The river then leaves Tijuca Forest into the Guararapes favela, then into the high-income Cosme Velho neighborhood, and then it is buried completely underground.

Untreated sewage is the primary source of pollution of the Carioca; the 7 kilometres (4.3 mi) stretch of the river in Guararapes and Cosme Velho are a great sources of unregulated sewage.

The river has a single wastewater treatment facility near its mouth before emptying into Guanabara Bay.

Biochemical evaluation of the river began in 1991 and water quality decreases annually.

[2][3] This article related to a river in Rio de Janeiro state, Brazil is a stub.