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

摘要评估、量化和预测大型伍迪·迪布里斯作为水文连通性驱动力的作用PI：M.巴亚尼·卡登斯该奖项由2009年美国复苏和再投资法案(公法111-5)资助。这项研究旨在了解和量化大型木质垃圾(LWD)在推动河流与其沉积物之间的水文连接和流体、质量和能量交换方面的作用。LWD在河流景观中普遍存在，并在各个尺度上控制河流水文、地貌、生物地球化学和生态。正因为如此，LWD重新引入现在是一种流行的栖息地和河流恢复工具。然而，修复治理项目的成功与否，有赖于对随钻测井S在溪流中的诸多功能有透彻的科学认识。我们对随钻测井作为渠道中的水流障碍如何推动地表水-地下水交换知之甚少。通过水槽试验、数值试验和现场试验，我们将量化地下水-地表水交换与随钻测井配置和渠道水力条件的关系。我们将进行水槽试验，量化不同条件下的地下水-地表水综合交换指标和局部交换指标。在水槽中，我们将改变随钻测井的直径和深度以及渠道弗劳德数。水槽实验还将考虑非等温条件，在非等温条件下，我们将对航道施加昼夜升温/冷却，并监测由随钻测流相互作用引起的沉积物中的热量传输。对有限的水槽试验进行了敏感性分析，采用耦合计算流体力学方法模拟了湍流自由表面明渠流动与地下水流动、热量和溶质运移。这些模拟将测试渗透率和冲刷形态对随钻测深引起的地下水-地表水质量、动量和能量交换的影响，并解决更广泛的随钻测井几何形状和渠道条件。作为受控的实际和数值实验的补充，我们将在现场活动中量化引入的随钻测井的影响范围，同时对一条测井附近的压力和温度进行详细的三维监测。这允许同时表征覆盖范围的信号和本地物理过程。利用现场、水槽和数值试验的综合信息，我们将建立随钻测井引起的地下水-地表水交换的预测关系式，作为易于测量的参数的函数，如达西-魏斯巴赫摩擦因数、弗劳德数、泥沙渗透率、随钻测井间隙和堵塞比。由此产生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.