山地河川の露岩化した河床における砂礫堆回復に関する実験的研究

抄録

To examine the usefulness of geotextile bags, which were filled with gravels, in a trial to recover gravel-beds without using power vehicles in mountain rivers, status of the bags and changes in bed materials around the bags were surveyed before and after flood events at a bedrock-exposed reach in the upper Kinu River. The bedrock- exposed reach was partly covered by pebbles and gravels at upstream areas of the installed bags after a flood, which indicates an effectiveness of the bags for the recovery of gravel-beds. A part of the bags were moved downstream for a few-meters distance by the flood, while it contributed on the deposition of gravels at its settling position. Since no damage on the bags was found, the bags can still be effective even if they move to and settle on other positions. Benthic invertebrates and fish appeared to increase in abundance after the retention of pebbles and gravels. Limitations and possibilities of installing geotextile bags on river restoration works were discussed.