Using a Hydrological Model to Simulate the Performance and Estimate the Runoff Coefficient of Green Roofs in Semiarid Climates

• Published in: Water (Basel) Vol. 10; no. 2; p. 198
• Main Authors: Herrera, Josefina, Flamant, Gilles, Gironás, Jorge, Vera, Sergio, Bonilla, Carlos, Bustamante, Waldo, Suárez, Francisco
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-02-2018
• Subjects: Analysis; Architectural design; Climate; Climatic conditions; Computer simulation; Green buildings; Green development; green roof; Green roofs; Hydrologic models; hydrological model; Hydrology; irrigation need; Moisture content; Precipitation (Meteorology); Rainfall; Roofing; Roofs; Runoff; Runoff coefficient; semiarid climate; Semiarid climates; Soil dynamics; Soil moisture; Soil testing; substrate moisture; Substrates; Sustainable design; Urban environments; validation; Water content; Water demand; Water depth; Chile
• ISSN: 2073-4441; 2073-4441
• DOI: 10.3390/w10020198

Green roofs offer a series of benefits to buildings and to the urban environment. Their use in dry climates requires optimizing the choice of their components (i.e., vegetation, substrate and drainage layer) for the specific local climatic conditions, in order to minimize irrigations needs while preserving the attributes of the roof. In this study, we calibrated and validated an existing hydrological model—IHMORS—for the simulation of the hydrological performance of green roofs. Simulated results were compared to experimental data obtained in an outdoor test facility on several green roof specimens, representing a variety of green roofs configurations. IHMORS was able to reasonably predict the soil moisture dynamics for all tested specimens. The specimens of 10 cm depth were the best simulated by the model, while some overestimation was observed during the model validation for the 5 and 20 cm depth specimens. The model was then used to estimate the number of days in which irrigation is needed, as well as analyze the water runoff control performance of all specimens. We related the amount of water retained by the substrate and depth, magnitude and intensity of precipitation event, and the initial substrate moisture. For all events, the lowest runoff coefficient was simulated for the 20 cm specimens. Our study showed the full potential of the model for estimating the water needs and the runoff control performances of different variants of green roofs.