Modelling Effectiveness of Green Infrastructures in Urban Flood Management

Abstract

Blue-green infrastructures (BGIs) have been considered as an effective measure to manage urban flooding with multiple hydro-ecological benefits. To recognize the effectiveness of BGIs at multiple scales requires a good model tool that is capable of reproducing the full hydraulic and morphological dynamic processes within the BGIs. Therefore, this study presents a dynamic model tool for assessment of BGIs’ multiple benefits. The model tool is based on two-dimensional (2D) shallow water equations in combination with advection-diffusion equation for fine suspended sediment transport. It is capable of not only predicting hydraulics in BGIs and rivers, but also reproducing the sediment transport processes where water pollutant is generally attached. To demonstrate the capability of the model in benefit evaluation of BGIs, the model is applied to two real-world case studies. This includes: (1) floodplain restoration and its hydraulic effects, and (2) effectiveness of an urban stormwater pond. The study cases involve various flow and time frame scenarios. The simulation results indicate that natural-based approach, such as floodplain restoration and building stormwater ponds, are effective for flow attenuation and sediment trapping. More specifically, stormwater ponds are suitable for more frequent smaller events (< 5-year), whilst floodplain restoration is more effective for extreme flood events (e.g. 30 – 100-year) where more floodwaters can be stored. From longer-term viewpoint, stormwater ponds lose storage capacity which requires maintenance. The model developed in this study is an effective tool for evaluation of BGIs’ effectiveness at various temporal and spatial scales and is applicable to any other similar cases.