Multifunctional climate adaptation measures – Responsibilities, cooperation and challenges Climate adaptation measures within already built-up urban environments is complex, due to several factors. A large number of actors are required for success, but both the responsibility of each actor and the distribution of responsibility between these actors are unclear. Success depends to a large extent on the ability to cooperate between the various actors operating in an area. This project uses interviews, co-production and literature studies to describe the challenges, identify blockages and support the collaboration between the various parties. The project identified uncertainties regarding the laws required to manage climate adaptation measures in built-up urban environments that we needed to address. This resulted in an expansion of the project with a focus on the law around climate risks regarding socially important activities which is presented in Climate adaptation of socially important activities – legal challenges, RISE report 2024:14, ISBN 978-91- 89896-59-8 written by Jenny Lundahl (2024). A newly created collaboration model is presented here focusing on the startup phase. It is supplemented with tips on methods and tools that can facilitate the work, and a description of different ways to sort how to single out responsibilities and where the cost for the measures taken will be localized.