RII Track-4: Improving Understanding of River Flood Dynamics by Relating Flow and Sediment Movement to Shapes of River Dunes in three dimensions

世界上大部分人口和商业活动都存在于沿着的河流走廊上。人类住区的可持续性及其对环境的影响与河流洪水和沉积物动力学密不可分。底形，如沙波纹和沙丘的移动土丘，是动态河流系统底部观察到的主要特征。它们的几何形状和运动与河流水流和泥沙输运密切相关，并且在复杂的反馈回路中相互影响。直接测量这些耦合反馈的所有成分在现代河流中具有挑战性，并且难以在其古老的沉积物中解释，阻碍了长时间尺度的完整理解。经过世纪的研究，人们试图将底形、运动和古代沉积物与形成它们的水流和沉积物输运条件联系起来。这方面的努力大多集中在二维框架上。该项目建立了一套新的实验和现场技术，在一个合作的设置，收集耦合测量的流量，泥沙输运和床形演变的三维。在这样做的过程中，这项工作将扩大新奥尔良大学的物理和智力能力，以解决超出本项目范围的泥沙输运研究问题。这种扩大的能力将扩大参与，并通过在新奥尔良一所高度多样化的公立大学建立一个具有最先进方法的高能力沉积物运输设施，为多样化的大学社区和东南部地区服务。底形是沉积物输运系统的主要可观测特征。它们的几何形状和运动学（运动）与水流和泥沙输运的动力学（力）密切相关。因此，底形及其地层要素是了解过去和现在河流状况的关键。冲积砂床系统的水沙运动条件与床形运动密切相关。底形用于输送河床物质沉积物，其形态从冲积河流系统中的水流中提取动量。了解它们的几何形状和行为可以为评估现代河流系统中床物质通量和剪切应力分配的模型提供信息，并增强对古代河流地层的解释。该项目旨在建立能力，建立实验室协议，并收集数据，以解决三个独立的假设：第一，横流，相对于下游，推移质颗粒漂移长度和速度随着湍流能量的增加而增加;第二，横流颗粒碰撞的可能性增加，从而能够建立三维的底形地形;第三，可以从地层学中底形的三维性和交集界面的曲率反演水流的紊流特征，即剪切速度。对这些假设的完整评估将提高根据水流和泥沙输运条件向前模拟底形几何形状和运动学的能力。这将支持用于定量解释过去的沉积物输运和流动条件的基础上观察地层的逆模型。该奖学金将与加州大学圣巴巴拉分校的研究人员合作，解决区域和国家相关的河流洪水动力学问题。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Much of the world’s population and commerce exist along river corridors. The sustainability of human settlements and the impacts they have on their environments are inextricably tied to river flood and sediment dynamics. Bedforms, migrating mounds of sand such as ripples and dunes, are a primary feature observed on the bottom of dynamic river systems. Their geometries and motions are closely tied to river flow and sediment transport and each one influences the other in complex feedback loops. Direct measurement of all components of these coupled feedbacks is challenging in modern rivers and difficult to interpret in their ancient sedimentary deposits, hindering complete, understanding over long timescales. Over a century of study has attempted to relate bedform shapes, motions, and ancient deposits to the flow and sediment transport conditions that form them. Much of this effort has focused on two-dimensional frameworks. This project establishes a new set of experimental and field techniques in a collaborative setting for collecting coupled measurements of flow, sediment transport, and bedform evolution in three dimensions. In so doing, this work will expand the physical and intellectual capacity of the University of New Orleans to address problems in sediment transport research that extend beyond the scope of this project. This expanded capacity will broaden participation and serve the diverse university community as well as the southeastern region by establishing a highly capable sediment transport facility with state-of-the-art methods at a highly diverse public university in New Orleans. Bedforms are a primary observable feature of sediment transport systems. Their geometries and kinematics (motions) are closely coupled to the dynamics (forces) of flow and sediment transport. As such, bedforms and their stratal elements are key to understanding river conditions, past and present. Flow and sediment transport conditions in sand-bed alluvial systems are tightly coupled to the kinematics of bedforms. Bedforms serve to transport bed material sediment, and their forms extract momentum from the flow in alluvial river systems. Understanding their geometry and behavior can inform models that evaluate bed material flux and shear stress partitioning in modern river systems, as well as enhance interpretation of ancient fluvial strata. This project seeks to build capacity, establish lab protocols, and collect data to address three independent hypotheses: First, that cross-stream, relative to downstream, bedload particle excursion length and velocity increase with increasing turbulent energetics of the flow; second, that increasing probabilities of cross-stream particle collisions enable the establishment of three-dimensionality of bedform topography; and third, that turbulent characteristics of flow, namely shear velocity, can be inverted from three-dimensionality of bedforms and the curvature of cross set bounding surfaces in stratigraphy. A complete assessment of these hypotheses will enhance the ability to forward model bedform geometries and kinematics based on flow and sediment transport conditions. This will bolster inverse models used to quantitatively interpret past sediment transport and flow conditions based on observations of stratigraphy. In collaboration with researchers at the University of California, Santa Barbara, this fellowship will address both regionally and nationally relevant problems of river flood dynamics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.