I can't say I'm surprised. Given the greenbelt issues, as well as Highways 413 and the Bradford Bypass through low-lying areas, the risk for flooding is increasing significantly. It's not in the PC's best interest to let this be public knowledge.
Wetlands provide enormous flooding buffers for the rest of society. Paving them over to add new highways or residential areas drastically reduces the infiltration those areas get, and increase the water impact downstream.
I work with drainage and reconstruction/repairs. The design standards for most cities are to match the 5-year rainstorm flow volumes from pre-development to post-development. So if you take the rainfall on a farmers field, for example, and figure out how much water leaves the site into the creeks and ditches nearby during a once-in-5-years rainstorm, you then have to match volume. That means that if you add a bunch of roads, curbs, gutters, roofs, and driveways, none of that area is letting water into the ground, and is actually providing a faster than existing path for the water to get to the creeks, but the total volume needs to be reduce to match. Matching the 5-year rainfall event is great, but flooding concerns at the 50 and 100-year events (or beyond) mean that at those rain volumes, the site is sending waaaaay more water downstream than it would've sent off before it was developed, or the system isn't sized appropriately and will cause flooding there.