日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 H (地球人間圏科学) » H-TT 計測技術・研究手法

[H-TT19] Geographic Information Systems and Cartography

2019年5月30日(木) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:小口 高(東京大学空間情報科学研究センター)、村山 祐司(筑波大学大学院生命環境科学研究科地球環境科学専攻)、若林 芳樹(首都大学東京大学院都市環境科学研究科)

[HTT19-P08] Analysis of Morphometric Parameters for Mountains Ranges and Landslides due to the July 2018 Heavy Rain in Western Japan Using GIS Data

*福場 俊和1小口 高2 (1.東京大学理学部地球惑星環境学科、2.東京大学空間情報科学研究センター)

キーワード:GIS、山岳地形、斜面崩壊、地形パラメータ

Morphometric parameters for mountains ranges have been analyzed in many studies. These studies in recent years used Digital Elevation Models (DEMs) to calculate values of morphometric parameters within mountains and provided consideration on landform evolution. In addition, morphometric parameters calculated by DEMs have been used for producing landslide hazard maps. This study investigates geomorphometric parameters within the Chugoku and Shikoku Mountains, Japan, and the relationships among the parameters. In addition, landslides caused by the July 2018 heavy rain in western Japan is also investigated and the relationships between the landforms of the mountains and the landslides are discussed. Altitude, slope angle, slope aspect and slope curvature are chosen for morphometric parameters to be investigated.

Morphometric parameters for the Chugoku and in Shikoku Mountains computed using DEMs and GIS have some characteristics common to the Japanese Alps. For example, for wide altitudinal zones, slope angle tends to be constant around 30 to 40 degrees even if altitude changes. However, the values of the constant slope angle are not the same, which may be due to geological differences or the difference in the formation age of mountains. Although the frequency distribution of slope aspect is similar to the Chugoku and Shikoku Mountains, anisotropy of slope aspect is different between the two mountains. This may be caused by differences in the formation age, formation mechanism, or geology of the mountains.

Analysis of landslides caused by the July 2018 heavy rain in Hiroshima using landslide data and DEMs revealed that landslides mostly occurred around 300 m in altitude, at 15 to 30 degrees in slope angle, and on concave slopes. Although the characteristics slope angles higher than 30 degrees point to frequent slope failures at high and steep mountain slopes in the Chugoku and Shikoku Mountains, landslides corresponding to one rainfall event do not necessarily follow this, because they depend on the distribution of rainfall during the event. Therefore, possibility of landslides in low and gentle mountains close to populated areas needs to be considered seriously for mitigating landslide disasters.