Guidance

About the guidance and planning for drainage and wastewater management

Published 20 May 2025

Applies to England and Wales

1. About these guidelines

These guidelines are for water companies responsible for providing sewerage services in accordance with the Water Industry Act 1991, section 94 (‘sewerage undertakers’). They are also useful for other Risk Management Authorities (RMAs) who work with sewerage undertakers.

The Water Industry Act 1991 states that sewerage undertakers are responsible for:

1. Providing, improving and extending a system of public sewers (whether inside its area or elsewhere) and cleansing and maintaining those sewers (and any lateral drains which belong to, or vest in, the undertaker) to ensure that that area is, and continues to be, effectually drained.
2. Making provision for the emptying of those sewers and such further provision (whether inside its area or elsewhere) as is necessary from time to time for effectually dealing, by means of sewage disposal works or otherwise, with the contents of those sewers.

Sewerage undertakers must also have regard to both:

• existing and likely future obligations to allow for the discharge of trade effluent into its public sewers
• the need to provide for the disposal of trade effluent which is so discharged

Following the commencement of section 79 of the Environment Act 2021, it is a statutory requirement under section 94A of the Water Industry Act 1991 (“the 1991 Act”) for sewerage undertakers to prepare, publish and maintain a Drainage and Sewerage Management Plan (hereinafter called a Drainage and Wastewater Management Plan or DWMP). This guidance sets out how those obligations can be met.

The first cycle of DWMPs were published in 2023 and completed against separate guidance. These documents provide updated guidance for developing DWMPs based on lessons learned from the first cycle of plan development, and to provide up-to-date guidance now that DWMPs have become statutory.

The purpose of this guidance is to assist you in developing plans that comply with relevant statutory obligations and with government policy relating to DWMPs. The guidance is not exhaustive, and you are encouraged to be innovative and ambitious in your planning. These documents use the following terminology throughout:

‘Must’ indicates a statutory requirement. If you do not follow a ‘must’ your plan will not be legally compliant.

‘Should’ indicates an action recommended to meet a ‘must’ and produce an adequate plan. If you decide to take a different approach you should clearly demonstrate how your plan continues to meet your obligations.

‘Could’ indicates approaches or actions that may further strengthen your plan and could be considered depending on the priorities of the company, area and stakeholders. You have flexibility in exploring alternative approaches.

2. Legal requirements

The DWMP is a plan for how the sewerage undertaker will manage and develop its drainage system and sewerage system so as to be able, and continue to be able, to meet its obligations under Part IV of the Water Industry Act 1991.

When you prepare and publish a DWMP, you must comply with the requirements of sections 94A-E of the Water Industry Act 1991, and any relevant secondary legislation made. Section 94A(3)(a-g) sets out what your DWMP must address, in particular:

• the capacity of your drainage and sewerage system
• an assessment of the current and future demands on your drainage and sewerage system
• the resilience of your drainage and sewerage system
• the measures you intend to take or continue for the purpose of meeting your statutory obligations
• the likely sequence and timing for implementing those measures
• relevant environmental risks and how those risks are to be mitigated
• any other matters specified in directions

The Water (Special Measures) Act introduces an additional requirement for DWMPs which, once commenced, will require you to address the use that is to be made of nature-based solutions, technologies and facilities within your drainage and sewerage system. The Government intends to commence this requirement later this year and it will apply in respect of this round of DWMPs.

Each year you must review your plan and send a statement of the conclusions of this review to the Minister. You should also send this to:

• the Environment Agency (EA) (English companies)
• Natural Resources Wales (NRW) (Welsh companies)
• Ofwat (English and Welsh companies)

If this annual review indicates a material change of circumstances, or if directed to do so by the Minister, you must prepare and publish a revised plan. This must be done no later than 5 years after your last plan was published.

In any event, a revised plan is required no later than the end of the period of 5 years beginning with the date the plan (or the revised plan) was last published.

2.1 Drainage and sewerage system

Your DWMP is the plan for how you will manage and develop:

1. Your drainage system, which is a structure designed to receive rainwater and other surface water, other than a natural watercourse, which you maintain and operate, and which is not part of your sewerage system.
2. Your sewerage system, that is the system comprising the system of public sewers, the facilities for emptying public sewers and the sewage disposal works and other facilities for dealing effectually with the contents of public sewers that you are required to provide by section 94 of the Water Industry Act 1991.
3. The lateral drains that you are required to maintain by section 94.^{[footnote 1]}

Your general duty to provide a sewerage system in section 94 of the Water Industry Act 1991 is supplemented by the requirements in regulation 4 of the Urban Waste Water Treatment (England and Wales) Regulations 1994.

