Urban areas may develop and change its character over time, but the urban drainage system is often 12 more constant in character – as the technical design life can be up to 100 years. The hydraulic capacity 13 of an existing urban storm water system is affected by future changes, e.g. rate of imperviousness 14 (urbanization), changes in the rainfall characteristics (e.g. by climate change) and system deterioration 15 (pipes and other facilities). Recently the urban planning process in Sweden and elsewhere has become 16 more appreciative of urban drainage issues, and the need to include these earlier in development 17 processes. In this paper a small urban catchment is used to study how future factors affect the 18 hydraulic capacity and the potential development of the area. Factors tested are scenarios of: (1) 19 Urbanization; (2) Climate change and (3) Pipe system deterioration. The results show that each of 20 these factors impact on the hydraulic capacity and that any sensitivity analysis should include all of 21 them to understand future development potential for the area. This type of investigation can increase 22 the understanding of the needs of the infrastructure provision in the area in a planning process context, 23 and provide information about appropriate areas of development within the catchment.