Evaluating the significance of event and post‐event sediment dynamics in a first order tributary using multiple sediment budgets
Evaluating the significance of event and post‐event sediment dynamics in a first order tributary using multiple sediment budgets
复制标题
使用多个沉积物预算评估一级支流中事件和事件后沉积物动力学的重要性
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
C. Winter
中科院分区：
文献类型：
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作者：
Richard M. Johnson;J. Warburton;A. Mills;C. Winter
抽象。很少在一段持续的时间内对高地集水区的沉积物转移进行调查，因此，对沉积物供应、储存和产量的变化性质往往缺乏充分的了解。最近对英国北方英格兰湖区湿猪鳃上游集水区（0.65 km 2，一级支流）的三项沉积物收支研究提供了2002-2008年期间沉积物转移动态变化的证据。2002年的第一次沉积物预算描述了山坡泥石流和渠道化泥石流事件的影响，前者是主要的预算组成部分。湿猪鳃沟泥石流的终止意味着绝大多数滑坡破坏物质没有转移到下游河流系统。然而，随后暴露的山坡沉积物的修改事件后的侵蚀过程和冲沟的发展导致了持续的侵蚀。第二次沉积物预算（2003年6月至2004年1月）表明，河道内泥石流沉积物下游的产沙量远远超过上游河流沉积物输送量两个数量级（c。4,000公斤，C。20公斤）。从裸露的山坡崩塌疤痕（c。1300公斤）低于渠道侵蚀（c. 3300公斤），从山坡和渠道沉积物来源的沉积物转移是敏感的高量级，低频率的触发事件，包括夏季雷暴，和冬季降雨/融雪事件。然而，线性回归分析仅表明气象条件与产沙量之间的关系很弱或不显著。2008年4月的最终沉积物预算显示了六年监测期内山坡（包括冲沟）和河道侵蚀/转移过程的重要性。在这个预算中，像第一个沉积物预算，山坡系统是稍微更占主导地位，因此表明了进一步的开关在山坡和渠道系统组件的相对重要性。在解释这些结果时，应考虑到预算组成部分，特别是未计量的剩余部分的潜在不确定性，因为误差幅度可能很大。这些结果表明，小源头流域的当代事件和事件后沉积物通量比短期调查最初提出的更为复杂。此外，显然需要对沉积物系统动态和相关水文气象条件进行持续、长期的监测，以了解未来气候变化可能如何影响高地沉积物系统。
Abstract. Investigations of sediment transfer in upland catchments are rarely conducted over a sustained period of time, consequently a full understanding of the changing nature of sediment supply, storage and yield is often lacking. Three recent sediment budget studies from the Wet Swine Gill headwater catchment in the Lake District, Northern England, UK (a 0.65 km2, first‐order tributary), provide evidence of changes in sediment transfer dynamics over the period 2002–2008. The first sediment budget in 2002 describes the impact of a hillslope debris slide and channelised debris flow event, where the former was the dominant budget component. The termination of the debris flow in the Wet Swine Gill channel meant that the vast majority of slide failure material was not transferred to the downstream fluvial system. However, subsequent modification of exposed hillslope sediment by post‐event erosion processes and gully development resulted in ongoing erosion. A second sediment budget (June 2003–January 2004) demonstrated sediment yield downstream of the in‐channel debris slide deposits far exceeds upstream fluvial sediment delivery by two orders of magnitude (c. 4,000 kg and c. 20 kg, respectively). Erosion of sediment from the exposed hillslope failure scar (c. 1300 kg) was less than channel erosion (c. 3300 kg), and sediment transfers from both the hillslope and channel sediment sources are sensitive to high‐magnitude, low‐frequency trigger events including summer thunderstorms, and winter rainfall/ snow‐melt events. However, linear regression analysis only demonstrates weak or insignificant relations between meteorological conditions and sediment yield. A final sediment budget in April 2008 shows the significance of both hillslope (inclusive of gullying) and channel erosion/ transfer processes over the six‐year monitoring period. In this budget, like the first sediment budget, the hillslope system is marginally more dominant, and therefore demonstrates a further switch in the relative significance of hillslope and channel system components. When interpreting such findings the potential uncertainty in the budget components, particularly in the unmeasured residual components, should be considered, as the magnitude of the error can be large. These results suggest that contemporary event and post‐event sediment flux in small headwater catchments are more complex than short‐term investigations would initially suggest. Furthermore there is a clear need for continued, longer‐term monitoring of sediment system dynamics and associated hydro‐meteorological conditions, in order to develop understanding of how future climate change may impact upland sediment systems.