Abstract
Widening the width is necessary to improve the water environment of the small watercourses in the urban area, besides the augmentation of the water flow or the improvement of the water quality.
At least 7m width of watercourse is found to be necessary, if most people regard this watercourse has enough width. Many streams in Japanese urban area have only less than 3-5m width, and footpath and greens along the watercourses are also needed to see it. Then widening the watercourse width in the urban area often becomes an urgent task.
