RAPID: Quantifying the Geomorphic and Sedimentological Responses to Dam Removal

随着人们对水坝造成的严重生态影响的认识不断提高，公众对拆除水坝的兴趣也越来越大，特别是一些估计表明，美国现有的75，000座水坝中，有许多将在几十年内达到其运行寿命的终点。 大坝拆除是生态改善的一个重要选择，但仍有几个悬而未决的问题，关于沉积物路由的细节，通道和洪泛区之间的连接，以及拆除大坝上方和下方地貌调整的类型和幅度。 新罕布什尔州南部阿舒洛特河（Ashuelot River）沿着斯旺齐大坝（Swanzey Dam）即将拆除，这为测试和改进沉积物通量和河道调整的预测模型以及指导河流恢复科学的未来发展提供了一个难得的机会。 大坝的拆除基本上是一个沉积物的点释放，在空间和时间上是离散的，并提供了一个实际规模的实验，在一个自然的河流。 达特茅斯学院地理系的弗朗西斯·Magilligan教授将综合使用传统和创新的实验室技术，包括航空激光雷达分析和使用同位素（铍-7和铅-210）作为沉积物示踪剂和计时器，收集大坝拆除前后的地貌和沉积数据，以量化生物物理条件的变化。 本计画所收集的资料将被用来在坡度、河道形成流量、粒径、泥沙通量、河道宽度等协变参数中，对河道平衡调整的长度与时间尺度进行定量模拟，这项研究将有助于对泥沙输移与储存，特别是河道与洪泛区之间的相互作用，在河流响应和从干扰的去除中恢复的过程中。 这种地貌信息将揭示河流达到新的平衡条件的方式，并将进一步展示与这些调整相对应的关键过程。 除了推进河流恢复的科学基础外，这项研究的结果将被主要利益相关者和机构利用，以推进正在进行的河流生态区域研究。 该项目的结果将进一步为管理人员和科学家提供信息，并将有助于指导全国的恢复工作。 随着美国各地即将拆除的众多大坝，这些结果还将为预测河道恢复的自然过程提供重要模板，并将进一步为区域河流恢复工作建立基线条件。

The growing awareness of the acute ecological impacts associated with dams has resulted in increasing public interest in their removal, especially as some estimates indicate that many of the existing 75,000 dams in the U.S. will reach the end of their operational lives within decades. Dam removal represents one important option in ecological amelioration, yet several unanswered questions remain about the specifics of sediment routing, the connectivity between the channel and the floodplain, and the type and magnitude of geomorphic adjustments above and below removed dams. The imminent removal of the Swanzey Dam along the Ashuelot River in southern New Hampshire provides a rare opportunity to test and improve predictive models of sediment flux and channel adjustments and to guide the future development of river restoration science. The removal of the dam is essentially a point release of sediment, discrete in space and time and provides an actual-scale experiment in a natural river. Professor Francis Magilligan from the Department of Geography at Dartmouth College will use a combination of traditional and innovative laboratory techniques, including aerial lidar analysis and the use of isotopes (Beryllium-7 and Lead-210) as sediment tracers and chronometers, to collect pre- and post-dam removal geomorphic and sedimentological data to quantify changes in biophysical conditions. The data collected in this project will be used to advance quantitative modeling of the length and time scale of channel equilibrium adjustments in the covariant parameters of slope, channel forming flows, grain size, sediment flux, and channel width following dam removal.This research will contribute basic knowledge on sediment transport and storage, especially the interaction between the channel and floodplain, during river response and recovery from the removal of a disturbance. This geomorphologic information will reveal the ways that streams attain new equilibrium conditions and will further demonstrate the key processes corresponding with these adjustments. In addition to advancing the science fundamental to river restoration, the results of this research will be leveraged by key stakeholders and agencies to advance ongoing regional studies on riverine ecology. Results from this project will further inform managers and scientists and will help guide restoration efforts nationally. With the upcoming removal of numerous dams across the U.S., these results will also provide an important template for predicting the natural processes of channel recovery and will further establish baseline conditions for regional river restoration efforts.