Stair-stream of Ushibusegawa 2

Nature and Culture

  We call the mountains and fields we mankind modify to keep landscapes and safety Satoyama. Then we would call the headstream zone of Ushibusegawa that.
  They have paved the ravine-slope with stones and constructed the stair-stream to avoid landslide and landcollapse. And have changed the condition of mountain-forests. The ecology system of there has been modified by mankind.
  However the nature has not domasticated by us. We manage only to negotiate and to get well relation with it somehow for a very short time. Only for a hundred years in millions years.

▲We can enjoy playing on the stream in summer. We can walk across it along the spotting stones.

■From 3d Dam to Stair-Stream■

▲Murmur brook waving gentlly The slope and stream paved with stones are the works to prevent erosion by water, thus to avoid landsliding flood. In such a way they let the stream not erode the bottom earth and not accumulate it on downstream. Accumulated earth would side down by heavy rainfall, thus would destroy the villages and the fields along downstream areas. ◆Landform and Stream◆ The flowing speed and enargy are different owing to the degree of inclination. Some places are steep other are gentle. As water flows down on terraced landform, it is very important how to design the shape of waterway owing to the diffference of inclination. Theu must invastigate precisely the effects of water-stream to erode, to transport and to accumulate the earth. They can not design the inclination and curvature of the waterway, without estimating those effects ― their direction and strength. The wonderful forms of waterways including the stair-stream are the result of the respect ond the insight to the nature-dynamism. ▲Serial spotting of stones on shallow and gentle waterway ◆Design of Stair-Stream◆ The further main stream flows down on the ravine-bottom line, the more volume of water flows by getting together its branches. It needs the more height of banks and more width. Architectural device for wasting or absorbing energy of water falling down espacially on the long steep slope. Then they adopt the construction method of the stair -stream paved with stones which had initiated in French Alps mountain, adding their own inovation. Flowing down on the long steep slope the water is getting the larger velocity by releasing its potential energy and its destructive force is also getting larger. Then by forming many falls sustained with stones and letting it fall down vertically at each stair, they would take away its potential energy and horizontal velocity continuously. Thus the water would lose its verocity and force befor being destructive. The stone-pavement at each stair-bottom of the falls endures and abosorbes falling impacts of water. How intelligent ! ▲Water flowing down on stair-stream ▲Water falls down, shining white. ▲Walking-way on stream-side ▲Looking at the stair-stream along sidewalk	Woods around waterway on plain place Dam at Aishimizusawa before confluence with main stream Small wooden bridge over confluence point The second dam and its fall
	Stone-walled banks guards curve Dam forms a fall of 3 meters height Earth piled thick on gentle slope of stream. It would be replaced regularly. It's becoming the main stream
	Comparering the dam with a person On both sides walkways with bridges
	The stair-strem is beginning just behind there
	Give thanks for water and beautiful landscape The stair-stream in light green of spring