Doctoral Dissertation Research: The Impact of Lateral Channel Confinement on River Morphology

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This doctoral dissertation project will address the complex ways in which the lateral, or riverbank, boundaries of a river impact the river's form. This includes how tributaries and hillslope erosion processes contribute sediment, and how laterally confining features such as roads, railroads, and bridge abutments alter both sediment contributions and channel morphology by modifying the flow regime of the river, thus altering the effectiveness of the river to erode or deposit material. This project will also provide new insights into how river shape and form is organized in terms of the distribution of sediment type, as well as channel width and depth in the downstream direction. The student will focus on investigating the role of tributaries and hillslope erosion processes as sources of additional sediment, and riverbank constrictions as locations where human activity has altered the natural river flow, often degrading habitat for culturally and environmentally important aquatic and riparian species. The findings of this project will contribute to the understanding of how rivers respond to changing lateral conditions. This information can be used in river restoration projects to enhance the health of river ecosystems. Additionally, the information gained from the research has the potential to inform future construction along rivers by providing a more thorough understanding of the importance of the link between a river and its floodplain. The methodologic approach to this project is designed to be low-cost and widely accessible, with the objective of showing the wide applicability of this approach to river conservation and restoration efforts across the country. As a Doctoral Dissertation Improvement award, this project will also provide support to enable a promising young scholar to establish a research career.This project focuses on deepening the "sediment links" concept. This theoretical approach frames river tributaries as sediment links, creating a series of distinct river sections, defined by local changes in channel slope and gravel size. The student proposes that lateral channel constrictions can be thought of as "sediment breaks" within this context, as places where the increase in shear stress at the channel bottom, due to a lack of floodplain access during high-flow events, will result in a similar morphologic change as sediment links, but due to an increase in erosion, rather than a surplus of supply. The methods used in this project research include the use of a small unmanned aerial system as well as underwater photography to generate primary data which will be used to quantify particle size distributions, channel depth, and channel width. Existing aerial imagery and LiDAR data will be used to classify channel constriction severity using accepted definitions. The data sources will be used to address several research questions relating the severity of channel constriction to the magnitude of departure in channel morphology variables from a natural control reach. The research questions will also further analyze the relationship between tributaries and local changes in channel morphology and patterns of water surface roughness and velocity vectors. This research will be conducted along the Rogue River in Southern Oregon, USA but its findings will be broadly applicable in other river systems.