Transient Response and Adjustment Timescales of Channel Width and Angle of Valley‐Side Slopes to Accelerated Incision

DOI DOI Web Site 参考文献87件
  • Naoya O. Takahashi
    Department of Earth Science Tohoku University Sendai Japan
  • J. Bruce H. Shyu
    Department of Geosciences National Taiwan University Taipei Taiwan
  • Shinji Toda
    International Research Institute of Disaster Science (IRIDeS) Tohoku University Sendai Japan
  • Yuki Matsushi
    Disaster Prevention Research Institute Kyoto University Uji Japan
  • Ryoga J. Ohta
    Faculty of Science and Engineering Chuo University Tokyo Japan
  • Hiroyuki Matsuzaki
    Micro Analysis Laboratory, Tandem Accelerator (MALT) The University Museum The University of Tokyo Tokyo Japan

説明

<jats:title>Abstract</jats:title><jats:p>Studying bedrock rivers during their transient states helps understand the response of a fluvial system to the changing boundary conditions. Although theoretical studies predict how river form adjusts to changes in incision or rock uplift rates, field constraints on the timescale of this adjustment are limited. We investigated the transient behavior of channels and hillslopes and estimated the adjustment times of channel width and angle of valley‐side slopes to accelerated incision based on knickpoint travel time. We documented channel slopes, channel widths, and hillslope angles along six rivers around an active normal fault in Iwaki, Japan, and identified river sections in a transient state. Channel slopes and basin‐averaged erosion rates determined from <jats:sup>10</jats:sup>Be concentrations are distinct between rivers near and distant from the fault, suggesting that past increases in fault throw rates triggered the knickpoint formation and the observed transient response. Adjustment time for width is at least 10<jats:sup>5</jats:sup> years and can take 10<jats:sup>6</jats:sup> years after the knickpoint passage. Adjustment time for hillslope angles is generally shorter than for channel width. However, the hillslope adjustment may take longer than previously reported if the effect of width adjustment on hillslope angles is significant or the complete adjustment of hillslope angles is considered. The fact that channel slope, channel width, and hillslope angle have distinct adjustment times underlines the importance of correctly identifying river sections that are fully adjusted to the new boundary conditions when inferring erosion or relative uplift rates for bedrock rivers.</jats:p>

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