Flood susceptibility measures the likelihood or propensity of a specific area to experience flooding based on its intrinsic, static environmental characteristics such as terrain, soil type, and drainage patterns. It is expressed as a percentage (0–100%) where higher values indicate a greater inherent susceptibility to flooding, independent of specific storm events or sea-level scenarios. The dataset is produced by Natural Resources Canada as part of the National Flood Susceptibility Index (2015).

The FSI is distinct from coastal flood risk projections, which model the extent of inundation under specific sea-level rise and storm surge scenarios. Flood susceptibility reflects intrinsic landscape vulnerability, while coastal flood risk reflects event-driven hazard. Properties with high susceptibility may be at elevated risk of surface water flooding, slow drainage, or waterlogging even during routine precipitation events.