Sea level rise is a new threat facing the coastal city of Boston (USA). Uncertainty around how much sea levels will rise, the effects on storm intensity and frequency, and what impacts these changes will have, make spatial adaptation in coastal cities a challenge that requires new practical and adaptive approaches. However, in landscape architecture, these approaches are currently lacking. This master thesis focuses on contributing to flood risk reduction in Boston by developing such an approach that helps create landscape architectural designs that account for significant uncertainties. The approach functions as a guide in the design process that can help landscape architects shift away from the ambition to achieve static, predefined outcomes and move towards creating adaptive designs. It was partly developed through review of existing planning approaches and draws upon the Pathways Mapping Tool that is turned into an iterative design tool that allows the designer to keep a broad view of all the possible adaptation options and it stimulates designers to look far into the future and think about long-term adaptation options. The design for Boston is used as a case study to test the approach. The case study resulted in an adaptive design for Boston that creates on-going development and improvement of a chosen area, providing it the ability to be responsive to its dynamic environment and adaptable to maintain its functionality. This way, the design accounts for uncertainty and validates the developed approach. The results indicate that the approach could be worthy of replication or broader dissemination, helping the wider global community of coastal cities in trying to address the challenge of adapting to an uncertain future climate.