Coupled surface and subsurface flow modeling of natural hillslopes in the Aburrá Valley (Medellín, Colombia) [(哥伦比亚麦德林)Aburrá山谷中天然山坡地表和地表以下水流的耦合模拟] [Modèle couplé de l’écoulement de surface et subsurface sur le versant naturel des collines de la Vallée de Aburrá (Medellín, Colombie)] [Modelagem de escoamento acoplado de superfície e subsuperfície em encostas naturais no Vale Aburrá (Medellín, Colômbia)] [Modelado acoplado de flujo superficial y subsuperficial de las laderas naturales en el Valle de Aburrá (Medellín, Colombia)]

Abstract

Numerical results are presented of surface-subsurface water modeling of a natural hillslope located in the Aburrá Valley, in the city of Medellín (Antioquia, Colombia). The integrated finite-element hydrogeological simulator HydroGeoSphere is used to conduct transient variably saturated simulations. The objective is to analyze pore-water pressure and saturation variation at shallow depths, as well as volumes of water infiltrated in the porous medium. These aspects are important in the region of study, which is highly affected by soil movements, especially during the high-rain seasons that occur twice a year. The modeling exercise considers rainfall events that occurred between October and December 2014 and a hillslope that is currently monitored because of soil instability problems. Simulation results show that rainfall temporal variability, mesh resolution, coupling length, and the conceptual model chosen to represent the heterogeneous soil, have a noticeable influence on results, particularly for high rainfall intensities. Results also indicate that surface-subsurface coupled modeling is required to avoid unrealistic increase in hydraulic heads when high rainfall intensities cause top-down saturation of soil. This work is a first effort towards fostering hydrogeological modeling expertise that may support the development of monitoring systems and early landslide warning in a country where the rainy season is often the cause of hydrogeological tragedies associated with landslides, mud flow or debris flow. © 2016 Springer-Verlag Berlin Heidelberg