11:00 AM - 11:15 AM
[HDS07-07] Research on the use of historical topographic data created from old illustrations and maps for disaster prevention
Keywords:Reconstruction of Historical Topography from Old Maps, Miyako City, Iwate Prefecture, 2011 Great East Japan Earthquake, 1896 Meiji Sanriku Earthquake and Tsunami
This report describes a method to reconstruct historical landforms using old maps and maps, to elucidate how landform changes and development are related to today's natural disasters, and to consider how to utilize this information for disaster prevention.
In this study, historical landforms were reconstructed in the area surrounding Miyako City, Iwate Prefecture. The oldest topographic map of the Miyako City area is an old topographic map drawn in 1916. The earliest topographic maps that depict the topography of Miyako City are an 1857 map depicting the mouth of the Hei River flowing through Miyako City, and an 1874 map depicting Miyako Village at that time. First, historical topography was drawn using GMT (Generic Mapping Tools) based on today's topographic data of Miyako City, and compared with the old topographic map of 1915 to draw the flow path and coastline of the Closing River at that time to reconstruct the historical topography of the Miyako area in the modern era. Similarly, the topography of the pre-modern period was restored based on the 1857 map and the 1874 village map. Comparing the reconstructed topography with the current topography, it can be seen that the topography of the mouth of the Closing River in the Miyako area has changed significantly, especially during the pre-modern and modern periods, when the middle bar of the river mouth was reclaimed and the city hall building was constructed there.
Next is the depiction of disaster information. Miyako City has been hit by tsunamis many times in its history, including the 2011 Great East Japan Earthquake, the 1896 Meiji Sanriku Earthquake, and the 1933 Showa Sanriku Earthquake. First, the tsunami inundation area of the 2011 Great East Japan Earthquake is depicted in GMT. In addition, we estimated and depicted the inundation area based on the "Iwate Prefecture Coastal Tsunami Map" created by Soshin Yamana, who conducted a survey of the affected areas after the 1896 Meiji Sanriku Earthquake and Tsunami.
The depiction of the Miyako area at the time of the Meiji Sanriku Tsunami by Soshin Yamana shows that the main facilities such as the county office, village office, and schools at that time were spared from the tsunami damage. Comparing this with the 1915 topographic map, we can see that the locations of these offices and schools have remained almost unchanged. In other words, the reconstruction of the Miyako area after the Meiji Sanriku Earthquake Tsunami left the pre-tsunami conditions largely unchanged, and the subsequent expansion of the urban area developed in the same manner.
In addition, when the historical topography is superimposed on the 2011 tsunami inundation area, the reclaimed land of sandbars that once existed at the mouth of the river was largely inundated, and the Miyako City Hall building at that time was also inundated. In 1854 and 1874, the Yamaguchi River runs through the center of the Miyako area, but today the Yamaguchi River has been rerouted due to river improvement, and the old river channel has been culverted. 2011 saw the tsunami entering along the old Yamaguchi River channel.
The superposition of historical topography and tsunami inundation information in the Miyako region indicates that tsunami inundation damage is more pronounced along rivers and coastlines that once existed. In addition, the topographic changes caused by development in the pre-modern, modern, and contemporary periods have made it difficult to determine the tsunami inundation hazard in these areas today. Visualization of historical landforms depicted on old maps and maps, as well as understanding the history of regional development and landform changes, will help disaster prevention measures in the event of a disaster.
In this study, historical landforms were reconstructed in the area surrounding Miyako City, Iwate Prefecture. The oldest topographic map of the Miyako City area is an old topographic map drawn in 1916. The earliest topographic maps that depict the topography of Miyako City are an 1857 map depicting the mouth of the Hei River flowing through Miyako City, and an 1874 map depicting Miyako Village at that time. First, historical topography was drawn using GMT (Generic Mapping Tools) based on today's topographic data of Miyako City, and compared with the old topographic map of 1915 to draw the flow path and coastline of the Closing River at that time to reconstruct the historical topography of the Miyako area in the modern era. Similarly, the topography of the pre-modern period was restored based on the 1857 map and the 1874 village map. Comparing the reconstructed topography with the current topography, it can be seen that the topography of the mouth of the Closing River in the Miyako area has changed significantly, especially during the pre-modern and modern periods, when the middle bar of the river mouth was reclaimed and the city hall building was constructed there.
Next is the depiction of disaster information. Miyako City has been hit by tsunamis many times in its history, including the 2011 Great East Japan Earthquake, the 1896 Meiji Sanriku Earthquake, and the 1933 Showa Sanriku Earthquake. First, the tsunami inundation area of the 2011 Great East Japan Earthquake is depicted in GMT. In addition, we estimated and depicted the inundation area based on the "Iwate Prefecture Coastal Tsunami Map" created by Soshin Yamana, who conducted a survey of the affected areas after the 1896 Meiji Sanriku Earthquake and Tsunami.
The depiction of the Miyako area at the time of the Meiji Sanriku Tsunami by Soshin Yamana shows that the main facilities such as the county office, village office, and schools at that time were spared from the tsunami damage. Comparing this with the 1915 topographic map, we can see that the locations of these offices and schools have remained almost unchanged. In other words, the reconstruction of the Miyako area after the Meiji Sanriku Earthquake Tsunami left the pre-tsunami conditions largely unchanged, and the subsequent expansion of the urban area developed in the same manner.
In addition, when the historical topography is superimposed on the 2011 tsunami inundation area, the reclaimed land of sandbars that once existed at the mouth of the river was largely inundated, and the Miyako City Hall building at that time was also inundated. In 1854 and 1874, the Yamaguchi River runs through the center of the Miyako area, but today the Yamaguchi River has been rerouted due to river improvement, and the old river channel has been culverted. 2011 saw the tsunami entering along the old Yamaguchi River channel.
The superposition of historical topography and tsunami inundation information in the Miyako region indicates that tsunami inundation damage is more pronounced along rivers and coastlines that once existed. In addition, the topographic changes caused by development in the pre-modern, modern, and contemporary periods have made it difficult to determine the tsunami inundation hazard in these areas today. Visualization of historical landforms depicted on old maps and maps, as well as understanding the history of regional development and landform changes, will help disaster prevention measures in the event of a disaster.