Experimental study on the hydrological performance of green roofs in the application of novel biochar

• Published in: Hydrological processes 2020-11, Vol.34 (23), p.4512-4525
• Main Authors: Huang, Shan, Garg, Ankit, Mei, Guoxiong, Huang, Disheng, Chandra, Rahul Balaji, Sadasiv, Shaji Gayathri
• Format: Article
• Language: English
• Subjects: biochar; Carbon sequestration; Charcoal; detention; Green buildings; green roof; Green roofs; Heavy rainfall effects; Hydraulic conductivity; Hydraulic performance; Hydraulics; Hydrologic processes; Hydrologic studies; Hydrology; Moisture content; Nutrient cycles; Nutrient retention; Parameter estimation; Permeability; Ponding; Rain; Rainfall; Rainfall simulators; Rainmaking; Retention; Roofs; Runoff; Soil; Soil amendment; Soil columns; Soil improvement; Soil investigations; Soil permeability; Soil suction; Soil water; Soil water potential; Soils; Sustainable design; vegetation; Water content; Water potential
• ISSN: 0885-6087; 1099-1085
• DOI: 10.1002/hyp.13881

Biochar has the potential to be a soil amendment in green roofs owing to its water retention, nutrient supply, and carbon sequestration application. The combined effects of biochar and vegetated soil on hydraulic performance (e.g., saturated hydraulic conductivity, retention and detention, and runoff delay) are the crucial factor for the application of the novel biochar in green roofs. Recent studies investigated soil water potential (i.e., suction) either on vegetated soil or on biochar‐amended soil but rarely focused on their integrated application. With the purpose of investigating the hydraulic performance of green roofs in the application of biochar, the combined effect of biochar and vegetated soil on hydrological processes was explored. Artificial rainfall experiments were conducted on the four types of experimental soil columns, including natural soil, biochar‐amended soil, vegetated natural soil, and vegetated biochar‐amended soil. The surface ponding, bottom drainage and the volumetric water content were measured during the rainfall test. Simulation method by using HYDRUS‐1D was adopted for estimating hydraulic parameters and developing modelling analysis. The results indicated that the saturated hydraulic conductivity of vegetated soil columns were higher than bare soil columns. The addition of biochar decreased the saturated hydraulic conductivity, and the magnitude of decrease was much significant in the case of vegetated soil. The influence of vegetation on permeability is more prominent than biochar. The vegetated biochar‐amended soil has the highest retention and detention capacity, and shows a preferable runoff delay effect under heavy rain among the four soil columns. The results from the present study help to understand the hydrological processes in the green roof in the application of biochar, and imply that biochar can be an alternative soil amendment to improve the hydraulic performance. The hydrological performance of green roofs in the application of novel biochar was evaluated and discussed in context on the basis of the experimental study and simulation analysis.