Reducing flood risk through the modelling of Nature-Based Solutions

An innovative solution is now available for water utilities operators who are looking to appraise the benefits of Nature Based Solutions (NbS) for reducing flood risk.

NbS are becoming more widely recognised as a pragmatic and cost-effective approach to flood risk management, which often has the added benefit of enriching ecosystems, improving aesthetics, and enhancing amenity value.

Hard engineering will always have a key role in urban drainage design, but it is possible to use natural processes to augment and sometimes replace traditional methods. The challenge of using NBS has, until now, been the difficulty in knowing where best to situate them and assessing their positive impacts.

Flood risk modelling experts Ambiental, a company of Royal HaskoningDHV Digital, has formed a successful partnership with Viridian Logic who provide Natural Flood Management and ecosystem service solutions for valuation, planning, and decision support. In combination they have developed a unique modelling solution which is used for prioritising NbS. It allows customers to design the most effective NbS in the best locations to solve their target problems.

Using NbS to reduce flooding for natural flood management can be low-cost, resilient to climate change and offer a host of other benefits to people as well as wildlife. Traditionally, the design of NbS has relied on Geographic Information Systems (GIS) which can lead to inappropriate solutions sited in the wrong places. Through collaboration the two companies have solved this problem by amalgamating GIS and hydrology into a single modelling system, which can determine which natural solutions to create and where best to create them to reduce flooding most effectively.

Maximise return on investment for nature-based solutions

The joint Ambiental-Viridian approach identifies ways to reduce flooding as efficiently as possible and then quantifies the benefits that the various options will deliver. This is well aligned with a growing desire by water utilities providers for natural solutions to flooding that can also deliver co-benefits. The joint offering, which can be delivered in combination with Ambiental’s suite of flood risk management tools, is able to determine the optimum solutions for reducing flood damage, minimising the cost of defences and maximising additional benefits.

The images show examples from Kent, UK of how the FloodNbS model outputs can be used to identify beneficial catchment interventions such as hedgerows and leaky dams.

The service offers a phased approach that reduces cost at each stage of the process – from initial broad modelling for stakeholder engagement, through to more detailed design. It can integrate flood, drought, diffuse pollution and erosion with all the non-water nature-based services such as carbon, biodiversity etc. This helps water companies to meet multiple objectives from the same interventions.

FloodNbS outputs a detailed ranking of all potential NBS solutions across a catchment, assessing how effective they will be within local constraints. The flood hazard maps, and risk analytics data demonstrate how reductions in flood risk can be achieved through any combination of the highest ranked solutions.

Using this approach it is possible to integrate NbS with traditional engineered approaches to get holistic, best value solutions. It can help reduce sewer loadings from overland and groundwater inundation and reduced pumping costs. It supports Smart Landscape Design initiatives where NbS is used to deliver diverse benefits to multiple entities who can each contribute to the implementation cost.

Angus Middleton, Commercial Director of Viridian Logic explains that “this unique capability helps bring together new and innovative, natural flood mitigation approaches with the traditional, engineered flood protection methods. Furthermore, it can identify co-benefits such as improving water quality and connecting disparate habitats, which in turn helps with scheme acceptance and potentially unlocks alternative funding streams”.

Justin Butler, CEO of Ambiental Risk Analytics, a company of Royal HaskoningDHV commented, “In combination with the well-established Flood modelling, engineering and Sustainable Urban Drainage Systems (SuDS) services available through Ambiental and Royal HaskoningDHV, it is felt that this new capability further unlocks the potential for using natural solutions for mitigating flood risk as well as improving environmental performance in land use planning and redevelopment markets”.

The service is currently used by water companies in the UK to demonstrate the impact of NbS interventions on reducing peak flood flows and alleviating flood risk to drainage infrastructure and the communities which they serve. James Airton, Natural Capital Strategy and Planning Manager, Environment and Asset Strategy, at United Utilities stated that “We have been really impressed with the tools. The quality of the mapping and modelling work has been fantastic”.

The modelling service is also helping organisations unlock funding opportunities through providing a strong evidence base for proving the benefits of NbS. The partnership is exploring the potential for providing these services internationally and it serves as a strong example of how through innovative collaboration we can improve the natural world and enhance society together.