The northeastern caldera walls of Aso Volcano in Kumamoto, Japan have a relief of approximately 300 m. The walls form long steep hillslopes, in which the upper part has a slope of more than 30 degrees and the lower part has a slope of 20 to 25 degrees. During an extreme rainstorm in July 2012, many landslides were initiated from the upper parts of the hillslopes and the hillslopes collapsed over a long distance. Eroded sediment and large woody debris reached approximately 200 m from the toes of the hillslopes, causing serious damage in residential areas. The present criterion for designating landslide hazard areas does not include the hillslopes in which the horizontal distance between the upper steeply inclined segment (more than 30 degrees in slope) and the footslope residential areas exceeds 50 m. A new criterion applicable to long-runout landslides in this kind of hillslope is required. We researched the distribution of sediment and woody debris in depositional areas of five selected landslides using LiDAR DEMs and aerial photos, analyzed sediment depth and wood size that can affect damage to houses, and discussed a new idea for designating the hazard area and for partitioning the area based on the hazard ranks of house damage. The landslide hazard area should be designated as the area within a distance of 1.5 to 3 times the hillslope height from a concave break line in slope. On this occasion, it is important to designate the hazard area regardless of the maximum distance 50 m in the present criterion even if the height of the hillslope is large. The hazard area can be partitioned into three hazard ranks based on the depth of sediment deposited and the amount of large wood transported.
In 1900, the Laboratory of Forest Hydrology and Erosion Control Engineering (SABO) was founded in the Imperial University of Tokyo (present the University of Tokyo), which was the first educational organization for studying and learning this field. I have considered the educational system of SABO in about 15 years since around 1900, the process of discussion for founding the Laboratory of SABO, the process of choosing suitable foreign teachers and the educational conditions before Dr. Kitao MOROTO who was the first Japanese professor at the Laboratory of SABO. In Japan, we did not have an educational system for SABO before 1900, however, some experts in forestry science qualitatively commented that the functions of the forest were to protect sediment runoff and preserve water resources. Because at the end of the 19 th century, many sediment disasters occurred, SABO law was enacted in 1897, and the educational system of SABO was established in the Forest Science Department, the Imperial University of Tokyo, through promotional activities of Prof. Shitaro Kawai and persons involved. As the first foreign instructor for teaching SABO, Karl Hefele was chosen and came to Tokyo in 1901. He did not have much knowledge about SABO, then he returned to Germany only two years later. After then Amerigo Hofmann became a teacher at the Laboratory of SABO and stayed in Tokyo for about five years. He left great achievements of not only “Hofmann works” in Seto City but also many documents including those published in Austria and in Italy after coming back to Europe. Dr. Kitao Moroto supported Hofmann's performances in Japan as an associate professor. In this paper the condition of the education on SABO is described in the incipient period of modern SABO on the basis of the literature and field investigations. This paper will contribute to the future exchange between Japan and European countries in the field of SABO based on these historical relationships.
In 1900 the Laboratory of Forest Hydrology and Erosion Control Engineering (SABO) was founded in the Imperial University of Tokyo (present the University of Tokyo), which was the first educational organization for studying and learning this field. As the first foreign teacher for teaching SABO, Karl Hefele was chosen and came to Tokyo in 1901. He did not have much knowledge about SABO, then he returned to Germany only 2 years later. After then Amerigo Hofmann became the teacher holding the Laboratory of SABO and stayed in Tokyo about 5 years. He left many footprints which are not only “Hofmann works” in Seto city, Aichi prefecture, but also many papers and books published in Austria and in Italy before or after coming back to Europe. “Hofmann works” is very famous as the performance of Amerigo Hofmann in Japan, however this is only one result which is distinctly known as his performance in Japan. And the detailed career of Amerigo Hofmann is not known in Japan. In this paper the footprints of Amerigo Hofmann are described in the incipient period of modern SABO on the basis of literature and field investigation. This paper is to contribute to the future exchange between Japan and European countries in the field of SABO based on these historical relationships.