands and sandy spits, so that low frequency analysis does not represent the actual evolution of the barriers, leading to misinterpretations. This is related to the considerably dynamic behavior of these barriers which over a period of 1 year may present a 3 km² magnification. In addition, the successive alternations between enlargement and shrinkage in the area of these barriers correspond to uninterrupted accretion and erosion cycles that nullify any trends of growth or decrease in these areas. The morphodynamic analysis allowed differentiating two types of barriers: migrant and stationary. The migration movement results from the joint action of the meteo-oceanographic forcing that causes continuous updrift sediment loss followed by downdrift sediment gain. This process pushes the whole barrier westward at rates of up to 100 meters per year, however preserving its shape . The migration of barriers can cause opening, rotation, translation and closure of tidal channels. The stationary barriers, in turn, have features that attenuate the energy of waves and currents, avoiding large sediment losses and, consequently, their migration. The barriers also act as sediment source for the transgressive dune fields. Therefore, migrating islands may coalesce with the shoreline providing sediment to adjacent dune fields. Dune fields separated from the beach zone by lagoons and tidal inlets receive low sedimentary input which causes the development of extensive wind deflation covered by lag deposits. The maintenance of these conditions may favor the extinction of these dune fields

MEMBROS DA BANCA:
Presidente - 2218779 - HELENICE VITAL
Externo à Instituição - Andre Giskard Aquino da Silva - UFRN
Externo à Instituição - LEAO XAVIER DA COSTA NETO - IFRN