Caracterização sedimentológica e geoambiental no sistema estuarino lagunar Jequiá – litoral sul de Alagoas

Abstract

The active sedimentary processes in lagoons, such as erosion, transport and deposition, create distinct sedimentary and morphological features. The study of these features or the direct observation of the active mechanisms (waves, tides, winds and river entrances) provides us with a better understanding of these processes. This dissertation aims to produce current information that can subsidize environmental and economic management activities in the lagoon based on efforts to preserve coastal ecosystems (beaches, rivers, mangroves, estuaries and lagoons), and on land use strategies (urban occupation and tourism). It is also worth noting that this study will serve to update the Management Plan of the RESEX of the Jequiá lagoon. Therefore, the present research aims to compare the data collected by other authors with the current situation of The Jequiá Lagoon, characterize the geological and geomorphological aspects and perform the geoenvironmental zoning of the area. The study area is located in the municipality of Jequiá da praia 68km from Maceió. It comprises the lagoon estuarine region of Jequiá and its canal, which occupies about 1,803 hectares, being limited by the cliffs of the Barreiras Formation in its interior and the Atlantic Ocean in the coastal part made through a channel of 6 km. The methodology of this study was based on bibliographic and cartographic survey, field steps for sediment collection, laboratory steps, surveys for geoenvironmental zoning and elaboration of the impact matrix. In total, 45 samples were collected throughout the lagoon body and its canal, whose particle size study presented sand as a single textural easy, with variation of the average diameter of medium, fine and very fine sand. The textual distribution of sediments in the lagoon system involved the gravel, sand and mud fractions, showing a direct relationship with the hydrodynamics acting in the system. In general, the behavior of the standard deviation of the average diameter of the grains in the lagoon system varies from moderately selected to poorly selected. In the lagoon system there is variation in asymmetry from very negative asymmetry to very positive asymmetry, while the variation of kurtosis values in the granulometric distribution is related to the estuarine-lagoon transition zone, being classified from very platyptic to extremely leptocúrtica. The municipality of Jequiá da Praia is an environment rich in natural resources and lacks studies focused on the impacts generated, mainly, by the great urban growth of recent decades, deforestation, lack of sanitation, disposal of solid waste, fertilization of sugarcane, necrochorume, among others that need to be mitigated urgently. It can also be affirmed, with the data analyzed in the matrix of impacts that the most sensitive areas are the lagoon and its margins, with the villages occupying the Permanent Preservation Areas (APP) and the canal. These occupations, where there should be natural vegetation, generate negative impacts such as deforestation and siltation, both for the lagoon and for the canal. It is also one of the most important tourist centers of the southern coast of the state, along with Coruripe and Piaçabuçu (mouth of São Francisco). Having as main attractions the beach of two Bars, the trails and boat trips in the mangroves, besides being a fishing pole. That is why these environments require good planning and tourism, to minimize environmental degradation, and generate sustainable actions for the preservation and recovery of environments.