**1. Introduction**

The country where the aging society is progressing due to depopulation, such as Japan, many researchers have suggested that urban planning should consider an intensive urban structure, such as the "compact city," as the future vision of an aging society. In addition, Japan is one of the countries with high risk of natural disasters, such as the 2011 Great East Japan Earthquake and frequent huge flood damage. This chapter first explains the recent trends of urban planning in Japan and the policy of mitigation of natural disaster risks in this context. After that, we will explain the measures to reduce the risk of natural disasters in urban areas, and the role of planning support system (PSS) for their examination, including some examples.
