The paper analyzes the rainfall-flow-sediment relationships obtained after two monitoring years in a small semi-agricultural catchment in Apennines mountain range (Italy) with temperate mediterranean climate. The climate seasonality involves intra-annual variability in the hydrological response. Flow characteristics are correlated with rainfall depth, while duration, erosivity and previous rainfall are correlated with flow parameters depending on the season. The lack of a well defined relationship between these variables may be due to the flow mechanisms themselves, that vary with seasons. In summer Hortonian flow dominates, while in the other seasons runoff is generated by the Dunnian mechanism or by a combination of both mechanisms. Sediment concentration and soil loss are more correlated with streamflow than with rainfall parameters. Silt is the most eroded fractions. There is a significant correlation between the mean diameter of soil particles and the flow within the same flood event, but in general the relationship is influenced by supply condition (soil moisture, initial baseflow, etc).