Study on hydraulic properties of biochar-modified bilayer substrate green roofs

Abstract

[Objective] Rapid urban development has exacerbated flooding and heat island effects, while green roofs can help mitigate these issues, especially as the substrate soil significantly affects stormwater management. A bilayer substrate green roof with biochar-modified soil can effectively improve rainwater management performance. [Methods] Laboratory experiments and numerical simulations were combined to investigate the hydraulic performance of bilayer substrate green roofs. The hydraulic processes under artificial rainfall conditions were observed using test columns, and the inverse solution method was used to estimate the unsaturated hydraulic parameters of the substrate soil. Numerical simulations were conducted to explore the effectiveness of biochar bilayer substrates in stormwater management. [Results] The result showed that different biochar application method exhibited different performance in delaying and reducing peak flow. Under the selected rainstorm condition, the bilayer substrate structure with 3 cm of natural soil and 12 cm of biochar-modified soil demonstrated better stormwater management performance. [Conclusion] The result indicate that modifying soil with biochar and using a bilayer substrate exhibits flexibility and efficiency in green roofs. This provides preliminary guidance for roof greening design, offers a design direction for optimizing stormwater management in green roofs, and lays the foundation for future research.

Keywords

green roofs / biochar / modified soil / stormwater management / bilayer substrate / hydraulic properties / numerical simulation