Landslide hydrology: from hydrology to pore pressure

Abstract

Rainfall-triggered landslides are among the most widespread hazards in the world. The hydrology in and around a landslide area is key to pore pressure buildup in the soil skeleton which reduces shear strength due to the buoyancy force exerted by water in a saturated soil and to soil suction in an unsaturated soil. Extraordinary precipitation events trigger most of the landslides, but, at the same time, the vast majority of slopes do not fail. The intriguing question is: 'When and where exactly can a slope become triggered to slide and flow downwards?' The objective of this article is to present and discuss landslide hydrology at three scales-pore, hillslope, and catchment-which, taken together, give an overview of this interdisciplinary science. We argue that 'filling, storing, and draining' of water are all equally relevant to understand and to quantify landslide behavior. Furthermore, by addressing landslide hydrology from both earth sciences and soil mechanics perspectives, we aim to manifest the hydrological processes in hillslopes and their influence on behavior and triggering of landslides and vice versa. The challenge of landslide hydrological research is matching, at hillslope scale, causal hydrological processes with detailed physics of triggering mechanisms. At the same time, mass movements initiate changes in the hydraulic character of the soil which are important for better understanding short-and long-term hydrogeomorphic responses of soil and hillslope. Interdisciplinarity is key in advancing our knowledge on water flows in (un)stable slopes.© 2015 Wiley Periodicals, Inc. How to cite this article:WIREs Water 2016Water , 3:439-459. doi: 10.1002Water /wat2.1126 INTRODUCTION 'Landslide hydrology,' as postulated in the title, is neither an established research field nor is strictly defined in literature, but will be understood intuitively. The term 'landslide' is defined as the perceptible downward sliding of a mass of soil (debris and earth) or rocks under the influence of gravity, 1 and the term 'hydrology' deals with water occurrence, circulation, and distribution in and at the earth surface.2 Landslide hydrology therefore is the interdisciplinary study of water transfer, storage, and pressure buildup in the earth surface, linked to the destabilization and displacement of (part of a) slope before, during, and after a hydrological triggering event. The term 'landslide hydrology' is intuitive, as the relationship between water and landslide hazards is well-known. The water can originate from many different sources, such as precipitation, snow melt, and pipe leakage and drainage canals. The physical triggering mechanisms behind this well-known relation between water and landslides are the reduction of shear strength due to the buoyancy force exerted by water in a saturated soil, and the reduction of soil suction in an unsaturated soil. Although earthquakes trigger landslides, the vast majority of landslides is triggered by (extraordinary) precipitation events. 3The challenge in landslide research is ...

Invited perspectives: Hydrological perspectives on precipitation intensity-duration thresholds for landslide initiation: proposing hydro-meteorological thresholds

“…However, the database contains mainly shallow landslides and debris flows (Guzzetti et al, 2007). Clearly, this indicates the role of hydrology or, to be precise, the balance between infiltration, storage and drainage capacity of a slope (Bogaard and Greco, 2015).…”

Analysis of plant root–induced preferential flow and pore-water pressure variation by a dual-permeability model

“…It is a remaining challenge on how to deterministically quantify the impact of preferential flow on slope hydrology and stability (Uchida 2004;Hencher 2010;Bogaard and Greco 2016). Many preferential flow models have been developed such as a pore-network model, dual-or multi-continuum conceptualization of soil porous media (see review by Köhne et al (2009)).…”

On the hydrological properties of mountain soils, from measurement to the geotechnical implications

“…Within all these schemes, one has also to think about the role of preferential flow phenomena, which can greatly influence the triggering system. Moving from the understanding of the slope hydrology to the failure mechanisms, thus linking the soil hydrology with its geotechnical implications, is still a major challenge [4].…”