The editorial incorrectly mixes up large scale riverine floodplains and the overland flooding risk the IBC completed to identify 1.8M properties with other types of urban flood risk, beyond river valleys. IBC hired JBA Risk to do 'table land' overland flooding analysis - just a rough estimate of what happens in cities when runoff weaves off roads and between houses during extreme rainfall. That analysis ignored the municipal pipe network underneath so not actually useful to  engineers engaged in flood mitigation at all - and IBC won't share the risk data with municipalities, even if aggregated to forward sorting areas (1st 3 characters of postal codes). The bottom line is no policies should be determined based on the IBC risk "guesstimates". Most urban flood risk is related to sewer pipe back-up that was omitted from the IBC work.

Here is mapping of overland flood risk mapping in Toronto (engineers share):
http://www.cityfloodmap.com/2017/01/city-of-toronto-overland-flow-map-100.html