Process-Based Characterization of Near-Surface Hydrologic Response and Hydrologically Driven Slope Stability

浅层滑坡反复造成生命损失、公共和私人财产的物质损害，以及山区栖息地的极端退化。作为这个问题的及时性的一个例子，俄勒冈州森林实践法案被修改(针对1996年两次泥石流造成的5人死亡)，以通过和执行森林实践规则，这些规则将减少快速移动的山体滑坡的发生、时间和影响。拟议的研究将集中在基于物理的表征近地表水文响应和坡面稳定性启动过程的集水规模的陡峭山坡。这一特征将基于CoosBay试验性集水区(CB1)的复杂数值模拟。860m 2 CB1位于俄勒冈州海岸山脉。CB1是一个没有沟渠的山谷，面朝北，平均坡度为43。在CB1地区，海岸山脉呈现出陡峭、解剖精细的山坡，其中泥石流是主要的地貌过程。CB1的仪器用于描述三次喷洒/示踪试验(1990年和1992年)的近地表水文响应的时空变异性，包括一个由雨量计、压力计、张力计、TDR导波对、蒸渗仪、气象传感器和堰组成的详尽的网格。从1990年到1996年，CB1的降雨量、流量和总水头都是连续测量的。近地表水文响应将用综合水文模型(INHM)进行精确的模拟。综合InHM采用一阶耦合方法，定量模拟了三维变饱和渗流和溶质在多孔介质和大孔隙中的运移，以及二维在地表和明渠中的渗流和溶质运移。对InHM的特定水文响应机制没有先验假设。拟采用的两种斜坡稳定性模型分别是无限长边坡模型和线弹性变形方程的二维有限元解。研究分三个阶段进行。在第一阶段，将对三个CB1喷头/示踪器实验进行基于事件的流体流动和溶质运移的InHMM模拟，以表征水文响应和孔压分布。在第二阶段，将对水文响应进行长期的InHM模拟(针对CB1的七年记录)，以产生连续的孔压分布。在第三阶段，将使用两个斜坡稳定性模型进行斜坡稳定性模拟(由第一阶段和第二阶段的水文响应模拟驱动)，以评估CB1的斜坡破坏起始。CB1数据集(流量、压力水头、土壤水分含量和溶质浓度)将用于模型性能的严格评估。水文响应和坡度稳定性的耦合模拟将被用来评估已知稳定时刻和已知不稳定时刻(即1996年11月的CB1破坏)的边坡破坏。从理论上讲，所提出的模拟工作将有效地展示在类似于CB1或更高的野外条件下，水文响应模型不如HM模型全面的实用性和/或局限性。还有可能指导新模型的结构(比InHM更简单)，以便在决策管理领域根据主导响应--假设假设情景下InHM结果的概括--来指导使用。就更广泛的影响而言，拟议研究的结果将有助于优化未来水文响应/滑坡启动研究和实时灾害预警系统的数据收集网络。拟议工作的一个主要贡献是培养了一名博士生。

0409133LoagueShallow landsliding repeatedly causes loss of life, physical damage to public and privateproperty, and extreme habitat degradation in mountainous regions. As an example of thetimeliness of this problem, the Oregon Forest Practices Act was modified (in response to fivedeaths, resulting from two 1996 debris flows) to adopt and enforce forest practice rules that willreduce the occurrence, timing, and effects of rapidly moving landslides.The proposed research will focus on a physics-based characterization of near-surfacehydrologic response and slope stability initiation processes for steep hillslopes at the catchmentscale. This characterization will be based upon sophisticated numerical simulations for the CoosBay experimental catchment (CB1). The 860m 2 CB1 is located in the Oregon Coast Range. CB1is an unchanneled valley, with a north-facing aspect, that has an average slope of 43. In the areaof CB1, the Coast Range exhibits steep, finely dissected hillslopes where debris flows are thedominant geomorphic process. The instrumentation at CB1, used to characterize the spatial andtemporal variability in near-surface hydrologic response for three sprinkler/tracer experiments (in1990 and 1992), includes an exhaustive grid of rain gages, piezometers, tensiometers, TDRwave-guide pairs, lysimeters, meteorological sensors, and weirs. Continuous measurements ofrainfall, discharge, and total head are available for CB1 from 1990 through 1996.Rigorous simulation of near-surface hydrologic response will be conducted with theIntegrated Hydrology Model (InHM). The comprehensive InHM quantitatively simulates, with afirst-order coupled approach, 3D variably-saturated flow and solute transport in porous mediaand macropores and 2D flow and solute transport over the surface and in open channels. There isno a priori assumption of a specific hydrologic-response mechanism with InHM. The two slopestability models to be employed in the proposed study are the infinite slope model and a 2Dfinite-element solution to the linear elastic deformation equations.The proposed research would be conducted in three phases. In phase I, event-based InHMsimulations of fluid flow and solute transport will be conducted for the three CB1 sprinkler/tracerexperiments to characterize hydrologic-response and pore water pressure distributions. In phaseII, long-term InHM simulations of hydrologic response (for the seven year CB1 record) will beconducted to generate continuous pore water pressure distributions. In phase III, slope stabilitysimulations (driven by hydrologic-response simulations in phases I and II), with the two slopestability models, will be conducted to assess slope failure initiation for CB1. The CB1 data sets(discharge, pressure head, soil-water content, and solute concentration) will be used in a rigorousassessment of model performance. The coupled simulation of hydrologic response and slopestability will be used to evaluate slope failure at times of known stability and times of knowninstability (i.e., the November 1996 CB1 failure).Related to intellectual merit, the proposed simulation effort will effectively demonstrate theutility and/or limits of hydrologic-response models less comprehensive than InHM for fieldconditions similar to CB1 and beyond. It will also be possible guide the structure of new models(simpler than InHM) for use in the decision-management arena based upon dominant responsegeneralizations of InHM results for what if scenarios. Related to broader impact, results from theproposed study will be useful for the optimization of data collection networks for both futurestudies of hydrologic response/landslide initiation and real-time hazard warning systems. Amajor contribution of the proposed work is the training of a PhD student.