Automated GIS-Based Hydrological Modeling Framework for Flood Hydrograph Estimation in Ungauged Mediterranean Catchments: A Case Study of Sicily

Biagio Saya 

The estimation of design flood hydrographs in ungauged Mediterranean catchments
remains a persistent challenge for hydrological engineering, flood hazard assessment, and
territorial risk planning. The absence of discharge observations, coupled with the high
temporal concentration of precipitation and the marked geomorphological variability of
small basins, renders conventional calibration-based approaches only partially applicable.
Within this context, the present study proposes a fully automated GIS-based framework,
implemented in Python and integrated into the QGIS environment via the PyQGIS API,
for the derivation of flood hydrographs in Sicilian basins.
The framework couples regional rainfall frequency analysis, distributed SCS-CN runoff
abstraction, and time-area routing into a single computational chain. The procedure is
designed to process multiple catchments simultaneously, significantly reducing operator
dependence while ensuring strict methodological reproducibility. Three hydrological formulations
are compared: the Rational Method, a synthetic Chicago-type hyetograph,
and a kinematic time-area convolution scheme. The resulting workflow is highly suited to
flash-flood-prone Mediterranean watersheds, where a rapid hydrological response, limited
data availability, and the need for consistent regional design criteria demand a robust and
scalable modeling approach.