CASCADE : a toolbox for network-scale sediment connectivity assessment

Sediment connectivity is fundamental for the functioning of fluvial eco-systems. Human disturbances to naturalsediment transport processes caused, e.g., by dam construction or deforestation, are hence potentially detrimentalto river ecosystems and ecosystem services. However, the alteration of the natural sediment transport processesis often underestimated or ignored while planning human interventions around or on river systems, leading tounforeseen impacts on the whole river system and costs for the people depending on its resources.Modelling sediment connectivity and reaction to anthropic alterations represent a necessity to increase theunderstanding of the river process, to estimate impacts and plan effective measures. Since river are deeply con-nected systems, models should adopt a whole-network perspective, which traditional sediment transport modellingtechniques often fail to provide. CASCADE (CAtchment Sediment Connectivity And DElivery) (Schmitt et al.,2016) is a modelling framework that combines concepts of network modelling with empirical sediment transportformulas to provide spatially fully distributed information on sediment transport and, connectivity in large rivernetworks.CASCADE is a flexible modelling framework which takes advantage of increasing availability of geomor-phic data and hydrologic data in large-basins or at global scales to describe sediment connectivity in data rich aswell as data scarce environments.In this work, we present the CASCADE toolbox, an open source toolbox containing the functions andscripts necessary to run CASCADE and to provide advanced function for interactive analysis of sedimentconnectivity. The toolbox is designed to provide an estimation of the basin-scale, cumulative altering effects onsediment transport and connectivity caused by different anthropic and natural influences. The toolbox allowsfor easy integration of dams or other barriers as well as for coupling models for increased hillslope sedimentgeneration.Moreover, the CASCADE toolbox contains different user customization options, like the possibility to change thetransport formulas employed. With its effective and flexible data requirements, its computational efficiency and itscustomization options, CASCADE is designed for river basin management even in those contexts where sedimentconnectivity is so far not commonly considered and its impacts underestimated. Applications include optimizationof dam portfolios for minimal sediment trapping, identify dominant sources of sediment for reservoir storage loss,or visualizing basin-scale sediment connectivity under different sediment management strategies.