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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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Geomorphic river diversity can be explained by a mix of catchment scale controls. • Imposed controls (slope and valley bottom) do not adjust over geomorphic timeframes. • Flux controls (bed material and stream power) are interactions between fluxes. • Assessing controls along long profile can explain the pattern of river diversity. A mix of catchment-scale controls operate to determine geomorphic river diversity in a catchment. These are contextualised here as imposed and flux controls. Imposed controls do not adjust over geomorphic timeframes and produce the environmental setting in which a river functions. Flux controls are dynamic interactions between flow and sediment that heavily influence geomorphic river diversity. We measure and statistically analyse the network scale mix of imposed and flux controls occurring along longitudinal profiles of various shape. We use this to explain the diversity, pattern and sequence of river types at different positions in a catchment. Using the Richmond River catchment, New South Wales, Australia, as our case study we analyse the imposed controls of slope and valley bottom width and the flux controls of bed material size and gross stream power for five river types, ranging from confined continuous rivers in headwaters to laterally unconfined discontinuous rivers in lowland plains. We find that slope and gross stream power are strong, positively correlated controls on all river types, but act most strongly on rivers with continuous channels. In contrast, bed material size is a dominant control on rivers with discontinuous channels. Slope and gross stream power are also critical for determining the downstream pattern of river types along longitudinal profiles. However, the relationship between these controls is complex as not all rivers are influenced by these controls in the same way. Understanding the mix and patterns of controls operating along longitudinal profiles can be used to explain the variability and pattern of river types we see in the landscape. [ABSTRACT FROM AUTHOR]

Contemporary river forms and processes can be heavily influenced by the legacies of anthropogenic disturbances to river systems. Knowledge of the historical range of river adjustment can be used to develop an understanding of a river's 'expected' character and behaviour. Drawing upon the case study of Richmond River Catchment, New South Wales, Australia, we track the history of geomorphic river adjustment from the time of European colonisation in the mid-late nineteenth century. We use this study to develop an approach, called the ' Behavioural sensitivity logical tree ' that can be applied to assess and quantify reach scale behavioural sensitivity, defined as the ease with which geomorphic units and associated water, sediment and vegetation interactions adjust within the expected behavioural regime. We use the results to categorise rivers as Fragile , Active sensitive , Passive sensitive , Insensitive and Resistant. Fragile rivers have a behavioural sensitivity >75% and have the propensity to undergo wholesale river change such that a new river type and behavioural regime is created. Active sensitive rivers have a behavioural sensitivity ranging from 50%–75% and have the ability to re-configure within their contemporary behavioural regime. The behavioural sensitivity of Passive sensitive rivers lies between 20%–50%. These rivers have the ability to maintain their behavioural regime and withstand adjustment. Insensitive rivers have a behavioural sensitivity ranging from 5%–20%. They do not readily adjust and may contain significant antecedent elements that limit geomorphic adjustment. Resistant rivers have a behavioural sensitivity <5% and because of the imposed geological setting cannot readily adjust. We further discuss the evolutionary nature of behavioural sensitivity itself and how rivers can dynamically evolve and shift to a different sensitivity category over time in response to different forms of direct and indirect disturbances. Unlabelled Image • Legacies of post-colonisation anthropogenic disturbance can influence contemporary river forms and behaviour. • We develop an approach that can be applied to any catchment to assess and quantify reach scale geomorphic river sensitivity. • The approach can be used to categorise rivers as Fragile, Active sensitive, Passive sensitive, Resistant and Insensitive. • Geomorphic river sensitivity can dynamically evolve with time. [ABSTRACT FROM AUTHOR]