Modelling sediment (dis)connectivity across a river network to understand locational‐transmission‐filter sensitivity for identifying hotspots of potential geomorphic adjustment

Abstract

Rivers act as ‘jerky conveyor belts’ that transmit fluxes of flow and sediment downstream. This transmission of fluxes can be highly variable within a drainage basin resulting in either abrupt or gradational sediment (dis)connectivity patterns and processes. This study assesses sediment (dis)connectivity across a basin as a means to understand the locational, transmission and filter sensitivity properties of a fluvial system. Drawing upon the case study of Richmond River Catchment, New South Wales, Australia we use the concepts of effective catchment area and buffers, along with graph theory and an empirical sediment transport model CASCADE (Catchment Sediment Connectivity and Delivery), to assess (1) the degree to which modelled sediment cascades along the river network are connected or disconnected (2) how the position, pattern and configuration of (dis)connection facilitates or restricts geomorphic adjustment in different parts of a catchment, and (3) use the findings as a basis to explain the locational‐transmission‐filter sensitivity of the catchment. We use this analysis to segregate supply limited and transport limited reaches and identify various controls on sediment dynamics: in‐stream sediment storage units, junctions between different geomorphic river types, tributary confluences and sediment storage units within partly confined floodplain units. Such analysis lays the foundation for network scale identification of potential hotspots of geomorphic adjustment.

(Dis)connectivity in hydro‐geomorphic systems – emerging concepts and their applications

“…Poeppl et al, In press). In this SI, five contributions have dealt with connectivity in mountain environments, with a specific focus on fluvial processes by Hinshaw et al (2022; South Fork McKenzie River basin, Cascade Mountains, Oregon, USA), Kemper et al (2022; Yampa River basin, Rocky Mountains, Colorado, USA), and Khan et al (2021; Richmond River catchment, Great Dividing Range, Australia), on hillslope processes by Martini et al (2022; Rio Cordon catchment, Italian Alps), or on both environments as shown by Turley et al (2021; Tahoma Creek catchment, Cascade Mountains, Washington, USA). Two papers investigated connectivity relationships in river and catchment systems (Bizzi et al, 2021: Vjosa River, Albania; González‐Romero et al, 2021: Segura River catchment, Spain), while two contributions had a specific focus on delta, estuary and wetland environments (Hiatt et al, 2022; Singh et al, 2022; Sonke et al, 2022).…”

“…The spatial dimensions of (dis)connectivity focused on in this SI are likely representative of the distribution of studies in general, where most focus is on the role of longitudinal connectivity of water, sediment and plant propagules. There is a clear focus on longitudinal connectivity of sediment (Bizzi et al, 2021; Kemper et al, 2022; Khan et al, 2021; Turley et al, 2021), followed by that of water fluxes in estuarine channels and wetlands (Hiatt et al, 2022; Sinha et al, 2022). Three studies combined aspects of longitudinal and lateral connectivity, either in the channel‐floodplain (Hinshaw et al, 2022) or the catchment perspective (González‐Romero et al, 2021; Turley et al, 2021).…”

“…This distinction between SC and FC is an artificial one that tries to separate the influence of system structure on dynamical processes (Turnbull et al, 2018), yet is nevertheless useful as it allows simplification of the characterization/quantification of connectivity. As seen from the collection of studies within this SI, there is a general tendency to focus within geomorphology on either SC (e.g., Martini et al, 2022) or FC (e.g., Bizzi et al, 2021; Khan et al, 2021), and rarely do studies focus on both (but see Hiatt et al, 2022), often because the approaches used make it challenging to make such a distinction.…”

The impact of plants on fine sediment storage within the active channels of gravel‐bed rivers: A preliminary assessment

“…lakes and ponds) to compute budget components and reveal human impacts (Foster et al, 2021). Laboratory analyses of sediment samples have provided an indirect means of estimating proportional source contributions by 'fingerprinting' sediment characteristics (Pulley et al, 2017;Walling et al, 1998Walling et al, , 2006, with further advances extending the spatial and temporal scales of quantification using information from aerial and satellite imagery, lidar data and modelling (Bizzi et al, 2021;Khan et al, 2021;Piégay et al, 2020).…”

Long-term erosion and the impact of wildfires: two different approaches

“…Rivers act as a network of channels that carry water, sediment, and energy downstream (1). On the heterogeneous area of the watershed, some areas might be responsive to disturbance events (e.g., wildfires and droughts), while others may be resistant to the change (Khan et al, 2021).…”