Quality Mark: Can EIA policy alone prevent flooding?

Daniel Allum-Rooney argues for a more flexible approach to flood risk management

Flooding is a natural process that has shaped our environment since long before humans started to exploit the fertile land it created. It is only through the encroachment of the built form that flooding started to impact our way of life and became the issue that is prevalent across the world today.

The issue of flood risk and development has come to the fore with the failing of flood defence infrastructure around Wainfleet, Lincolnshire, in June 2019. Elsewhere across the county, there were hundreds of reports of localised flooding after intense rain storms.

Inevitably, questions arise. Why are these areas susceptible to flooding? Why are so many homes and businesses at risk? This article looks at flood risk policy in the context of recent events, and explains why it is important that we adapt for the future. We try to resolve flooding problems through specialist engineering but, inevitably, nature has the last word. We need to take heed and work with natural forces, not against them. Specific flood risk policy has been incorporated into planning and development for around 20 years, initially starting with Planning Policy Guidance Note 25. Policy has always been centred around the hierarchy of Avoid > Mitigate > Compensate, encouraging new developments in areas that are at the lowest risk of flooding (Flood Zone 1). Where this is not possible, policy dictates that suitable mitigation is provided to ensure that flood risk can be managed in new developments, and that appropriate compensation is included so there is no cumulative detriment on floodplain storage or conveyance.

Environmental impact assessments (EIAs) focus on the impact not only to the proposed development, but also to the local area – including the potential for cumulative impacts. Information available on flood risk now includes Environment Agency mapping, Strategic and Preliminary Flood Risk Assessments and anecdotal evidence of previous flood events. They must consider all reasonable future scenarios, too, including climate change, failure of flood defence infrastructure and changes to flood management strategies.

This is highlighted in events such as Wainfleet where – ordinarily – engineered, raised defences protect the area from flooding. When these failed, nearly 600 homes were evacuated, and up to 130 properties flooded. New developments will need to consider that such a breach event could occur, and make sure mitigation is proportionate to the risk posed. However, as highlighted by Environment Agency chair Emma Howard Boyd, in her statement when releasing consultation on draft flood strategy for the future: “We can't win a war against water by building away climate change with infinitely high flood defences“.

Managed retreat is one option for dealing with future flood risk, but as the market value of UK real estate represents 21% of the total net wealth and contributes 5.4% of GDP, the economic impact of such a strategy needs to be considered. The restriction of building in certain areas needs to be carefully considered, as it could damage the economy and force development to take place in other areas that may also be unsuitable for development.

Substantial policy shifts are not required to simply manage water more effectively in the urban environment. Rotterdam, for example, employs a subsidy for building and retrofitting green roofs while making them mandatory on all municipal buildings, and has taken to designing parts of the urban realm as 'water plazas' which allow excessive rainfall to be stored in areas that are used as amenity space. This prevents flooding to the highway network and critical infrastructure.

Rather than tightening flood risk policy, the draft National Flood and Coastal Erosion Risk Management Strategy for England should seek to outline a comprehensive strategy of resilience and adaptability to future flood risk and climate change, which can be implemented in part through new development and renovation and retrofit to existing property. If there is clarity on what is necessary – such as ensuring buildings are constructed so that they can be adapted to meet future flood risks and including rainwater source control measures on all new buildings – then the property and construction industry can respond and adapt accordingly. Making new developments resilient includes making them flexible and adaptable to future changes in climate and flood risk. Policy needs to follow suit. Rigid policies, requirements and standards may make developments less adaptable, and therefore more vulnerable to the impacts of flooding.

You cannot always prevent flooding, but you can prepare for it.

Daniel Allum-Rooney is an associate at BWB Consulting Ltd.

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