Your drainage and sewerage systems include assets and systems such as foul and combined sewerage, surface water sewerage, and sewage treatment facilities.

The focus of your DWMP should be on assets owned by you, as the sewerage undertaker.  Your plan should also consider the communities and landscapes in which they are situated and the impact of other drainage systems and pathways on the performance of your systems (and vice versa) to ensure that you understand and effectively manage the risks ‘to’ and ‘from’ your systems.

Understanding these interactions will need collaboration with other RMAs and alignment of the development of your DWMP with their drainage management and flood risk management strategies.

When preparing your plan, you should consider the role of the full extent of your assets, including wastewater treatment works. Your plan should consider the risks to the service that you are required to deliver under the Water Industry Act 1991, resulting from a current or potential future: lack of capacity, asset or system failure (‘poor asset health’), or insufficient resilience to external pressures.

You should also consider the operation, maintenance and enhancement of your systems and assets to meet current and future challenges.

In Wales, whilst sewerage undertakers are not duty bound to drain adopted highway (unless by agreement), the integrated management of surface water runoff through partnership working with local authorities is essential to meet current and future drainage needs across communities.

The DWMP should demonstrate how you have proactively engaged with the local authority when considering solutions to improve asset performance, including options for partnership working. Such partnerships present enhanced opportunities to manage the targeting and removal of surface water from the combined adopted sewerage network in a more sustainable manner, as well as providing opportunities to co-create interventions with other RMAs to deliver wider community benefits. 

3. Available capacity

Available capacity is a relative term. The drainage and sewerage system is not full all the time; the systems are designed to have spare capacity that is only used in event of peak flows (such as high rainfall or customer demand). All drainage systems have a limit as to how much water they can capture and what can be passed on to wastewater treatment works and watercourses.

As inputs to sewerage infrastructure often increase overtime, at times that spare capacity reduces, and systems fill up more frequently, so the chance of flooding and storm overflow spills increase up until a point when the sewerage undertaker acts and makes improvements to the system.

This reduction in spare capacity may be caused by an increase in population growth (and thereby more users for the infrastructure, without consistent upgrades in capacity to meet this); climate change causing more regular instances of extreme rainfall events; and increasing urban development exacerbating issues of surface run-off into combined sewers triggering storm overflows.

Your DWMP must identify the actions you propose to take or continue to take, to build in sufficient capacity for meeting both current and future demand. Ensuring sufficient capacity in your network to meet demand is key to meeting your duty under section 94 of the Water Industry Act 1991 to effectually drain your area. This includes identifying areas of acute pressure and planned development through early engagement with Local Planning Authorities (LPAs).

While it is important you proactively plan for future capacity needs in the face of challenges such as climate change, population growth and urban creep, your DWMP should recognise that current poor asset health and poor operational performance can reduce the design capacity of the drainage and sewerage system.

Reduced capacity may potentially lead to failure to effectually drain and meet requirements of your general duty to provide a sewerage system under the Urban Waste Water Treatment Regulations (England and Wales) 1994.

You should consider the capacity of your wastewater treatment works, sewer capacity and the ability of your network to carry surface water and flood waters during high rainfall and other extreme weather. You should consider the impact of climate change on the performance of your assets and, consequently, the capacity of the system.

4. Current and future demand

When assessing the current and future demands on your drainage and sewerage system, you should consider the condition of your assets and their ability to cope with:

• both existing demand and the projected future demand based on population growth calculations
• known planned development in your area such as new towns or major urban development
• the effect of climate change and other risk factors such as extreme weather

When assessing demand, you should consider the compliance of your assets with the Urban Waste Water Treatment Regulations (England and Wales) 1994. You should consider the ability of your assets to collect, treat and transmit urban, domestic and industrial wastewater.

5. Current and future resilience

Resilience is the ability to cope with, and recover from, disruption to normal operation. In addition, it covers the anticipation of trends and suitable agility to maintain services for people and protect the natural environment now, and in the future.

Your DWMP must address the current and future resilience of your drainage and sewerage system. To do this, you should understand your assets and plan and act appropriately to deliver short and longer-term resilience. 

