The escalating frequencies and changing patterns of climate change effects such as precipitation rates and sea levels on existing floodplain catchments should raise a red flag regarding the un-coped design and planning criteria that designers and decision makers need to account for. In addition, the sustainability of the engineering infrastructure, which is under pressure from changing climate patterns, is vital. As a result, it is important to continuously assess and appraise the existing infrastructure—for instance, the reliability and resiliency of floodplain catchments—and therefore lessen the threatening impacts and risks. Research on flood emergency management is crucial in order to reduce the potential hazard of life and property loss. A flood impact assessment methodology is proposed and examined. The key technologies include a flood-routing simulation based on a twodimensional (2D) hydrodynamic model and a flood risk assessment based on performance assessment indicators. The 2D hydrodynamic model can quickly calculate flood-submerged areas, floodwater depth distribution and flood-routing times. The flood risk assessment has improved the efficiency of flood emergency management and could offer more help in relation to risk indications. The research results provide a developed tool to analyse flood risk rapidly and ensure that schemes are in place for flood resistance.