São Luís, Maranhão
Geography

The island of Upaon-Açu is located between two large estuarine systems that are the bays of São Marcos on the west side and São José on the east in the central region of Golfão Maranhense. The two bays are interconnected in the southwest by the channels of the Strait of Mosquitoes and Strait of Coqueiros (separating the island of Upaon-Açu from the island of Tauá-Mirim).

In the São Marcos bay, the watershed of the Mearim river and its tributaries flows, while in the São José/Arraial bay the watersheds of the Itapecuru and Munim rivers break. In this region, the amplitude of the tides can exceed seven meters. The region presents numerous streams and tidal channels. Several agents have modeled relief such as those of climatic, hydrological and oceanographic origin, as well as intense wind, marine and fluvial activity, with vegetation characterized by remnants of the Amazonian Forest, Mangroves and Campo de Perizes, an extensive fluvial plain with predominantly herbaceous, located on the mainland.

The climate is characterized as hot, semi-humid, tropical of equatorial zone, with two distinct seasons that go from damp (January to June) the drought (July to December), with average rainfall of 2,200 mm per year. Some of the conservation units of the island are: APA das Reentrancias Maranhenses; APA of Upaon-Açu-Miritiba-Alto Preguiças, APA of Itapiracó; APA of the Maracanã Region; and the Bacanga State Parks, the Jansen Lagoon and the Rangedor.

On the Strait of Mosquitoes, there are road and railroad bridges linking the mainland to Upaon-Açu Island: the Marcelino Machado bridge, BR-135, composed of two parallel inlet and outlet bridges (456 and 454 meters in length); the metal bridge Benedito Leite, belonging to the São Luís-Teresina Railway; the duplicate bridge belonging to the Carajás Railway; the metal bridge that supports the Italuís waterway, which carries water from the river Itapecuru to the city of São Luís.

There is also a ferry service, between São Luís and Alcântara; and São Luís International Airport.

The municipality contains part of the 1,535,310 hectares (3,793,800 acres) Upaon-Açu/Miritiba/Alto Preguiças Environmental Protection Area, created in 1992. The city is home to the Sítio Rangedor State Park, formerly the fully protected Sítio Rangedor Ecological Station. The municipality also contains a small part of the Baixada Maranhense Environmental Protection Area, a 1,775,035.6 hectares (4,386,208 acres) sustainable use conservation unit created in 1991 that has been a Ramsar Site since 2000. The 2,634 hectares (6,510 acres) Bacanga State Park is just south of the city.
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