LA RISPOSTA IDROLOGICA DEI PICCOLI BACINI IDROGRAFICI ALLA SCALA DI EVENTO E NEL DOMINIO DELLE FREQUENZE DI ACCADIMENTO: UN'ANALISI DEI FENOMENI DOMINANTI MEDIANTE L'USO DI MODELLI IDROLOGICI IN CONTINUO OPERANTI ALLA SCALA ORARIA

Hydrological modelling of small catchments remains a challenging task, particularly in regions characterized by high spatial variability of processes and limited availability of observational data. In such contexts, the simulation of hydrological processes in the time domain and the estimation of flood extremes in the frequency domain are often treated separately, limiting a consistent and integrated representation of catchment response. This work proposes a methodological framework aimed at bridging these two domains through the integration of hydrological models operating at different temporal and spatial scales. The analysis is developed at two levels: a regional scale, covering the entire Basilicata region (Southern Italy), and a local scale, focusing on the Fiumarella di Corleto catchment, which is characterized by a long-term hydro-meteorological monitoring network. Time-domain modelling is carried out using the distributed DREAM model at the event scale, to simulate catchment response to intense rainfall and reproduce flood hydrographs, and the conceptual HBV model in continuous mode, to represent long-term water balance and seasonal variability of streamflow. The Fiumarella catchment is used as a detailed case study to analyse hydrological processes and assess the physical consistency of the simulations. In the frequency domain, the QT-DREAM model is applied at regional scale to estimate design floods and hydrographs across the Basilicata region. The model is based on the theory of derived flood distributions and incorporates the concept of variable contributing area (partial area coverage), which depends on soil saturation conditions and the spatial distribution of rainfall. The results highlight the consistency between time-domain simulations and frequency-domain estimates, showing how the integrated modelling approach allows for a more comprehensive representation of runoff generation mechanisms and flood variability across scales. The proposed framework provides a unified methodological approach for hydrological analysis in small catchments, with applications in design flood estimation and flood risk management, particularly in poorly gauged regions.