Characterized by the presence of the Atlantic Forest, ecotourism, high biodiversity, an environmental protection area and so on, the Coastal Basin is one of 16 Basins in Paraná State, Brazil. In this work, hydrogeomorphological processes were analyzed for 4 watersheds (Nhundiaquara, Marumbi, Tagaçaba and Guaraqueçaba) in the Coastal Basin. Using maps, the geomorphological characteristics, such as drainage area, coefficient of compactness, form factor, drainage density, steepness and stream order, were determined for each watershed. No significant differences for these factors were found between the four watersheds. Using rainfall and runoff data provided by SUDERHSA, the hydrograph separation in annual water balance was carried out with two methods:

(1) the graphical method proposed by HEWLETTE & HIBBERT (1967) and
(2) the numerical model HYCYMODEL. Through the calibration of HYCYMODEL for the rainfall-runoff processes of the watersheds, the values of the 9 parameters of this model were determined.

The results obtained from both methods were almost equal, showing that the baseflow was approximately 29% of the total discharge for Nhundiaquara and Marumbi and 75% for Tagaçaba and Guaraqueçaba. Parameters D₁₆ and D₅₀, expressing the soil layer thickness, were found to be much smaller for Nhundiaquara and Marumbi than for Tagaçaba and Guaraqueçaba. Therefore it is concluded that a thinner soil layer generates large values of direct runoff in Nhundiaquara and Marumbi and that an opposite phenomenon occurs in Tagaçaba and Guaraqueçaba.