SGER: Dam removal and the response of gravel-bed rivers to sediment pulses

本研究将利用在MT哥伦比亚河克拉克福克（Clark Fork）拆除米尔敦大坝（Milltown Dam）所产生的现场规模实验，调查沉积物在砾石河床中对沉积物脉冲的响应，研究沉积物的运输和河道的演变。通过收集拆除大坝前后的河道条件以及高流量时期米尔敦水库的河床和悬载运输的数据，这项研究将解决有关河流过程、沉积物运输和沉积以及水坝去除的基本问题。本文将探讨细粒沉积物脉冲如何渗入并影响装甲河床的流动性，沉积物输沙和沉积的时空格局，以及沉积物脉冲输沙的有效流量。这项研究将提供一个极好的机会来评估以前的河流研究或小河道的实地研究是如何扩大到更大的河流的，这些研究是关于沉积物运输和河流过程相关方面的许多已知基础。这里收集的数据还将在地貌响应和沉积物地球化学对栖息地和生物过程的影响的背景下进行评估。米尔镇大坝的拆除将于2008年春季开始，并持续到次年冬季，这尤其值得注意，因为(1)就水库沉积物的潜在下游运输量而言，这是迄今为止美国最大的大坝拆除（大约300万立方米，另外200万立方米正在机械拆除）；(2)大坝是美国最大的超级基金场址克拉克堆场（Clark ForkComplex）的下游端，水库沉积物主要由受污染的尾矿组成；(3)发生在地区重要河流上，该河流包括联邦濒危物种鳟鱼的指定重要栖息地。因此，对这一大坝拆除的系统研究将在多个层面上产生更广泛的影响，包括了解与重大大坝拆除相关的沉积物和金属运输，为即将计划的大型水坝拆除提供见解，以及为理解砾石驱动因素如何应对泥沙通量增加做出更广泛的贡献。该项目还将产生更广泛的影响？跨学科性质，通过对地貌过程、地球化学、水文和鱼类反应的分析，将结合起来了解大坝拆除对下游的影响。该项目将帮助一名新教师建立河流地貌过程的研究项目，并将直接支持一名研究生和一名本科生。该项目还将促进蒙大拿大学和萨里什-库特奈学院之间的持续合作，萨里什-库特奈学院是马萨诸塞州巴勃罗的一所部落学院，其学生将在PI的指导下协助实地数据收集和分析。此外，与米尔敦大坝拆除相关的数据收集和分析将被纳入研究生和本科生的地貌学和地球化学课程，该项目将促进教学和研究的整合。离蒙大拿大学很近

This study will investigate sediment transport and channel evolution in gravel-bed riversin response to sediment pulses, taking advantage of the field-scale experiment that will becreated by the removal of Milltown Dam on the Clark Fork of the Columbia River, MT. Throughdata collection on pre- and post-dam removal channel conditions and on bedload and suspendedload transport out of Milltown reservoir during high flow periods, this research will addressfundamental questions about fluvial processes, sediment transport and deposition, and damremoval. Several hypotheses will be investigated about how pulses of fine sediment infiltrateinto and affect the mobility of armored river beds, about spatial and temporal patterns ofsediment transport and deposition, and about effective discharges for transporting sedimentpulses. This research will provide an excellent opportunity to evaluate how previous flumeresearch or field studies of small channels, upon which much of what is known about sedimenttransport and related aspects of fluvial processes is based, scale up to larger rivers. Thedata collected here will also be evaluated in the context of the implications of geomorphicresponses and sediment geochemistry for habitat and biological processes.Removal of Milltown Dam, which will begin in spring 2008 and continue the following winter,is especially notable because (1) it is the largest dam removal to date in the United Statesin terms of the volume of reservoir sediment potentially available for downstream transport(approximately 3 million m3; another 2 million m3 are being mechanically removed); (2) thedam is the downstream end of the largest Superfund site in the United States, the Clark ForkComplex, and reservoir sediments are composed largely of contaminated mine tailings; (3) itis occurring on a regionally important river that includes designated Critical Habitat forbull trout, a federally threatened species. Systematic study of this dam removal will thereforehave broader impacts on multiple levels, including for understanding the sediment and metalstransport associated with a significant dam removal, for the insights it lends to upcomingplanned removals of large dams, and for its broader contribution to understanding how gravel-bedrivers respond to increased sediment fluxes. Broader impacts will also derive from the project?sinterdisciplinary nature, whereby analyses of geomorphic processes, geochemistry, hydrology,and fish response will be combined to understand downstream effects of dam removal.This project will help a new faculty member build a research program in fluvial geomorphicprocesses and will directly support one graduate and one undergraduate student. The projectwill also foster ongoing collaboration efforts between University of Montana and Salish-KootenaiCollege, a tribal college in Pablo, MT, whose students will assist field data collection andanalysis under the guidance of the PI. Further, data collection and analysis related to MilltownDam removal will be incorporated into graduate and undergraduate geomorphology and geochemistrycourses, an integration of teaching and research that will be facilitated by the project?sclose proximity to the University of Montana.