Development of simplified tools for erosion assessment and prediction in semi-alluvial clay-bed rivers

冲积河的河床和河岸是由水流输送的泥沙组成的，因此可以自由地调整其形状，以最好地输送流入的水流和泥沙。加拿大东部大部分地区的河流流经由粘性冰川沉积物组成的地区，包括冰川海洋粘土。这些河流是半冲积的，因为它们切入这些非冲积基质，但部分河床可能被冲积物质的表面饰面覆盖。考虑到加拿大的冰川历史，它的许多河流（如果不是大多数的话）都可以被描述为半冲积河。这些河流的管理是一项艰巨的挑战，因为对它们的粘性河床沉积物的可蚀性或它们稳定的河道几何形状所知相对较少。所提出的研究将1)改进和比较动员粘性粘土床材料所需的临界床剪切应力的测量方法，2)开发一种简化的方法来解释粘土的可蚀性

An alluvial river has bed and banks composed of sediment transported by the flow, thus is free to adjust its shape to convey best its incoming flow and sediment. Rivers in much of eastern Canada flow through regions comprised of cohesive glacial sediments, including glaciomarine clays. These rivers are semi-alluvial, in that they are incising into these non-alluvial substrates, yet portions of the channel bed may be covered with a surficial veneer of alluvial material. Given the glacial history of Canada, many if not most of its rivers can be characterized as semi-alluvial. Management of these rivers is a difficult challenge, because relatively little is known about erodibility of their cohesive bed sediments or their stable channel geometry. The proposed research will 1) improve and compare methods for measurement of the critical bed shear stress required to mobilize a cohesive clay bed material, and 2) develop a simplified approach to account for erodibility of clay bed material when defining stable river geometry for channel design purposes. In the first stage of the research, cohesive bed sediments from Feedmill Creek, Ottawa will be tested for critical shear stress using three different methods: fluvial shear stress in a piston flume, normal stress using an industry standard jet tester, and by surface shear strength using a novel device developed at the University of Ottawa. In the second stage of the research, the one-dimensional hydraulic model SWMHYMO will be adapted to predict equilibrium cohesive-bed channel dimensions subject to unsteady continuous full year discharge hydrographs. This project is a collaboration with JF Sabourin and Associates Ltd, who will utilize the research results to improve management of semi-alluvial rivers in Eastern Canada.