Modeling Bed-Surface Dynamics In Gravel-Bed Rivers

0106561 Wilcock河床表面粗化，广义上称为粗化，是砾石河流的普遍特征。装甲强烈影响渠道水力学，determinespopulation的谷物可供运输，并定义habitatfor水生无脊椎动物，鲑鱼产卵，和幼鱼。一般和预测性的了解流，运输，和底栖生态inravel-bed河流，需要有能力预测床面组成的功能，水和泥沙供应。一般来说，床面与当时的条件并不平衡，因此不能从现场观测的简单相关性中推断出原因和影响。相反，我们转向实验室进行受控观测，并转向计算模型来捕捉现场的变化和瞬态条件。几十年来一直在进行粗化观测，并且已经开发出能够预测粗化的算法。然而，数据和模型中的关键要素都缺失了，经验和理论还没有融合成一个完整的模型。这项工作旨在通过从双方建设来弥合这一差距。在经验方面，我们将使用一个laboratoryflume的流量，运输和床面成分的耦合观测，以描述的表面和subsurfacegrain尺寸的演变与前所未有的空间和时间的细节。 在理论方面，我们将开发一个运输和装甲模型，其中包括大小相关的垂直转移之间的颗粒表面和地下（运动分选）。这种机制可以纳入当前的模型，但必要的传递函数仍然没有定义，并将确定使用的数据，从实验部分的这个项目。 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和一组具有渐进的河床淤积和退化的运行。 其结果将是一个基于经验的、经过测试的模型，能够预测该领域典型的复杂瞬态条件下的运输和铠装。

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.