Rates and processes of channel response to dam removal with a sand‐filled impoundment
Rates and processes of channel response to dam removal with a sand‐filled impoundment
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填砂蓄水池拆除大坝的河道响应速率和过程
DOI：
10.1029/2010wr009733
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发表时间：
2011
影响因子：
5.4
通讯作者：
M. Collins
中科院分区：
文献类型：
--
作者：
A. Pearson;N. Snyder;M. Collins
大坝拆除工程在河流恢复中发挥着越来越重要的作用，并提供了前所未有的机会来研究扰动后的沉积动力学。我们拆除了新罕布什尔州南部苏黑根河上104米高的梅里马克村坝（MVD），以测量填砂蓄水池中河道演变的过程和速率。2007年至2010年，我们重复调查了11个横截面和纵向剖面，并收集了沉积物样品，以测量河道形态和床面结构的变化。2008年8月的大坝拆除导致几乎瞬时的基准面下降3.9 m，并导致两阶段的河道响应。最初的过程驱动阶段（2个月）的特点是快速切割和清除蓄积的沙子（高达1013 t d−1），然后是渠道拓宽。一旦切割至基准面，沉积物去除速率减慢（30.7 t d−1），调整成为事件驱动，前一个蓄水池分为非冲积部分和冲积部分，受河道两岸植被的影响，侵蚀和沉积。在大坝拆除和两次大洪水发生两年后，河流已经挖掘了79%的原始沉积物。前蓄水池内河岸植被的建立以及高流量事件的规模和频率将对持续响应产生重大影响。在填沙蓄水池中，最初的河道发展和沉积物侵蚀发生得很快（数周至数月），但剩余沉积物的挖掘发生得较慢，这取决于植被反馈和洪水事件。
Dam removal projects are playing an increasingly important role in stream restoration, and offer unparalleled opportunities to study sediment dynamics following disturbance. We used the removal of the ∼4‐m high Merrimack Village Dam (MVD) on the Souhegan River in southern New Hampshire to measure processes and rates of channel evolution in a sand‐filled impoundment. From 2007 to 2010, we repeatedly surveyed 11 cross sections and the longitudinal profile, and collected sediment samples to measure changes in channel morphology and bed texture. The dam removal in August 2008 resulted in a nearly instantaneous base level drop of 3.9 m and caused a two‐phased channel response. The initial, process‐driven phase (2 months) was characterized by rapid incision and removal of the impounded sand (up to 1013 t d−1), followed by channel widening. Once incised to base level, the rate of sediment removal slowed (30.7 t d−1) and adjustments became event‐driven, and the former impoundment segmented into a nonalluvial section and an alluvial section with erosion and deposition influenced by vegetation on the channel banks. Two years after the dam removal and two high‐magnitude floods, the river has excavated 79% of the original sediment. Continued response will be substantially influenced by the establishment of bank vegetation within the former impoundment and the magnitude and frequency of high discharge events. Initial channel development and sediment erosion occurs rapidly (weeks to months) in sand‐filled impoundments, but excavation of the remaining sediment occurs more slowly depending on vegetation feedbacks and flood events.