Maintaining and improving resilience will require you to identify and manage a complex range of risks to make sure your assets operate effectively to meet current and future service needs. This includes the successful management of assets, which are often intergenerational in life, and operational systems on a day-to-day basis while also ensuring mitigations are in place to manage the impact of low probability, high impact events.

These core company activities are vital to the effective operation of a wastewater system but may not be obvious or visible to customers or wider stakeholders. You can demonstrate resilience by considering and applying the Cabinet Office (2011) “4 R’s” for resilience:

1. Resistance – the ability of systems to be unaffected by external or internal events under a range of conditions.
2. Reliability – the ability of assets to continue to function without fault under a range of conditions.
3. Redundancy – the provision of capacity and/or duplicate assets or systems to continue to provide service despite failures.
4. Response and recovery – the activities to quickly and effectively resume service despite failures.

You should consider resilience of your assets and systems to external stresses, including all sources of flooding and coastal erosion, climate extremes, power outages and other utility failures, for example mobile communication outages.

Corporate level risks, such as pandemics and cyber-attacks, do not need to be explicitly included in your DWMP but should be covered in wider company resilience planning, given their relevance to operational resilience. When considering resilience you should utilise asset management principles such as the International Organization for Standardization (ISO) ISO 55000, found on the ISO website.

5.1 Asset health

Asset health refers to the capability of your drainage and sewerage assets to meet service requirements whilst maintaining their physical condition, in consideration of both current and future operational and environmental factors.

Asset health is an indicator of a company’s ability to continue to perform its functions for the benefit of customers, the environment and wider society now and in the future.

Poor asset health is when assets deteriorate to a point where the risk of failures (which will impact on customers, the environment and wider society) exceeds the company’s risk tolerance. The health of companies’ assets is a crucial element of achieving resilience in the water and wastewater sector in England and Wales.

In addressing the resilience of your drainage and sewerage systems in your plan, you should consider potential impacts on the performance of your drainage and wastewater systems arising from asset health. For example:

1. Treatment works, pumping stations and outfalls can block or suffer mechanical or electrical failure leading to pollution from emergency overflows, sewer flooding, or failure to meet treated effluent discharge permit conditions.
2. Sewer blockages are the most common cause of sewer flooding and can also cause pollution. Blockages can be caused by a combination of sewer misuse (such as improper disposal of wet wipes or cooking fats, oils, grease) and underlying sewer defects.
3. Ofwat expects sewerage undertakers to strategically plan to address sewer blockages through routine cleansing programmes based on monitoring, performance data and deterioration models.
4. Sewer collapses (including rising main bursts) can cause flooding and pollution, but also disruption to traffic and community life through road closures and clean up or remediation.
5. Ofwat expects sewerage undertakers to minimise sewer collapse impact through a risk-based inspection and rehabilitation programme.
6. Poor sewer condition can be a cause of excess groundwater infiltration that takes up the hydraulic and treatment capacity of the systems and can also lead to increased spills at overflows and increased sewer flood risk.
7. Poor sewer condition can also potentially cause pollution to groundwater through exfiltration.

Your DWMP should formalise and document a plan of strategic, risk-based interventions to address asset health issues, as well as setting out the magnitude of the expenditure required.

Your plan should cover all proposed interventions and activities required to:

• extend drainage and wastewater systems to areas not currently served including first time sewerage where appropriate and new developments
• maintain and improve the performance of drainage and wastewater systems to meet current and upcoming regulatory requirements and societal expectations
• maintain and operate the drainage and wastewater systems including treatment to ensure that the area is and continues to be effectually drained

6. Measures to take or continue

Your plan must identify the actions you intend to take, or continue to take, for the purposes of meeting (and continuing to meet) your obligations as a sewerage undertaker under Part IV of the Water Industry Act 1991. Under section 94(1) you must:

1. Provide, improve and extend such a system of public sewers (whether inside your area or elsewhere) and so to cleanse and maintain those sewers (and any lateral drains which belong to or vest in you) to ensure that that area is, and continues to be, effectually drained.
2. Make provision for the emptying of those sewers and such further provision (whether inside your area or elsewhere) as is necessary from time to time for effectually dealing, by means of sewage disposal works or otherwise, with the contents of those sewers.

Your duty under section 94(1) is supplemented by the requirements in regulation 4 of the Urban Waste Water Treatment (England and Wales) Regulations 1994.

