FABDEM

FABDEM (Forest And Buildings removed DEM), from the University of Bristol and Fathom, takes Copernicus DEM GLO-30 and uses machine-learning height-correction to remove building and vegetation canopy bias — the single biggest source of error when a raw surface model gets fed into a flood or drainage model expecting bare-earth terrain.

For 2D hydraulic and floodplain modelling at global/national scale, FABDEM is frequently the best free option available, and it has become a common baseline in flood-model benchmarking literature. Free for non-commercial use (CC BY-NC-SA 4.0); commercial licensing is available as FABDEM+ through Fathom.