Learning from the US for Green Infrastructure delivery in the UK

Working in a company with over 40,000 employees around the world provides some interesting opportunities for collaboration. Following discussions with a few cities in the UK around water management and resilience I got in contact with the team delivering green infrastructure in the US.

I posed some of the questions from one city to Andrew Reese, who has been leading stormwater management work for 30 years in cities including Philadelphia, Atlanta, Charlotte, Nashville and others.

Examples of Green Infrastructure in Atlanta (Rayburn and Reese, 2014)

Questions on Green Infrastructure (GI) implementation in the USA

Are US cities driving GI/ SuDS programmes for flood risk management (rather than water quality as a side benefit of flood risk management)?

Flood risk isn't really driving programmes in the US but is increasingly being seen as a benefit of programmes. Stormwater management and combined sewer overflows or CSOs are the main drivers linked to water quality. Green infrastructure is showing flood risk reduction benefits for retrofit rather than new large-scale flood control programmes. An example is underground injection wells linked to high infiltration speed rain gardens have been used successfully in Seattle.

Resilience planning has led to more GI for flood risk management. Examples from Los Angeles and Atlanta include digging up whole streets and integrating gravel catch basins, which can capture stormwater for a whole neighbourhood in one street.

How are US cities managing to limit unwanted distributional impacts of bill rises to pay for the work?

Amec Foster Wheeler have worked on over 70 stormwater use fee programmes. By providing residents with the option for credits on GI for their property this helps address increases in fees. Another option has been rate relief programmes for means tested poor individuals (e.g. food stamps) which can be paid for by a voluntary rounding up of customer bills and placing this into a fund or through direct application to the utility. Nashville and Philadelphia have well developed credit and incentive mechanisms.

What are the lessons we need to learn/ be aware of that don't appear in best practice guides/ case studies?

The main problems in the US in order are:

1. Issues from poor construction practice; 
2. Early maintenance not undertaken; 
3. Poor design. 

The Atlanta stormwater design guidelines provides a good example of best practice used on over 1400 projects to date, not just for the guidance, but where the use of inspectors and assistance during construction helped to ensure the right processes were put into place and that stormwater features were adequately stabilised over time. Two inspection visits during construction led to significantly lower failure rates. Similar examples exist for the pacific North West where pipes and guidance were provided for domestic projects or in Nashville to support 600 raingardens. This additional support has been essential for implementation but isn't captured in the guidance alone.

How will the new GI estate be managed in a drought?

Special designs have been developed in the Western USA using native plants and xeriscaping. From a UK perspective I think we need more research into the performance of biotention systems during drought, however they can be designed to hold back smaller rain events and use these to keep plants alive during drought as is the case in Australia. Stormwater reuse for irrigation has been a wider use of GI in Melbourne.

Implications for the UK

Climate change and population growth are placing increasing pressures on water management in urban approaches. Following the 2007 floods the Pitt Review led to the development of the Flood and Water Management Act 2010 and subsequent requirements in planning for green infrastructure through sustainable drainage systems (SuDS). However, issues remaining for implementation include the need for better partnership and funding arrangements, research and guidance development to support best practice, and more effective adoption and long term maintenance of these features.

The stormwater utility fee approach may provide an opportunity for water companies in the UK to address increasing impermeable surfaces and urban creep. However, this would need to be balanced against existing issues of water poverty in the industry. A similar approach has been applied in the UK by water companies offering social tariffs and water efficiency options for customers who have a water meter compulsorily installed (Southern Water is one example).

As we deliver large scale SuDS retrofit programmes and incorporate these into planning for new developments we should ensure sufficient support and capacity building is provided around the guidance to reduce failure rates. The experience from the US further supports capacity building organisations and initiatives in the UK.