Assessing the resilience of urban drainage systems requires the consideration of future threats that will disrupt the system performance and trigger urban flooding failures. However, most existing resilience assessments of urban drainage systems rarely consider the uncertainties from future urban redevelopment and climate change, which leads to the underestimation of future disturbances toward system performance. This paper fills in the gap of assessing the combined and relative impacts of future impervious land cover and rainfall changes on flooding resilience in the context of a densely-infilled urban catchment severed by an urban drainage system in Salt Lake City, Utah, the USA. An event-based flooding resilience index is proposed to measure climatic and urbanized impacts on flooding resilience from system-level to junction-level, enabling engineers to harvests high-resolution infrastructure adaptation strategies at the vulnerable spots. Impact comparison shows that imperious urban surface induces more effects on the system performance curves by magnifying the maximum failure level, lengthening the recovery duration, and aggravating the flooding severity than future rainfall changes. A nonlinear logarithm resilience correlation is found, and this finding shows that flooding resilience is more sensitive to the land imperviousness change due to urban redevelopment than rainfall intensity change in the case study. This research work predicts the system response to the uncertainties induced by climate change and urban redevelopment, improving the understanding of impacts analysis and contributing to the advancement of resilient urban drainage systems in changing environments.