Mt. Fuji & Sabo Project

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Project Overview

About 70% of the land in Japan has been formed by mountains. It belongs to the Ring of Fire and its land is a part of the Asian monsoon region. Therefore, people's lives have been threatened by variety of disasters, volcanic eruptions, earthquakes, debris flow caused by heavy rain, landslide, and collapse of cliff. The action to prevent those disasters are called "SABO", in Japan.

Mt. Fuji Sabo Office promotes 2 projects on disaster prevention.
1. Prevention of sediment-related disasters:
 Measures for the Osawa alluvial fan and measures for torrents at the southwest base of the mountain.
2. Volcanic Sabo investigation:
 Investigation for the prevention of sediment-related disasters are caused by volcanic activities of Mt. Fuji.

What is a Sabo?

About the root of a word "Sabo" and Sabo facilities, we explain it here.
What is a SABO?

Sabo projects to prevent from sediment-related disasters

Mt. Fuji, the highest mountain in Japan, has an appearance so beautiful that it symbolizes for our country.
At the southwest foothills of Mt. Fuji, there are main artery transportations including the Tokaido Line and the Tomei Highway. Many people from around the world visit here to see Japan's leading tourist destination, Mt. Fuji. Large-scale projects are also underway like the Second Tomei Expressway for example, so it has become an important area. The Fuji Sabo Office observes the Mt. Fuji southwest area and develops sediment-related disaster prevention measures.

Measures for Osawa alluvial fan

Originating from the Osawa failure at the altitude of 3730m, the Osawa River runs down on the slopes of Mt.Fuji and through Osawa Alluvial Fan that spreads across at 700m above sea level. After changing its name to the Urui River near Osawagawa Ohashi Bridge located further down, the river runs through the cities of Fujinomiya and Fuji, discharging itself into Tagonoura Port. It also runs into the Fujigawa River via Hoshiyama Canal Discharge Channel at times of flooding. Sediments that originate in the Osawa failure accumulates at the bottom of the Osawa River at its head and is swept down by rainfalls and melted snow water, accumulating again at Osawa Alluvial Fan.
The flooded water carries them further down, causing problems such as intrusion of debris and flooded rivers in residential areas. Sediments that flow into the Tagonoura Port can also hamper free navigation of ships.
Our projects for the Osawa failure collapsing aim to prevent these problems.

There are two possible strategies for this goal: first, we need to prevent further sand erosions from the Osawa failure, where the vast majority of sand-debris originates. Secondly, control the accumulation and flooding of sediments on the Osawa Alluvial Fan.

The first strategy is to prevent sand erosion in the Osawa failure. There are technical difficulties at the moment due to its geographical features and the severe weather conditions near the summit of Mt. Fuji. We have, however, been exploring possible feasible schemes, enforcing various surveys, and testing projects.
Meanwhile, the second strategy, control schemes on the alluvial fan is much easier to enforce and more effective, as they lead directly to a disaster prevention in the lower reaches of the Osawa River. Therefore, we have been pursuing projects in which the debris flow has securely stopped and accumulated the sand pocket established on the alluvial fan. Also, when the amount of sediment carried by flooded water is too much, sand basins are located further down. Thus, the main purpose of our activities in the Osawa River is to prevent sediment-related disasters. Channel works in the Osawa River’s lower reaches are also a part of our jobs.

Volcanic Sabo Investigation

Mt. Fuji is an active volcano that has erupted regularly from the beginning of recorded history; it has been erupting for more than 10,000 years since the formation. Since the Hoei eruption of 1707, it has remained quiet for about 300 years. It has been predicted that enormous disasters occurs by its eruption. The low-frequency earthquakes that occurred in the underground of Mt. Fuji in 2000 gave attention to the experts, and the volcanic disaster prevention measures for Mt.Fuji started to be researched in earnest.
In June 2004, the Review Committee for Mt. Fuji Volcanic Hazard Map published the "Mt. Fuji Volcano hazard map", and the peripheral municipalities of Mt. Fuji have begun activities for disaster prevention measures.
The Fuji Sabo Office has engaged in the investigation for the prevention of sediment-related disasters caused by volcanic activities of Mt. Fuji.

Investigations and activities include:
 Investigation of Fuji Volcanic Sabo plans (Sabo facility placement plans)
 Development of observation system
 Cooperation with related organizations
 Planning the scheme of real-time hazard map