Dinâmica morfológica e sedimentar do litoral de Maricá (RJ) nas últimas décadas e susceptibilidade às ondas de tempestade

Abstract

Human interventions on the coast have affected coastal dynamics and evolution around the world. On the coast of Maricá, in the State of Rio de Janeiro, urban expansion intensified after the construction of the Rio-Niterói bridge in 1974, with a significant increase in the number of residences and tourism in the region. This occupation, in general, deserves special attention due to the high dynamics of this coastline, subject to the occurrence of high-energy events associated with the incidence of storm waves. These events have historically caused damage to buildings and other urban structures, floods and compromised the balance of coastal environmental systems. In this sense, the present study aims to analyze the morphological and sedimentary dynamics of the beaches in the municipality of Maricá in recent decades, in response to events associated with the incidence of storm waves. To this end, 35 new beach topographic profiles were acquired throughout 2022. These data were subsequently integrated with results from studies carried out in recent decades by several authors. The calculation of the emerged volume of sediments, analysis of geoindicators and various photographic records were also carried out. To this end, the beaches of Itaipuaçu, APA and Barra de Maricá, Cordeirinho and Ponta Negra were selected. The results show a high topographic variability of the beach, with emphasis on the western sector of Itaipuaçu, with a variation of 45 m in width between maximum and minimum. The calculation of the volume of emerged sediments shows that the beach sectors present a sedimentary balance, except for the beaches of Barra de Maricá and Ponta Negra (P8) which presented a reduction in volume (42.75% and 31.54% respectively) in the recent decades. The beaches of Itaipuaçu and Barra de Maricá were the ones that received the most interventions to the detriment of the others and are, consequently, the areas that showed a high susceptibility to coastal erosion. The problems detected on the beaches of Barra de Maricá and Ponta Negra (destruction of the road and homes, respectively), cause concern and alert to the occurrence of erosion processes on this stretch of coast. The observed morphosedimentary variability results from rapid changes in wave energy that hit the coast, especially when associated with storm conditions. In addition to the high dynamics, resulting from direct exposure to these storm waves, on the coast of Maricá one must pay attention to the proximity of urban structures in relation to the beach's dynamic sand strip, which does not occur in the stretch corresponding to the APA of Sissy boy. Therefore, as it is a dynamic coastline, with a high degree of susceptibility to the incidence of large storm waves along the entire beach arc and erosion in places with a reduction in sediment volume, it is essential to adopt measures to protect the coastal area. coast and mitigate the impacts of constructions close to and/or within the beaches, through nature-based solutions or even through the removal of these rigid structures. In view of the above, it is necessary to continuously monitor this coastline and the existing problems, due to its high susceptibility to coastal erosion.