Abstract
The lower reach of Gounokawa River has a lower river improvement security level than the upper reaches. It will take long time for dike construction to be completed and therefore the rapid improvement of the river improvement security level cannot be expected. On the other hand, bamboos planted as flood reduction measures have been still left as flood defense forests. However, the expansion of the growth range and having withered on the stalk of the bamboos become the problem for the river improvement. Therefore it is important to maintain flood defense forests in consideration of the river improvement effect. In this study, I evaluated positive and negative aspects of the flood defense forests and examined an improvement method using a 2-D shallow-water flow model.
