Investigation of Water Flow in Single-Layer and Multi-Layered Constructed Technosols of Green Roof

The performance of constructed soil systems with multiple layers for green roof applications was evaluated in this study. These systems may have advantages over single-layered soils, such as reduced evapotranspiration, increased infiltration, contaminant removal, and plant support. However, the water and solute fluxes across the interfaces between different layers are poorly understood. An experimental set-up of 18 rhizoboxes with two and four-layered soil systems was built on the roof in an open-air setting. Two green roof substrates were used to create the layers. The water balance components were measured to assess the hydraulic functioning of the soils. Invasive and noninvasive methods were applied to investigate the phenomena of capillary barrier, finger flow, and air entrapment in the multi-layered soils. Retention curves of substrates were determined. A modeling approach for water and solute fluxes in natural soils was adapted to multi-layered constructed soils. The results of the first six months of monitoring are presented and discussed. The study should provide valuable insights into the design and management of green roofs with multi-layered soils.