Regional prediction of landslide hazard using probability analysis of intense rainfall in the Hoa Binh province, Vietnam.

The main objective of this study is to assess regional landslide hazards in the Hoa Binh province of Vietnam. A landslide inventory map was constructed from various sources with data mainly for a period of 21 years from 1990 to 2010. The historic inventory of these failures shows that rainfall is the main triggering factor in this region. The probability of the occurrence of episodes of rainfall and the rainfall threshold were deduced from records of rainfall for the aforementioned period. The rainfall threshold model was generated based on daily and cumulative values of antecedent rainfall of the landslide events. The result shows that 15-day antecedent rainfall gives the best fit for the existing landslides in the inventory. The rainfall threshold model was validated using the rainfall and landslide events that occurred in 2010 that were not considered in building the threshold model. The result was used for estimating temporal probability of a landslide to occur using a Poisson probability model. Prior to this work, five landslide susceptibility maps were constructed for the study area using support vector machines, logistic regression, evidential belief functions, Bayesian-regularized neural networks, and neuro-fuzzy models. These susceptibility maps provide information on the spatial prediction probability of landslide occurrence in the area. Finally, landslide hazard maps were generated by integrating the spatial and the temporal probability of landslide. A total of 15 specific landslide hazard maps were generated considering three time periods of 1, 3, and 5 years

Rainfall Threshold and Landslides in the Post-orogenic Complex of the Esino River Basin, Central Italy

Hydrogeological hazards are widespread and recurrent in Italy, requiring constant monitoring, prevention and mitigation activities. This paper contributes to the landslide forecast debate, analysing the relationship between rainfall and landslides in the eastward section of the Esino river basin located in the Marche region (central Italy). This area of similar hydrogeological properties is characterized by post-orogenic quaternary sediments prone to rainfall-induced shallow landslides. The preliminary investigation revealed the occurrence of 232 landslides, most of all shallow and small-sized, from 1953 to 2011. Rainfall data from neighbouring rain gauges were compared with the historical series of landslides both on annual and monthly basis. Moreover, the intensity-duration empirical model is applied to describe a new empirical triggering threshold valid for the study area. Threshold rainfall conditions are described by the equation: I=1.61 7D 120.21 I 1.61 D 0.21 where I = mean rainfall intensity (mm/h) and D = rainfall duration (h). Such equation represents the conditions that in the past decades activated 90 % of all landslides occurred within the area. This rainfall threshold could be used to forecast landslides occurrence in the post-orogenic complex of the Esino river basin