[DSRP Evidence](https://dsrpevidence.org/)

# Scale-dependent hydrological controls on storm runoff volume and its turbidity in nested catchments of the Eastern Italian Alps

## Details

**Authors** Kenta Koyanagi, Andrea Andreoli, Giovanna Nordio, Hugo Gaudron, Ronald Pöppl, Francesco Comiti

**Year** 2026

**Publisher** Journal of Hydrology: Regional Studies

**Kind of work** article

**Discipline** Hydrology

**Secondary disciplines** Geography, Environment & Sustainability

**Applied** false

[Read it at the publisher](https://doi.org/10.1016/j.ejrh.2026.103569) 
10.1016/j.ejrh.2026.103569

## In authors' words

### Abstract

Study Region We developed a new experimental nested catchment in the Eggen-Ega River basin, Eastern Italian Alps, comprising four 27 m2 hillslope plots and three watersheds draining 2.34, 42.4, and 166 km2. 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 km2 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 m2 plots to a 2.34 km2 headwater, turbidity in the larger 42.4 km2 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.

### What they set out to do (purpose)

To understand the scale-dependent magnitude and controls of turbid stormflow transfer across Alpine catchments.

### Who or what was studied (sample)

One experimental nested catchment in the Eggen-Ega River basin, Eastern Italian Alps: four 27 m2 hillslope plots and three watersheds of 2.34, 42.4, and 166 km2, monitored over 23–41 rainfall events (April–October 2024).

### How they did it (methods)

Hierarchical nested-catchment monitoring of runoff volume and turbidity at four spatial scales, relating each to rainfall event characteristics.

### What they found (results)

Storm runoff coefficients scaled negatively with drainage area (power-law exponent −1/10), and rainfall intensity and saturation controlled sediment delivery at plot and headwater scales but not turbidity at the 42.4 km2 catchment scale.

## Commentary

### In short

The study shows that a catchment is a nested system whose parts and wholes respond differently to the same rainfall input, so that what is observed about the rainfall-runoff relationship depends on the scale from which it is observed.

**Patterns it shows** S, R, P

**Added** 2026-10-03

**How to cite this** Kenta Koyanagi, Andrea Andreoli, Giovanna Nordio, Hugo Gaudron, Ronald Pöppl, Francesco Comiti (2026). Scale-dependent hydrological controls on storm runoff volume and its turbidity in nested catchments of the Eastern Italian Alps. Journal of Hydrology: Regional Studies.