The beaches and rocky shores of Baía de Sepetiba, within the boundaries of the city of Rio de Janeiro, form a coastal landscape of great geographic and environmental complexity, marked by the scant presence of the crystalline basement of the Maciço da Pedra Branca and the full expression of the fluvio-marine plains of the west zone. This coastal edge stretches from the point of Barra de Guaratiba to the boundary with the municipality of Itaguaí, at the far end of the Baía de Sepetiba, encompassing a coastal strip that includes few sandy beaches and an abundance of mangroves, interrupted by rare rocky shores interspersed with low marine-energy features.
In the southern stretch, the beach of Barra de Guaratiba, located where it meets the Ocean, lies at the transition to the bay and features prominent granite headlands that jut out over the sea, shaping coves and promontories. From there, sheltered by the barrier island of Restinga da Marambaia, an extensive fringe of mangrove coastline dominates the shore, interspersed with the mouths of rivers flowing down from the Serra de Guaratiba and Maciço da Pedra Branca; the plain, bathed directly by the calm waters of the Baía de Sepetiba, displays the typical features of a low-energy beach, with wide tidal variation and an extensive intertidal plain. Its sedimentary formation rests on mangrove areas and recent deposits, shaped by the drainage of the Portinho, Piracão, and Piraquê rivers. Their lower courses trace preserved meanders, their curving patterns separating sedimentary islands covered in mangrove vegetation or opening into apicum formations within salt-marsh plains.
This extensive fringe of tidal flats is interrupted by the promontory of Pedra de Guaratiba, a rocky headland of granite outcrops and rounded boulders that emerge from the flat areas, forming solid-ground sites that supported the historical occupation of the area, including the fishing colony that gave rise to the neighborhood. The urban core that developed around the Pedra maintains a historical relationship with the sea, sustained by traditional practices such as artisanal fishing and shellfish farming, which still withstand growing real estate pressure and environmental changes. The region is also home to the Igreja de Nossa Senhora de Desterro, one of the city's oldest churches, built in the 17th century, making up a cultural landscape that blends historical heritage, religiosity, and coastal geography.
Image description: This is an aerial photograph of a coastal area. On the left, we see a large body of water, possibly a bay, with sunlight reflecting off the surface. Along the right side, there is a continuous line of houses and buildings, forming a coastal city. Between the water and the city, there are green areas that appear to be natural areas or parks. In the more distant background, we see more green areas and some buildings, indicating an urban extension.Praia da Pedra in Pedra de Guaratiba, a centuries-old fishing colony on Baía de Sepetiba.
A low-energy, fine-sand beach arc stretches from Pedra de Guaratiba to the neighborhood of Sepetiba, forming the touristic Praia da Brisa, a typical bay-bottom beach under strong tidal influence. Likewise, the crystalline rock outcrops, as extensions of the isolated mountain ranges of the West Zone, supported Sepetiba's occupation process. Worth highlighting are two rocky points that separate the local beach arcs: Ponta Ipiranga and Ponta do Piaí, which further separate Praia do Recôncavo and Praia de Sepetiba as far as Ilha da Pescaria.
Image description: This is an aerial photograph of a beach and urban area. On the left side, we see the vast blue ocean, stretching out to the horizon. Moving toward the center of the image, we see a strip of light-colored sand extending along the coast. On the right, there is a dense line of green vegetation, which appears to be mangrove. Closer to the right, we see an urban area with scattered houses and buildings. In the background, in the distance, mountains covered in haze can be seen, creating an interesting contrast against the clear, blue sky.Praia da Brisa with Ponta Ipiranga and the two small islands in sequence: Ilha do Tatu and Ilha da Pescaria, both with rocky outcrops.
From there to the end of the municipality, up to the mouth of the Guandu River, the coastline is once again dominated by the tidal flats that outline the entire boundary of the Santa Cruz Air Base, where the mouths of the parallel channels of the Santa Cruz lowlands mark the end of Rio's territory.
These beaches, with fine sand and shallow waters, are strongly influenced by the input of river sediments coming from the Guandu river basin and other channels in the lowlands. In this stretch, mangrove environments predominate, with halophytic vegetation and mudbanks that emerge at low tide, along with navigable channels used by small artisanal fishing boats. The Sepetiba region, in particular, combines elements of a popular seaside resort with intense urban and port pressure, being marked by water degradation, landfills, and construction over areas that were once wetlands.
Image description: The image is a photograph of a beach with a boat in view. On the left side, there is a colorful boat, mainly blue and red, with a blue cover over it. The boat is tied to a rope that extends toward the right side of the image. On the boat, there are several boxes and a white bucket. In the background, there is a vast expanse of calm water, with a few small ripples. On the horizon, there is a line of dense trees, forming a forest. The sky is clear and blue, indicating a sunny day.Fine sedimentary aspect of Praia da Pedra beach, typical of a Bay bottom, where the action of tides predominates over that of waves. The fine sediment settles in wide plains. In the background, the beaches covered by restinga vegetation, in the Restinga da Marambaia.
Despite the advance of urbanization and pollution, the Baía de Sepetiba still holds reflections of its original richness, with breeding areas for marine species and migratory birds, which underscores its ecological importance and its vulnerability in the face of the current model of coastal development.
Still part of the municipality, a small stretch of the Restinga da Marambaia stands as a natural divide between the Baía de Sepetiba and the open sea. About 42 km long, it is a young sedimentary formation made up of sandy ridges running parallel to the sea, interspersed with dune fields, lagoons, and restinga vegetation. Although part of its territory belongs to the city of Rio de Janeiro, Marambaia is controlled by the Armed Forces, which has limited its occupation and helped preserve its ecosystems, making it one of the last great natural refuges on the Rio coastline.
