Geomorphological control on variably saturated hillslope hydrology and slope instability

Water Resources Research
By: , and 

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Abstract

In steep topography, the processes governing variably saturated subsurface hydrologic response and the interparticle stresses leading to shallow landslide initiation are physically linked. However, these processes are usually analyzed separately. Here, we take a combined approach, simultaneously analyzing the influence of topography on both hillslope hydrology and the effective stress fields within the hillslope itself. Clearly, runoff and saturated groundwater flow are dominated by gravity and, ultimately, by topography. Less clear is how landscape morphology influences flows in the vadose zone, where transient fluxes are usually taken to be vertical. We aim to assess and quantify the impact of topography on both saturated and unsaturated hillslope hydrology and its effects on shallow slope stability. Three real hillslope morphologies (concave, convex, and planar) are analyzed using a 3-D, physically based, distributed model coupled with a module for computation of the probability of failure, based on the infinite slope assumption. The results of the analyses, which included parameter uncertainty analysis of the results themselves, show that convex and planar slopes are more stable than concave slopes. Specifically, under the same initial, boundary, and infiltration conditions, the percentage of unstable areas ranges from 1.3% for the planar hillslope, 21% for convex, to a maximum value of 33% for the concave morphology. The results are supported by a sensitivity analysis carried out to examine the effect of initial conditions and rainfall intensity.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Geomorphological control on variably saturated hillslope hydrology and slope instability
Series title Water Resources Research
DOI 10.1002/2015WR017626
Volume 52
Issue 6
Year Published 2016
Language English
Publisher AGU Publications
Contributing office(s) Office of the AD Hazards
Description 18 p.
First page 4590
Last page 4607
Online Only (Y/N) N
Additional Online Files (Y/N) N