This lecture covers the principles and technical elements of urban water drainage, including the source of wastewater, discharge regulations, and the protection of public health and the environment. It discusses the different types of water to evacuate, the historical hierarchy of objectives, and the challenges related to wastewater discharges. The lecture also explores the unitary and separate systems for managing wastewater and rainwater, as well as the issues and benefits associated with each system. Additionally, it addresses the importance of infiltration of clear water, detention measures, and flood management in urban areas.