Nature Based Solutions to support urban regeneration and resilient placemaking
- Joshua Gittins
- Jul 19, 2024
- 7 min read
Updated: Aug 2, 2024
An overview
© Arup – Mansfield Sustainable Urban Drainage System[1]
Nature-based Solutions (NbS) leverage nature and the power of healthy ecosystems to protect people, optimise infrastructure and safeguard a stable and biodiverse future[2].
In this article we introduce the concept of NbS, the benefits brought by these interventions and the key legislation for the implementation of NbS projects in the UK. We further provide an example of a type of NbS (stormwater parks) to exemplify how towns and cities across the UK can adopt NbS for urban flood risk management.
What are Nature-based Solutions?
The suite of NbS available is wide-ranging and complex, yet the principle is simple:
Measures to reinstate natural processes or enhance existing infrastructure to embed natural ecosystem processes within their function to address ‘societal challenges’.
This principle can be applied in an urban, peri-urban or rural context, and aims to benefit people and nature simultaneously.
‘Societal challenges’ encompasses a broad spectrum of issues including climate change, social cohesion, flood resilience, water security, biodiversity and human health. We have provided solutions to these challenges through traditional design and engineering. However, it has been recognised that ‘business-as-usual’ is not sustainable, and we need to tweak current approaches to urban planning and environmental management to be more resilient to increasing challenges and reverse trends.
The International Union for Conservation has pioneered a ‘global standard’[3] for NbS, to support practitioners with the development and delivery of NbS in an effective manner (i.e. long-lasting, economically viable, and realisation of multiple benefits). It recognises that NbS can be as diverse in their design and scale as the societal challenges they have been designed to combat.
Some examples of NbS, depending on their location:
Urban greening (e.g. green/living walls or roof structures, pocket parks);
Sustainable urban Drainage Systems (SuDS) (e.g. tree pits, attenuation ponds and rain gardens);
Upstream Natural Flood Management (e.g. soil management, river restoration).
These examples, fall on a ‘Grey to Green’ continuum of NbS, reflecting their integration with existing infrastructure (e.g., implementation during different design stages) and the existing natural processes present at a site.
The ‘Grey to Green’ continuum[4] ranges from a traditional ‘Grey’ Project or Scheme (e.g. constructed with little or no ecological consideration) to ‘Natural’ (e.g. naturally occurring habitat). In the context of NbS, however, the ambition is to re-integrate natural ecosystem function into non-natural land-use. And therefore, NbS sits in the middle of the Grey to Green’ continuum (e.g. Green grey solution, hybrid solution, prompted recovery).
Benefits and making the case for Nature-based Solutions
Interventions adhering to NbS principles should be optimised based on project goals, drivers and context. Despite this, they are known to deliver multiple benefits (or ‘co-benefits’) rather than just addressing the specific ‘challenge’ they have been implemented for and provide community resilience[5].
For example, a green wall may benefit biodiversity by providing a corridor for pollinators, but in addition may provide localised air quality improvements, temperature regulation countering urban heat island effect, and placemaking benefits related to physical and mental health and wellbeing.
The implementation of NbS can also make significant cost-savings in the long-term. Potentially lower up-front expenditure and lower long-term operating and maintenance costs are an attractive proposition. So, what’s the downside?
There are some considerations that need to be accounted for when thinking about delivering NbS interventions:
They are novel: NbS can be considered ‘uncertain’ by regulators in how they can deliver a service to a particular agreed standard – or they can be thought to be complex systems in terms of measuring and evidencing benefits. Early engagement with regulators and consenting bodies is usually advised.
Accounting for their benefits: traditional business case models require the measurement, quantification and monetisation of specific benefits. As discussed above, at times it can be complex to account for the wide range of benefits brought by NbS. Working together in a multi-disciplinary team can be useful to evidence properly the value of a wider range of benefits in a business case.
They require strategic thinking: addressing the challenges of uncertainty and benefits accounting is best done by looking to deliver at-scale. Effective stakeholder engagement and strategic planning (e.g. longer term, more joined-up within and with neighbouring Local Planning Authorities) to align more localised efforts can be beneficial.
Capturing and accounting for the ‘value’ of these multiple benefits is one of the significant challenges for NbS delivery, especially under difficult funding conditions. The HMT Green Book[6], DEFRA’s Enabling a Natural Capital Approach (ENCA)[7] and the UKGBC Value of Urban Nature Based Solutions[8] (amongst others) provide resources and guidance for the economic valuation of the environment in the UK. However, traditional business case methods find it difficult to demonstrate whether there is an appropriate business case to spend capital investment, public or private, on NbS implementation due to uncertainties around ‘when’ and ‘how much’ benefit related to NbS will be realised. This requires those looking to implement NbS to get creative, and work with a multi-disciplinary team to understand the value of these multiple benefits (e.g., using Natural Capital tools).
If done well, the potential investment profile of implementing NbS is associated with accumulating benefits over time (e.g. habitat matures, ecosystem processes reinstate). Where there is a consistent initial capital cost, transitioning to operating and maintenance costs at an equivalent level or lower. This differs from traditional grey infrastructure, where there is a large upfront capital cost as the benefit is realised, then operating and maintenance costs to maintain performance to a set standard. Overall, grey infrastructure costs would likely be higher, and the benefit capped at the design standard. Whereas multiple benefits from an NbS solution may continue to accumulate, and adaptive management be better able to tweak the outcomes or benefits to match the required challenges.
