Impact of "green" roofs on rainwater management: review of scientific research and perspectives of use

Abstract

The multifaceted advantages of "green" technologies are analyzed, one of which is the effective management of rainwater in urbanized regions, which allows solving a number of important problems, such as: local waste disposal; reduction of runoff volumes due to evapotranspiration from vegetation and open surfaces; retention of rainwater in the soil; reduction of peak flow values due to temporary storage of water in the substrate and drainage layer; improving the quality of rainwater, which then falls into the soil or is collected in separate reservoirs for further use for technical or domestic purposes. Based on the analysis of experimental studies by world-class scientists, it is shown that for extensive "green" roofs, the average efficiency of rainwater retention is estimated between 45% and 60%, and the cumulative annual retention is about 50% and 60%, depending on the local climate. The results of a study on determining the degree of reduction of rainwater runoff from the surfaces of "green" roofs, which were conducted on two model roofs (extensive and intensive) in Poland, are given. It is well-founded that the rainwater absorbed by the layers of the "green" roof slowly evaporates over a long period of time, which means maintaining a more stable relative air humidity in the vicinity of the building. The method of determining the amount of rainwater runoff from the surface of "green" roofs, as well as determining the daily load of rainwater drainage on the analyzed site, is presented. It was established that about 44% of rainwater from torrential rains is retained in the layers of the "green" roof, and in the case of an intensity not exceeding 5 mm/day, rainwater is completely retained by both intensive and extensive roofs. The advantages of "green" technologies in the process of filtering rainwater, which can be collected in tanks and used for technical needs, are considered. The prospects of rainwater management using "green" roofing systems on roofs in different countries of the world and, in particular, in Ukraine, were analyzed. The ranking of the total area and density of "green" roofs used for rainwater management in different cities of the world for 2022 is given. The authors developed and presented a recommended system of measures for the development and implementation of "green" roofs in Ukraine.