A stormwater system, Bay Meadows in San Francisco Bay Area. Credit: Jack Mong

+ The challenge for green infrastructure now is delivering at a scale and pace that cleans our waterways and combats climate change.

More and more cities around the world are adopting green infrastructure, which uses trees, soils and other planting to manage urban water by mimicking the natural hydrological cycle. 

Done well, green infrastructure reduces flooding, improves water quality and replenishes groundwater. It also brings multi-faceted benefits such as beautifying neighbourhoods, increasing property values, reducing the heat island effect and absorbing carbon dioxide.

Today, with green infrastructure being implemented in both new-build and retrofit projects at varying scales, I think it may have finally become the new normal. It is no longer the alternative strategy for consideration. This follows decades of evolution from practitioners, agencies, academics and standards. 

Many places are making great use of green infrastructure. New cities are planning for more green space to reduce environmental impact while promoting the public realm. For example, New Songdo City in South Korea was a new city planned and built with 40% green space.

Existing cities are doing good work too. The Llanelli Green Infrastructure Project in Wales uses a unique retrofitting approach to flood risk management that relies on water sensitive urban design.

New York City is aiming to invest US$2.4bn in green infrastructure over the next 20 years. It’s planning over 7,000 “curbside gardens” in the streets to reduce combined sewer overflows.

Meanwhile, Washington DC has implemented a stormwater credit trading programme that encourages retention of stormwater on-site to mimic the natural water cycle.

For planners and engineers involved in green infrastructure, it’s an exciting time. The challenge until recently was gaining consensus, developing guidelines and finding success in pilot projects; the challenge now is delivering at a scale and pace that cleans our waterways and combats climate change.

There are still some hurdles to overcome. For example, there needs to be a better understanding of financial mechanisms and economic models that can enable green infrastructure to be adopted at a wide scale. And appropriate models need to be identified for different cities. 

Maintenance is always the number one concern, but cities are seeking partnerships with other agencies, private organisations and the general public to ensure long-term performance. 

Green infrastructure design standards will continue to evolve as research, lessons learned and monitoring results accrue. Cities must continue learning from each other. And cross-agency design standards for green infrastructure are also essential; as this is a unified, multidisciplinary (and multi-agency) effort. 

In October 2014, the White House identified green infrastructure as a priority. After decades of shifting the way we manage water in cities, a new normal has been achieved and the debate is over. Now we need to build on this new normal and push forward with research, partnerships and innovation.