Modeling Bed-Surface Dynamics In Gravel-Bed Rivers

[106561 . 61]河床表面粗化，广义上称为装甲化，是砾石河流的普遍特征。装甲强烈影响水道水力，决定可用于运输的谷物的数量，并定义水生无脊椎动物，鲑鱼产卵和幼鱼的栖息地。要对砾石河床内的水流、运输和底栖生态有一个普遍和预测性的了解，就需要有能力预测河床表面组成作为水和沉积物供应的函数。一般来说，床面与当代条件不平衡，因此不能从野外观测的简单相关推断出因果关系。相反，我们转向实验室进行控制观测，并使用计算模型来捕捉现场的变化和瞬态条件。对装甲的观察已经进行了几十年，并且已经开发出了能够预测装甲的算法。然而，数据和模型中都缺少关键要素，经验和理论还没有融合成一个完整的模型。这项工作旨在通过双方的建设来弥合这一差距。在经验方面，我们将使用实验室水槽对流动、输运和床表面组成进行耦合观察，以便以前所未有的时空细节描述地表和地下粒度的演变。在理论方面，我们将开发一个运输和装甲模型，包括颗粒在地表和地下之间的大小依赖的垂直转移（运动学分选）。该机制可以纳入当前模型，但必要的传递函数仍未定义，将使用本项目实验部分的数据进行识别。该模型的测试将基于不同沉积物供应配置之间的内部比较，以及一组具有渐进式床化和退化的运行。结果将是一个基于物理的、经过测试的模型，能够在复杂的、瞬态的典型野外条件下预测运输和装甲。

0106561WilcockBed surface coarsening, broadly termed armoring, is a pervasive feature ofgravel rivers. Armoring strongly influences channel hydraulics, determinesthe population of grains available for transport, and defines the habitatfor aquatic invertebrates, salmonid spawning, and juvenile fish. A generaland predictive understanding of flow, transport, and benthic ecology ingravel-bed rivers requires an ability to predict the bed surfacecomposition as a function of water and sediment supply. In general, the bedsurface is not in equilibrium with contemporary conditions, so cause andeffect cannot be deduced from simple correlations of field observations.Instead, we turn to the laboratory for controlled observations and tocomputational models to capture the varied and transient conditions in thefield.Observations of armoring have been made for decades and algorithms capableof predicting armoring have been developed. Key elements are missing inboth data and models, however, and the empirical and the theoretical havenot yet merged into a complete model. This work aims to bridge that gap bybuilding from both sides. On the empirical side, we will use a laboratoryflume to make coupled observations of flow, transport, and bed surfacecomposition in order to describe the evolution of surface and subsurfacegrain sizes with unprecedented spatial and temporal detail. On thetheoretical side, we will develop a transport and armoring model thatincludes size-dependent vertical transfer of grains between surface andsubsurface (kinematic sorting). This mechanism can be incorporated incurrent models, but the necessary transfer functions remain undefined andwill be identified using the data from the experimental portion of thisproject. Testing of the model will be based on internal comparisonsbetween different sediment supply configurations and a set of runs withprogressive bed aggradation and degradation. The result will be aphysically-based, tested model capable of predicting transport and armoringunder the complex, transient conditions typical of the field.