Characteristic relationship between rivers and safety in Japan is summarized at first to understand the background of river improvement works. Typical examples of existing facilities for the management of rivers are described with short history. Then social concem with environmental aspects related with rivers is described. It is shown that ecoIogical aspect becomes most important factor after the concept of 'sustainable development' and 'diversity of species'. Examples to enhance natural features in recent river works are studied and design principles for nature oriented river works are obtained.