The great decline of suspended sediment load in the Po River (Italy) over the last 100 years

This study investigates how a sequence of human impacts has profoundly altered suspended sediment yields in the Po River, the largest fluvial system in Italy, over the last 100 years. By integrating long-term data on suspended sediment transport with a detailed analysis of anthropogenic drivers—including land-use changes, inchannel mining, damming and river training works—we reconstruct the spatiotemporal trajectory of sediment dynamics across the river system. Results reveal a marked reduction in suspended sediment yields, occurring asynchronously along the Po River: declines of about 􀀀 48% first emerged in the middle course during the 1920s–1940s, primarily due to dam construction in the western catchment, and later, with comparable intensity, in the lower course (1950s–1980s), largely driven by river training interventions, sediment deposition within the active channel, and sediment retention in flood detention basins along the Apennine tributaries. Considering the entire investigated time window (1924–2019), the river exhibits a substantial long-term reduction in annual suspended sediment yields, exceeding 􀀀 72% at the catchment closure. These reductions in fine sediment transport have contributed to trigger substantial geomorphological transformations affecting the delta region. The findings underscore the complexity of interpreting sediment dynamics under overlapping anthropogenic pressures and highlight the need for integrated management strategies aimed at restoring sediment fluxes and connectivity. In particular, the partial reactivation of sediment deposits accumulated within anthropogenically induced traps along the main stem could represent a promising, though complex, strategy to mitigate sediment deficits and support more sustainable management of the delta.