Flooding is one of the most frequently occurring and damaging natural disasters worldwide. Quantitative flood risk management (FRM) in the modern context demands statistically robust approaches (e.g. probabilistic) due to the need to deal with complex uncertainties. However, probabilistic estimates often involve ensemble 2D model runs resulting in large computational costs.Additionally, modern FRM necessitates the involvement of a broad range of stakeholders via co-design sessions. This makes it necessary for the flood models, at least at a simplified level, to be understood by and accessible to non-specialists. This study was undertaken to develop a flood modelling system that can provide rapid and sufficiently accurate estimates of flood risk within a methodology that is accessible to a wider range of stakeholders for a coastal city – Can Tho city, Mekong Delta, Vietnam. A web-based hydraulic tool, Inform, was developed based on a simplified 1D model for the entire Mekong Delta, flood hazard and damage maps, and estimated flood damages for the urban centre of Can Tho city (Ninh Kieu district), containing the must-have features of a co-design tool (e.g. inbuilt input library, flexible options, easy to use, quick results, user-friendly interface). Inform provides rapid flood risk assessments with quantitative information (e.g. flood levels, flood hazard and damage maps, estimated damages) required for co-designing efforts aimed at flood risk reduction for Ninh Kieu district in the future.