ADAPTATION MEASURE 021
ENVIRONMENT
BODY ADAPTATION
BEHAVIOR ADAPTATION
BEFORE
Conventional gray infrastructure development has diluted the relationship between nature and livelihoods, leading to a decline in ecosystem services.
AFTER
The natural environment is maintained and ecosystems are nurtured through community-based water use and disaster prevention/mitigation systems that shape rich local cultures and ecosystems.
Local communities throughout Japan have diverse forms of water use and traditional mechanisms for controlling water and sediment. Valley water and spring water become networks that flow through rivers and waterways, and are used for food, clothing, and shelter, as well as deeply connected to livelihoods such as rice cultivation and fishing.
Either too much or too little river water affects people's livelihoods. Therefore, there are control technologies and mechanisms in local communities not only for emergencies such as floods and mudslides, but also in everyday life to deal with the movement of water and sediment. The "Shimatsu" or "Kawato and Sutegawa", which are believed to have started in the Edo period (1603-1868) at the foot of Mt. Hira in Shiga Prefecture, are examples of communities at the edge of an alluvial fan that use the abundant water for disaster prevention and mitigation while also considering the relationship with the surrounding forests and other factors. These systems have contributed to maintaining the sandy beaches along the lakeshore and nurturing a rich ecosystem.
CASE.01
Shimatsu is a device to remove sand contained in water from mountainous areas when it is used. Shimatsu are set near water intakes from the main stream, in mountain valleys near the main stream, and near villages, which are suitable locations for returning accumulated sand to the main stream of the river. When the discharge sluice is opened, water and sand flow out through the ditch into the main stream. The shape can be straight, polygonal, or oval. In irrigation channels where the water is strong, stones are piled up at the introduction of shimatsu to reduce the momentum of the water by hitting it with them.
Shimatsu at Minamihira, Shiga (Katsue Fukamachi)
When flooding is expected, the sluice gate can be closed in front of shimatsu to prevent water and sand from flowing in. It is a method of controlling water and sediment combined with methods of deterring sediment from surging in the case of an emergency (e.g., stone dikes) and the protection and management of the surrounding erosion-control forests.
Shimatsu at Minamihira, Shiga (Katsue Fukamachi)
CASE.02
SINCE 16th century
Kawato is a small-scale device or space in a network of irrigation canals throughout a community in which each house raises the water level by using boards or other means, or draws water into the yard to store. They are managed jointly by neighborhood associations and agricultural organizations as part of water for domestic and agricultural use.
Valley water and spring water are natural blessings that support food, clothing, shelter, and livelihood, but too much water can lead to natural disasters. For this reason, the state of kawato has been used as a guide to determine when to respond to natural disasters, for example, by visiting upstream irrigation canals when the water volume becomes higher. The upstream kawatos are used for controlling the flow of water throughout the channel by diverting the increased water flow to the adjacent fields.
Another way to manage water by letting it escape is to set up a sutegawa for a portion of the irrigation canal that does not flow through the village.
When the water level rises, the leader of the community association controls the flow and volume of water by channeling the valley water into a sutegawa to return it to the main stream. In everyday life, people use sutegawa to do laundry and other tasks that would contaminate the water.
There are lore and places of worship to enjoy the clean water. When the masonry of the irrigation canals crumble, they are repaired jointly by inhabitants.
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