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A debris flow chronology and analysis of controls on debris flow occurrence in the Upper Colorado River Valley, Rocky Mountain National Park, CO.

机译：科罗拉多州落基山国家公园上科罗拉多河谷的泥石流年代学和泥石流发生控制的分析。

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摘要

The role of debris flows along the Upper Colorado River was recently highlighted when the Grand Ditch, a 19th-century water-conveyance ditch, overtopped from snowmelt in 2003 and triggered a large debris flow along Lulu Creek, a tributary of the Colorado. Historical aerial photographs indicate that at least two other debris flows have been triggered from the Grand Ditch over the last century. This study examines the natural regime of debris flows in the Colorado River headwaters to assess whether the Grand Ditch has increased magnitude and frequency of debris flow occurrence on the west side of the Colorado River valley. Ten distinct sites of debris flow deposition were mapped using aerial photographs and field exploration, dated from tree cores and tree scars, and analyzed for magnitude using field-estimated volumes of deposition. Six of these ten depositional sites are on the west side of the valley, and several of them have evidence of multiple debris flows. Forty scarred survivor trees and 38 cores from even-aged stands were dated, with corresponding dates of debris flow occurrence ranging from 1923 to 2003. At least 19 debris flows have occurred in this catchment over the last century, but only those at the across-from-Specimen Creek, Lady Creek, Lulu Creek, and Little Yellow sites appear to have been large enough to affect the Colorado River. There is not a substantial difference in the frequency of total debris flows catalogued at the ten sites of deposition between the east (8) and west (11) sides of the Colorado River valley over the last century, but three of the four largest debris flows originated on the west side of the valley in association with the Grand Ditch, while the fourth is on a steep hillslope of hydrothermally altered rock on the east side of the valley. Although ability to interpret the debris flow record is limited by frequent disturbance and burial of older deposits, and estimates of magnitude have high uncertainty, these data suggest that the Grand Ditch has altered the natural regime of debris flow activity in the Colorado River headwaters by increasing the frequency of debris flows large enough to reach the Colorado River. Likelihood of debris flow occurrence is augmented by steep slopes and hydrothermally altered rock, which are both common in the vicinity of the Grand Ditch. This study demonstrates the applicability of dendrochronology for dating geomorphic events in Rocky Mountain National Park and provides context for restoration following debris flows.
机译：最近，当19世纪的输水沟大沟（Grand Ditch）于2003年从融雪中越过并在科罗拉多州的支流露露溪（Lulu Creek）上引起大量泥石流时，泥石流在上科罗拉多河上的作用最近得到了强调。历史航空照片表明，上个世纪大沟引发了至少另外两个泥石流。这项研究检查了科罗拉多河上游水域的泥石流自然状况，以评估大沟是否增加了科罗拉多河谷西侧泥石流的发生幅度和发生频率。使用航拍照片和野外勘测绘制了十个不同的泥石流沉积位置，这些位置可追溯到树芯和树疤，并使用野外估计的沉积量对震级进行分析。这十个沉积地点中有六个位于山谷的西侧，其中一些具有多处泥石流的迹象。记录了四十棵伤痕累累的幸存者树木和来自平均年龄林分的38个核心的日期，相应的泥石流发生日期为1923年至2003年。在上个世纪中，该流域至少发生了19处泥石流，但仅在来自标本溪，淑女溪，露露溪和小黄河的遗址似乎足够大，足以影响科罗拉多河。上个世纪，在科罗拉多河谷东（8）和西（11）之间的十个沉积地点分类的总泥石流频率没有实质性差异，但在四个最大的泥石流中有三个起源于与大沟有关的山谷西侧，而第四个则位于山谷东侧的热液蚀变岩石的陡峭山坡上。尽管对泥石流记录的解释能力受到频繁的扰动和埋藏较老沉积物的限制，并且震级估算具有很高的不确定性，但这些数据表明，大沟已通过增加科罗拉多河上游水源改变了泥石流活动的自然规律。泥石流的频率足以到达科罗拉多河。陡坡和热液蚀变岩石增加了泥石流发生的可能性，这在大沟附近都很常见。这项研究证明了树状年代学在落基山国家公园中对地貌事件定年的适用性，并为泥石流后的恢复提供了背景。

著录项

  • 作者

    Grimsley, Kyle J.;

  • 作者单位

    Colorado State University.;

  • 授予单位 Colorado State University.;
  • 学科 Geology.;Geomorphology.
  • 学位 M.S.
  • 年度 2012
  • 页码 97 p.
  • 总页数 97
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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