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  1. Article: Non‐Monotonic Floodplain Responses to Changes in Flooding Intensity

    Barefoot, Eric A. / Nittrouer, Jeffrey A. / Straub, Kyle M.

    Journal of geophysical research. 2021 Oct., v. 126, no. 10

    2021  

    Abstract: Overbank flooding is common along most rivers, and it influences the dispersal of sediment to floodplains. While variable discharge is a critical aspect of fluvial landscape evolution, it is typically modeled by simplifying the hydrograph to an ... ...

    Abstract Overbank flooding is common along most rivers, and it influences the dispersal of sediment to floodplains. While variable discharge is a critical aspect of fluvial landscape evolution, it is typically modeled by simplifying the hydrograph to an equivalent steady discharge: the channel‐forming discharge. However, for all formulations used to simplify hydrographs, many different inputs can produce the same channel‐forming discharge. Here, we investigate how hydrographs with different flood intensities affect channel mobility, sediment accumulation patterns, and alluvial morphology using a suite of physical experiments where a fan delta grew by dispersing a cohesive sediment mixture into a basin. The experiments spanned three levels: no flooding, low‐intensity flooding, and high‐intensity flooding, while the time‐averaged water and sediment discharge was equivalent between all flooding regimes. Across this gradient, channel mobility, alluvial morphology and sediment dispersal scaled non‐monotonically with flooding intensity, and the data suggest that levee‐building feedbacks are the cause. We found that flood intensity modulates the relative balance between sediment delivery to channel margins, which nourishes levee growth, and the intensity of overbank flow, which inhibits levee growth. When flooding was absent, levees experienced consistent overbank flow and sediment delivery, leading to moderate levee aggradation and sporadic levee breaches. In contrast, when low‐intensity flooding was imposed, levees experienced enhanced sediment delivery by low‐amplitude floods, but only intermittent scouring. A further increase in flood intensity generated intense overbank flows that inhibited levee growth altogether. These results imply the existence of an optimum levee‐building condition, where flooding conditions stabilize channels through levee‐building feedbacks.
    Keywords basins ; floodplains ; geophysics ; hydrograph ; landscapes ; research ; sediment yield ; sediments
    Language English
    Dates of publication 2021-10
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ISSN 2169-9003
    DOI 10.1029/2021JF006310
    Database NAL-Catalogue (AGRICOLA)

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  2. Article ; Online: Similarity of stream width distributions across headwater systems.

    Allen, George H / Pavelsky, Tamlin M / Barefoot, Eric A / Lamb, Michael P / Butman, David / Tashie, Arik / Gleason, Colin J

    Nature communications

    2018  Volume 9, Issue 1, Page(s) 610

    Abstract: The morphology and abundance of streams control the rates of hydraulic and biogeochemical exchange between streams, groundwater, and the atmosphere. In large river systems, the relationship between river width and abundance is fractal, such that narrow ... ...

    Abstract The morphology and abundance of streams control the rates of hydraulic and biogeochemical exchange between streams, groundwater, and the atmosphere. In large river systems, the relationship between river width and abundance is fractal, such that narrow rivers are proportionally more common than wider rivers. However, in headwater systems, where many biogeochemical reactions are most rapid, the relationship between stream width and abundance is unknown. To constrain this uncertainty, we surveyed stream hydromorphology (wetted width and length) in several headwater stream networks across North America and New Zealand. Here, we find a strikingly consistent lognormal statistical distribution of stream width, including a characteristic most abundant stream width of 32 ± 7 cm independent of discharge or physiographic conditions. We propose a hydromorphic model that can be used to more accurately estimate the hydromorphology of streams, with significant impact on the understanding of the hydraulic, ecological, and biogeochemical functions of stream networks.
    Language English
    Publishing date 2018-02-09
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 2041-1723
    ISSN (online) 2041-1723
    DOI 10.1038/s41467-018-02991-w
    Database MEDical Literature Analysis and Retrieval System OnLINE

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