The complexity of funding and implementation are key risks to the effective delivery of NbS. We want to avoid practitioners feeling like they cannot pursue NbS due to funding constraints – and ‘dilute’ the design of NbS to solve a hyper-focussed, solitary problem if constrained by funding. Long term planning and multi-disciplinary input is required to avoid these.
Cityscape Nature-based Solutions – Opportunities for nature-driven design under a new legislation
High-density urban planning and development management has more recently been challenged with integrating and restoring nature in England [9],[10]. Given the spatial constraints, demand for services, and shrinking budgets, this is a significant challenge and perceived barrier to NbS implementation. However, strategic retrofitting schemes, nature-driven re-development, and the creative use of multi-functional areas all offer opportunities to re-balance nature in towns and cities, for people.
The Environment Act (2021)[11] is now the dominant legislative driver of nature recovery linked to development in England – a driver which can benefit from the early adoption of nature-driven design and the implementation of NbS. Especially important for urban centres, the implementation of NbS in line with an understanding of the new Biodiversity Net Gain Statutory Metric can ensure that development delivers the required improvements for habitats. Potentially coupled with the ability to generate a surplus of Biodiversity Units to fund wider regeneration projects. Local Nature Recovery Strategies[12] are now the mechanism seeking to coordinate these actions at a strategic scale.
‘Sustainable urban Drainage Systems’: An example of NbS in urban settings
Conventional engineering strategies to reduce urban flood risk, such as stormwater storage, have enormous capital and maintenance costs attached. Despite being effective at combatting flood risk, they have little to no benefits outside of their primary function. In contrast, an approach used to manage urban flood risk management via NbS can be to create a SuDS, utilising a network of green-spaces created to allow water to drain into the underlying soil but also provide wider recreational and biodiversity benefits. These multifunctional areas provide space to socialise and exercise, but are designed to accept floodwater during storm events to alleviate flooding in other areas of the city.
Using pockets of purposely created semi-natural habitats (e.g. grasslands, wetlands) to store water during a storm can also help to treat the water, boosting water quality and the associated biodiversity. A network of multifunctional SuDS, designed at the strategic scale for a town or city, showcases how reinstating natural processes can be as effective as their ‘conventional engineering’ counterparts with the key difference of providing long-term savings and co-benefits.
Mansfield’s case study is a good example to illustrate the implementation of NbS in an urban setting[13]. To address major risks of urban flooding and watercourse pollution, Mansfield, in central England, is placing SuDS across the town. Arup helped design and implement an urban flood resilience scheme based on biodiversity interventions instead of traditional systems, turning the entire town into a sponge[14]. Some of the benefits brought by this system include managing surface water and reducing risk of future flooding, providing resilience to climate change. To date, Mansfield SuDS is the largest retrofit of blue-green infrastructure in England – creating up to 6.5 hectares of additional green space in Mansfield, storing 58 million litres of surface water (the equivalent of 60% of anticipated network storage requirement by 2050).
The success of any city-scale NbS project hinges on the ability of a diverse suite of people to come together, with a shared vision for realising the multiple benefits that nature can provide as a fundamental pillar for long-term resilience. The value-added of a nature-centred approach to urban regeneration provides an attractive strategy towards building thriving towns and cities in the UK.
Josh Gittins is a Senior Scientist, working for Arup’s Climate & Sustainability Services based in Bristol. He specialises in the restoration and recovery of the natural environment, and how we can implement nature-based solutions across the built environment to better facilitate sustainable development. Josh has a diverse background, having worked across academia, consultancy and the public sector on environmental consenting and urban planning challenges straddling England and Wales.
If you have any questions on this topic, or would like support, please contact your Delivery Associate, or email DeliveryAssociatesNetwork@Arup.com
References and footnotes
[4] © Martin et al., 2021. Catalyzing Innovation: Government Enablers of Nature-Based Solutions. Sustainability: 13(4). DOI: 10.3390/su13041971
[6] Paragraphs 6.45 to 6.51 (‘Assessing and valuing effects on the natural environment’) are particularly relevant are particularly relevant for guidance on monetising the environment, alongside Annex 1, paragraphs A1.2 to 29 (Non-market valuation: Environmental and natural capital).
[7] The ENCA provides multiple resources and datasets which can be useful including overall guidance, an assessment template, a services databook, an assets databook, some featured tools, and case studies which can be accessed here.
[10] In Wales, ‘Net Benefit for Biodiversity’, a concept imposing similar requirements to BNG, is driven by the Wellbeing for Future Generations (Wales) Act 2015, the Environment Act (Wales) 2016, and the Local Government Elections (Wales) Act 2021. There is a variable approach in Northern Ireland and no specific mandate for net gain of biodiversity through the Planning System for Scotland.
[13] Mansfield sustainable flood resilience | Green recovery | Wonderful on Tap | Severn Trent Water (stwater.co.uk)
