River Responses to Natural and Human-induced Changes in Sediment Supply

本项目探讨了河流对自然和人为泥沙供应变化的响应过程和结果，以更好地建立河道形态调整和泥沙运输机制的预测模型。河流反映和响应水流和泥沙供应的变化，努力通过相互调节一系列河道性质来保持平衡。然而，最近的研究表明，这些反应的类型和幅度以未知的方式受到沉积物供应变化的制约。研究人员将利用现有/拆除的水坝附近和下方的河流，减少/增加沉积物供应，作为实验设计，以捕捉这些潜在的反应。由于其重点是大坝和大坝拆除，项目结果将与流域管理者相关，特别是在国家现有大坝基础设施不断老化的情况下，造成重大的环境、社会和经济风险。这个项目将从代表性不足的群体中招收不同的学生。通过在会议和公开会议上发表文章和演讲，成果将传播给广泛的科学家和区域利益攸关方。该项目的首要目标是量化河道形态演变，以确定泥沙供应的短暂和/或持续变化，并证明形态演变如何影响水力特性和随后的泥沙输送。研究人员将采用一种研究设计，该设计基于详细的地理空间现场测绘和通道调查，结合监测带有射频识别（RFID）示踪剂的砾石碎屑的流动性，并嵌入加速度计，量化河岸水力特性、阈值水流功率和河床结构对沉积物供应变化（积极和消极）的响应。通过利用大坝就位和拆除提供的自然实验，该研究将提高我们对扰动后河道演变的理解，从而提高我们对基本河流过程的理论理解，这可以应用于其他地貌环境。广泛传播的结果对河流修复至关重要，对自然和社会都有影响。该奖项反映了美国国家科学基金会的法定使命，并通过基金会的知识价值和更广泛的影响审查标准进行了评估，认为值得支持。

This project explores the processes and outcomes of river responses to both natural and human-induced changes in sediment supply to better develop predictive models of channel morphlogic adjustments and the mechanisms of sediment transport. Rivers reflect and respond to changes in streamflow and sediment supply striving to maintain equilibrium by mutually adjusting an array of channel properties. Yet, recent research reveals that the type and magnitude of these responses is conditioned in unknown ways by variations in sediment supply. The investigators will use stream reaches at and below existing/removed dams that decrease/increase sediment supply as an experimental design to capture these potential responses. With its focus on dams and dam removal, project outcomes will be relevant to watershed managers, especially as the nation’s existing dam infrastructure continues to age, posing significant environmental, social, and economic risks. This project will recruit diverse students from underrepresented groups. Through articles and presentations at conferences and public meetings, results will be disseminated to a broad array of scientists and regional stakeholders.The overarching goal of this project is to quantify the channel morphologic evolution to transient and/or sustained changes in sediment supply and to demonstrate how morphologic evolution conditions hydraulic properties and subsequent sediment transport. The investigators will utilize a research design that is based on detailed geospatial field mapping and channel surveying combined with monitoring the mobility of gravel clasts tagged with radio-frequency identification (RFID) tracers and with embedded accelerometers to quantify the variation in bankfull hydraulic properties, threshold stream power, and bed architecture in response to changes (both positive and negative) in sediment supply. By taking advantage of the natural experiments provided by both dam emplacement and removal, the research will improve our understanding of channel evolution following a disturbance and thereby advance our theoretical understanding of fundamental river processes that can be applied in other geomorphic settings. The broadly disseminated results are essential for river restoration, with implications for both nature and societyThis 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.