Abstract
This study proposes a landslide disaster assessment model combining a fully three-dimensional, physically-based landslide model with high precision of in situ survey data such as surface slip signs, geologic drilling results, underground water observation, and displacement monitoring results over time to perform distribution of potential landslide zones and the size of landslides (area and volume) in the Antong hot spring area in Hualien, Taiwan. The distribution of potential landslide zones in the study area was represented by slope stability safety factors. The results of the analysis showed that the toe of the slope and two upward slopes in the study area were potential landslide areas with safety factors of 1.37, 0.92, and 1.19, respectively. The 3D model analysis results indicated that a landslide could occur at a depth of 20 m at the toe of the slope. Monitoring results for 2015 and 2016 showed that the sliding depth at the toe of the slope was approximately 22.5 m; consequently, the error of landslide depth was only 2.5 m. The simulated results and in situ monitoring results were in good agreement. In addition, the simulated landslide volume was also compared with the results of an empirical equation commonly used in Taiwan to determine their differences. The landslide volumes estimated using the empirical equation were only approximately 38.5% in zone 1, 42.9% in zone 2, and 21.7% in zone 3 of that generated by the proposed model. The empirical equation was used to calculate the landslide volume according to the landslide area, which was subsequently converted into landslide depth. However, the obtained landslide depth was considerably lower than that derived from the in situ monitoring, implying that an empirical estimation approach may result in serious underestimation. Thus, the proposed model could predict landslide area and volume in advance to assist authorities in minimizing loss of life and property damage during a heavy rainfall event.
Highlights
Taiwan is located at the boundary of the Eurasian Plate and the Philippine Plate and is characterized by a landscape dominated by mountains
The case analysis results of this study revealed the distribution of slope stability safety factors, which were analyzed using the proposed model, showing that the toe of the slope (Zone 1) with abundant groundwater due to the nearby Antong river and the upward steep slope (Zones 2 and 3)
According to the various design and construction codes commonly used in Taiwan, the model analysis resulted in safety factors for the study area, including the potential landslide areas
Summary
Taiwan is located at the boundary of the Eurasian Plate and the Philippine Plate and is characterized by a landscape dominated by mountains. The island has a West Pacific subtropical climate. The active geological effects on the island, i.e., the yearly spring and summer monsoons and multiple typhoons in summer and autumn, are characteristics that dispose Taiwan to a high risk of landslides [1,2]. Landslides are a key influence on ground surface morphology and surface erosion [3,4]. Various types of landslides cause enormous loss of life and property [5]. Mountain communities in Taiwan are mostly located in remote areas, evacuation efforts before a disaster occurs are time-consuming and labor-intensive. These communities become isolated during disasters because of inaccessibility, which impedes inward- and outward-bound transportation.
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