Is it fair to require the individual house owners to pay for their own sustainable drainage system (green roof, natural infiltration, rain water basins), without any kind of contribution?
Yes to some extend but it is not realistic. There should be some nice advantages to do so and a legal requirement.
No.
That depends on if they are obliged to obtain a sustainable system. Else the income should be taking into account so everybody is equally positioned towards paying for the system.
no
No. But it is also a very big problem that the municpalities have problems with maintening the installations at private households. That is a problem with this technique.
No. As I see it, it is not the house owners who are the problem but the whole society. Infrastructure, parking places etc. prevent the water from infiltrating.
No. It should be finansed through taxes somehow. Maybe people should be able to obtain bonuses by acting more green (e.g. by investing in a green roof)
For the last question: I'm studying environmental technology
Yes if they then is given a reduction in taxation because of reduced amount of water going to the water treatment plant fom there ground.
It's hard to tell. It depends on the income of the individual owner. Expenses could be shared amongst the citizens in the form of a taxation system.
No. The succes of the system depends on the participaction of everyone. The guy who has paid for his own drainage system should not suffer because the neighbor has not.
Sustable drainage systems should therefore be plant and carried out by the municipalities