The impact of climate change, water scarcity, land use change, population growth and also population shrinking can only be predicted with uncertainties. Especially for assets with a long planning horizon this is a critical part for planning and design. One solution is to make centralized organized water infrastructure with a long-planning horizon resilient and adaptive. For existing centralized infrastructure such a transition would be to increasingly implement decentralized measures. But such a transition can cause severe impacts on existing centralized infrastructure. Low flow conditions in urban drainage systems can cause sediment deposition, and for water supply systems water age problems may occur. This work focuses on city-scale analysis for assessing the impact of such measures. For that a coupled model for integrated city-scale analysis is applied and further developed. In addition, a geographic information system (GIS)-based approach for sensitivity analysis is enhanced and also implemented in that model. The developed approach is applied to assess the water infrastructure of an alpine case study. With the obtained results it is demonstrated how the planning process is enhanced by indicating where and where not to implement decentralized measures in an existing water infrastructure.