The Ribeira de Iguape River is 470 kilometres (290 mi) long, and is the largest in São Paulo to have no dams along its length.

[6] In its upper course the Ribeira de Iguape runs through the mountains of the Serra do Mar, and has turbulent waters that are popular for rafting.

[4] From the port town of Registro the river flows quietly through the coastal plain, reaching the Atlantic Ocean in Barra do Ribeira near Iguape, São Paulo.

[3] Near the river mouth, some of the water does not flow directly into the sea but is diverted by the Valo Grande canal into the Mar Pequeno between the mainland and the Ilha Comprida.

[3] At the end of the 1980s the Companhia Brasileira de Alumínio (CBA) was authorized to use the river to produce electricity for its plant through building the Tijuco Alto Dam between the cities of Adrianópolis, Paraná and Ribeira, São Paulo.

The two state licenses were annulled in 1994 through a public civil action that argued that the Ribeira de Iguape was a federal river, and only the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA) could authorise the dam.

Quilombola communities in the affected areas had mobilized to form the Committee of the Campaign Against the Dams of the River Ribeira de Iguape.

Through most of its length the Ribeira de Iguape flows through relatively under-populated agricultural country with large areas of Atlantic Forest.

[19] In January 2014 a spill of an oily substance was detected moving down the river near the Itaoca municipality, which had been hit by a storm in which five people and died and about 20 were missing.

Civil Defense alerted all municipalities to take preventative measures, and warned that people should not drink the river water until the spill had dissipated.