Convective Core Dynamics and Sensitivity of Runoff Generation to Short-Duration Mediterranean Storms

Short-duration rainfall extremes in Mediterranean regions are frequently produced by convective storms that concentrate most precipitation within narrow temporal windows. Standard Depth–Duration–Frequency (DDF) and Intensity–Duration–Frequency (IDF) approaches convert a selected duration and return period into constant-intensity design storms, neglecting the temporal structure that governs runoff generation in fast-responding catchments. This study quantifies the bias introduced by this simplification using long-term 10 min rainfall records and a duration-consistent event-selection procedure. Events lasting 30, 40, 50 and 60 min were extracted from local VAPI(Progetto Speciale per la Valutazione delle Piene in Italia) DDF relationships and converted into dimensionless temporal profiles; hydrological sensitivity, however, was evaluated only for the 30- and 40 min storms, as longer durations were included solely in the rainfall analysis. The 30- and 40 min profiles exhibit marked convective concentration, with the most intense 10 min interval contributing up to 41.8% and 31.7% of total rainfall. Controlled SWMM (Storm Water Management Model) 5.2 simulations on a conceptual 6-ha peri-urban catchment, performed within a non-predictive sensitivity experiment, show that variable-intensity storms tend to increase peak discharge and shorten time to peak compared with constant-intensity storms of identical depth. These results indicate that constant-intensity DDF/IDF storms may underestimate peak runoff for short durations, underscoring the importance of incorporating locally derived temporal rainfall profiles in Mediterranean environments characterized by increasingly irregularshort-duration convective rainfall.