Study Region We developed a new experimental nested catchment in the Eggen-Ega River basin, Eastern Italian Alps, comprising four 27 m 2 hillslope plots and three watersheds draining 2.34, 42.4, and 166 km 2 . Study Focus We aimed to understand scale-dependent magnitude and controls of turbid stormflow transfer across the Alpine catchments. We monitored runoff volume and turbidity at four spatial scales and assessed their dependence on the characteristics of 23–41 rainfall events between April and October 2024. New Hydrological Insights for the Region Storm runoff coefficients exhibited a negative power-law scaling with drainage area (exponent: −1/10), suggesting stronger scale-dependent runoff fluctuations at finer scales, critically limiting the representativeness of small-scale, single-point stream gauging in the region. On the contrary, the mean runoff coefficients at 42.4 and 166 km 2 were both 0.01, suggesting sufficient region-specific drainage sizes to average out the uniqueness of monitoring locations and timing. While rainfall intensity and saturation (event depth and duration) exerted primary controls on event-scale sediment delivery from 27 m 2 plots to a 2.34 km 2 headwater, turbidity in the larger 42.4 km 2 catchment was more variable and less sensitive to rainfall predictors, likely due to sediment routing beyond the timescale of individual storm events. Our novel nested catchment approach highlights scale-dependent observations of turbid stormflow, calling for extended monitoring of nested catchments across the Alpine regions.
Koyanagi et al. (2026) studied this question.