5:15 PM - 6:45 PM
[HGM03-P14] GIS analysis for creating a geomorphological and geological zoning map in response to ground disasters focusing on earthquakes
Keywords:DEM, landslide, co-seismic landslide, geological map, ground
Landslides are major ground disasters induced by earthquakes. In addition to direct human damage, it has a large impact on roads and other infrastructures. It is important to understand vulnerable areas in advance, and disaster prevention and mitigation has become an urgent issue. On the other hand, estimating the possibility of landslides occurring during an earthquake is an important technology that contributes to immediate disaster response. In Japan, the Rokko Formula (Uchida et al., 2004), which is a discriminant formula designed based on the damage caused in the Rokko Mountains during the 1995 Southern Hyogo Prefecture Earthquake, and a modified version (Kamiya et al., 2012) are used for estimating landslides in the event of an earthquake. More recently, a formula for estimating the landslide density based on slope gradient has been published, based on the case of the Aso area during the 2016 Kumamoto earthquake (Sakai et al., 2022). These formulas were derived based on areas with specific lithologies, such as granite mountains and volcanic areas, and require correction or coefficient adjustment based on zoning maps in order to correspond to more diverse slopes across the country.
In this research, we collected geospatial information covering the entire country, including the fundamental geospatial data (GSI) and the 1:200,000 seamless geological map (AIST), and are creating a geomorphological and geological zoning map. First, we generated polygon data for the entire country, dividing unit slopes, from a 30m DEM created using the DEMs of fundamental geospatial data. Furthermore, the topography is classified mainly by slope, height above the nearest drainage (HAND), and pit/peak density (TEXTURE), supplementarily using the distribution density of convex points (CONVEXITY) and areas close to the water surface height. Similar terrain classification maps using DEMs have been used as one of the parameters for estimating soil property values for surface soil in the Forest Soil Digital Map (FFPRI), and can also be used as in various countries as a proxy for the susceptibility to earthquake shaking, for estimating the probability of landslides, soils, etc. In addition, topographically similar characteristics can be seen on the slopes where landslides occur, and it has become clear that shallow landslides in particular tend to concentrate in specific legends of the DEM terrain classification map, such as hilly mountains (Iwahashi et al., 2021). However, in areas where the topsoil and geological structure are fragile, such as volcanic areas, there have been cases of frequent landslides, even in the topographies where shallow landslides are generally rare. Furthermore, the proportion of large-scale landslides tends to increase as the upper slope becomes longer. However, in earthquakes where strong shaking is observed, even slopes that are not very long and have high textures tend to collapse on large scales, and it was also found to be affected by geology. In order to create a geomorphological and geological zoning map that can respond to ground disasters during earthquakes, topographical classification alone is insufficient, and geological information such as lithology and topsoil information must be attributed to polygons of unit slopes.
References
Iwahashi J, Yamazaki D, Nakano T, Endo R (2021):Classification of topography for ground vulnerability assessment of alluvial plains and mountains of Japan using 30 m DEM. Progress in Earth and Planetary Science, 8:3. DOI: 10.1186/s40645 -020-00398-0
Kamiya I, Otoi Y, Nakano T, Koarai M (2012):Improvement and real time calculation of Rokko formula, a discriminant function for risk assessment of slope failures by earthquake. Photogrammetry and Remote Sensing, 51(6), 381 -386.
Sakai Y, Uchida T, Hirata I, Tanehira K, Fujiwara Y (2022):Interrelated impacts of seismic ground motion and topography on coseismic landslide occurrence using high-resolution displacement SAR data, Landslides, doi: 10.1007/s10346-022-01909-4.
Uchida T, Kataoka S, Iwao T, Matsuo O, Terada H, Nakano Y, Sugiura N, Osanai N (2004):A study on methodology for assessing the potential of slope failures during earthquakes. Technical Note of National Institute for Land and Infrastructure Management, No. 204 , 91p.
In this research, we collected geospatial information covering the entire country, including the fundamental geospatial data (GSI) and the 1:200,000 seamless geological map (AIST), and are creating a geomorphological and geological zoning map. First, we generated polygon data for the entire country, dividing unit slopes, from a 30m DEM created using the DEMs of fundamental geospatial data. Furthermore, the topography is classified mainly by slope, height above the nearest drainage (HAND), and pit/peak density (TEXTURE), supplementarily using the distribution density of convex points (CONVEXITY) and areas close to the water surface height. Similar terrain classification maps using DEMs have been used as one of the parameters for estimating soil property values for surface soil in the Forest Soil Digital Map (FFPRI), and can also be used as in various countries as a proxy for the susceptibility to earthquake shaking, for estimating the probability of landslides, soils, etc. In addition, topographically similar characteristics can be seen on the slopes where landslides occur, and it has become clear that shallow landslides in particular tend to concentrate in specific legends of the DEM terrain classification map, such as hilly mountains (Iwahashi et al., 2021). However, in areas where the topsoil and geological structure are fragile, such as volcanic areas, there have been cases of frequent landslides, even in the topographies where shallow landslides are generally rare. Furthermore, the proportion of large-scale landslides tends to increase as the upper slope becomes longer. However, in earthquakes where strong shaking is observed, even slopes that are not very long and have high textures tend to collapse on large scales, and it was also found to be affected by geology. In order to create a geomorphological and geological zoning map that can respond to ground disasters during earthquakes, topographical classification alone is insufficient, and geological information such as lithology and topsoil information must be attributed to polygons of unit slopes.
References
Iwahashi J, Yamazaki D, Nakano T, Endo R (2021):Classification of topography for ground vulnerability assessment of alluvial plains and mountains of Japan using 30 m DEM. Progress in Earth and Planetary Science, 8:3. DOI: 10.1186/s40645 -020-00398-0
Kamiya I, Otoi Y, Nakano T, Koarai M (2012):Improvement and real time calculation of Rokko formula, a discriminant function for risk assessment of slope failures by earthquake. Photogrammetry and Remote Sensing, 51(6), 381 -386.
Sakai Y, Uchida T, Hirata I, Tanehira K, Fujiwara Y (2022):Interrelated impacts of seismic ground motion and topography on coseismic landslide occurrence using high-resolution displacement SAR data, Landslides, doi: 10.1007/s10346-022-01909-4.
Uchida T, Kataoka S, Iwao T, Matsuo O, Terada H, Nakano Y, Sugiura N, Osanai N (2004):A study on methodology for assessing the potential of slope failures during earthquakes. Technical Note of National Institute for Land and Infrastructure Management, No. 204 , 91p.