We suggest to construct small scale dry dams in a river instead of a large scale dam in order to prevent a flood disaster and preserve a natural environment. In recent years, a flood control dam without a slide gate in spillway, known as a ’dry dam’, has been reviewed, planned and built in some sites. In this study, the effects of some slide gates in a bottom spillway which can be opened and closed automatically depending on hydraulic pressure called ’pressure gate’ for a dry dam are examined. In addition, width of a crest spillway gate is discussed to reduce rapid increase of flow discharge in the situation of overflowing. It is demonstrated that a dry dam has an additional ability to reduce damage from a flood surge. Small scale dry dams must be regarded as a flood retarding basin fitting to a natural environment. Therefore, construction of small scale dry dams is one of the powerful options to adapt a natural environment and global warming.
