Collaborative Research: Emergent Hydrological Properties Associated with Multiple Channel-Spanning Logjams

合作研究：与多航道堵塞相关的新兴水文特性

• 批准号: 1819134
• 负责人: Kamini Singha
• 金额: $ 36.92万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1819134&HistoricalAwards=false
• 关键词: Collaborative; Research; Emergent; Hydrological; Properties; Collaborative; Research; Emergent; Hydrological; Properties

In this proposal we look to quantify relationships among river shapes, logjams, and the movement of water around jams and through surrounding sediments. In doing so, we will advance understanding of (i) how logjams affect water quality and stream communities in forested watersheds, (ii) the effects of historical and continuing human alteration of river corridors in forested regions, and (iii) how to design artificial logjams in rivers to manage stream temperature, nutrients, and aquatic communities. Our work will be shared with resource managers and practitioners to help with issues associated with river management and restoration. Student participation will include (i) K-12 students via course materials that will be developed in collaboration with elementary school teachers; (ii) undergraduate students involved in field data collection and analysis, including students from diverse backgrounds; and (iii) graduate students responsible for the primary data analysis and interpretation, who will have the opportunity to work with and mentor the undergraduate researchers.The benefits of large wood (LW) in river corridors are numerous, including the potential to enhance hyporheic exchange flow (HEF). Existing work has focused on HEF near single logs or single logjams. However, natural channels in forested regions with minimal human alteration commonly contain abundant dispersed LW pieces and multiple logjams spaced irregularly along the channel. We have little indication of whether multiple channel-spanning logjams produce an additive or nonlinear effect on HEF, but these alternatives have important implications for understanding river ecosystem function and for river management and restoration. Our primary objective is to quantify how HEF changes with increasing channel heterogeneity associated with channel-spanning logjams. We will use field measurements, physical experiments, and numerical models to evaluate the characteristics of HEF associated with different spatial densities of channel-spanning logjams. We expect nonlinear relations between logjams and HEF to result from increased bedforms such as pools that maximize flux rates, increased head gradients associated with decreased downstream spacing between logjam-induced backwaters, and thicker deposits of sand and gravel, which act together to create steep hydraulic head gradients within thick, permeable bed sequences. We also expect a nonlinear relation between logjams and HEF at the transition to anabranching as a result of the enhanced HEF between divided channels. Implications of this work will be with respect to engineered logjams, which are currently being added to rivers, but with no systematic understanding of how the effects of LW addition scale with river size, the volume and spatial distribution of wood addition, or the characteristics of the wood and the channel, constraining our ability to design LW-based river restoration to achieve a desired level of HEF. As part of our research, we will develop curriculum for a local K-12 school.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.

在此提案中，我们希望量化河流形状，logjams之间的关系，以及果酱周围和周围沉积物周围的水的运动。 通过这样做，我们将提高对（i）logjams如何影响森林流域中的水质和溪流社区的理解，（ii）历史和持续的人类对森林地区河流走廊的变化的影响，以及（iii）如何设计河流中的人造logjams来管理河流温度，营养素和水上社区。我们的工作将与资源经理和从业人员分享，以帮助解决与河流管理和恢复相关的问题。学生的参与将包括（i）K-12学生通过与小学教师合作开发的课程材料； （ii）参与现场数据收集和分析的本科生，包括来自不同背景的学生； （iii）负责主要数据分析和解释的研究生，他们将有机会与本科研究人员合作和指导。大型木材（LW）在河流走廊中的好处很多，包括增强低血交换流量（HEF）的潜力。现有的工作集中在单个日志或单个logjam附近的HEF上。但是，人类改变最小的森林区域中的自然通道通常包含丰富的分散的LW碎片和多个沿通道不规则间隔的logjam。我们几乎没有迹象表明多个跨通道的logjam是否会对HEF产生添加剂或非线性影响，但是这些替代方案对理解河流生态系统功能以及河流管理和恢复具有重要意义。我们的主要目的是量化HEF如何随着与跨通道logjam相关的通道异质性的增加而变化。我们将使用现场测量，物理实验和数值模型来评估与跨通道logjams不同空间密度相关的HEF的特征。我们预计，logjams和Hef之间的非线性关系是由于床形的增加而导致的，例如，池，使通量速率最大化，头部梯度增加，与logjam诱导的回水之间的下游间距降低相关，以及厚厚的沙子和砾石沉积物，这些沉积物与厚厚的床层产生陡峭的水力梯度。我们还期望由于分裂的渠道之间的增强HEF的增强，logjams和Hef之间的非线性关系。 这项工作的含义将是关于目前正在添加到河流的工程logjams的，但没有系统地了解LW添加规模与河流尺寸的影响如何，木材添加的体积和空间分布或木材和木道的特征，从而限制了我们设计LW基于LW的河流恢复的能力，无法达到HEF的理想水平。 作为我们研究的一部分，我们将为本地K-12学校开发课程。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响评估标准来评估的。