International Research Fellowship Program: Modeling the Morphodynamics of Bedrock Meandering

0965064纳尔逊国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。 该计划的奖项提供了联合研究的机会，以及使用独特或互补的设施，专业知识和国外的实验条件。纳尔逊与意大利热那亚大学的乔瓦尼·塞米纳拉博士合作。蜿蜒的基岩河流是自然界视觉上壮观的例子？形成模式的能力。基岩曲流的起源和行为已经争论了世纪，但今天我们仍然无法回答关于它们的非常基本的问题;例如，曲流是如何在基岩中形成的，以及是什么决定了曲流波长的选择？本项目的目的是开发一个理论的基岩曲流地形动力学模型，作为能够回答这些问题的重要一步。主机和PI正在使用现有的研究文献和可用的地形数据集，以开发一个全面的描述基岩曲流在自然界中，并建立在现有的理论冲积曲流和最近的进展，我们的理解基岩侵蚀的力学，这些意见被用来开发一个理论基岩曲流形成。理论发展包括：1）估算跃移推移质和悬移质磨蚀引起的局部垂直和侧向侵蚀以及风化引起的基岩破坏的新方法：2）基本状态的线性稳定性分析，以确定侧向侵蚀是否可能提供弯曲增长的机制; 3）开发弯曲渠道中流动的3D模型，其轴可以显示弯曲和扭转;以及4）开发渠道中心线的3D平面形状演变方程，以说明预测的渠道行为。该项目促进了地貌学家和理论形态动力学家之间的合作。由于对基岩河流的行为知之甚少，该项目有可能大大拓宽我们对基岩系统的基本理解。我们提出的工作将结合联合收割机的最先进的理论形态动力学的冲积曲流和基岩切割，和理论框架，我们开发的将是第一个采用纯侵蚀机制，包括沉积物供应的影响，并本质上是三维的。这项工作的新方面，特别是纳入沉积物供应有限的影响，应适用于广泛的地貌问题，包括可能的人为或气候对河流行为的影响。我们希望这个项目将为理论家和地貌学家现在和将来的持续国际合作提供机会。

0965064NelsonThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support an eighteen-month research fellowship by Dr. Peter A. Nelson to work with Dr. Giovanni Seminara at the University of Genoa in Italy.Meandering bedrock rivers are visually spectacular examples of nature?s ability to form patterns. The origin and behavior of bedrock meanders have been debated for over a century, yet today we are still unable to answer very basic questions about them; for instance, how do meanders form in bedrock, and what determines the selection of a meander wavelength? The aim of this project is to develop a theoretical morphodynamic model for bedrock meandering as an important step toward being able to answer these questions. The host and PI are using available studies in the literature and available topographic datasets to develop a comprehensive description of bedrock meanders in nature, and, building upon existing theory for alluvial meandering and recent advances in our understanding of the mechanics of bedrock erosion, these observations are used to develop a theory for bedrock meander formation. Theory development includes the following: 1) new approaches to estimate local vertical and lateral erosion due to abrasion from saltating bed load and suspended load, and bedrock breakdown due to weathering; 2) a linear stability analysis of a basic state to ascertain whether lateral erosion may provide a mechanism for bend growth; 3) the development of a 3D model for flow in a curved channel whose axis may display both bending and torsion; and 4) the development of a 3D planform evolution equation for the channel centerline to illustrate predicted channel behavior. This project promotes cooperation between geomorphologists and theoretical morphodynamicists. Since so little is known about the behavior of bedrock rivers, this project has the potential to dramatically broaden our basic understanding of bedrock systems. Our proposed work will combine the state-of-the-art in theoretical morphodynamics of alluvial meandering and bedrock incision, and the theoretical framework we develop will be the first of its kind to employ a purely erosive mechanism, to include the effects of sediment supply, and to be intrinsically 3D. The novel aspects of this work, particularly the incorporation of sediment supply-limited effects, should be applicable to a broad range of geomorphic problems, including possible anthropogenic or climatic effects on river behavior. We expect this project will provide opportunities for continual international collaboration between theoreticians and geomorphologists now and in the future.