Rainwater drainage management for urban development based on public-private partnership

The Urban Development Corporation (UDC) is one of the biggest implementatio n bodies for urban development in Japan. UDC has developed rainwater infilt ration technology since 1975. This technology has effectively reduced runof f to a river and sewer system in the new town project areas. Recently, UDC has developed a new system which is defined as a "Rainwater Recycle Sewer S ystem", which is supported by "Rainwater Storage and Infiltration Technolog y (RSIT)" applicable to new town creation and urban renewal. The new system consists of two elements: RSIT components based on Public-Private Partners hip (PPP) and a stormwater drainage system. Herein, the private sector is r esponsible for the main part of RSIT, and the public sector is responsible for the stormwater drainage from the development area. As a result, the cap acity of public facilities, such as rainwater sewers and stormwater reservo irs, can be reduced effectively. In parallel, the initial/running cost of p ublic facilities is expected to be reduced. In conclusion, the authors woul d stress the importance of a co-maintenance system also based on PPP, which will be required especially in order to properly operate the whole system for the long term.