Abstract
Rainfall-induced landslides form an important natural threat in Vietnam. The purpose of this study is to explore regional landslide susceptibility mapping in the mountainous district of A Luoi in Thua Thien Hue Province, where data on the occurrence and causes of landslides are very limited. Three methods are applied to examine landslide susceptibility: statistical index, logistic regression and certainty factor. Nine causative factors are considered: elevation, slope, geological strata, fault density, geomorphic landforms, weathering crust, land use, distance to rivers and annual precipitation. The reliability of the landslide susceptibility maps is evaluated by a receiver operating characteristic curve and the area under the curve is used to quantify and compare the prediction accuracy of the models. The certainty factor model performs best. This model is optimized by maximizing the difference between the true positive rate and the false positive rate. The optimal model correctly identifies 84% of the observed landslides. The results are verified with a validation test, whereby the model is calibrated with 75% randomly selected observed landslides, while the remaining 25% of the observed landslides are used for validation. The validation test correctly identifies 81% of the observed landslides in the training set and 73% of the observed landslides in the validation set.
Highlights
Landslides caused by tropical storms are common in the mountainous areas of Vietnam and have a major impact on local living conditions [1]
The statistical index (SI) method is based on a bivariate statistical comparison of a landslide inventory map with a categorical causative factor map [17,29]
For application of the logistic regression (LR) model, numerical maps are used for elevation, slope, fault density, drainage distance and precipitation, and the classes of geology, geomorphology, land use and weathering crust are substituted by their corresponding landslide frequency ratio
Summary
Landslides caused by tropical storms are common in the mountainous areas of Vietnam and have a major impact on local living conditions [1]. Rainfall-induced landslides are generally caused by changes in pore water pressure, which lead to a reduction of soil strength and slope instability. These changes are often produced by an increase in the groundwater level [3,4,5,6], an increase in the saturation degree of the soil [7,8,9,10], or by the formation of a perched water table [11]. Causative factors for predicting landslide susceptibility must be carefully assessed on the basis of relevance, availability and scale This is difficult in Vietnam because systematic studies and inventories of spatial characteristics and land-use have only been initiated recently. Lee and Dan [12] evaluated the landslide susceptibility in the province of
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