Overnight formation of a bouldery alluvial fan by a torrential rain in a granitic mountain (Mt. Seoraksan, Republic of Korea)
Overnight formation of a bouldery alluvial fan by a torrential rain in a granitic mountain (Mt. Seoraksan, Republic of Korea)
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花岗岩山上的暴雨一夜之间形成了巨石冲积扇（韩国雪岳山）
DOI：
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Y. Sohn
中科院分区：
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作者：
Jisu Kim;K. Woo;K. Lee;Y. Sohn
山韩国雪岳山是一座崎岖的花岗岩山脉，极其陡峭的斜坡和强烈的季节性降雨主要通过岩崩和溪流促进了基岩暴露和地貌变化。虽然环境不适合形成冲积扇，但2006年夏季的一场大雨在一夜之间形成了一个长170米、宽330米的砾石冲积扇。该扇由几米高的卵石土丘和平缓起伏的卵石条/片组成，这些卵石条/片以河流纵向条形图案排列。他们被解释为已形成的高度主管和湍流sheetfloods，暂时有高浓度的洪水流量的属性。整个冲积扇的形成由一个单一的，偶然的水文气象事件被推断为可能的，因为在源区达到了阈值条件。降雨事件在达到阈值之前不会产生极端影响，但可能会引发谷底巨石沉积物的大规模重新流动。因此，雪岳山冲积扇表明了地貌阈值在引起流域水文性能急剧变化中的作用。雪岳山冲积扇的形态和沉积学表明，该扇是一个现代的例子sheetflood为主的冲积扇，这在很大程度上被忽视，尽管他们的潜在的多样性和丰富的冰川冰缘，热带和温带环境。
Mt. Seoraksan, Korea, is a rugged granitic mountain where extremely steep slopes and strongly seasonal rainfall have facilitated bedrock exposure and geomorphic changes mainly by rockfalls and streamflows. Although the environment was not suitable for alluvial fan formation, a bouldery alluvial fan, 170 m long and 330 m wide, formed overnight by a heavy summer rain in 2006. The fan consists of several meter-high boulder mounds and gently undulating cobble bars/sheets that are arranged in a fluvial longitudinal bar-like pattern. They are interpreted to have formed by highly competent and turbulent sheetfloods, which temporarily had the properties of hyperconcentrated flood flows. Formation of the whole alluvial fan by a single, casual hydro-meteorological event is inferred to have been possible because a threshold condition was reached in the source area. A rainfall event, which would have had no extreme effects before reaching the threshold, could probably trigger massive remobilization of bouldery sediments on the valley floors. The Seoraksan alluvial fan thus demonstrates the role of a geomorphic threshold in causing drastic changes in the hydrologic performance of the watershed. The morphology and sedimentology of the Seoraksan alluvial fan suggest that the fan is a modern example of a sheetflood-dominated alluvial fan, which has largely been ignored in spite of their potential diversity and abundance in glacial to periglacial, tropical, and temperate environments.