Subsidy and grant programmes. In Stuttgart, up to 50% of expenses on erecting rooftop structures are compensated, and in London, there is a system of grants for private projects.
Green index. In London, developers must enact a series of greening and rainwater drainage measures, each of which is evaluated. In order to receive permission to build, a barrier set on a district-by-district basis must be met. Similar indexes are in effect in Berlin, Hamburg, Malmo, Helsinki, Seattle, Washington and other cities.
Changing the tariff policy. In Philadelphia, there is a flexible tariff structure for water drainage. This is a stimulus for those who drain the largest amounts of water to create green infrastructure elements in order to reduce their payments. In Munster, for example, the presence of a green rooftop gives building owners a discount on water drainage rates.