This book describes the planning principles and construction methods for rainwater infiltration systems and rainwater utilization systems. It includes discussions on legal aspects, the determination of soil permeability coefficients, and the calculation of heavy rainfall amounts for each location. Additionally, you will find information on design bases and forms of open drainage channels, as well as the hydraulic design of pipelines. Numerous examples of decentralized systems for infiltration, rainwater infiltration, and the planning and construction of rainwater utilization systems illustrate the topic. This informative compendium demonstrates how to plan with rainwater from an urban, environmentally relevant, design-oriented, and economic perspective.