Mapping valley bottom confinement at the network scale

Gary R. O'Brien*, Joseph M. Wheaton, Kirstie Fryirs, William W. Macfarlane, Gary Brierley, Kelly Whitehead, Jordan Gilbert, Carol Volk

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    16 Citations (Scopus)

    Abstract

    In this article, we demonstrate the application of a continuous confinement metric across entire river networks. Confinement is a useful metric for characterizing and discriminating valley setting. At the reach scale, valley bottom confinement is measured and quantified as the ratio of the length of channel confined on either bank by a confining margin divided by the reach length. The valley bottom is occupied by the contemporary floodplain and/or its channel(s); confining margins can be any landform or feature that makes up the valley bottom margin, such as bedrock hillslopes, terraces, fans, or anthropogenic features such as stopbanks or constructed levees. To test the reliability of calculating confinement across entire networks, we applied our geoprocessing scripts across four physiographically distinct watersheds of the Pacific Northwest, USA using freely available national datasets. Comparison of manually digitized and mapped with modeled calculations of confinement revealed that roughly one-third of reaches were equivalent and about two-thirds of the sites differ by less than ±15%. A sensitivity analysis found that a 500 m reach segmentation length produced reasonable agreement with manual, categorical, expert-derived analysis of confinement. Confinement accuracy can be improved (c. 4% to 17% gains) using a more accurately mapped valley bottom and channel position (i.e. with higher-resolution model inputs). This is particularly important when differentiating rivers in the partly confined valley setting. However, at the watershed scale, patterns derived from mapping confinement are not fundamentally different, making this a reasonably accurate and rapid technique for analysis and measurement of confinement across broad spatial extents.

    Original languageEnglish
    Pages (from-to)1828-1845
    Number of pages18
    JournalEarth Surface Processes and Landforms
    Volume44
    Issue number9
    Early online date25 Mar 2019
    DOIs
    Publication statusPublished - 1 Jul 2019

    Keywords

    • confinement
    • drainage network
    • fluvial geomorphology
    • river restoration
    • River Styles
    • rivers

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