Municipalities across the Baltic Sea Region face growing challenges as climate change intensifies heavy rainfall and environmental standards tighten. Stormwater runoff carries nutrients, heavy metals, and microplastics into rivers, lakes, and the Baltic Sea, increasing pollution and flood risks. Rapid urban growth further strains outdated drainage systems, making it difficult to balance climate resilience, water protection, and sustainable urban planning. The project helps municipalities, utilities, regulators, and communities manage stormwater more sustainably through transnational cooperation. It addresses barriers such as fragmented responsibilities, unclear legal frameworks, and limited experience with nature-based solutions like wetlands, green infrastructure, and permeable surfaces. Key activities include - mapping stakeholders to clarify roles, - building cross-regional networks of stormwater managers, - hosting workshops on legal and technical challenges, - and developing a joint methodology to apply local ecosystem-based solutions. By sharing knowledge and practical tools, the project will strengthen cooperation, reduce pollution and flood risks, and help cities meet EU water and climate standards. The results will contribute to cleaner waters, climate-resilient infrastructure, and healthier communities across the Baltic Sea Region.