Your plan must identify the likely sequence and timing for the implementation of these measures. Further details on the optioneering process by which you should identify the measures are available in in the document How to form, publish and maintain your drainage and wastewater management plan (DWMP) under sections 11 to 14.

Your DWMP should take a short, medium and long-term view and should have a planning horizon of at least 25 years. Your plan should consider future trends and changes within that planning period including potential changes in climate, development and population, statutory and regulatory priorities, economics, technological changes, and customer behaviours.

You should use an adaptive planning approach to allow for the significant uncertainties in those future trends. Further guidance on adaptive planning can be found in British Standard BS 8631.

Adaptation pathways can be used to varying degrees of details, with the extensive new analysis undertaken in the preparation of your DWMP used to inform appropriate pathways and investment decisions. This allows for a re-evaluation of planning decisions in the future, once there is more certainty on those trends and best value investment strategies are clearer. Where high uncertainty has a significant influence on options, consideration of modular or incremental solutions may be appropriate.

Your DWMP should provide the long-term framework and evidence base for developing your future 5-yearly company wastewater networks-plus business plans. Your published DWMP should represent the totality of expected drainage and sewerage investment need for at least the next 25 years, and the first 5 years of that period is equivalent to the next Asset Management Plan (AMP) from the price review.

Your business plans for the next AMP should consider the investment need identified in the DWMP within the context of your company’s wider investment plans across all your obligations, as well as deliverability and affordability constraints not covered in the preparation of your DWMP.

Your DWMP should inform and read across the drainage and sewerage investment elements into your business plan for the next price review. As your business plans consider the wider investment across all your obligations, as well as deliverability and affordability constraints, business plans may therefore modify actions set out in your DWMP to meet these constraints.

Your DWMP will need to be updated regularly, but your long-term plan will need to be well-defined and robust, identifying the actions you intend to take and the likely timing for delivery of those actions.

7. Using nature-based solutions

As set out above, the Water (Special Measures) Act introduces an additional requirement for DWMPs which, once commenced, will require you to address the use that is to be made of nature-based solutions, technologies and facilities within your drainage and sewerage system.

Once those requirements are commenced, when determining the measures you intend to take so as to be able, and continue to be able, to meet your obligations, your DWMP must define the use that is to be made of nature-based solutions, technologies and facilities within your drainage system and sewerage system.

Within this guidance nature-based solutions are considered to be actions to protect, sustainably manage and restore natural or modified ecosystems that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits. It is understood nature-based solutions will be part of a suite of other measures the sewerage undertaker needs to undertake to continue to meet current and future obligations.

Where practical, you should look for opportunities for nature-based solutions within the catchment that feeds any of your associated drainage or sewerage systems.

8. Relevant environmental risks and how to mitigate

Your DWMP must address relevant environmental risks in relation to your drainage and sewerage system, and how those risks are to be mitigated. You must detail the options you intend to pursue to mitigate relevant current and future risks.

To help address the relevant environmental risks arising from your drainage and sewerage system, you should consider the latest version of Defra’s Water Industry Strategic Environmental Requirements (WISER) or subsequent policy when preparing your DWMP, including whether options within your DWMP may provide cross-cutting outcomes for environmental benefit.

The WISER sets out a number of statutory and non-statutory environmental requirements which may be relevant to the planning of your infrastructure needs. Individual WISER requirements are not separately referenced in this guidance unless they are directly relevant.

Further details on environmental risks and other plans are given in the document How to form, publish and maintain your drainage and wastewater management plan (DWMP) under section 17, and guidance on specific environmental risks you should consider is given under section 10. The focus of your DWMP should be on assets owned by you as the sewerage undertaker.

It is important to note that you manage environmental risks outside of investment programmes to meet WISER. Expenditure on capital maintenance and wastewater supply-demand funding, through the Price Review, are also important for protecting the environment.

DWMPs should be the evidence base to inform the Water Industry National Environment Programme (WINEP) and National Environment Programme (NEP), capital maintenance and wastewater supply-demand investment need elements of your business plans.

9. Other matters to consider in the plan

In addition to reflecting how you will be able and continue to be able to meet your obligations under Part IV of the 1991 Act, your DWMP should also have regard to other relevant statutory obligations and policy requirements where these are relevant to drainage and sewerage responsibilities and infrastructure management.

