Abstract
To promote reasonable sabo works which consider not only disaster prevention but also environment preservation, it is necessary to estimate the structure of the river environment that should be preserved. In this study, it was tried to grasp the structure of the river environment systematically from the review of former literature, and the data of former sabo works was analyzed so as to make the actual state and issue of works clear. As a result, the river environment could be classified into six environment elements of disaster prevention, ecosystem, affinity with water, recreational function and area promotion. The river environment was recognized as the combination of them according to the condition of the location. The analysis of former sabo works showed certain relation between the frequency that each environment element was chosen as the purpose and the conditions of the location. However, the environment element and the devices adopted for the preservation have a tendency of uniformity. This fact seems to mean the issue that the estimation of the environment is not enough to achieve reasonable preservation.
