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

0409133 Loague浅层滑坡反复造成生命损失，对公共和私人财产的物理破坏，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）通过并执行森林实践规则，和快速移动的滑坡的影响。拟议的研究将集中在一个基于物理的表征近，流域尺度陡坡的地表水文响应和边坡稳定性启动过程。这种表征将基于CoosBay实验集水区（CB 1）的复杂数值模拟。860平方米的CB 1位于俄勒冈州海岸山脉。CB 1是一个无沟道的山谷，面向北，平均坡度为43。在CB 1地区，海岸山脉呈现出陡峭的、精细切割的山坡，泥石流是主要的地貌过程。在CB 1的仪器，用于表征空间和时间的变化，近地表水文响应的三个喷头/示踪剂实验（在1990年和1992年），包括一个详尽的网格雨量计，测压计，张力计，TDR波导对，蒸渗仪，气象传感器，堰。CB 1从1990年到1996年连续测量降雨、流量和总水头。近地表水文响应将用综合水文模型（InHM）进行严格模拟。综合InHM定量模拟，与一阶耦合的方法，三维变饱和流动和溶质运移在多孔介质和大孔隙和二维流动和溶质运移在表面上，并在开放的渠道。没有一个特定的水文响应机制与InHM的先验假设。研究中采用的两种边坡稳定性模型是无限边坡模型和线弹性变形方程的二维有限元解。在第一阶段，基于事件的流体流动和溶质运移的InHM模拟将进行三个CB 1喷头/tracerexperiments，以表征水文响应和孔隙水压力分布。在第二阶段，将进行水文响应的长期InHM模拟（针对7年CB 1记录），以生成连续的孔隙水压力分布。在第三阶段，将使用两个边坡稳定性模型进行边坡稳定性模拟（由第一阶段和第二阶段的水文响应模拟驱动），以评估CB 1的边坡破坏起始。CB 1数据集（流量、压头、土壤含水量和溶质浓度）将用于模型性能的严格评估。水文响应和边坡稳定性的耦合模拟将用于评估已知稳定性和已知不稳定性时的边坡破坏（即，1996年11月CB 1失败）。与智力价值有关，拟议的模拟工作将有效地证明水文响应模型的实用性和/或局限性，这些模型在类似于CB 1及以后的现场条件下不如InHM全面。它也将有可能指导新模型的结构（比InHM更简单），用于决策管理竞技场的基础上，主导响应概括的InHM结果，如果场景。有关更广泛的影响，从拟议的研究结果将是有用的优化数据收集网络的水文响应/滑坡启动和实时灾害预警系统的未来研究。拟议工作的一个主要贡献是培养一名博士生。

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.