Unsteady numerical modeling of river hydraulics and morphology changes

泥沙运动模型在河流水力学中被广泛使用，例如用于评估 大坝下游风险区的确定。现有的泥沙输运关系假定为稳态水力学。在许多可能发生泥沙运动的实际情况下，水力状态是非常不稳定的。水流不稳定是指现有的“稳定水流”关系所不能解释的动态效应，这种动态效应可能会产生巨大的影响，例如卡特里娜飓风对新奥尔良的灾难性影响，1997年北达科他州、明尼苏达州和马尼托巴省南部红河沿岸的红河洪水，以及1996年萨格奈的暴雨。 此外，在洪水过后，只有一些局部溪流恢复行动：局部堤岸稳定，局部泥沙清除……任何试图重建一个自给自足的自然系统的尝试都需要了解某条河流的地貌过程，以及这些过程如何得到现在(或未来)水流系统的支持。 我们的目标是开发一种综合的河流-河岸走廊方法，与流域尺度分析结合使用，以评估拟议走廊修复设计的长期效果。 这一新方法是参与河流修复项目的水利工程师、河流地貌学家、景观建筑师和河流生态学家的迫切需要。这些项目通常受到缺乏综合设计工具的挑战，无法评估重建的河流走廊的长期稳定性。

Sediment transport modelling is widely used in fluvial hydraulics, such as for the assessment of the determination of risk areas downstream of a dam. Existing sediment transport relationships assume steady state hydraulics. In many practical situations, in which sediment movement is likely, the hydraulic state is very unsteady. Flow unsteadiness introduces dynamic effects not accounted for by existing "steady flow" relationships which can have dramatic effects such as the catastrophic effect of Hurricane Katrina on New Orleans, the Red River Flood of 1997 along the Red River in North Dakota, Minnesota, and Southern Manitoba and the downpours of the Saguenay in 1996. Moreover, only some local stream restoration actions take place after such floods: local bank stabilization, local sediment removal.... Any attempt to recreate a self-sustaining natural system requires an understanding of the geomorphic processes that characterize a certain river and how these processes can be supported by present (or future) flow regimes. Our goal is to develop an integrated stream-riparian corridor approach to be used in conjunction with watershed-scale analysis, for evaluating the long-term effectiveness of proposed corridor rehabilitation designs. This new approach is a critical need for hydraulic engineers, fluvial geomorphologists, landscape architects, and stream ecologists involved in stream rehabilitation projects. These projects are usually challenged by the lack of integrated design tools to evaluate the long-term stability of reconstructed stream corridors.