The rainwater retention mechanisms in extensive green roofs with ten different structural configurations

Abstract

Rainfall infiltration, rainwater retention, runoff and evapotranspiration (ET) are important components of the water balance in green roofs. These components are expected to be influenced by variations in the structural configurations (i.e., substrate layers) of green roofs. This study explores the influence of layered soil and green roof configurations on the rainwater retention capacity (RRC) of the roofs as compared to conventional improvements (i.e., soil conditioning and enhanced substrate depth). Ten different extensive green roof modules were designed by varying the substrate materials, substrate depths, storage/drainage layers and vegetation layers. For all modules, the RRCs ranged from 34 to 59%. The RRCs of layered-soil were 1–4% higher than that for single-layer soil. The RRC increased by 13% in the presence of a water storage module. It can be concluded that highest RRC corresponds to a combination of high-permeability soil in the upper layer along with a relatively large water holding capacity in the deep layer. Water storage layer and layered soil could significantly delay the water stress in vegetation. The importance of wick irrigation, vegetation types, back-to-back rain events and the ET rate on the RRC were also discussed.

Connectors as a Key to Efficient Storm Water Management System: An In-Situ Assessment of Residential Estates in Poland

“…Even better results in retaining the rainwater have extensive green roofs that are promising elements of reducing rainfall runoff [31]. They obtain different results according to the layers and vegetation types [32,33]. According to the research in Opole, about 44% of the rainwater from torrential rains is retained in the layers of the green roof, and in the case of rains not exceeding 5 mm/day [34].…”

GR2L: A robust dual-layer green roof water balance model to assess multifunctionality aspects under climate variability

“…In terms of design, a multitude of green roof types are commercially available. Individual design considerations include the selection of plants, the soil layer-ranging from grow mats to soil substrate-and water storage such as specific retention layers with controlled outlets at specified heights (Pérez and Coma, 2018;Gößner et al, 2021;Wang et al, 2021).…”

“…In order to assess the effect of green roofs for stormwater mitigation or drought resilience their hydrological performance needs to be monitored and modeled. Existing studies provide monitoring-based analyses of evapotranspiration and storage capabilities (Gößner et al, 2021;Wang et al, 2021). In addition, models have been developed based on lysimeter data including smoothing approaches that are often required to cope with high-resolution lysimeter data and the associated temperature or wind-induced noise (Schrader et al, 2013).…”

Evaluation of a Green Roof for Heat Mitigation in a Building Located in a City with a Hot and Humid Climate

“…This phenomenon is global, but it has more harmful consequences in underdeveloped or developing countries, where the lack of adequate infrastructure makes urbanization a major socio-environmental challenge [1]. As the urban population density increases, the demand for new residential and commercial buildings directly influences the conversion of green areas into highly impermeable surfaces [3]. In addition to all the negative impacts resulting from the process of eliminating native vegetation, the expansion of urban land cover has caused an increase in temperature in these areas [4].…”

“…A relatively low-cost solution to reversing the negative impacts of UHIs is the reconstruction of the green area in these regions [8]. In this context, rooftops are elements of special interest, as they represent 20-50% of urban surfaces [2,3,7], and can be considered the elements that most cause thermo-energetic losses in buildings [9]. Green Roof (GR) converts unused roof space into planting areas, providing direct benefits to the building and its surroundings [3,4].…”