| 摘要 |
PURPOSE:To form V-notch in a predetermined place, by a method wherein a feed and exhaust pipe having feed and exhaust ports mutually separated is provided inside a part of the longitudinal direction of flexible film body and it is delayed to be fallen for the film body except a portion to be fallen at first. CONSTITUTION:A rubber weir 5 is fixed to a river-bed 1 and a slope 2 of a river bank, and is integrated with a set of rubber cylinders 8, 9 extending in the direction of the river width near a fixed base portion 7 on the inner wall of the rubber film 6 facing the upper stream side of the rubber weir 5. The outer ends of the cylinders 8, 9 are connected to the feed and exhaust pipes 4 for the faces of slope, and the closed inner ends are mutually separated with a distance (t) between them. The separated distance is arranged almost on the mid-point of the rubber weir. Thus, V-notch can be always formed in the predetermined place on the flexible film. |
