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首页> 外文期刊>Geological Society of America Bulletin >Channel narrowing by inset floodplain formation of the lower Green River in the Canyonlands region, Utah
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Channel narrowing by inset floodplain formation of the lower Green River in the Canyonlands region, Utah

机译：犹他州峡谷地区下落绿河的Inlet Flocplain形成的渠道缩小

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摘要

The lower Green River episodically narrowed between the mid-1930s and present day through deposition of new floodplains within a wider channel that had been established and/or maintained during the early twentieth century pluvial period. Comparison of air photos spanning a 74-yr period (1940-2014) and covering a 61 km study area shows that the channel narrowed by 12% from 138 +/- 3.4 m to 122 +/- 2.1 m. Stratigraphic and sedimentologic analysis and tree ring dating of a floodplain trench corroborates the air photo analysis and suggests that the initial phase of floodplain formation began by the mid-1930s, approximately the same time that the flow regime decreased in total annual and peak annual flow. Tamarisk, a nonnative shrub, began to establish in the 1930s as well. Narrowing from the 1940s to the mid-1980s was insignificant, because floodplain formation was approximately matched by bank erosion. Air photo analysis demonstrates that the most significant episode of narrowing was underway by the late 1980s, and analysis of the trench shows that floodplain formation had begun in the mid-1980s during a multi-year period of low peak annual flow. Air photo analysis shows that mean channel width decreased by similar to 7% between 1993 and 2009. A new phase of narrowing may have begun in 2003, based on evidence in the trench. Comparison of field surveys made in 1998 and 2015 in an 8.5 km reach near Fort Bottom suggests that narrowing continues and demonstrates that new floodplain formation has been a very small proportion of the total annual fine sediment flux of the Green River. Vertical accretion of new floodplains near Fort Bottom averaged 2.4 m between 1998 and 2015 but only accounted for similar to 1.5% of the estimated fine sediment flux during that period. Flood control by Flaming Gorge Dam after 1962 significantly influenced flow regime, reducing the magnitude of the annual snowmelt flood and increasing the magnitude of base flows. Though narrowing was initiated by changes in flow regime, native and nonnative riparian vegetation promoted floodplain formation and channel narrowing especially through establishment on channel bars and incipient floodplains during years of small annual floods.
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    Walker Alexander E.; Moore Johnnie N.; Grams Paul E.; Dean David J.; Schmidt John C.;

  • 作者单位

    Utah State Univ Dept Watershed Sci 5210 Old Main Hill Logan UT 84322 USA;

    Univ Montana Dept Geosci 32 Campus Dr 1296 Missoula MT 59812 USA;

    US Geol Survey Southwest Biol Sci Ctr Grand Canyon Monitoring &

    Res Ctr 2255 N Gemini Dr Flagstaff AZ 86001 USA;

    US Geol Survey Southwest Biol Sci Ctr Grand Canyon Monitoring &

    Res Ctr 2255 N Gemini Dr Flagstaff AZ 86001 USA;

    Utah State Univ Dept Watershed Sci 5210 Old Main Hill Logan UT 84322 USA;

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  • 正文语种 eng
  • 中图分类 地质学;
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