Series of techniques that manage surface water runoff by mimicking natural drainage processes to reduce flood risk, improve water quality, and enhance urban environments. Instead of traditional pipes, SUDs use natural processes like infiltration (soaking into the ground), attenuation (slowing down the flow), and passive treatment to handle rainwater as close to the source as possible. Key features include swales, permeable pavements, green roofs, and detention basins, which offer multiple benefits such as improved biodiversity and recreational opportunities.