Surface Water Flooding Study: Call for Evidence

Surface water flooding is the most common flood risk in England, with 3.2 million properties at risk.¹ Surface water flooding occurs when heavy rainfall overwhelms drainage infrastructure (which includes combined sewers) or does not soak into the ground, resulting in water ponding or surface overflow. Our approach will be based on the terms of reference for the Surface Water Flooding Study. The Commission will deliver recommendations to government by November 2022.

The study is complementary to wider work by the Commission on its second National Infrastructure Assessment. The Commission plans to publish its second National Infrastructure Assessment in Autumn 2023.

This call for evidence has been published at the same time as the Commission’s Second National Infrastructure Assessment: Baseline Report. The report provides a data-driven assessment of the performance of infrastructure across the Commission’s six sectors; sets out the key themes that will shape the future of infrastructure and presents the rationale for projects that the Commission has chosen to focus on over the next two years. This rationale includes further detail on the Commission’s initial thinking on the challenge of surface water flooding. The baseline report also acts as a call for evidence to support the wider development of the second National Infrastructure Assessment.

In undertaking its independent study, the Commission will:

1. analyse risks of surface water flooding and the opportunities to address these risks in the short term and long term.
2. consider the nature of surface water flooding in urban and rural locations and the role of drainage systems to manage and prevent surface water flooding, and any improvements needed to these systems.
3. assess the state of collaboration across different flood risk management authorities operating at the local, regional, and national level and consider implications of the effectiveness of current approaches to short-term and long-term surface water flood risk management and areas for improvement.

The Commission’s recommendations will feed into the water sector’s development of its Drainage and Wastewater Management Plans. Drafts of these are due in summer 2022 with final plans expected in spring 2023.² In addition, the study will contribute to government’s continued progress of its surface water management action plan³ and Ofwat’s next price review in 2024.⁴

 Understanding the size of the problem

• What previous analysis of key surface water flood risks has been undertaken which the Commission should be aware of and could build on?
• Considering the current responsibilities and approach to quantifying and mapping surface water flood risk, what data is available? What areas need to improve? How can this be achieved?
• What do you consider to be the key factors contributing to the risk of surface water flooding in urban areas and rural locations? Are there other variations to consider?

Infrastructure solutions

• What measures can help mitigate and improve the management of the risk of surface water flooding in both urban and rural locations in the short term (next 5 years) and long term (25 years)? Is there evidence on their cost, effectiveness, and scale of associated co-benefits?
• How might the solutions relevant to the urban surface water flood risk context need to differ for the rural challenge?
• Is there evidence of best practice, nationally or internationally, that can inform the development of effective approaches to the management of surface water flooding?
• What solutions are on the horizon to better manage assets to minimise surface water flooding and at more efficient cost?
• What are the costs and benefits of nature-based solutions and sustainable drainage systems (SuDS) in managing surface water flooding? How can these solutions contribute to biodiversity net gain?

Behaviour change and resilience

• What key individual and household behaviours increase the risk of surface water flooding? Is there evidence on successful schemes that have led to behaviour change?
• What challenges and opportunities are presented by the increased government focus on reducing spills from stormwater overflows?
• Considering that better asset management will be key to improving climate resilience, how should the appropriate balance between investment in existing and new flood and drainage infrastructure be assessed?

Governance and decision making

• What are the strengths and weaknesses of the current approach to taking account of and managing the risk of surface water flooding where responsibilities are split across different bodies? How should this be regulated and governed in future to support effective management of the risk?
• What improvements can be made to planning for, response and recovery following a surface water flooding event?

Funding and finance

• What is the long term (25 years) investment need for surface water flood risk management that will maintain and increase resilience? Please provide evidence or explain the rationale for your estimate.
• How should funding for investment in surface water flood risk management be split between consumers and taxpayers?

Note: the Call for Evidence for this study closed on 20 December 2021.

Evidence received will now be reviewed by the Commission. If further information or clarification of any evidence submitted is required, the Commission Secretariat will contact the evidence provider.

The Commission is not planning to accept responses to the call for evidence in hard copy. Please contact the Commission by the email address above if this poses a problem for your response. Representative groups responding to this call for evidence are asked to give a summary of the people and organisations they represent, and where relevant who else they have consulted in reaching their conclusions when they respond.

FoI and privacy statements

There may be occasions when the Commission will share the information you provide, including any personal data, with external analysts. This is for the purposes of call for evidence response analysis only. The Commission’s privacy policy can be found here. We may also publish any responses received to this call for evidence, excluding personal data. However, information provided in response to this call for evidence, including personal information, may be subject to publication or disclosure in accordance with the Freedom of Information Act 2000 (FOIA) or other relevant legislation. If you want information that you provide to be treated as confidential please be aware that, under the FOIA, there is a statutory code of practice with which public authorities must comply and which deals, amongst other things, with obligations of confidentiality.

In view of this, it would be helpful if you could explain to the Commission why you regard the information you have provided as confidential. If the Commission receives a request for disclosure of the information, it will take full account of your explanation, but cannot give an assurance that confidentiality can be maintained in all circumstances. An automatic confidentiality disclaimer generated by your IT system will not, of itself, be regarded as binding on the Commission.

The Commission is subject to legal duties which may require the release of information under the Freedom of Information Act 2000 or any other applicable legislation or codes of practice governing access to information.

1. Environment Agency, 2018, Surface water: the biggest flood risk of all
2. WaterUK, Drainage and Wastewater Management Plans
3. Defra, 2021 Surface Water Update: A government update
4. Ofwat, 2021 Price Review 2024