Geomorphological control on variably saturated hillslope hydrology and slope instability. Issue 6 (18th June 2016)

• Record Type: Journal Article
• Authors: Giuseppe, Formetta; Simoni, Silvia; Godt, Jonathan W.; Lu, Ning; Rigon, Riccardo
• Is Part Of: Water resources research. Volume 52:Issue 6(2016:Jun.)
• Page Start: 4590
• Page End: 4607
• Publication Date: 2016-06-18
• Subjects: shallow landslides -- failure probability -- suction stress; Hydrology -- Periodicals; 333.91
• DOI: 10.1002/2015WR017626
• Languages: English
• ISSNs: 0043-1397

Abstract

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. Key Points: Quantify the impact of topography on saturated‐unsaturated hillslope hydrology and slope‐stability Morphology impact on transient hydrology is not relevant at local but important at catchment scale Percentage of unstable areas was 1.3 for planar, 21 for convex, and 33 for convergent morphology