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Quantifying sediment connectivity: Moving towards a holistic assessment through a mixed methods approach

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Author(s): Michael Turley, Marwan A. Hassan, Olav Slaymaker

Document Type:
Publisher: Earth Surface Processes and Landforms
Published Year: 2021
DOI Identifier: 10.1002/esp.5191
ISBN Identifier:

The sediment connectivity concept is particularly suitable for tackling complex, multi-disciplinary questions through systems thinking. However, it is unclear how to directly measure connectivity, and so proxy variables are often applied by indices to provide estimates. In this study, we critically evaluate a broad range of connectivity indices encompassing structural and functional connectivity as well as hillslope channel coupling. We then discuss their role in providing a more holistic estimation of connectivity within the Tahoma Creek Watershed, WA. Of the 14 kilometers of channel below the glacier front, the upper 6 kilometers (0-6 km) are coupled to the adjacent hillslopes. Coupled reaches correspond to regions with a high proportion of area contributing sediment and relatively high connectivity values, where all measures decrease in the downstream direction. A significant transition occurs near river kilometer 6. Here the valley bottom abruptly widens, deposition occurs, and the hillslopes become decoupled from the active channel. This transitional reach is also identified as a geomorphic hotspot based on the network structure. The lower 8 kilometers of channel downstream of this reach are largely depositional and percent contributing area and connectivity values remain low, eventually reaching a minimum. Despite their limitations, we found each method to provide unique and useful information regarding connectivity. The effect of scale and event magnitude on connectivity is illustrated. We also found vegetation, topographic characteristics, and network structure to be important in high gradient glacio-volcanic landscapes. The choice of an index will depend on the research objectives, data availability, and the proxy variables that best describe the variability within the defined area.

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Suggested Citations:
In Text Citation:
Turley and others (2021) or (Turley et al., 2021)

References Citation:
Turley, M., M.A. Hassan, and O. Slaymaker, 2021, Quantifying sediment connectivity: Moving towards a holistic assessment through a mixed methods approach: Earth Surface Processes and Landforms, doi: 10.1002/esp.5191.