Four main geological formations from the state of Rio Grande do Sul, Southern Brazil. The study area (Quaternary deposits) as well as previous studies used in Dice Similarity Index analysis is entirely inserted in Coastal Plain. Key: 1 present study 2 Turuçu River basin; Burns et al. 20153 Corrientes Stream; Volcan et al. 20124 Tapes Butiazais; Becker et al. 20075 Fortaleza lagoon; Schifino et al. 20046 Lagoa do Peixe; Loebmann and Vieira 20057 Peat forest; Quintela et al. 20078 Rio Grande coastal streams; Tagliani 1995 9 Cassino coastal streams; Bastos et al. 201310 Taim wetland; Garcia et al. 200611 Lagoa Mangueira; Artioli et al. 2009.