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[MZZ48-05] The investigation of the relationship between the artificial terrain change of medieval mountain castles and the landslides in 2018
Keywords:Construction of a medieval Mountain castle, GIS, The Hiroshima Granite
The purpose of this study was to investigate the relationship between the artificial terrain change of medieval mountain castles and the landslides in Higashihiroshima City 2018.
There has been few reported on the relationship between medieval castles and the landslides.Because medieval castle ruins were not damaged.
The heavy rainfall in July 2018 caused many landslides in Higashihiroshima City. There are 165 ruins of medieval castle in this city and some of them were up stream of debris flows. The number of residence of this city is increasing continuously at the foot of mountain.
Therefore, it is necessary to clarify the risks of artificial terrain change of medieval mountain castles.
This study was performed with GIS (Geo Information System) and field study. In this research, totally 124 medieval castles were studied (Fig.1).
The analysis of GIS revealed that 59 of these medieval castles were associated with landslides.
Most of medieval castles were the fortress style, and built to mountainous terrain with construction work for defense. Those medieval mountain castles had a characteristic construction.
Typically, top of the mountain and mountainside used to be artificially modified to build medieval mountain castles. Workers created a flat area known as a Kuruwa, cut away at the ridge to form dry moats (Horikiri), and used the surplus soil accumulated during these tasks to build Dorui. Another structural feature was the Kirigishi, slopes around the Kuruwa that were made intentionally steeper. In addition, Unejo-tatebori, parallel trenches dug vertically into the Kirigishi slopes, was developed to prevent enemies coming up the slopes diagonally (Fig.2).
In the field survey, it was confirmed that some debris flows were generated from the lower part of Horikiri slope. It is highly suspected that defensive features of medieval mountain castles could have affected the flow of rainwater.
Furthermore, this city is mainly composed of the Hiroshima granite, which is relatively vulnerable to the terrain modification. The analysis by GIS revealed that 85% of medieval mountain castles that were associated with landslides, were located in The Hiroshima granite.
The analysis by GIS (Geo Information System) and field study suggest that Horikiri, the construction of a medieval mountain castle, is one of the causal factors with landslide.
Therefore, identifying the areas of those artificial terrain change could be effective to foresee future potential of debris flow path when landslide took place in the future.
There has been few reported on the relationship between medieval castles and the landslides.Because medieval castle ruins were not damaged.
The heavy rainfall in July 2018 caused many landslides in Higashihiroshima City. There are 165 ruins of medieval castle in this city and some of them were up stream of debris flows. The number of residence of this city is increasing continuously at the foot of mountain.
Therefore, it is necessary to clarify the risks of artificial terrain change of medieval mountain castles.
This study was performed with GIS (Geo Information System) and field study. In this research, totally 124 medieval castles were studied (Fig.1).
The analysis of GIS revealed that 59 of these medieval castles were associated with landslides.
Most of medieval castles were the fortress style, and built to mountainous terrain with construction work for defense. Those medieval mountain castles had a characteristic construction.
Typically, top of the mountain and mountainside used to be artificially modified to build medieval mountain castles. Workers created a flat area known as a Kuruwa, cut away at the ridge to form dry moats (Horikiri), and used the surplus soil accumulated during these tasks to build Dorui. Another structural feature was the Kirigishi, slopes around the Kuruwa that were made intentionally steeper. In addition, Unejo-tatebori, parallel trenches dug vertically into the Kirigishi slopes, was developed to prevent enemies coming up the slopes diagonally (Fig.2).
In the field survey, it was confirmed that some debris flows were generated from the lower part of Horikiri slope. It is highly suspected that defensive features of medieval mountain castles could have affected the flow of rainwater.
Furthermore, this city is mainly composed of the Hiroshima granite, which is relatively vulnerable to the terrain modification. The analysis by GIS revealed that 85% of medieval mountain castles that were associated with landslides, were located in The Hiroshima granite.
The analysis by GIS (Geo Information System) and field study suggest that Horikiri, the construction of a medieval mountain castle, is one of the causal factors with landslide.
Therefore, identifying the areas of those artificial terrain change could be effective to foresee future potential of debris flow path when landslide took place in the future.