In England, section 40 of the Natural Environment and Rural Communities Act 2006 places a biodiversity duty on public authorities, which are defined as including “statutory undertakers” as referenced in Part 11 of the Town and Country Planning Act 1990. For the purposes of section 40 of the Natural Environment and Rural Communities Act 2006, you as a sewerage undertaker are subject to the biodiversity duty as a “public authority”.

To meet this duty, you must from time to time consider what action you can take, consistent with the proper exercise of your functions, to conserve and enhance biodiversity.

Once you have carried out your considerations, you must, as soon as practicable, set appropriate policies and objectives for taking action, and then take that action. In making this consideration and taking any action, you must have regard to any relevant local nature recovery strategy, and any relevant species conservation strategy or protected site strategy prepared by Natural England.

You can read guidance on how public authorities can comply with the biodiversity duty. One way to contribute to meeting the duty may be to make the consideration required under the duty when preparing your DWMP.

In Wales, section 6 of the Environment (Wales) Act 2016 places a duty on public authorities to promote biodiversity, but with a broader focus on ecosystem resilience and integration with other sustainability objectives in Wales. Guidance for public authorities in Wales may be found on the GOV.WALES website.

In England, the most recent version of the Storm Overflows Discharge Reduction Plan (SODRP) is a key driver for investment in drainage and wastewater systems and your DWMP should reflect the targets and outcomes of this plan.

In Wales, storm overflow performance is to be monitored and based on reducing ecological harm. Your DWMP should reflect this driver as outlined in the Price Review Forum Strategic Steer paper and NRW guidance notes “How to classify storm overflow performance”, GN066, and “Unpermitted storm overflows”, GN021, both found on the Senedd website.

The guidance notes are underpinned by the Urban Waste Water Treatment (England and Wales) Regulations 1994 which emphasise reducing the frequency and volume of discharges and in doing so, ensuring compliance with water quality standards. By improving infrastructure and operational practices, you will reduce dependence on storm overflows.

The risks you assess in your DWMP, and the options you pursue to manage them should be consistent with your other statutory responsibilities under the Water Environment (Water Framework Directive) (England and Wales) Regulations (2017), the Conservation of Habitats and Species Regulations 2017, the Environment Act 2021, the Flood and Water Management Act 2010, the Water Industry Act 1991 and the Urban Waste Water Treatment (England and Wales) Regulations 1994.

In Wales, additional statutory requirements are set out in the Environment (Wales) Act 2016 and Well-being of Future Generations (Wales) Act 2015. These documents includes guidance on how collaboration could be carried out as part of your DWMP process.

10. Follow the guiding principles

We expect your DWMP to meet the following key principles which have been developed from the Guiding Principles in March 2022 and updated in August 2022.

10.1 Leadership

You should demonstrate leadership in the development and delivery of your DWMP and associated duties as a sewerage undertaker. You should work with other stakeholders (such as local catchment partnerships, Internal Drainage Boards (IDBs), LPAs and Lead Local Flood Authorities, LLFAs), responsible authorities and private drainage asset owners to identify and deliver multi-beneficial solutions with individual or joint action and investment, including those outside of the sole responsibility of the sewerage undertaker, to drive the collaborative development and governance of your plan.

You should seek to build on any existing stakeholder organisations and groups, such as those you have established in Cycle 1, as well as for Regional Flood and Coastal Committee (RFCCs) and River Basin Management Plans (RBMPs), wherever possible.

10.2 Governance

You should create a working framework that ensures you and your stakeholder organisations can:

1. Collaborate with each other and with communities to ensure that, where practicable, your DWMP aligns with, and supports, other plans and policies related to drainage, flood risk management and waterborne-pollutant systems and pathways.
2. As well as company specific plans, include flood risk management and other plans prepared by LLFAs, RBMPs prepared by the EA in England and NRW in Wales, and asset management plans for highways and rail networks.
3. Be transparent with each other and with the general public in assessing and communicating the current and future risks, the options for improvement and your preferred plans.
4. Contribute the required resources of people, money and facilities to develop your DWMP.
5. Provide an appropriate level of assurance and governance of your DWMP.

10.3 Input

1. Your plan should be based on an appropriate level of verified data and information to make it robust.
2. You should share data and information (including the coverage, accuracy and limitations of that data and information) as openly as possible.
3. You should value knowledge, using subject matter experts from all fields, to validate inputs and processes.

