Strategie di mitigazione per il controllo dei flussi di sedimenti nei bacini forestali interessati da operazioni forestali, dagli incendi boschivi e dalla siccità nel contesto del Cile centro-meridionale

Forest activities significantly impact hydrological and sediment processes in mountainous catchments, with considerable environmental implications. This thesis evaluates post-harvest and post-fire management practices to control and mitigate sediment fluxes in small catchments under intense forestry activity in south-central Chile, focusing on three primary objectives. First, the study characterizes the effects of forestry operations and climate variability on runoff and sediment transport. Analyzing 11 years of hydrometeorological and sediment data from four small catchments revealed distinct patterns across different intervention types. In the thinned catchment, operations consistently reduced runoff, contradicting common assumptions that streamflows increase following forest reduction. Conversely, harvested catchments showed initial runoff increases before declining due to a combination of vegetation regrowth and ongoing drought conditions. Suspended sediment load dynamics demonstrated catchment-specific responses, with rapid recovery to pre-harvest conditions after initial transport pulses. The methodology separated climate variability effects from forest operation impacts, enabling forest managers to distinguish between natural variability and anthropogenic influences. Second, the research characterizes the effect of post-harvest residue piling on sediment connectivity through Index of Connectivity (IC) analysis. Using LiDAR-derived digital terrain models, scenarios with and without residue piles were compared across two catchments. Results revealed that pile orientation relative to contour lines strongly influenced effectiveness, with parallel-to-contour arrangements reducing connectivity more effectively than perpendicular ones. Strategic placement regarding distance from drainage networks also proved crucial, highlighting the importance of spatial configuration over simple coverage percentage. Third, the study evaluates the effectiveness of post-fire woody dams for connectivity reduction. Following catastrophic wildfires in February 2023, emergency woody dam installations were assessed through IC analysis and retention capacity modeling. While catchment-scale connectivity changes were modest, significant local impacts were observed in dam retention areas. Notably, one catchment achieved equivalent total retention volume with fewer structures, demonstrating that strategic placement can outperform quantity alone in resource-constrained emergency responses. The study contributes methodological advancements for forest management planning, combining field monitoring, statistical analysis, and spatial modeling to evaluate practices across multiple scales. The findings highlight the importance of context-specific interventions tailored to local topographic, hydrological, and vegetation characteristics. Recommendations include optimizing spatial configuration of management interventions, adopting integrated monitoring approaches, and developing adaptive strategies for climate variability. This research demonstrates the value of evidence-based, spatially explicit approaches to forest management in south-central Chile. By strategically implementing post-harvest and post-fire management practices with careful consideration of landscape context, forest managers can effectively mitigate sediment impacts while maintaining economic viability of forestry operations in an increasingly variable climate.