Doctoral Dissertation Research: Connectivity and Discontinuity in River Systems

博士论文研究：河流系统的连通性和不连续性

• 批准号: 1103172
• 负责人: Francis Magilligan
• 金额: $ 1.2万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-15 至 2014-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1103172&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Connectivity; Discontinuity

The interchange of water, sediment, nutrients, pollutants and other matter is a fundamental process of river systems that affects channel form, ecologic integrity, and human activities. Contemporary river restoration and rehabilitation theory calls for process-based approaches that aim to protect and reinstate this connectivity at watershed scales. There are fundamental unanswered questions about this connectivity, however, which hinder efforts to understand and safeguard the physical and biological systems of rivers. In particular, it is unclear how disturbance and the recovery from disturbance, such as dam removal, affect connectivity and channel form; over what time and spatial scales does this recovery occur; and what characterizes the natural rates and dimensions of continuity and discontinuity. Recent developments in the use of isotopes as both tracers and chronometers can be applied to quantify the spatial and temporal aspects of connectivity and how it affects channel form, sediment residence time and nutrient flux. In addition, large-scale river restoration projects, such as dam removals, enable watershed-scale experiments to test predictions on connectivity. This doctoral dissertation research project will analyze the connectivity of riparian processes in pristine and disturbed river systems and investigate the effects of restoration on sediment transport, channel form and nutrient flux. The doctoral student will conduct a series of field experiments in New England, using innovative applications of lead-210, beryllium-7, and carbon-14 isotopes to determine residence time of instream sediment and add a temporal dimension to a widely used metric of instream sediment storage, V*. These same isotopes will be used in another manner in the riparian zone to establish the flux of sediment and nutrients between floodplains and channels. Building on recent advancements on effects of dam emplacement on channel morphology, this project will test predictions on channel adjustments due to dam removal, which reestablishes continuity of sediment.This project will advance both basic understanding of riverine systems and practical knowledge to guide river restoration efforts. Reestablishing the multiple dimensions of connectivity is a paramount goal in river restoration. This group of field experiments will examine what controls the spatial and temporal scales of sediment continuity, how connectivity is affected by dam emplacement and removal, and how variation in connectivity affects river channel form and nutrient exchange. These questions collectively typify the foremost challenges facing fluvial geomorphology and the science of river restoration -- the delineation and prediction of the multiple, interacting temporal and spatial scales of river response to disturbance. The field work will be conducted in New England, which is currently experiencing more than ten dam removals per year. In addition to advancing basic knowledge of river restoration and river response to disturbance, the results of this research will be leveraged by key stakeholders and agencies to advance their ongoing studies, and it will help managers and scientists guide restoration efforts regionally and nationally. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

水、沉积物、营养物、污染物和其他物质的交换是河流系统的基本过程，影响着河道形态、生态完整性和人类活动。 当代河流恢复和重建理论要求以过程为基础的方法，旨在保护和恢复这种连通性在流域尺度。 然而，关于这种连通性，还有一些根本性的问题没有得到回答，这阻碍了人们理解和保护河流的物理和生物系统的努力。 特别是，目前还不清楚如何干扰和恢复干扰，如大坝拆除，影响连接和渠道的形式;在什么时间和空间尺度上发生这种恢复;以及什么特点的自然率和连续性和不连续性的尺寸。 最近在使用同位素作为示踪剂和计时器方面的发展，可用于量化连通性的空间和时间方面，以及它如何影响河道形态、沉积物停留时间和养分通量。 此外，大规模的河流恢复项目，如大坝拆除，使流域规模的实验，以测试对连通性的预测。 本博士论文研究项目将分析在原始和扰动河流系统的河岸过程的连通性，并调查恢复对泥沙输运，河道形态和营养盐通量的影响。 博士生将在新英格兰进行一系列实地实验，使用铅-210，铍-7和碳-14同位素的创新应用来确定瞬时沉积物的停留时间，并为瞬时沉积物储存量的广泛使用的度量增加时间维度，V*。 这些相同的同位素将以另一种方式用于河岸带，以确定河漫滩和河道之间的沉积物和营养物通量。 该项目基于大坝对河道形态影响的最新进展，将测试大坝拆除后河道调整的预测，重建沉积物的连续性。该项目将提高对河流系统的基本认识和指导河流恢复工作的实用知识。 重建连通性的多个维度是河流恢复的首要目标。 这组实地实验将研究是什么控制沉积物连续性的空间和时间尺度，大坝的安置和拆除如何影响连通性，以及连通性的变化如何影响河道形态和养分交换。 这些问题共同代表了河流地貌学和河流恢复科学所面临的最大挑战-描绘和预测河流对干扰的多个相互作用的时空尺度。 现场工作将在新英格兰进行，该地区目前每年有十多座大坝被拆除。 除了推进河流恢复和河流对干扰的反应的基本知识外，这项研究的结果将被主要利益相关者和机构利用，以推进他们正在进行的研究，并将帮助管理人员和科学家指导区域和国家的恢复工作。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。