D-CASCADE MODEL APPLICATION IN PREDICTING BED MATERIAL TRANSPORT: ASSESSING THE IMPACT OF SLOPE UNCERTAINTY ON SEDIMENT FLUXES ESTIMATION IN THE PO RIVER

Characterizing sediment fluxes and their evolutionary trends is vital for effective sediment management and river basin planning. The slope is a critical parameter for estimating sediment fluxes. This study investigates how different slope scenarios impact bed material flux modeling in the Po River basin, utilizing the D-CASCADE model, and validates simulated sediment fluxes with two reference datasets—one site-specific and one at the network scale. Four slope scenarios were delineated using diverse DEMs and computation methods, followed by simulations to analyze bed material transport. Discrepancies in model outcomes highlight the sensitivity of sediment flux modeling to slope variations and DEM resolution. Three scenarios exhibit similar bed material flux trends, albeit with varying magnitudes. Simplistic slope computation methods, prone to user subjectivity, led to unrealistic mobilization spikes, which were mitigated by smoothing operations. Finer resolution DEMs increased sediment disconnectivity around the Isola Serafini dam, while coarser resolutions yielded higher mobilized sediment fluxes. The model shows heightened sensitivity to slope variations in lowland areas with higher discharge values. Validation results, falling within the same order of magnitude and variability range as observations, are deemed satisfactory despite uncertainties. The study underscores the D-CASCADE model's utility in simulating sediment fluxes and stresses the necessity for spatially distributed evidence to enhance model calibration and validation. Further sensitivity analyses are deemed crucial for refining model accuracy and reliability.