London Flood Review concludes with recommendations for capital’s future flooding resilience

The findings of an independent review, commissioned by Thames Water, examining the severe flooding that affected many parts of London in July 2021 have been released.

The release of the investigation’s final report marks the fourth and final publication from the London Flood Review (LFR). It summarises the review findings and puts forward recommendations so that lessons can be learned and future impacts are mitigated.
The LFR sought to:
  • better understand the extent and causes of the 2021 floods,
  • assess how the drainage systems performed,
  • and to recommend how the increasing risks of future flooding events can be managed.
Outcome of review: 
  • The speed and severity of rainfall which fell during the two storms was the main cause of the flooding, with both rainfall events exceeding the current design capacity of the below ground systems. For example, despite there being available capacity in the sewer systems, flows of water were often held up by the gullies which did not have the capacity to deal with such extreme flow rates.
  • The LFR acknowledges that weather events like those that occurred in July 2021 are likely to occur more frequently in the future. Consequently, as flooding is not any one organisation’s responsibility, the Review notes that the many parties which manage flood risk in the capital must work together to identify solutions to manage multiple sources of flooding and identify potential funding to ensure that the impacts of flooding are managed effectively.
The LFR’s recommendations, grouped around five core themes of governance, funding, evidence, communications and strategic planning, include but are not limited to:
Governance: 
  • Establishing a body with a strategic view and governance with all parties contributing so that surface water and sewer systems can be assessed together, and investments designed to optimise outcome across different organisational boundaries.
Funding:
  • Seek opportunities for partnership working in areas of known flood risk to spread the cost of potential schemes.
Evidence: 
  • Sharing data across multiple organisations relating to flood risk assets, the understanding of high-risk areas and vulnerable customers, including across Boroughs where flood risk may originate from other areas.
  • Improving forecasting and monitoring of extreme events.
  • Using data and digital tools to assess sewer network performance more rapidly and prioritise responses in extreme events.
Communications:
  • Improving preparedness for emergencies and enabling cross-organisational collaboration at short notice, including establishing roles and responsibilities in advance so this is clear ahead of any emergency.
  • Supporting homeowners and tenants to understand how they can protect their homes from flooding, including opportunities to build in resilience.
Strategic planning: 
  • Protecting those at highest risk of flooding by installing anti-flood devices such as non-return valves, Flooding Local Improvement Projects (FLIPs) or flood gates where appropriate depending on careful assessment of the causes of flooding.
  • Adopting a suite of flood risk measures, including a combination of green (i.e. Sustainable Drainage Systems (SuDS)) and grey/traditional engineering solutions, which can be installed in alignment with the planning policy, to provide an agreed level of service across all organisations.
  • Influencing planning policy and working with developers to reduce flood risk to others from new developments and basement renovations.
  • Encouraging asset owners to fully understand, develop and maintain their assets so they perform at their optimum level during high intensity events.
  • Understanding how the combined above-ground and below-ground systems operate when capacities are exceeded, who will be affected and how the landscape can be altered to allow safe passage of flood waters to areas away from properties.

Commenting on the publication of the final report, LFR Chair, Mike Woolgar said: 

“Climate change is making many existing ways of managing drainage less effective. The events of July 2021 are likely to be indicative of events we may see more frequently in the future. Our review of these events demonstrates the critical nature of collaborative working between all those who bear responsibility for water and flood risk management.

“We’ve set out a number of recommendations, and while we recognise that there are limitations as to what may be achieved with the current funding and resources available, there is important work to be done in balancing the benefits they provide to customers at risk, and on the costs required to build and operate mitigation assets. Partnership working can bring different funding streams, so we recommend that flood risk organisations actively seek these in the future. I look forward to seeing the recommendations taken forward by those named within the report.”

The LFR has been led by an independent expert group (IEG) of external specialists to ensure objectivity and impartiality, chaired by water strategist Mike Woolgar and supported by flood modelling expert Professor Roger Falconer and city resilience expert Lykke Leonardsen from Copenhagen. To assist with the review, the IEG established a strategic stakeholder panel (SSP) which helped shape the objectives and provided input, guidance and feedback. This group comprised senior representatives from the Greater London Authority, Transport for London, London Councils, the London Drainage Engineers Group, the Environment Agency, the Consumer Council for Water, the Thames Regional Flood and Coastal Committee. Ofwat also joined the SSP to act as an observer throughout the process.

Sarah Bentley, Chief Executive Officer, Thames Water:

“As severe weather events look to become increasingly common, these recommendations will play an integral part in ensuring Thames Water continues to improve its service, deliver for its customers, protect the environment and give back to the communities we serve.

“While there is much as an organisation we can learn from this review, the clear takeaway is the necessity of collaboration. Ensuring that our network can operate effectively, while minimising the risk of impact of future flooding, must be the shared focus of all organisations with responsibility for London’s water network and drainage systems. We look forward to working closely with our partners in surface water management to build greater resilience for people living and working in London and the Thames Valley.”

The London Flood Review is the first step in identifying possible actions to improve resilience to extreme weather events in the future. The Final report, including next steps as well as Report Stages One – Three, can be found in full on the London Flood Review website: www.londonfloodreview.co.uk.

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