Guidance

Reducing the Risks of Surface Water Flooding: Terms of Reference

Published 27 October 2021

The National Infrastructure Commission (NIC) will conduct a study on effective approaches to the management of surface water flooding in England.

Surface water flooding is caused by a combination of factors including rainfall, soil permeability, drainage system capacity and maintenance, and physical barriers. It is often localised, complex, disruptive to homes and business and can cause serious pollution to rivers and coastal waters with impacts on environmental quality, biodiversity, and public health and amenities.

Surface water flooding is the most common flood risk in England, with 3.2 million properties at risk (62% of those at risk of flooding). With more intense rainfall, climate change and population growth we are at greater risk of surface water flooding, with significant incidents occurring this year.

Effective surface water flooding solutions are likely to require a holistic approach to water management at both local and landscape scale with actions needed across a range of sectors and including both built infrastructure and nature-based solutions.

This study will provide a robust assessment, based on evidence and economic impact, of how responsible bodies can better manage and mitigate surface water flooding through outcomes and actions, including through infrastructure. It will specifically include:

• Undertaking analysis to gain a better understanding of the risks of surface water flooding (including sewage overflows) and the opportunities that exist to address these in the short-term (circa five years including informing the next water company price review) and long-term (circa 25 years)
• Determining the role of and improvements needed to England’s drainage systems to manage and prevent surface water flooding in both urban and rural economies in the short-term and long-term. This will include opportunities for harnessing nature-based solutions, such as sustainable urban drainage systems (SuDS), other blue-green infrastructure, and natural flood management, alongside hard engineering solutions such as sewer system design and / or capacity retrofitting.
• An assessment of current approaches to manage surface water and exploring the options for ensuring the optimum mix of short and long-term actions are being taken, including considering the optimum cost-benefit analysis of each infrastructure option and how these can be combined to provide greater resilience and value for money. This may also include improving current levels of governance, performance, preparedness and understanding, local flood planning, spatial and development planning, data sharing, funding and investment.

This study will cover England only, as flooding and water management is a devolved function. The government expects flood risk management authorities to support the Commission as it carries out the study through sharing available data. In undertaking the study, the NIC should also work with infrastructure providers, engineering sector and environmental NGOs to maximise the breadth of understanding and opportunities.

This study will focus on infrastructure and so will not cover actions such as individual behaviour change and advanced weather forecasting, as these are outside the remit of the NIC.

The NIC should deliver a final report to government by November 2022, setting out recommendations to government. All recommendations should be consistent with the Commission’s current fiscal and economic remits.