Human-caused climate change is intensifying the frequency and intensity of heavy rain events. Heavy rains are generally understood as precipitation events with a high amount of rainfall. These events usually occur locally. Due to their high intensity, they can lead to flash floods, floods, erosion and overloading of the sewer network. Although climate change adaptation and adaptation to heavy rain events have become integral items of the climate policy agenda over the last decade, they still pose major challenges for German municipalities. In this thesis, the key challenges hindering municipalities when planning and implementing measures to adapt to heavy rain events are investigated and a novel tool to mitigate these challenges is proposed. The status quo in municipalities and the challenges they face were established using a survey, detailed one-on-one interviews and extensive literature research. On the basis of the results obtained, the hypothesis is formulated that municipal adaptation planning can be improved by instruments that support interdisciplinary communication, capacity building and/or decision-making. A GIS-based planning tool is developed to help planners assess the need for action as well as to determine the adaptation potential of municipalities. The latter includes their capabilities to formulate conceptual plans, which can be used to support decision-making in the adaptation and planning process on the appropriate protective measures to implement. The hypothesis and usefulness of the planning tool were verified in a target group workshop. The overriding root cause of many of the challenges can be found in the lack of legislative requirements or institutional agreements. Specifically, there are challenges posed by existing or non-existing legal bases, coordination mechanisms within and between sectors, unclear roles and responsibilities and differences in planning cultures. These make it difficult to assess the need for action and reach consensus on the cost and effectiveness of individual measures. Uncertainties in climate change projections complicate finding agreement on adaptation strategies, putting existing risk management approaches to the test. Furthermore, climate change adaptation strategies necessarily involve a wide range of stakeholders with different interests and understanding of the issues. These uncertainties affect municipal planning practice. At the municipal level, the main obstacles can be localised in the initial planning phase, the identification of the need for action and the adaptation potential as well as developing options and their assessment. The rather restrained strategy development and implementation to date is attributed, among other things, to scarce financial and human resources, institutional obstacles. Moreover, not only an assessment of cost and effectiveness of protective measures is needed but also instruments and tools to support decision-making processes. Through capacity development, targeted approaches to communication and awareness raising, the creation of a common adaptation culture is achieved. It is important that the different disciplines involved (e.g. water managers & municipal planning) learn from each other in order to build and expand each other's awareness and capacities with regard to climate change adaptation. Tools, methods, technologies and practices can be used to support collaboration and explicit intra-municipal communication. Thereby, synergies are exploited and obstacles and restrictions are recognized early on and can be jointly eliminated. The GIS planning tool developed in this thesis encourages communication and collaboration between planning experts. It is suitable for determining the municipal’s adaptation potentials as well as the need for action during heavy rain events. As such, it contributes to finding a common consensus in issues related to adaptation to heavy rain events
