CAREER: Experimental and Theoretical Investigation of Sediment Supply and Sorting in Meandering Rivers

蜿蜒的河道是景观中最具标志性的特征之一，这些大弯曲的河流的迁移直接关系到洪泛平原沿线的社区和土地所有者。曲流的形成和迁移机制一直是科学家和工程师关注的问题。然而，在这些渠道的知识方面仍然存在相当大的差距，特别是关于泥沙供应、河床沉积物粒度和河床地形之间的动态相互作用。本CAREER项目的科学重点是利用实验室水槽实验、分析理论和数值模拟来探索这些关系。这项研究的结果将应用于紧迫的社会问题，如防洪、河道维护、河流修复和大坝拆除。这项研究将与一项教育和推广计划相结合，旨在向K-12学生和公众介绍河流科学和管理的重要问题，并改善工程专业本科生和研究生的教育体验。该项目的科学目标是：1)研究河道曲率如何影响河床地形和表面分选的平衡模式；2)研究泥沙供应的变化如何影响曲流河道的分选和河床地形；3)探索混合粒径泥沙和可变泥沙供应的曲流河道中自由沙坝和强迫沙坝的相互作用。将进行一套全面的水槽实验来检验几个假设。第一个实验将使用详细的流量和沉积物运输测量来检查控制不同曲流曲率平衡条件的机制。第二个实验将集中在泥沙供应对沙洲-池形态的影响以及弯曲河道中自由沙洲和强制沙洲之间的相互作用。与意大利同事一起，该项目将开发一个包含沉积物供应和谷物分类的河流曲流理论模型。这个新的模型，连同二维数值模型，将扩展对曲流河道过程的认识，使之超越实验室所能达到的尺度。

A non-technical description of the project's broader significance and importanceMeandering river channels are one of the most iconic features of the landscape and the migration of these large bends in rivers are a direct concern to communities and landowners along the flood plain. The mechanisms of meander formation and migration have long attracted the attention of scientists and engineers. There remain, however, considerable gaps in knowledge of these channels, especially regarding the dynamic interactions among sediment supply, grain-size of river bed sediment, and the river-bed topography. The scientific focus of this CAREER project is to explore these relationships using laboratory flume experiments, analytical theory, and numerical modeling. The results of this research will have applications to pressing societal issues such as flood protection, stream channel maintenance, river restoration, and dam removal. The research will be integrated with an educational and outreach program designed to introduce K-12 students and the public to important issues in river science and management, and to improve the educational experience of undergraduate and graduate engineering students.A technical description of the projectThe scientific objectives of this project are 1) to investigate how channel curvature affects equilibrium patterns of bed topography and surface sorting, 2) to examine how changes in sediment supply affect sorting and bed topography in meandering channels, and 3) to explore the interactions of free and forced bars in meandering channels of mixed grain size sediment and variable sediment supply. A comprehensive suite of flume experiments will be conducted to test several hypotheses. The first experiments will use detailed flow and sediment transport measurements to examine the mechanisms controlling equilibrium conditions at different meander curvatures. The second experiments will focus on questions related to sediment supply effects on bar-pool morphology and the interactions between free and forced bars in curved channels. In conjunction with Italian colleagues, the project will develop a theoretical model for river meandering that incorporates sediment supply and grain sorting. This new model, along with two-dimensional numerical models, will extend knowledge of processes of meandering channels beyond the scales achievable in the laboratory.