Analysis of human exposure to landslides with a GIS multiscale approach

Decision-making plays a key role in reducing landslide risk and preventing natural disasters. Land management, recovery of degraded lands, urban planning, and environmental protection in general are fundamental for mitigating landslide hazard and risk. Here, we present a GIS-based multi-scale approach to highlight where and when a country is affected by a high probability of landslide occurrence. In the first step, a landslide human exposure equation is developed considering the landslide susceptibility triggered by rain as hazard, and the population density as exposed factor. The output, from this overview analysis, is a global GIS layer expressing the number of potentially affected people by month, where the monthly rain is used to weight the landslide hazard. As following step, Logistic Regression (LR) analysis was implemented at a national and local level. The Receiver Operating Characteristic indicator is used to understand the goodness of a LR model. The LR models are defined by a dependent variable, presence–absence of landslide points, versus a set of independent environmental variables. The results demonstrate the relevance of a multi-scale approach, at national level the biophysical variables are able to detect landslide hotspot areas, while at sub-regional level geomorphological aspects, like land cover, topographic wetness, and local climatic condition have greater explanatory power.

Analisis Alih Fungsi Lahan Menggunakan Regresi Logistik Ordinal

The occurrence of landslides can not be separated from conditions that are prone to landslide movements such as steep slopes and high rainfall. The occurrence of landslides is also exacerbated by the indiscipline of the community in using land according to its function, which is called land conversion which can be a trigger factor for landslides. Conducting research on land use change is important to see the impact caused by human activities. The purpose of this study was to analyze the effect of land conversion on landslide hazard levels in Samigaluh District, Kulon Progo Regency. The method in this research was descriptive quantitative using primary data, namely field surveys and secondary data collection. The steps on this research were conducting field observations about the occurrence of land conversion and then retrieving level of landslide hazard at the observation point of land use change. Data analysis was performed using ordinal logistic regression. The result of the analysis showed that the p value (0.036) <0.05 which meant H0 was rejected. Thus, at the 95% confidence level it could be said that the variable of land use change affected the level of landslide hazard in Samigaluh District, Kulon Progo Regency. This output could be considered for the community to use the land according to its function. Key words: Land Function Change; Landslide; Ordinal

Analysis of the Characteristics of the Land Creeping (Slow-Moving) at Seomyeon, Suncheon-Si Area

This study was conducted to prevent land creeping by examining various features such as geology, topography, and physical characteristics, using the case of a land-crawled region. The first land creeping occurred in Seomyeon Suncheon-si in 2000, and the second occurred in 2020; the damaged surface area of the second event was approximately 21.7 times that of the first, and it was discovered Sunchoen-si Landcreep occur because of forest road cut affected. After 1 h, it was moderate at a soil depth of 20, 100, 200, and 250 cm from the surface soil, according to a measurement result of soil dispersity. It was severe at soil depths of 100, 200, and 250 cm, and the clay soil between the bedrock was mild to severe, and it was determined to be severe in locations where groundwater was leaching. The objective study area was a typical land creeping-type landslide caused by weathered rocks, and this area belonged to a type of convex terrain ground (凸) form. The land creeping occurred in the convex area (凸). As a result of analyzing the landslide hazard grade, the creeping land area is found to be different from ordinary landslides because it includes most areas of landslide hazard grade 3–5 and out of the grade. Results show that the land creeping has proceeded in the directions of S15°E, S20°E, S25°E, and S30°E, which is consistent with the direction following the flow duration of groundwater determined using the electrical resistivity survey method.

Analisis Tingkat Bahaya Longsor pada Jalan Nasional untuk Prioritas Penanganan dengan Metode AHP: Studi Kasus Jalan pada Satker PJN III dan PJN IV

Landslides are a very dangerous threat to the roads. Good management is required to prevent the problems occurring from extensive possible landslides. This is because the number of potential landslide points on the National roads are numerous. Maintenance and prevention are crucial to keep these disasters from occurring. Therefore these need to be a priority. The locations in question are: The National Road in the Provence of North Sumatra, the area of Satker PJN Ill (Satuan Kerja Pelaksanaan Jalan Nasional III) and The Satker PJN IV (Satuan Kerja Pelaksanaan Jalan Nasional IV). There are 26 roads in the Satker PJN III and IV areas with 34 that have occurred. The method that is used in this study is the AHP (Analytical Hierarchy Process). Method using two stages: The first stage is to analyze the level of landslide hazard on the road. The second stage is to determine the priority level for the handling of each landslide point for each section of the road. The parameters used determining the level of landslide hazard are: Soil, slope, landcover, rainfall, subgrade and drainage conditions, at the same time as using the landslide hazard perimeters, landslide dimensions, slope engineering and every day traffic

Landslide Susceptibility Mapping in the Vrancea-Buzău Seismic Region, Southeast Romania

This study presents the results of a landslide susceptibility analysis applied to the Vrancea-Buzău seismogenic region in the Carpathian Mountains, Romania. The target area is affected by a large diversity of landslide processes. Slopes are made-up of various types of rocks, climatic conditions can be classified as wet, and the area is a seismically active one. All this contributes to the observed high landslide hazard. The paper analyses the spatial component of the landslide hazard affecting the target area, the regional landslide susceptibility. First, an existing landslide inventory was completed to cover a wider area for the landslide susceptibility analysis. Second, two types of methods are applied, a purely statistical technique, based on correlations between landslide occurrence and local conditions, as well as the simplified spatial process-based Newmark Displacement analysis. Landslide susceptibility maps have been produced by applying both methods, the second one also allowing us to simulate different scenarios, based on various soil saturation rates and seismic inputs. Furthermore, landslide susceptibility was computed both for the landslide source and runout zones—the first providing information about areas where landslides are preferentially triggered and the second indicating where landslides preferentially move along the slope and accumulate. The analysis showed that any of the different methods applied produces reliable maps of landslide susceptibility. However, uncertainties were also outlined as validation is insufficient, especially in the northern area, where only a few landslides could be mapped due to the intense vegetation cover.