Investigating Suspended Sediment And Large Wood Dynamics in a Mountain Forested Catchment

Suspended sediment plays a crucial role in shaping stream morphology and maintaining ecological balance, yet the main controls on its sources and dynamics in forested mountain catchments are still poorly documented. In this study we aimed at assessing suspended sediment spatio-temporal sources and transport dynamics in a Mediterranean mountain catchment. A relevant role might be played by large wood debris in suspended sediment retention and release: large wood structures can significantly influence sediment dynamics by trapping sediments and creating stable habitats for aquatic organisms. This aspect is particularly relevant in forested mountain streams where wood accumulation can alter flow patterns and sediment transport mechanisms.

The experimental activities were carried out in the densely forested Re della Pietra catchment located in Tuscany, Central Italy.

To assess suspended sediment spatio-temporal dynamics, field measurements were conducted since December 2024, including monitoring of turbidity at the catchment outlet using a high-definition turbidimeter, stream stage measurements, soil moisture measurements at two depths, and the main meteorological variables.

Preliminary results show a significant correlation between turbidity, rainfall intensity and stage variation, suggesting that rainfall intensity is crucial in suspended sediment release and transport patterns. Notably, pronounced turbidity peaks were observed during moderate to intense storm events occurred during the wet season but did not correlated to meteorological variables. The analysis of the hysteresis loops between turbidity and stream stage (as a proxy of discharge) reported that the 15% of the loops were clockwise, suggesting that suspended sediment primarily originates from local sources, mostly during the wet season.

The study highlights the relationships between suspended sediment transport, large wood debris, and hydrological variables, emphasizing the need for further investigation of the factors affecting suspended sediment transport in forested mountain environments. The determination of flow rating curve is in progress, and future analysis will consider suspended sediment concentration and discharge data. The large wood impact will be studied through the visual analysis of the photographic documentation produced by cameras located at the catchment outlet.