Floods in Odense

sustainable

I think a combination of both systems is the best solution.

sustainable drainage

I would prefer the sustainable drainage. Because the sustainable would mean more nature, more recreational areas, at the same time working a practical purpose with low maintenance costs (new sewage costs a lot).

Conventional... cause its already there.

If I only could choose one: sustainable system, because it works and it create a different atmosphere and have other benefits such as reducing peak flows and cleaning water. But I think both systems could work very well together.

Sustainable drainage system

The sustainable system. Because it naturally infiltrates to the groundwater and it would be very beneficial for the society with more green recreational areas.

I would chose the most efficient.

hmm, that depends...