IMPACTO ANTRÓPICO NO PROCESSO DE ASSOREAMENTO DA ENSEADA DA JAPUÍBA, ANGRA DOS REIS (RJ)

Anthropic impact in the silting process of Japuíba Bight, Angra dos Reis (RJ)

Abstract

This study investigates the Japuíba Bight (Angra dos Reis municipality) aiming to characterize the process of silting up affecting the region and to infer on its causes. Bathymetric, sedimentological and photo-aerial surveys were carried out to analyze the temporal evolution of bathymetry, sedimentary texture and areas of interest in the vicinity of the bight. Bathymetric data from 1979 and 2018 were processed, resulting in comparative maps of bathymetry and silting/erosion. With the analysis of the sediments the textural distribution was obtained. It occurs in the bight a process of silting, mainly along an East-West zone in front of the Airport of the city of Angra dos Reis, proximal to the coast line along the whole study and between the Redonda and Bois islands. The results suggest that the Japuíba and Gamboa river’s drainage along with smaller rivers are the main sources of sediments to the bight. The total silting volume and the rate were 1,252,642.75 m³ and 0.97 cm/y, respectively. It is proposed here that significant anthropic impact in the form of unplanned urban occupation, river form and native vegetation alterations and dredging was responsible for the process of silting up at the Japuíba Bight.