Modeling Bed-Surface Dynamics In Gravel-Bed Rivers

砾石河床河床表面动力学建模

• 批准号: 0106561
• 负责人: Peter Wilcock
• 金额: $ 20.5万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-15 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0106561&HistoricalAwards=false
• 关键词: Modeling; Bed; Surface; Dynamics; Gravel

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.

砂砾石河普遍存在表面粗化现象，也就是广义的装甲。盔甲强烈影响航道水力学，决定可供运输的谷物数量，并定义水生无脊椎动物、鲑鱼产卵和幼鱼的栖息地。对水流、输运和底栖生物生态的一般和预测性了解沟床河流需要有能力预测河床表面组成作为水和泥沙供应的函数。一般来说，床面与当时的条件不平衡，因此不能根据现场观测的简单相关性来推断原因和影响。相反，我们求助于实验室进行受控观测，并使用计算模型来捕捉现场各种不同的瞬变条件。几十年来一直在进行装甲观测，并开发了能够预测装甲的算法。然而，数据和模型中都缺少关键因素，经验和理论还没有融合成一个完整的模型。这项工作旨在通过从双方建设来弥合这一差距。在实验方面，我们将使用实验室水槽对流动、输运和床面组成进行耦合观测，以前所未有的空间和时间细节描述表面和亚表面颗粒尺寸的演变。在理论方面，我们将开发一个运输和装甲模型，该模型包括取决于大小的谷物在地表和地下之间的垂直转移(运动学分选)。这一机制可以结合到当前的模型中，但必要的传递函数仍未定义，将使用该项目实验部分的数据来确定。模型的测试将基于不同泥沙供应配置之间的内部比较，以及一组具有渐进性河床淤积和退化的运行。结果将是基于形而上学的、经过测试的模型，能够预测在复杂的、现场典型的瞬变条件下的运输和装甲。