強混合型河川感潮域での河岸ガタ土堆積と水際植生管理に関する研究

摘要

The Rokkaku river basin faces to the Ariake bay where the maximum tidal range is about 5m at the river mouth. This estuary is characterized by well mixed tidal area and suspended matters are usually transported by tidal dynamics. Sediment transport induces shoaling of river channel, thus it is important to maintain the cross-section of river for reducing the damage of flooding. In addition, mud sedimentation might be some possibility of accelerating the growth of Phragmites communis and vice versa. In this study, the behaviors of cohesive sediment and the growth of Phragmites communis on the banks of river were investigated in the Ushizu river. As a result, it was shown that mud sedimentation was accelerated over the average water level, and the growth rate of Phragmites communis and the network structures of the underground stem were measured. The interaction between siltation and vegetation close to the edge of water in the river bank is highlighted, and an idea of vegetation control is suggested.%a) 長期にわたるガタ土堆積のモニタリングょり，平均水 位を境に岸側で堆積傾向，流心侧でわずかに堆積もしく は洗掘傾向で，年平均水位を境としたガタ土堆積速度は, 岸傾で+1. 0～+l. 5mtn/day,流心側で-0. 2〜-0. 1mm/dayで あった. b) 河岸斜面上での流れ場とSSの測定から，上げ潮·下げ 潮での流れ場の非対称性や転流時前後での急激なSS低下 などを明らかにした.