Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western Japan
Land cover changes in mountainous regions are potential precursors to landslide disasters. However, the effects of past long-term land cover changes on the characteristics of recent landslides remains underexplored. We studied land cover evolution over a 56-year period on Omishima Island in western...
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MDPI AG
2023-12-01
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| Series: | Water |
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| author | Takashi Kimura Go Sato Takatsugu Ozaki Nguyen Van Thang Akihiko Wakai |
| author_facet | Takashi Kimura Go Sato Takatsugu Ozaki Nguyen Van Thang Akihiko Wakai |
| author_sort | Takashi Kimura |
| collection | DOAJ |
| description | Land cover changes in mountainous regions are potential precursors to landslide disasters. However, the effects of past long-term land cover changes on the characteristics of recent landslides remains underexplored. We studied land cover evolution over a 56-year period on Omishima Island in western Japan to examine the spatial relations of landslides in the July 2018 storm event based on rainfall, land cover trajectories, and topography. We generated land cover maps for 1962, 1981, and 2018 by aerial photo interpretation. We also identified 512 new landslides. Based on 47-year precipitation records, we estimated the return periods of 1- to 264-h rainfalls during the storm using the generalised extreme value (GEV) distributions. Return periods showed wide variation when the derived GEV distributions were applied to 1-km grid rainfall distributions. Despite such pronounced spatial variations in rainfall, we did not observe a clear correlation between rainfall intensity and landslide distribution. In contrast, land cover trajectories had a pronounced effect on landslide occurrence. Landslides were more concentrated on slopes that experienced land cover changes after 1962. A comparison of slopes on farmland developed between 1962 and 1981 (mainly citrus orchards) indicated that landslide density and area ratio were significantly lower on slopes that had reverted to forests than on those remaining as farmland. However, the values of the reforested slopes exceeded those of forests and farmlands that remained since before 1962. Our geospatial analysis revealed that even if the field had shifted to forests, the effects of reduced slope stability due to orchard development had remained for at least 37 years. This suggested that the impacts of converting forests to orchards last longer than harvesting in managed plantation forests. |
| first_indexed | 2024-03-08T20:17:12Z |
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| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-08T20:17:12Z |
| publishDate | 2023-12-01 |
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| series | Water |
| spelling | doaj.art-708788c9744346a49cf2d426b3660b8b2023-12-22T14:49:41ZengMDPI AGWater2073-44412023-12-011524421110.3390/w15244211Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western JapanTakashi Kimura0Go Sato1Takatsugu Ozaki2Nguyen Van Thang3Akihiko Wakai4Graduate School of Agriculture, Ehime University, Matsuyama 790-8566, JapanFaculty of Environmental Studies, Tokyo City University, Yokohama 224-8551, JapanFaculty of Environmental Studies, Tokyo City University, Yokohama 224-8551, JapanFaculty of Civil Engineering, Thuyloi University, Hanoi 10000, VietnamGraduate School of Science and Technology, Gunma University, Kiryu 376-8515, JapanLand cover changes in mountainous regions are potential precursors to landslide disasters. However, the effects of past long-term land cover changes on the characteristics of recent landslides remains underexplored. We studied land cover evolution over a 56-year period on Omishima Island in western Japan to examine the spatial relations of landslides in the July 2018 storm event based on rainfall, land cover trajectories, and topography. We generated land cover maps for 1962, 1981, and 2018 by aerial photo interpretation. We also identified 512 new landslides. Based on 47-year precipitation records, we estimated the return periods of 1- to 264-h rainfalls during the storm using the generalised extreme value (GEV) distributions. Return periods showed wide variation when the derived GEV distributions were applied to 1-km grid rainfall distributions. Despite such pronounced spatial variations in rainfall, we did not observe a clear correlation between rainfall intensity and landslide distribution. In contrast, land cover trajectories had a pronounced effect on landslide occurrence. Landslides were more concentrated on slopes that experienced land cover changes after 1962. A comparison of slopes on farmland developed between 1962 and 1981 (mainly citrus orchards) indicated that landslide density and area ratio were significantly lower on slopes that had reverted to forests than on those remaining as farmland. However, the values of the reforested slopes exceeded those of forests and farmlands that remained since before 1962. Our geospatial analysis revealed that even if the field had shifted to forests, the effects of reduced slope stability due to orchard development had remained for at least 37 years. This suggested that the impacts of converting forests to orchards last longer than harvesting in managed plantation forests.https://www.mdpi.com/2073-4441/15/24/4211land cover changeshallow landsliderainfall return periodslope stability |
| spellingShingle | Takashi Kimura Go Sato Takatsugu Ozaki Nguyen Van Thang Akihiko Wakai Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western Japan Water land cover change shallow landslide rainfall return period slope stability |
| title | Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western Japan |
| title_full | Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western Japan |
| title_fullStr | Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western Japan |
| title_full_unstemmed | Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western Japan |
| title_short | Land Cover Trajectories and Their Impacts on Rainfall-Triggered Landslide Occurrence in a Cultivated Mountainous Region of Western Japan |
| title_sort | land cover trajectories and their impacts on rainfall triggered landslide occurrence in a cultivated mountainous region of western japan |
| topic | land cover change shallow landslide rainfall return period slope stability |
| url | https://www.mdpi.com/2073-4441/15/24/4211 |
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