Explore the principles and challenges involved in the design and implementation of sustainable urban drainage systems $($SUDS$)$ within a metropolitan environment. Consider the hydrological, environmental, and engineering aspects that must be integrated to effectively manage stormwater runoff while minimizing ecological disruption. Discuss the various techniques and technologies employed in SUDS, such as permeable pavements, green roofs, and retention basins, and how they contribute to reducing flood risks and improving water quality. Evaluate the potential conflicts and synergies between SUDS and existing urban infrastructure, considering aspects such as land use, maintenance, and cost implications. Additionally, reflect on the role of policy, regulations, and public engagement in the successful adoption and implementation of SUDS in urban planning. How can civil engineers balance technical feasibility with environmental sustainability and community needs in the context of evolving climate conditions and urbanization pressures?