Bradfield sounds good, but you can't tinker with nature to that degree without some sort of massive unexpected effects elsewhere in the ecosystem. Nature is perfectly balanced as it is. It's people who need to change, by orienting themselves properly around nature. That means not building in low lying flood prone areas. Duh!!!
"But we must have high density inner city living!!"
I'd say: "fine, you build where you like, but don't expect the government to bail you out. Get proper insurance, read your fine print, and away you go".
Where on Earth were the council urban planners when this building was going ahead? It's their job to warn governments of the looming disasters due to improper urban planning.
The solution is extremely simple. Stop trying to make it complicated with nutty schemes and expensive damns.