Anthropogenic ecosystem of green roofs from the perspective of rainwater management

In Bielsko-Biała (Poland), thanks to the initiative of the originator and architect, a green intensive roof was created on a shopping centre. This roof primarily serves as a garden that enhances the qualities of the residential area, but also as a means of absorbing some rainwater and slowing down the runoff. The water collects in the rainwater retention tank located under the building. Rainwater also evaporates, and its surface runoff is slowed down as it passes through the vegetation on the green intensive roof. This paper addresses some of the operational problems of a selected green roof. The Water Law introduces the obligation to pay chargesfor the reduction of natural terrain retention. Shopping centres usually occupy large areas of land, but their roofs are rarely used for rainwater management and the installation of biologically active surfaces. Green roofs undoubted advantage is the increase of biologically active surface in urban areas. It is also an oxygen--producing surface as well as reducing urban heat islands and attractive place for honeybees and butterflies. The roof in question meets the requirements of a retention facility mentioned in the Water Law Act. It isa multifunctional system for rainwater management. The analysis suggests that the roof under study is nota self-sustaining ecosystem and requires human intervention.