Abstract Rainfall-induced shallow landslides cause significant damage involving loss of life and property. Many hydrological processes such as rainfall infiltration, soil water dynamics, and slope stability are controlled by unsaturated soil properties, such as unsaturated hydraulic conductivity. Natural soils often exhibit a certain degree of anisotropy in hydraulic conductivity due to stratification and compaction mechanisms in soil formation processes. In this paper we investigate the effect of soil hydraulic conductivity anisotropy (SHCA) on hillslope hydrology and stability using a three-dimensional hydrological model coupled with a probabilistic infinite slope stability model. The model is applied in two independent case studies. The first aims to quantify the combined effect of different anisotropy ratios (lateral/normal saturated hydraulic conductivity) and hillslope morphologies (convex, concave, and planar) on slope stability. Anisotropy ratios are assumed in this case higher than one (1, 2, 10). Results show that increasing the anisotropy ratio (from 1 to 10) anticipates the failure time (from 12 to 9 h after the start of rainfall) and that in concave morphologies the unstable area tends to be wider than planar and convex. The second application aims to simulate the soil moisture dynamic and the probability of failure at different depths (100, 500, and 900 mm) of a stratified volcanic soil, making leverage on the model flexibility to accommodate SHCA. No assumptions are made on the anisotropy ratio in this case study. Our results, based on model parameter calibration and verification against in-situ soil moisture measurements during the year 2009, showed good model performance in simulating the soil moisture dynamic (Kling-Gupta Efficiency higher than 0.78) and confirmed no failure for the simulated year. The promising results support the aspiration that the physically based hydrological model can complement and improve the current predictions of landslide early warning systems.

中文翻译：

---

量化各向异性土层对山坡水文和稳定性的三维影响

摘要 降雨引起的浅层滑坡造成重大破坏，造成生命财产损失。许多水文过程，如降雨入渗、土壤水动力学和边坡稳定性，都受非饱和土壤性质（如非饱和导水率）的控制。由于土壤形成过程中的分层和压实机制，天然土壤通常表现出一定程度的水力传导率各向异性。在本文中，我们使用三维水文模型和概率无限边坡稳定性模型研究了土壤导水率各向异性 (SHCA) 对山坡水文和稳定性的影响。该模型应用于两个独立的案例研究。第一个旨在量化不同各向异性比（横向/正常饱和导水率）和山坡形态（凸面、凹面和平面）对边坡稳定性的综合影响。在这种情况下，假设各向异性比大于 1 (1, 2, 10)。结果表明，增加各向异性比（从 1 到 10）可预测失效时间（从降雨开始后 12 到 9 小时），并且在凹形形态中，不稳定区域往往比平面和凸形更宽。第二个应用程序旨在模拟分层火山土壤的不同深度（100、500 和 900 毫米）的土壤水分动态和失效概率，利用模型的灵活性来适应 SHCA。在这个案例研究中没有对各向异性比做出任何假设。我们的结果，基于模型参数校准和 2009 年现场土壤水分测量的验证，在模拟土壤水分动态（Kling-Gupta 效率高于 0.78）方面表现出良好的模型性能，并确认模拟年份没有失败。有希望的结果支持基于物理的水文模型可以补充和改进滑坡预警系统的当前预测的愿望。