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[MZZ42-01] Relation between straw snake events and geological disaster in Kinki and Chugoku regions, Japan
Keywords:religious event, straw snake, deblis flow, landslide
There are many traditional events that use large snakes made of straw, in the Kinki and Chugoku regions. Some of them are accompanied by legends related to large snake or dragon, and some give us hints about the background of the birth of the event.
The traditional event "Jagata-matsuri" is held every year to dedicate a large snake nearly 10m in length to a shrine in Niimi City, Okayama prefecture (Fig.). This event is said to have started in the Kamakura period, and is accompanied by a legend that a plague spread after the snake that ravaged the fields was exterminated. In front of the shrine where the straw snake is dedicated, there is a straight valley with a length of about 5.7km and an elevation difference of about 450m. This valley is designated as a debris flow special warning area on the hazard map. These facts remind us of the connection between the legend of large snake and debris flow disasters.
In addition to this example, there are 11 events that have legends about large snakes, and in 9 of them, snake destroy fields or harm people in the Kinki-Dhugoku region. When they were superimposed on the hazard map, 7 places were held near flood inundation risk areas, and 4 places were held near debris flow warning areas.
Tug-of-war events using straw snakes are characteristically distributed in Tottori Prefecture, the northern part of Hyogo Prefecture, and around Wakasa Bay. Among them, 'Wada no tsunahiki’ in Kami Town, Hyogo Prefecture and 'Entabiki' in Toyooka City, Hyogo Prefecture are accompanied by legends about large snakes.
The former is an event held on June every year and has been designated as an intangible cultural heritage of Kami Town. In this tug-of-war, there is a legend about a large snake that attacked people, and that disasters continued in the village after the snake was exterminated. This area is the confluence of two rivers. The upper reaches of the revers consist mainly of Neogene and Quaternary sedimentary rocks. Many landslides morphology developed in this area, and debris flow and landslide hazard zones are designated in many places.
A tug-of-war event called Entabiki was held in Toyooka in September 2017 for the first time in 20 years. In this area, there is a myth that when the gods cleared the Toyooka Basin, which was a sea of mud, they finally tore off a large snake that was blocking the flow of the river (Hyogo Prefectural Museum of History, 2009) . Based on this myth, people pull snakes made of straw until they are torn apart. The mountains surrounding the Toyooka Basin are mainly composed of Neogene pyroclastic rocks and Paleogene granites. They are easily eroded and form wide valley bottom plain. However, due to the presence of hard Quaternary basalt in the lower reaches of the river, the valley narrows and forms a so-called bottleneck topography.
As a result, thick sediment accumulated in the basin and a wetland was formed, which led to a long history of fighting flood damage and clearing wetland. The myth of cultivating the mud sea corresponds to the history of the formation of this area.
Summarizing the relationship between the traditions of the straw snake events and geology, in many cases these are closely related to geological disasters such as debris flows, floods, and landslides. It is considered that the consciousness of people who have faced or coexisted with geological disasters many times has created traditions, and the straw snake events are the embodiment of these traditions. Kojin-matsuri festivals and road-cutting events that are not accompanied by legends seen in various places may have been established in the same way.
The traditional event "Jagata-matsuri" is held every year to dedicate a large snake nearly 10m in length to a shrine in Niimi City, Okayama prefecture (Fig.). This event is said to have started in the Kamakura period, and is accompanied by a legend that a plague spread after the snake that ravaged the fields was exterminated. In front of the shrine where the straw snake is dedicated, there is a straight valley with a length of about 5.7km and an elevation difference of about 450m. This valley is designated as a debris flow special warning area on the hazard map. These facts remind us of the connection between the legend of large snake and debris flow disasters.
In addition to this example, there are 11 events that have legends about large snakes, and in 9 of them, snake destroy fields or harm people in the Kinki-Dhugoku region. When they were superimposed on the hazard map, 7 places were held near flood inundation risk areas, and 4 places were held near debris flow warning areas.
Tug-of-war events using straw snakes are characteristically distributed in Tottori Prefecture, the northern part of Hyogo Prefecture, and around Wakasa Bay. Among them, 'Wada no tsunahiki’ in Kami Town, Hyogo Prefecture and 'Entabiki' in Toyooka City, Hyogo Prefecture are accompanied by legends about large snakes.
The former is an event held on June every year and has been designated as an intangible cultural heritage of Kami Town. In this tug-of-war, there is a legend about a large snake that attacked people, and that disasters continued in the village after the snake was exterminated. This area is the confluence of two rivers. The upper reaches of the revers consist mainly of Neogene and Quaternary sedimentary rocks. Many landslides morphology developed in this area, and debris flow and landslide hazard zones are designated in many places.
A tug-of-war event called Entabiki was held in Toyooka in September 2017 for the first time in 20 years. In this area, there is a myth that when the gods cleared the Toyooka Basin, which was a sea of mud, they finally tore off a large snake that was blocking the flow of the river (Hyogo Prefectural Museum of History, 2009) . Based on this myth, people pull snakes made of straw until they are torn apart. The mountains surrounding the Toyooka Basin are mainly composed of Neogene pyroclastic rocks and Paleogene granites. They are easily eroded and form wide valley bottom plain. However, due to the presence of hard Quaternary basalt in the lower reaches of the river, the valley narrows and forms a so-called bottleneck topography.
As a result, thick sediment accumulated in the basin and a wetland was formed, which led to a long history of fighting flood damage and clearing wetland. The myth of cultivating the mud sea corresponds to the history of the formation of this area.
Summarizing the relationship between the traditions of the straw snake events and geology, in many cases these are closely related to geological disasters such as debris flows, floods, and landslides. It is considered that the consciousness of people who have faced or coexisted with geological disasters many times has created traditions, and the straw snake events are the embodiment of these traditions. Kojin-matsuri festivals and road-cutting events that are not accompanied by legends seen in various places may have been established in the same way.