Linking sediment connectivity to remotely sensed, reach-scale morphology identifies correlations between network-scale sediment regimes and local river processes and forms

Connectivity describes the transport between sediment sources and sinks in fluvial networks, defining source-sink relations in the domains of sediment flux, delivery times, and supplied grain sizes. Connectivity embalms both sediment deliveries to individual reaches and sediment transport regimes on the network scale, and is a central driver behind fluvial biotic and abiotic processes, and related ecosystem services. Yet, river basin management is missing quantitative tools for studying connectivity in larger fluvial networks. With the CASCADE (Catchment Sediment Connectivity and Delivery) model we recently introduced a framework that quantifies sediment deliveries from each sediment source to all the connected sinks as individual cascading processes. This allows quantifying all domains of sediment connectivity at the reach scale as well as analyzing the resulting network-scale sediment regimes. CASCADE is applicable also for very large and poorly monitored river networks. We implement CASCADE for a large river network (7500 km) in SE Asia and quantify all domains of connectivity for all reaches in the network. We derive some relevant river morphological features for a subset of reaches in the network from high resolution satellite imagery and find significant links between observed forms and sediment connectivity information derived from CASCADE. CASCADE opens up novel opportunities to clarify the link between network scale sediment regimes and local morphologic processes and forms. This is of concrete interest for river basin management because CASCADE allows to assess impacts of anthropic disturbance on river sediment regimes and to anticipate resulting changes in local fluvial processes and related eco-system services.