9:30 AM - 9:45 AM
[MIS10-03] Utilization of Hydrogeomorphology and Flood History in the Mt.Kurikoma Area Geopark
Keywords:Geopark, Flood, Hydrogeomorphology
Mt. Kurikoma Area Geopark, located in Kurihara City, Miyagi Prefecture, has a history of repeated flood disasters in the past, with the Hasama River, which is part of the Kitakami River system, flowing through the area. On the other hand, the activities of the Geopark have mainly focused on the Arazawa Landslide caused by the 2008 Iwate-Miyagi Nairiku Earthquake, and the flood disasters in the plains and the landform development of Izunuma and Uchinuma have been limitedly revealed and utilized for educational purposes. Therefore, in order to make use of it in the new guide program of Mt. Kurikoma Area Geopark, we conducted the surveys for landforms, geology and literatures, and studied the transition of the disaster environment around Izunuma and Uchinuma from the Holocene to the Anthropocene. In addition, the detailed landform development of the area around Izunuma and Uchinuma is scheduled to be published in Sugiura et al. (2025).
The Hasama River, which flows through the Mt.Kurikoma Area Geopark, is formed by the confluence of the Ichihasama, Nihasama and Sanhasama rivers, which originate on the southeastern slopes of Mt. Kurikoma. The Hasama River then flows into the Kitakami River in the northern part of Ishinomaki City, and finally empties into the Pacific Ocean. Because the slopes of lower Hasama River and their tributaries are gentle from the mouth of the Kitakami River, it is prone to flooding caused by backwater.
The Hasama River basin was under the control of the Sendai Date clan, and in particular, the history of flooding from the 17th century onwards is recorded in documents such as the “Wakayanagi Town History (1974)” and the “Hasama River Story (Onodera, 1981)”, which delves further into the subject and focuses on the Hasama River basin. The earliest record of fluvial hazard in the Hasama River area is the flood caused by heavy rain in June 1579, and the most recent one occurred around Izunuma on July 15, 2022. Organizing the disaster records in these “human records” spatiotemporally, we can clarify the locations where disasters occurred and the frequency of wind and water damage in the plains of the Mt. Kurikoma Area Geopark. On the other hand, there are not enough human records of floods before 1579. Therefore, we carried out tracing the landform development of the lower Hasama River and clarifying its flood history by conducting topographical and geological surveys for the natural levees, fomer river channels, and borehole data that remain in the Hasama River basin.
Izunuma is a lagoon that was formed after the Jomon transgression and the subsequent recession of the coastline. The distribution and excavation of archaeological sites has revealed that people lived on the edges of hills during the Jomon period, and that settlement in the plains began after ~ 6,000 years ago. After the formation of the channel and the alluvial plain in the lower Hasama River, the Izunuma Lake has been maintained by the mainstem deposits of Hasama River as the blocked-valley lake, and changes in the river course has associated with flooding. Survey for natural levees and former river channels brought the result that the river channel was abandoned before the 13th century in one of the villages that is still inhabited today.
In this study, we approached the history of regional landform development and history of fluvial hazards by mutually complementing the parts that cannot be filled in by human-recorded documents and the parts that cannot be filled in by topographical and geological surveys. By conducting surveys using a hybrid method, we can connect people with topography and geology, and this will help us to learn more about the region and communicate this information.
The Hasama River, which flows through the Mt.Kurikoma Area Geopark, is formed by the confluence of the Ichihasama, Nihasama and Sanhasama rivers, which originate on the southeastern slopes of Mt. Kurikoma. The Hasama River then flows into the Kitakami River in the northern part of Ishinomaki City, and finally empties into the Pacific Ocean. Because the slopes of lower Hasama River and their tributaries are gentle from the mouth of the Kitakami River, it is prone to flooding caused by backwater.
The Hasama River basin was under the control of the Sendai Date clan, and in particular, the history of flooding from the 17th century onwards is recorded in documents such as the “Wakayanagi Town History (1974)” and the “Hasama River Story (Onodera, 1981)”, which delves further into the subject and focuses on the Hasama River basin. The earliest record of fluvial hazard in the Hasama River area is the flood caused by heavy rain in June 1579, and the most recent one occurred around Izunuma on July 15, 2022. Organizing the disaster records in these “human records” spatiotemporally, we can clarify the locations where disasters occurred and the frequency of wind and water damage in the plains of the Mt. Kurikoma Area Geopark. On the other hand, there are not enough human records of floods before 1579. Therefore, we carried out tracing the landform development of the lower Hasama River and clarifying its flood history by conducting topographical and geological surveys for the natural levees, fomer river channels, and borehole data that remain in the Hasama River basin.
Izunuma is a lagoon that was formed after the Jomon transgression and the subsequent recession of the coastline. The distribution and excavation of archaeological sites has revealed that people lived on the edges of hills during the Jomon period, and that settlement in the plains began after ~ 6,000 years ago. After the formation of the channel and the alluvial plain in the lower Hasama River, the Izunuma Lake has been maintained by the mainstem deposits of Hasama River as the blocked-valley lake, and changes in the river course has associated with flooding. Survey for natural levees and former river channels brought the result that the river channel was abandoned before the 13th century in one of the villages that is still inhabited today.
In this study, we approached the history of regional landform development and history of fluvial hazards by mutually complementing the parts that cannot be filled in by human-recorded documents and the parts that cannot be filled in by topographical and geological surveys. By conducting surveys using a hybrid method, we can connect people with topography and geology, and this will help us to learn more about the region and communicate this information.