Ambientes costeiros amazônicos: avaliação de modificações por sensoriamento remoto

• Autor(a) principal: Santos, Valdenira Ferreira dos
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal Fluminense (RIUFF)
• Texto Completo: https://app.uff.br/riuff/handle/1/17876
• topic: Sensoriamento remoto; Meio ambiente; Estuário; Interpretação de dados; Ecossistemas costeiros amazônicos; Modificações ambientais; Costa amazônica; Environmental changes; Remote sensing; Amazonian coast; CNPQ::CIENCIAS EXATAS E DA TERRA::OCEANOGRAFIA::OCEANOGRAFIA GEOLOGICA::GEOFISICA MARINHA

The coastal plain of the State of Amapá, located on the northernmost region of Brazil, on the Amazonian coast, comprises an environmental diversity represented mainly by mangroves, lakes, swamps forests and flooded basins, related to flood plains influenced by tides and estuaries. In this study, the modifications recorded in this plain are evaluated, focusing in the region of the Araguari estuary, and the processes responsible for these changes are presented. The natural processes that influence the modifications in this plain are related to ENSO events (El Niño Southern Oscillation), position of the Intertropical Convergence Zone (ITCZ), influence of the Amazon River and tides influenced by tidal bore. The anthropogenic processes are associated with water buffalo ranching. All these factors are presented and discussed in the form of processes and products. The environmental information is from previous data and also collected in the field. The base information came from remote sensing data (aerial photographs, radar imagery - RADAR GEMS 1000 from RADAM Project, JERS- 1 and RADARSAT-1, images from optical sensors - MSS, TM and ETM+ from Landsat satellites, digital elevation model data - DEM SRTM), digitally processed for multi-sensor, multi-scale and multi-date approach. Historical maps since 16th century had also been utilized. The analyses allowed the identification of patterns of land use and cover as well as the natural and anthropogenic geomorphic features. The identified patterns and features were grouped into two main types of environments: fluvial influenced by tides (flood plain) and estuarine plain (mangrove, intertidal zone and estuarine channel). It was also possible to establish indicators to characterize the environmental modifications in the region, from multitemporal analyses of remote sensing and historical data. The tidal bore phenomenon can also be identified in the estuary by RADARSAT-1 images. The correlation between the remote sensing and historical data indicates that the Araguari River mouth had two channels until the 18th century, one to the west and the other to the south of the so-called Land of Carpori. The current configuration of the floodplain at the north and south of the estuary, and of its last meander is recent. The events related to these transformations occurred between the end of the 18th century and middle of 19th century, with indications of anthropogenic influences in some of these events. The results of multitemporal analysis of remote sensing data from the 1950s and related information had evidenced modifications in the floodplain and the estuarine plain. In the floodplain, they are related to the development of drainage networks, some of which influenced by the development of cattle ranching (e.g. the Igarapé Santana). Others had their opening influenced by great flooding events that had been correlated to ENSO phenomenon (e.g. Igarapé Novo in the Gurijuba River). In the estuarine plain, the modifications are associated with the formation of channel bars, mouth bars, changes in the tidal channels and erosional processes in the margins of the estuary. These modifications are more evident in the mouth of the Araguari River and are mainly a result of tide action and the tidal bore 3 phenomenon, which is a powerful sediment transport agent. It was also possible to analyze the phenomenon s behavior and its records throughout the estuary from observations done prior, during and after its passage. The agents associated to these modifications can influence erosional and depositional processes that act within estuarine environments of fluvial meandering systems. The results from the evaluation of remote sensing data and the techniques applied in this study had demonstrated the potential of the remote sensing tool and historical maps in the study of modifications in highly dynamic tropical coasts (of difficult access). However, these tools may present some difficulties in application to the Amazon coast, which is a region under very dynamic natural and antrophogenic processes that overlap in a short timescale, when comparing with other coastal regions