Surface Tensions

Working together against flash flooding

Author: Professor Samer Bagaeen   |  

Surface Tensions

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As the impacts of climate change become clearer every year, the UK must be better prepared for the manifold impacts of extreme weather events, including floods. In England alone, some 5.4 million homes – one-in-six – are at risk of flooding, with many of them susceptible to surface water flooding. Flood resilience is a public infrastructure challenge that must be gripped tightly at every level of place – from our major cities and towns through to villages.  Surface tensions leverages successes around capital investment in infrastructure but also puts forward the argument that this alone will not make for effective response to surface water flooding. What is needed most of all is inter-agency collaboration and levers embedded in planning policy to enable government agencies, local government, housebuilders, and the water companies to deliver effectively.

Key points

The ongoing housing supply crisis in England requires more houses to be built, all of which have potential to increase the risk of surface water flooding. The challenge is in constructing modern infrastructure which does not increase the risk of surface water flooding and is more resilient to it when it occurs. The effects of climate change are already being felt across the UK, with major flooding events arriving almost year-on-year, particularly in the unpredictable form of surface water flooding. Yet, even in this dramatic context, our resilience against disaster could be threatened by any major capital investment programme cutbacks.  With the risk of flash floods elevating, the need to shore up institutional alignment and capacity whilst investing in sustainable infrastructure is more pressing now than ever before.

The risk of surface water flooding

The amount of rain from extremely wet days increased by 17 percent from the period of 1961-1990 to 2008-2017. Under a high emission scenario, by 2070 rainfall in the UK could be as much as 47 percent lower in the summer and 35 percent higher in the winter than at present. The effects of this increase will be felt most acutely in built-up areas, as urbanisation and surface water are intimately linked together. The impact of the former on the latter owes to an increase in built and manipulated surfaces, roads, and other physical infrastructure. This changes the spatial distribution of processes such as infiltration and recharge, evapotranspiration, and run-off production. These factors are further detrimental to proper drainage in the increasing number of very hot dry spells when the ground becomes less able to soak up rainwater.

Sustainable drainage systems (SuDS) are increasingly being seen as a solution to this challenge. They provide an alternative to the direct channelling of water through networks of pipes to nearby watercourses. Implementing SuDS, as well as upgrading existing infrastructure to cope with increased rainfall, requires coordination across the broad governance of the built environment – from the planning of new homes to the redevelopment of existing housing stock, across the management of connective infrastructure and nearby land, to the engagement of the wider local public sector and civil society.

Institutional roles and responsibilities

In England, the Department for Environment, Food and Rural Affairs (DEFRA) is the policy lead for flood and coastal erosion risk management. Lead local flood authorities (LLFAs), which are either county councils or unitary authorities, lead in managing local flood risks. Local Resilience Forums are the foundation of England’s emergency planning and response arrangements for a wide range of resilience issues, including flooding. They bring together a number of organisations to produce Multi Agency Flood Plans (MAFPs).  On the central government side of emergency action, the Environment Agency (EA) works with the Met Office on flood guidance statements to improve capability for short term forecasts, to aid local authorities’ response to surface water flooding. In terms of long-term forecasting, however, the EA only maps current risks for planning permission purposes.

The separation of responsibilities between some of these authorities is problematic on the ground when flooding occurs, given the uncertainty over the geography of specific instances of flooding and our ability to predict where, for example, a thunder storm may form. Furthermore, given that only current risks are mapped, new development is being allowed to be delivered in places where future risks are not known. This is consistently identified by stakeholders as the biggest concern: that flood plains are being built on and consistently losing space for water, in turn adding pressure to drainage infrastructure and increasing the risk of surface water flooding.

The planning system

The planning system, codified in the National Planning Policy Framework (NPPF), is the primary legislative underpinning of flood management in new and old developments. The NPPF was strengthened in April 2015, with a new expectation that sustainable drainage systems would be provided in all new major developments (nine houses or more). What is still missing is that minor developments (nine houses or less, infill or permitted development) do not get seen by LLFAs and there are concerns that even in unitary authorities, these developments do not come under sufficient scrutiny from resource-stretched planning teams.

While many of these dwellings will have been subject to flood impact assessments for the minor development itself, there is no obligation for their applications to be considered as part of the LLFA flooding strategy. The same is true of permitted development. To overcome these obstacles, what is needed is a strong strategic planning authority. LLFAs, the EA, and all other risk management authorities need to work closely together and ensure that the plans they are making, both locally and nationally, link up.

Moving forward

Funding is one of the major issues in delivering resilience against surface water flooding. Notwithstanding the general need for capital investment in infrastructure, government grant criteria can be overly restrictive, especially for smaller projects. There is a need to help people understand what they can do themselves through flood action groups to recognise flood risk. Throughout such work, the need for well-coordinated and informed partnerships at the local level is crucial. Partnerships should start at grassroots with planning and talking to those who have experience of past flooding, aggregating up to a full programme of investments in both infrastructure and institutional capacity.


The most prominent finding of the engagement carried out with stakeholders as part of this research was the need for greater partnership working:

  • There should be more joined-up working and stronger communication between lead local flood authorities and risk management authorities, particularly on matters of land use. This also involves the Environment Agency.
  • Collaboration between developers, landowners, lead local flood authorities (LLFAs) and central government agencies to understand and manage flood risk and resilience must be encouraged and incentivised across all new developments.

Beyond that, there are actions to be taken by both central and local government to ensure greater resilience to flooding in general and surface water flooding in particular:

Central government:

  • Produce a comprehensive flood infrastructure funding programme that is less restrictive and targeted toward places most at risk.
  • Encourage ‘bottom-up’ practice by streamlining the funding process for smaller, district or community-based projects.
  • Produce a legal framework for local resilience forums that is informed by local experiences.
  • Strengthen accountability and support mechanisms for communities affected by flooding – ensuring that they are relative to the scale of the flooding and subsequent damage.
  • Introduce provisions for all, including minor, developments to be monitored by lead local flood authorities regarding their flood risk management.
  • Training should be provided to planning departments of lead local flood authorities as part of a more strategic push to ensure that infrastructure projects and their contracts have strong, actionable flood provisions.
  • The next revision of the National Planning Policy Framework must require local plans to demonstrate how lead local flood authorities have assessed aggregate risk across the whole area, as well as how flood impacts will avoided, controlled, mitigated, and managed.

Local government:

  • For infrastructure and procurements concerning flooding, lead local flood authorities should move away from human-engineered barriers and toward natural drainage systems that work to slow the flow of surface water and relieve pressure on sewers.
  • Lead local flood authorities should identify land that is required for current and future flood management and safeguard it from other developments.
  • In absence of flood resilience provisions in building regulations, lead local flood authorities should look to build such provisions into infrastructure projects and their constituent contracts.
  • Lead local flood authorities should ramp up public engagement in surface water flood risk localities to produce a contextualised support package and contribute to a mapping of relative flood risk from neighbourhood to neighbourhood.

Research kindly sponsored by:

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