10.4 Analysis

Your plan should be comprehensive.

1. Your plan should identify all risks from, and to, all of your drainage and wastewater systems, including risk pathways and risk interactions.
2. Your plan should be long-term, outlining the actions you will need to take during a period of at least the next 25 years, considering possible future changes and trends including potential changes in climate, development and population, statutory and regulatory priorities, economics, technological changes and customer behaviours.
3. Your plan should be based on robust methods and analysis, considering the sensitivity of plan decisions and outcomes to uncertainties in the data and assumptions and ensuring the methods you use are proportionate to the issues being addressed.
4. Your plan should be holistic, considering all the risks, benefits and outcomes in an integrated way.

10.5 Outputs

Your plan should:

1. Identify the issues and challenges facing your drainage and sewerage system into the short, medium and long-term.
2. Identify the solutions and investment needed to meet those issues and challenges that delivers equitable, long-term best value, considering the value to customers, the environment, the economy and different socio-economic groups including equity between generations.
3. Be resilient to ensure you can continue to deliver the expected level of service to your customers in the face of potential asset failures and external events (including utility failures and extreme weather).
4. Be deliverable over the short, medium and long-term with responsibilities and the required funding, resources and skills for that delivery identified.
5. Be sustainable considering the environment, resource use and carbon emissions, and aim to deploy a range of interventions going beyond only manufactured capital.

10.6 Outcomes

Your plan should identify your preferred options to reduce the risks that drainage and sewerage systems pose. In many cases, a suitable risk level will be determined with reference to policy requirements.

In others, it may need to be agreed through engagement with a range of stakeholders. You should prioritise management of the greatest risks, and you should not allow unacceptable increase in any individual risk. This includes risks to:

1. People from flood and public health risks.
2. The environment (including habitats).
3. The economy (including transport, development, tourism and recreation).

Your plan should deliver wider environmental and social outcomes for nature and the community from placemaking, regeneration, climate resilience, improvements to the water environment, and biodiversity.

You should seek to deliver social and environmental benefits whilst delivering your core services, beyond the minimum required to meet statutory obligations. Using a natural capital approach could support you to do this.

10.7 Innovation

Your plan should consider, and where practicable, adopt innovative methods and solutions where these support better and more efficient outcomes.

11. Alignment with flood risk management planning

This guidance provides advice on enhancing partnership arrangements, working with stakeholder organisations and flood RMAs, aligning with other plans and planning processes. In the management of surface water flooding, it is particularly important to improve alignment between flood and water planning and delivery.

Your DWMP should be developed closely with other stakeholders, and align and support other plans, strategies and policies related to flood risk management and drainage. You should take care that your DWMP does not duplicate other work or planning, and you should seek to deliver shared outcomes where applicable.

In England you must act in a manner consistent with the National Flood and Coastal Erosion Risk Management Strategy (FCERM Strategy) when performing FCERM functions.

To support this alignment and joint delivery, you should follow the following principles during the preparation of your DWMP: 

1. Close engagement with flood RMAs, for example LLFAs, IDBs, the EA in England and NRW in Wales, and other interested parties within your local community. This should ensure a common vision, clear actions, owners, and accountability. Engagement should include consultation, offering to explain your plans and strategies, shared communications with other stakeholders.
2. Identifying and ensuring collaborative working, bringing together the right people to deliver action in the most cost-effective way. This means ensuring that the collaborative group supporting the preparation of your DWMP includes flood stakeholders and RMAs and builds on, and enhances, existing partnership arrangements (for example catchment partnerships, local flood partnerships, RFCCs and others).
3. Taking account of and sharing the latest evidence to identify where surface water flood risk is greatest and where the most benefit can be delivered with individual or joint action and investment. This could include the latest national and local flood risk data, including the use of LLFAs’ flood investigations (under section 19 of the Flood and Water Management Act 2010) to strengthen the evidence of investment need in managing combined sewer and surface water flooding.
4. Considering the full portfolio of solutions to mitigate surface water flooding, including sustainable drainage and green/blue infrastructure, designing for exceedance and property flood resilience. This will include delivering the most cost-beneficial actions, taking account of the National Infrastructure Commission’s (NIC) solutions hierarchy.

Government will consider opportunities to disseminate further guidance and good practice examples to help to deliver these principles.

1. See s.94(A)(2) and (9) of the Water Industry Act 1991 ↩