Topographic index-based hydrological models have gained wide use to describe the hydrological control on the triggering of rainfall-induced shallow landslides at the catchment scale. A common assumption in these models is that a spatially continuous water table occurs simultaneously across the catchment. However, during a rainfall event isolated patches of subsurface saturation form above an impeding layer and their hydrological connectivity is a necessary condition for lateral flow initiation at a point on the hillslope. Here, a new hydrological model is presented, which allows us to account for the concept of hydrological connectivity while keeping the simplicity of the topographic index approach. A dynamic topographic index is used to describe the transient lateral flow that is established at a hillslope element when the rainfall amount exceeds a threshold value allowing for (a) development of a perched water table above an impeding layer, and (b) hydrological connectivity between the hillslope element and its own upslope contributing area. A spatially variable soil depth is the main control of hydrological connectivity in the model. The hydrological model is coupled with the infinite slope stability model and with a scaling model for the rainfall frequency-duration relationship to determine the return period of the critical rainfall needed to cause instability on three catchments located in the Italian Alps, where a survey of soil depth spatial distribution is available. The model is compared with a quasi-dynamic model in which the dynamic nature of the hydrological connectivity is neglected. The results show a better performance of the new model in predicting observed shallow landslides, implying that soil depth spatial variability and connectivity bear a significant control on shallow landsliding.
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|Titolo:||Modelling shallow landslide susceptibility by means of a subsurface flow path connectivity index and estimates of soil depth spatial distribution|
|Autori:||L., Cristiano; M., Borga; Rigon, Riccardo; P., Tarolli|
|Titolo del periodico:||HYDROLOGY AND EARTH SYSTEM SCIENCES|
|Anno di pubblicazione:||2012|
|Numero e parte del fascicolo:||16|
|Codice identificativo Scopus:||2-s2.0-84868552162|
|Codice identificativo ISI:||WOS:000311514600003|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.5194/hess-16-3959-2012|
|Appare nelle tipologie:||03.1 Articolo su rivista (Journal article)|