Abstract
BackgroundThree groups of factors related to topography, geology and hydrology have influence on the triggering of shallow landslides in soil material. In this paper a single representative factor (T-factor) for the topography is proposed, which can be used to define threshold values for the possibility of shallow soil slides. This study was carried out in the Dayi area, Guizhou Province, China. During a heavy rainfall event on June 6, 2011, 230 shallow soilslides were triggered. In some slopes, no shallow landslides were triggered even though some of the topographical factors point to unstable high probability.ResultsWe isolated and analyzed the influence of the topography on the triggering of shallow landslides in catchments with almost identical hydrological and geological conditions and propose a new T-factor as a topographical indicator which is a combination of the slope angle, the upslope contributing area, the cross-section, and the free-face of a (potential) shallow landslide. Higher T-factor values are related to higher probabilities of shallow landsliding. The probability assessment with the topographical factor T was successfully validated in other areas of the USA and Japan.ConclusionsWithout information on the geological and rainfall conditions, a quick and primary prediction of shallow landsliding using the topographical factor T is proposed. Additionally a new R-factor is proposed as a rainfall indicator, which is a combination of the 1 hour rainfall and cumulative rainfall before the landslide event and the annual rainfall. Higher R-factor values are generally related to higher probabilities of shallow landsliding. The primary probability factor P, which is the combination of T and R, gives a final indication of the probability of shallow landsliding.
Highlights
Three groups of factors related to topography, geology and hydrology have influence on the triggering of shallow landslides in soil material
We focus on the shallow landslides occurred in soil
The large number of shallow landslide events in the Dayi area, Guizhou, China, triggered by a large rainfall event in June 2011, provided a good opportunity to study the influence of topographical factors on the triggering of shallow landslides
Summary
Three groups of factors related to topography, geology and hydrology have influence on the triggering of shallow landslides in soil material. Shallow landslides are common in mountainous areas after intense rainfall or long term rainfall. Shallow translational landsliding is the most commonly observed failure mode in soil material (Meisina and Scarabelli 2007). The occurrence of these landslides is controlled by various spatial and climatic factors, such as geology, topography, hydrogeological. The shallow landslides are mainly influenced by topographical factors: slope gradient (a very sensitive factor) and lateral concavity in relation to the upstream contributing area which induced convergence of subsurface water flow, increase in groundwater height and decrease in slope stability. As hydrological processes are considered to have a major influence on slope stability, Yu et al Geoenvironmental Disasters (2017) 4:24 the occurrence of landslides is controlled twofold by slope gradient and lateral concavity (Hennrich and Crozier 2004)
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