Understanding the movement of fluvial sediments from mountain torrents to alluvial plains is crucial for the health and functionality of river ecosystems, flood control, and water availability. Network-scale sediment connectivity models have emerged in recent decades but robust validation with field measurements is urgently needed. In the present study, a series of DODs (Dem Of Differences), taken at two locations along the Tagliamento River, in Northeastern Italy, over the period 2021-2024, are analyzed by using the Morphological method to estimate sediment volume fluxes and the VMD method (variational mode decomposition) to quantify the spacing of erosional and depositional units as a proxy for sediment traveling distances, also called path-lengths. These field-based estimations are used to validate the numerical model D-CASCADE simulated over the same time period. They are also validated against former analyses reported in literature. Results present good agreements between the field-based estimations, the numerical simulations, and the past studies in terms of sediment path-length and fluxes. In addition, the reach-scale budgets generated by the DODs and the numerical model show the same trend for the most active years in terms of floods, validating the numerical model’s ability to predict net erosional and depositional reaches in the network. The presented results constitute a step forward in validating and refining our understanding of sediment transport processes in a large Alpine River, connecting mountain sediment sources to the alluvial plains. This study provides practical implications for the sustainable management of riverine ecosystems.