江の川におけるオオカナダモの繁茂要因と抑制条件に関する検討

抄録

A luxuriant growth of Egeria densa occurred in the downstream of Haji Dam, Gonokawa River, Japan. The relation between the cover degree of Egeria densa and velocity revealed that Egeria densa is difficult to growth in the place where the velocity is over 0.8 m/s. As a test construction, we installed the bagged rubble stone in the middle of the river section with the luxuriant growth to expand the area where the velocity is over 0.8 m/s. The monitoring reveal that this improvement is effective to prevent the fixing Egeria densa. We observed that the fixing is depend on the growth of root and the river bed material, and the fixed Egeria densa is hard to remove even under the high velocity environment. The result indicates that we need to prevent the fixing at an early stage of the growth.