Doctoral Dissertation Research: The Impact of Lateral Channel Confinement on River Morphology

这个博士论文项目将讨论河流的横向或河岸边界对河流形态的影响的复杂方式。这包括支流和山坡侵蚀过程如何贡献泥沙，以及横向限制特征(如公路、铁路和桥台)如何通过改变河流的水流状况改变泥沙贡献和河道形态，从而改变河流侵蚀或沉积物质的有效性。该项目还将提供关于河流形态和形态如何根据沉积物类型分布以及下游方向的河道宽度和深度进行组织的新见解。学生将专注于研究支流和山坡侵蚀过程作为额外泥沙来源的作用，以及河岸狭窄作为人类活动改变自然河流流量的位置的作用，这往往会破坏具有文化和环境重要性的水生和河岸物种的栖息地。该项目的研究结果将有助于理解河流如何应对不断变化的横向条件。这些信息可用于河流恢复项目，以加强河流生态系统的健康。此外，从研究中获得的信息有可能为未来的河流建设提供信息，因为它提供了对河流及其泛滥平原之间联系的重要性的更彻底的理解。该项目的方法论方法旨在低成本和广泛使用，目的是显示这种方法在全国河流保护和恢复工作中的广泛适用性。作为博士论文改进奖，该项目还将提供支持，使有前途的年轻学者能够建立自己的研究生涯。该项目的重点是深化“沉淀链接”的概念。这种理论方法将河流支流作为泥沙连接，创建了一系列不同的河段，由河道坡度和砾石大小的局部变化来定义。这位学生提出，在这种情况下，侧向河道收缩可以被视为“泥沙断裂”，因为在高流量事件期间，由于缺乏泛滥平原通道，河道底部剪应力的增加将导致类似于泥沙连接的地貌变化，但由于侵蚀增加，而不是供应过剩。该项目研究中使用的方法包括使用小型无人驾驶航空系统以及水下摄影来生成原始数据，这些数据将用于量化颗粒尺寸分布、通道深度和通道宽度。现有的航空图像和激光雷达数据将用于使用公认的定义对航道收缩严重程度进行分类。这些数据来源将被用来解决几个研究问题，这些问题与航道狭窄的严重程度有关，与航道形态变量偏离自然控制河段的程度有关。研究问题还将进一步分析支流与局部航道形态变化的关系，以及水面粗糙度和流速矢量的模式。这项研究将在美国俄勒冈州南部的罗格河沿岸进行，但其发现将广泛适用于其他河流系统。

This doctoral dissertation project will address the complex ways in which the lateral, or riverbank, boundaries of a river impact the river's form. This includes how tributaries and hillslope erosion processes contribute sediment, and how laterally confining features such as roads, railroads, and bridge abutments alter both sediment contributions and channel morphology by modifying the flow regime of the river, thus altering the effectiveness of the river to erode or deposit material. This project will also provide new insights into how river shape and form is organized in terms of the distribution of sediment type, as well as channel width and depth in the downstream direction. The student will focus on investigating the role of tributaries and hillslope erosion processes as sources of additional sediment, and riverbank constrictions as locations where human activity has altered the natural river flow, often degrading habitat for culturally and environmentally important aquatic and riparian species. The findings of this project will contribute to the understanding of how rivers respond to changing lateral conditions. This information can be used in river restoration projects to enhance the health of river ecosystems. Additionally, the information gained from the research has the potential to inform future construction along rivers by providing a more thorough understanding of the importance of the link between a river and its floodplain. The methodologic approach to this project is designed to be low-cost and widely accessible, with the objective of showing the wide applicability of this approach to river conservation and restoration efforts across the country. As a Doctoral Dissertation Improvement award, this project will also provide support to enable a promising young scholar to establish a research career.This project focuses on deepening the "sediment links" concept. This theoretical approach frames river tributaries as sediment links, creating a series of distinct river sections, defined by local changes in channel slope and gravel size. The student proposes that lateral channel constrictions can be thought of as "sediment breaks" within this context, as places where the increase in shear stress at the channel bottom, due to a lack of floodplain access during high-flow events, will result in a similar morphologic change as sediment links, but due to an increase in erosion, rather than a surplus of supply. The methods used in this project research include the use of a small unmanned aerial system as well as underwater photography to generate primary data which will be used to quantify particle size distributions, channel depth, and channel width. Existing aerial imagery and LiDAR data will be used to classify channel constriction severity using accepted definitions. The data sources will be used to address several research questions relating the severity of channel constriction to the magnitude of departure in channel morphology variables from a natural control reach. The research questions will also further analyze the relationship between tributaries and local changes in channel morphology and patterns of water surface roughness and velocity vectors. This research will be conducted along the Rogue River in Southern Oregon, USA but its findings will be broadly applicable in other river systems.