Geometrical Variation Analysis of Landslides in Different Geological Settings Using Satellite Images: Case Studies in Japan and Sri Lanka

Abstract

Over the past three decades, Sri Lanka has observed a substantial rise in landslide occurrences linked to intensified rainfall. However, the lack of comprehensive landslide inventories has hampered the development of effective risk analysis and simulation systems, requiring Sri Lanka to rely heavily on foreign-developed models, despite the difficulty of fully examining the similarities between the characteristics of landslides in Sri Lanka and the areas where the model has been developed. Satellite images have become readily available in recent years and have provided information about the Earth’s surface conditions over the past few decades. Thus, this study verifies the utility of satellite images as a cost-effective remote-sensing method to clarify the commonalities and differences in the characteristics of landslides in two regions Ikawa, Japan, and Sabaragamuwa, Sri Lanka, which exhibit different geological formations despite similar annual rainfall. Using Google Earth satellite images from 2013 to 2023, we evaluated land-slide density, types, and geometry. The findings reveal that Ikawa exhibits a higher landslide density and experiences multiple-type landslides. In contrast, both areas have similar initiation areas; however, Sabaragamuwa predominantly experiences single landslides that are widespread and mobile. The findings also reveal that various characteristics of landslides are mainly influenced by varied topography. Here, we confirmed that even in areas where comprehensive information on landslides is conventionally lacking, we can understand the characteristics of landslides by comparing landslide geometry between sites using satellite imagery.

Risk Assessment in Landslide-Prone Terrain within a Complex Geological Setting at Kadugannawa, Sri Lanka: Implications for Highway Maintenance

“…However, the contribution of these factors varies, with specific factors affecting each landslide [7][8][9]. In general, the number of rainfall-triggered landslides is expected to increase, especially in tropical climates, due to climate change [10][11][12][13]. Bracko et al (2022) [14] show that the change in precipitation patterns will especially impact soils of low permeability.…”

“…However, in Sri Lanka, detailed investigations of landslides or slope failures have generally been conducted over larger areas, rather than focusing on individual small failures that occurred in close proximity. Comparing regions with similar precipitation patterns in Sri Lanka and Japan, it was found that the topography has a strong impact on the spread and mobility of landslides in Sri Lanka [13]. Further factors influencing landslides or slope failures within a small area can vary due to a variety of reasons, such as variations in vegetation intensity, anomalies in soil texture, and different geological conditions, as well as anthropogenic influences such as slope cutting, the construction of poorly designed buildings, alterations in surface water flow paths, and changes in land use [24].…”