Frequent inundation has become a serious problem in urban areas all over the world in recent years. It is necessary to improve rainwater retention and infiltration in the urban watershed. The purpose of this study is to report how private rainwater-retention/harvesting tools/facilities can be spread gradually but steadily in the city, as a smart way to responding to urban flood-disaster risks. Rainwater harvesting tanks (0.2 m(3)) were installed intensively in 2010 and a rainwater harvesting house (42 m3) was constructed in 2012 in the city of Fukuoka, Japan after the city experienced a flood disaster in 2009. The former enhanced users' daily preparedness for emergency, and the latter inspired construction of a rainwater-harvesting housing complex (108m(3)) in an adjacent city. An elementary school is under construction from November of 2014 by another, nearby municipality inspired by these facilities. The school premises are located on the land reclaimed from an old irrigation pond. Thus the school needs to be adapted to this condition. 3,800 m(3) of rainwater can be retained within the school premises. The water is used to flush the toilet and water flowers to be grown by pupils. The amounts of retention and discharge will be monitored, and the data will be utilized for science education. In big cities, people tend to depend too much on the top-down, mega-system involving dredging rivers, strengthening drainage systems, constructing flood walls, etc., which invites more man-made, impervious surfaces in urban areas. Bottom-up, individual and/or collaborative approaches should be adopted in order to achieve multiple purposes of preventing/mitigating disasters, preserving/conserving ecosystems and nurturing/rebuilding communities in the city. (C) 2015 The Authors. Published by Elsevier Ltd.