The Role of Large Wood in Promoting Channel-Floodplain Connectivity for River Restoration

大木材在促进河道-洪泛区连通性和河流恢复中的作用

• 批准号: 2229839
• 负责人: Ellen Wohl
• 金额: $ 40.29万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2229839&HistoricalAwards=false
• 关键词: Role; Large; Wood; Promoting; Channel

River restoration has initially focused on channel morphology and subsequently gradually expanded to include reconnection of channels and floodplains. Although stream ecologists have recognized the critical ecological role of floodplains for decades, and hydrological, geomorphic, and biogeochemical research now increasingly emphasizes the importance of floodplains, floodplains do not receive the legal protection of navigable water and have been extensively altered throughout the US. Consequently, one of the issues now at the forefront of river management and restoration is how to effectively re-connect altered channels and floodplains. Reconnection requires multiple changes of differing importance in specific settings. Large wood (LW) reintroduction or retention falls within this scope, but guidelines have not been developed regarding how much LW to reintroduce, in what configuration, and where. This research will address an important gap in knowledge regarding the quantitative impacts of LW jams on channel-floodplain hydrologic connectivity and how these impacts can inform river restoration design. Large wood can be a dominant driver of channel and floodplain complexity. LW can alter the local distribution of hydraulic forces, sediment dynamics, hyporheic exchange flows, channel cross-sectional and planform geometry, and channel-floodplain connectivity. These effects operate in a nonlinear fashion as accumulations of LW in a logjam and in progressively larger and more closely spaced logjams create emergent patterns in these response variables. However, thresholds can not yet be predicted for the magnitude of change in response variables with respect to LW quantity or spatial distribution. This is important in the context of river restoration, which reintroduces LW in channels despite inability to predict hydraulic, geomorphic, or ecological responses. This knowledge gap of quantitatively predicting the physical effects of LW on channel-floodplain hydrologic connectivity will be addressed by by (i) measuring LW and associated connectivity in diverse field settings; (ii) assessing threshold responses in connectivity due to river morphologic and LW characteristics; and (iii) developing guidelines for representing LW characteristics and associated hydraulic responses in numerical models. In this context, the project defines channel-floodplain hydrologic connectivity as being present when flow overtops the morphological channel banks and spreads onto the adjacent floodplain. The project objectives are to: (1) collect data from natural channels on LW jam characteristics and associated influences on channel-floodplain connectivity; (2) use these data to develop guidelines for calibrating LW characteristics and hydraulic responses in numerical hydraulic models; and (3) co-generate knowledge and best practices with river restoration practitioners for long-term monitoring of LW jam benefits. The project will integrate new knowledge of how LW jams influence channel-floodplain interactions with ongoing and future investments in river restoration projects, and planned activities are aimed to advance the sustainability of river restoration design, promote restoration monitoring and citizen-science learning to diverse stakeholders and restoration practitioners, and improve STEM education focused on sustainable and resilient natural systems. This award is co-funded by the Environmental Sustainability program in CBET/ENG and the Hydologic Sciences program in EAR/GEO.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.

河流恢复最初侧重于河道形态，随后逐渐扩大到包括重新连接的渠道和洪泛区。尽管河流生态学家几十年来已经认识到洪泛区的关键生态作用，水文学、地貌学和地球化学研究现在越来越强调洪泛区的重要性，但洪泛区没有得到通航水域的法律的保护，在美国各地已经发生了广泛的变化。因此，目前河流管理和恢复的最前沿问题之一是如何有效地重新连接改变的河道和洪泛区。重新连接需要在特定设置中进行多个不同重要性的更改。大型木材（LW）的再引入或保留福尔斯属于这一范围，但尚未制定关于再引入多少LW，以何种配置和在何处的指导方针。这项研究将解决一个重要的知识差距，定量影响LW堵塞渠道洪泛区水文连通性，以及这些影响如何可以通知河流恢复设计。大型木材可以是渠道和河漫滩复杂性的主要驱动力。LW可以改变当地的水力分布，泥沙动力学，潜流交换流，渠道横截面和平面形状的几何形状，和渠道漫滩连接。这些效应以非线性的方式运作，因为LW在一个堵塞中的积累以及在逐渐变大和间隔更近的堵塞中在这些响应变量中产生紧急模式。然而，阈值还不能预测响应变量相对于LW量或空间分布的变化幅度。这是很重要的河流恢复的背景下，重新引入LW的渠道，尽管无法预测水力，地貌，或生态响应。定量预测LW对河道-洪泛区水文连通性的物理影响的知识缺口将通过以下方式解决：（i）测量LW和不同领域设置中的相关连通性;（ii）评估由于河流形态和LW特性导致的连通性阈值响应;以及（iii）制定在数值模型中表示LW特性和相关水力响应的指南。在这种情况下，该项目定义通道洪泛区的水文连通性是存在的，当流量超过形态通道银行和蔓延到相邻的洪泛区。该项目的目标是：（1）从天然河道中收集有关LW堵塞特性以及对河道-洪泛区连通性的相关影响的数据;（2）使用这些数据制定用于校准数值水力模型中LW特性和水力响应的指南;以及（3）与河流恢复从业者共同生成知识和最佳实践，以长期监测LW堵塞的益处。该项目将把LW堵塞如何影响河道-洪泛区相互作用的新知识与河流恢复项目的持续和未来投资相结合，计划的活动旨在促进河流恢复设计的可持续性，促进恢复监测和公民科学学习，以不同的利益相关者和恢复从业者，并改善以可持续和有弹性的自然系统为重点的STEM教育。该奖项由CBET/ENG的环境可持续性计划和GEO/ESTA的水文科学计划共同资助。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。