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

这项研究将利用密苏里州哥伦比亚河克拉克福克上的米尔敦大坝拆除后的野外试验，研究砾石河床河流中泥沙的输运和河道演变。通过收集大坝除险前后河道条件以及丰水期米尔敦水库输沙和悬移质输沙资料，本研究将解决河流演变、泥沙输移和除坝等基本问题。关于细颗粒泥沙如何渗入和影响装甲河床的流动，泥沙输运和沉积的时空模式，以及输送泥沙脉冲的有效流量的几个假说将被研究。这项研究将提供一个极好的机会，来评估以前对小型河道的研究或实地研究如何扩大到更大的河流，许多关于河流沉积输送和相关方面的已知知识都是基于这些研究或实地研究的。这里收集的数据也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。米尔敦大坝的拆除尤其值得注意，它将于2008年春季开始并持续到下一个冬天，因为(1)就可能用于下游运输的水库沉积物的体积而言，这是美国迄今为止最大的大坝拆除行动(大约300万立方米；另有200万立方米正在被机械清除)；(2)大坝是美国最大的超级基金遗址克拉克·福克综合体的下游末端，水库沉积物主要由受污染的尾矿组成；(3)它发生在一条具有地区性重要意义的河流上，其中包括被指定为联邦濒危物种牛鲑鱼的关键栖息地。因此，对大坝清除的系统研究将在多个层面上产生更广泛的影响，包括了解与大规模大坝清除相关的泥沙和金属迁移，为后续的大型大坝计划清除提供洞察力，以及更广泛地有助于了解碎石驱动器如何应对泥沙通量增加。该项目还将产生更广泛的影响--烧结型学科性质，将地貌过程、地球化学、水文学和鱼类反应的分析结合起来，以了解大坝拆除的下游影响。该项目将帮助一名新教师建立河流地貌过程研究计划，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利什-库特奈学院之间正在进行的合作努力，萨利什-库特奈学院是密歇根州巴勃罗的一所部落学院，其学生将在PI的指导下协助收集和分析实地数据。此外，与拆除米尔敦大坝有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，这将是教学和研究的一体化，这一项目将促进离蒙大拿大学不远的地方。

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.