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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Cascades of sub-decadal, channel-floodplain changes in low-gradient, non-vegetated reaches near a dryland river terminus: Salar de Uyuni, Bolivia
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Cascades of sub-decadal, channel-floodplain changes in low-gradient, non-vegetated reaches near a dryland river terminus: Salar de Uyuni, Bolivia

机译：级联的级联，渠道 - 洪泛区的低梯度变化，非植被达到旱地终端附近：玻利维亚撒拉德UYUNI

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摘要

The terminus of the ephemeral Rio Colorado is located at the margins of Salar de Uyuni, Bolivia, the world's largest salt lake. The low-gradient (0.0006mm(-1)), non-vegetated reaches approaching the terminus provide an excellent natural laboratory for investigating cascades of channel-floodplain changes that occur in response to quasi-regular flows (at least once annually) and fine-grained sediment supply (dominantly silt and clay). High-resolution satellite imagery (0.65m, various dates from 2004 onwards) and field data reveal widespread, pronounced and rapid morphodynamics on sub-decadal timescales, including channel erosion and chute cutoff formation, and development of crevasse channels and splays, floodouts (unchannelled surfaces at channel termini), and erosion cells (floodplain scour-transport-fill features). In particular, following high annual precipitation (400mm) in 2004-2005 and two subsequent high magnitude daily precipitation events (similar to 40mm), all of which led to widespread flooding, numerous crevasse splays formed between 2004 and 2016, avulsions occurred at nearby floodouts, and erosion cells downstream of the splays and floodouts underwent striking morphological changes. High-precision GPS data reveal two preferential localities for erosion cell development: partially or fully abandoned channels with crevasse splay remnants, and topographic lows between channels. In this overall low-gradient setting, comparatively high gradients (up to similar to 0.0006mm(-1)) at the edge of splay deposits and topography created by crevasses and abandoned channels may initiate knickpoint retreat and thereafter erosion cell development. Abandoned channels with splays tend to give rise to narrow, deep erosion cells, while topographic lows promote relatively shallow, wide erosion cells. In both situations, erosion cells may extend upslope and downslope, and eventually connect to form straight channels. The channel-floodplain morphodynamics near the
机译：短暂的Rio Colorado末端位于世界上最大的盐湖玻利维亚玻利维亚的撒拉德Uyuni边缘。低梯度（＆ 0.0006mm（-1）），不植被达到终端，提供了一个优异的自然实验室，用于调查响应准则流量的级联变化的级联变化（至少每年一次）和细粒度的沉积物供应（主要淤泥和粘土）。高分辨率卫星图像（＆ 0.65米，从2004年开始的各种日期）和现场数据在亚铲时间尺寸上揭示了广泛的，发音和快速的形态学性，包括渠道侵蚀和寒冷的截止地层，以及裂缝渠道的发展，泛滥（在频道末端的不经过干扰的表面）和侵蚀细胞（泛洪水冲刷 - 运输 - 填充功能）。特别是，在2004 - 2005年的年度降水量（＆ 400mm）之后，随后的两次高幅度降水事件（类似于40mm），所有这些都导致了广泛的洪水，2004年至2016年之间形成了众多裂缝的裂隙，发生了禽流炮附近的泛洪和折射细胞下游的剧烈和洪水突出了醒目的形态变化。高精度GPS数据显示侵蚀细胞开发的两个优惠地方：部分或完全废弃的渠道与裂隙次数滞留，以及通道之间的地形低度。在这种整体低梯度设置中，在展开沉积物和由裂隙和废弃的通道产生的地形的边缘处的相对高的梯度（最高可达0.0006mm（-1））可以启动Knickpoint Reteat和此后的侵蚀细胞发育。遗弃频道的剧烈频道往往会产生狭窄的深深的侵蚀细胞，而地形低点促进相对较浅，宽的侵蚀细胞。在这种情况下，侵蚀细胞可以延伸上坡和下坡，并最终连接形成直线。频道 - 洪泛平坦形态学附近

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