Abstract
Rainfall is one of the most important triggers of both shallow debris flows and deep-seated landslides. The triggering mechanism involves the process of water infiltration into the failure zone. For deep-seated landslides, the deeper and more extensive failure surfaces delay the effect of the process and thus delay landslide initiations. The delay is difficult to assess, especially if the sites only have scarce or insufficient monitoring data. Under these circumstances, we illustrate that the occurrences of landslides can be estimated by their correlations with the phenomenological water storage index (WSI) of a given catchment. In the present study, a total of five deep-seated landslides in TienChih (4) and SiangYang (1) are investigated. The displacements of the landslides were recorded by global positioning system (GPS) and the WSI was modelled using the tank model. The result demonstrates that the WSI correlates closer in time to the landslide motion than the rainfall, and the WSI thresholds for the landslides are inferred. Thus, this technique can be applied as an associated method to evaluate landslide initiation.
Highlights
In Taiwan, with continuous global positioning system (GPS) network data, eight deepseated creeping landslide sites were identified and their causes were associated with hydrological loading, Hsu et al (2014)
We find that the peak of the water storage index (WSI) correlation function occurs at approximately 13 h while those of h1 and rainfall intensity (RI) correlation functions are at − 22 and −34 h
The rainfall-triggered TienChih and SiangYang deep-seated creeping landslides were compared with the regional water cycles
Summary
In Taiwan, with continuous global positioning system (GPS) network data, eight deepseated creeping landslide sites were identified and their causes were associated with hydrological loading, Hsu et al (2014). The evidence was based on relating the creeping landslide events to the rainfall intensity (RI) or accumulated precipitation. We further inspect the landslide events with a simple phenomenological quantitative hydrological model. The model, known as the tank model of Sugawara and Funiyuki (1956) and Sugawara (1961, 1995), can provide a simple idealized sketch for a regional water cycle: including precipitation, infiltration and runoff discharge. Because of the wide extent area and deep failure surface of deep-seated landslides, the rainfall triggering mechanism involve delicate infiltration processes with site geological conditions.
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