Composite Barrier Systems for Climate Adaptation

Abstract

Composite barrier systems, which are two-layer systems of materials (fine-grained material overlying coarse-grained material) of contrasting hydraulic properties, can be used to mitigate the effects of climate change in urban areas, including flooding and shrink swell deformation. Here, a series of experiments were carried out to test a range of materials, including 20-30 mm gravel, recycled crushed concrete, topsoil, and topsoil amended with water treatment residual (WTR). The consideration of waste products here aims to improve the sustainability of composite barrier systems for climate adaptation. The results indicate that WTR-amended topsoil is suitable for use as a fine-grained material in composite barrier systems owing to its enhanced water retention properties. However, while crushed concrete can be used in the coarse-grained layer to form a capillary barrier when the system is dry, once breakthrough has occurred, transmission of water through the barrier is quicker than in composite barriers with 20-30 mm gravel. As such, 20-30 mm gravel is recommended for use in the coarse-grained layer. Two large-scale, outdoor lysimeters were set-up using the recommendations derived from the column experiments. The lysimeter experiments were subjected to a series of simulated rainfall events to enable initial interpretations of composite barrier performance.