Oral Presentation World Sustainable Built Environment Conference 2026

Can blue-green infrastructure increase the flood resilience of cities? (132597)

Pui Kwan Cheung 1 2 , Marie Dade 2 , Sinead Nicholson 1 3 , Matthew Burns 2 , Negin Nazarian 3 4 , Stephen Livesley 2 , Sebastian Pfautsch 1
  1. Urban Transformations Research Centre, Western Sydney University, Sydney, NSW, Australia
  2. School of Agriculture, Food and Ecosystem Sciences, The University of Melbourne, Melbourne, VIC, Australia
  3. School of Built Environment, University of New South Wale, Sydney, NSW, Australia
  4. Australian Research Council Centre of Excellence for the Weather of the 21st Century, Sydney, NSW, Australia

Urbanisation is often associated with the conversion of vegetated, pervious surfaces to unvegetated, impervious surfaces. This increases the risk of urban pluvial flooding because a larger amount of stormwater runoff will be generated upon rainfall from the impervious surfaces. Urban pluvial flooding occurs when the stormwater runoff is generated faster than the urban drainage system can remove it. Urban blue-green infrastructure is an increasingly popular solution for cities to manage stormwater and flood risk. Many studies have used stormwater runoff volume and peak flow rate to quantify the stormwater benefits of blue-green infrastructure. However, these two metrics are not direct measures of the flood severity and damage. This study has identified two more direct measures – flood depth and flood area. We conducted a system literature review to assess the impacts of implementing blue-green infrastructure on urban flood depth and flood area. We focused on five types of blue-green infrastructure: stormwater harvesting systems, bioretention systems, urban trees, green roofs, and urban parks. Our review found that the median reduction in flood depth across all five types of blue-green infrastructure was 13% (N=11) with urban trees being the least effective (1%) and stormwater harvesting systems the most effective (15%). The median reduction in total flood area was 8% (N=10) with urban trees being the least effective (0%) and green roofs the most effective (38%). We also found that blue-green infrastructure cannot substantially reduce flood depth or area in large floods. However, there is emerging evidence that suggests that the long-term economic benefits of blue-green infrastructure lies on its ability to reduce small and medium floods. More studies are needed to examine the long-term economic benefits of blue-green infrastructure.