The Una do Prelado River is the largest in the 84,425 hectares (208,620 acres) Juréia-Itatins Ecological Station, a strictly protected area of well-preserved Atlantic Forest created in 1986.

[2] The final section in the east divides the Juréia-Itatins Ecological Station from the Itinguçu State Park, a 5,040 hectares (12,500 acres) conservation unit created in 2006.

Near the sea the river separates into two branches which later recombine, enclosing the Ilha do Ameixal, which holds the Ilha do Ameixal Area of Relevant Ecological Interest.

[3] The Una do Prelado River is a blackwater river fed by various streams from the north side of the Serra da Juréia and the Atlantic side of the Serra dos Itatins.

[1] The river is tidal for most of its length, with seawater reaching as far as 30 kilometres (19 mi) from its mouth in dry periods.