Riverscape mapping and hyperscale analysis of the sediment links concept

Abstract

Longitudinal patterns in channel complexity play an important role in our understanding of fluvial systems. The spatial scales over which external controls such as tributaries, landslides and debris flows, alter channel form and influence the broader basin-wide trends in channel form. Channel complexity across a basin has important implications for how we conceptualize basin-wide trends in channel form such as downstream hydraulic geometry and the sediment links concept. This study takes a hyperscale approach to mapping channel morphology across 200km of the Rogue River in Southwest Oregon - that is high-resolution data over large spatial extents allowing analysis to be conducted simultaneously at and across multiple spatial scales. Using a sUAS and digital photosieving we measured gravels on exposed gravel bars for the study area. We also measured thalweg depth in the field using a singlebeam echo sounder. Slope and channel width were derived using existing GIS datasets. We used these data to create a hyperscale view of the Rogue River examining the impact of tributary and non-tributary sediment links. We used a statistical approach to determine if changes in channel form were truly unique in the context of larger-scale channel variability. Our findings show inconsistent statistical significance of the identified lateral sediment sources (LSS) between variables - e.g. a statistically significant change in slope would not necessarily correlate with an increase in unit stream power. There were many LSS which triggered statistically significant changes to channel form. We used hyperscale graphs to reveal the complexity and spatial trends associated with the relationships between a given sediment link and channel form. The results of this study illustrate the complexity with which sediment links impact channel form and the distances below a given sediment link that a detectable signal exists, if a detectable signal exists.