Sustainable urban drainage system $($SUDS$)$ design involves theoretical considerations of integrating natural and engineered solutions to manage stormwater runoff, reduce flooding, and improve water quality in urban areas. Develop a comprehensive theoretical framework elucidating principles of SUDS design strategies, including permeable pavements, green roofs, and constructed wetlands. Explore theoretical models for assessing SUDS performance, such as hydrological modeling, water quality modeling, and ecosystem services valuation, and discuss theoretical approaches to implementing SUDS in urban planning, development regulations, and stormwater management practices, aiming to enhance urban resilience, biodiversity, and ecosystem services provision.