THE MAINTENANCE POLICY THAT UTILIZED THE EFFECTIVENESS TO THE FLOOD CONTROL OF FLOOD DEFENCE FOREST IN THE LOWER REACH OF GOUNOKAWA RIVER

Abstract

In the lower reach of Gounokawa River, a lot of dike-undeveloped districts exist, and a river improvement security level is low. In addition, it is expected that the population decreases by more than 30% in the next 30 years in the local area. Therefore it is difficult to carry out river improvement and maintenance at the past degree of progress.

On the other hand, bamboos planted as flood reduction measures still play an important role as flood defense forest. Therefore, in the lower reach of Gounokawa River, it becomes important to utilize the river improvement effect that flood defense forest has. We evaluated a river improvement effect in this study quantitatively for flood defense forest of the lower reach of Gounokawa River and examined the maintenance policy could that utilize such river improvement effect.