Hydrological Performance of Green Roofs

There should be a balance between artificial environment and natural environment. As forests, fields, gardens and urban lands are being replaced with bituminous, concrete and unnatural surfaces, necessity of recovering green and blue spaces and natural areas is becoming more and more critical. Green roof is a tool in strategy of making more pervious areas and beating more impervious areas. Green roof is lately becoming part of urban storm water management. Considering this fact, new construction solutions help green roofs become blue roofs. Typical green roof is becoming an increasingly popular solution of impervious roof top of the building. New construction solutions with temporary water reservoirs help the original green roof become retention blue roof. Storm water management should enable the natural processes to infiltrate, evapo-transpire or capture and use storm water on or near the site, potentially generating other environmental benefits. The water cycle should be managed to close the loop, although this is not always possible. Rainwater needs to be harvested and recycled. Surface water needs to be retained within the site and returned to the land for the recharging of groundwater by means of filtration beds, pervious roadways and built surfaces, retention ponds and bio- swales. Water used in the built environment needs to be recovered and reused wherever possible. The aim of this article is to lay out technical specifications of different green roofs in terms of water retention, discharge coefficient and water storage. In this article, different roofs with vegetation on the top of the roofs are described. Diverse roof layers creating diverse roof constructions have different features. Capability of different roofs for catching rainwater, reducing pollutants, compared to typical water runoff, entering watershed and keeping liters out of the city sewer system are one of the main goals of this article. Novelty in co-operation of landscape and dwelling is bringing nature to the city, making green and blue fashionable, making green-blue roof fifth living façade of the building, designing healthy and vegetated towns. Very old method of improving sustainability is introducing green and blue key elements in the environmental strategy