Assessing, Quantifying, and Predicting the Role of Large Woody Debris as a Driver of Hydrologic Connectivity

评估、量化和预测大型木质碎片对水文连通性的驱动作用[j] M. Bayani cardenas本奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。本研究旨在了解和量化大型木质碎屑（LWD）在推动河流及其沉积物之间的水文联系和流体、质量和能量交换中的作用。随钻测井在河流景观中无处不在，在各个尺度上控制着河流水文、地貌、生物地球化学和生态。正因为如此，随钻测井重新引入现在是栖息地和河流恢复的流行工具。然而，恢复和管理计划的成功取决于对随钻测井的全面科学理解。流中的许多函数。作为通道中的流动障碍，我们对随钻测井如何驱动地表水-地下水交换知之甚少。通过水槽、数值和现场试验，我们将量化地下水-地表水交换与随钻器配置和通道水力条件的关系。我们将进行水槽实验，量化各种条件下综合和局部地下水-地表水交换指标。我们将改变随钻直径和深度，以及水槽运行中的通道弗鲁德数。水槽实验还将考虑非等温条件，在这些条件下，我们将对通道施加日变暖/冷却，并监测由LWD-current相互作用引起的沉积物的热量传递。在有限水槽实验的基础上，采用耦合计算流体动力学模拟，对具有地下水流动、热量和溶质运移的自由地表明渠湍流进行敏感性分析。模拟将测试渗透率和冲刷形态对LWD诱导的地下水-地表水质量、动量和能量交换的影响，并解决更广泛的LWD几何形状和通道条件。除了受控的实际和数值实验外，我们还进行了一项现场试验，在该试验中，我们将量化引入的随钻测井的范围效应，同时对一条测井曲线附近的压力和温度进行详细的三维监测。这允许同时表征达到规模的信号和本地物理过程。利用现场、水槽和数值实验的综合信息，我们将开发随钻诱发地下水-地表水交换的预测关系，作为易于测量的参数的函数，如达西-韦斯巴赫摩擦系数、弗劳德数、沉积物渗透率、随钻间隙和堵塞比。由此得出的预测关系可以指导河流管理和恢复决策，以及生物地球化学和生态学研究。

AbstractAssessing, Quantifying, and Predicting the Role of Large Woody Debrisas a Driver of Hydrologic ConnectivityPI: M. Bayani CardenasThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This study seeks to understand and quantify the role of large woody debris (LWD) in driving hydrologic connections and exchanges of fluid, mass, and energy between rivers and their sediment. LWD is ubiquitous in the fluvial landscape and controls fluvial hydrology, geomorphology, biogeochemistry, and ecology at all scales. Because of this, LWD reintroduction is now a popular tool for habitat and river restoration. However, the success of restoration and management programs depends on a thorough scientific understanding of LWD?s many functions in streams. We know little about how LWD, as a flow obstacle in channels, drives surface water-groundwater exchange. Through flume, numerical, and field experiments, we will quantify the relationship of groundwater-surface water exchange to LWD configuration and channel hydraulic condition. We will conduct flume experiments to quantify integrated and local groundwater-surface water exchange metrics under various conditions. We will vary LWD diameter and depth as well as channel Froude number in flume runs. The flume experiments will also consider non-isothermal conditions where we will impose diurnal warming/ cooling of the channel and monitor heat transfer through the sediment induced by LWD-current interaction. Supplementing the limited flume experiments are sensitivity analyses using coupled computational fluid dynamics simulations of turbulent free-surface open channel flow with groundwater flow and heat and solute transport. The simulations will test the influence of permeability and scour morphology on LWD-induced groundwater-surface water mass, momentum, and energy exchange and address a broader range of LWD geometry and channel conditions. Complementing the controlled actual and numerical experiments is a field campaign in where we will quantify the reach-scale effects of introduced LWD simultaneous with detailed three-dimensional monitoring of pressure and temperature in the vicinity of one log. This allows concurrent characterization of reach-scale signals and local physical processes. Using the combined information from field, flume, and numerical experiments, we will develop a predictive relationship for LWD-induced groundwater-surface water exchange as a function of easily measured parameters such as the Darcy-Weisbach friction factor, Froude number, sediment permeability, and LWD gap and blockage ratios. The resulting predictive relationship can guide stream management and restoration decisions as well as biogeochemical and ecological research.