Guidance

How to form, publish and maintain your drainage and wastewater management plan (DWMP)

Published 20 May 2025

Applies to England and Wales

The steps you need to take to develop and publish your plan. It starts with early engagement with regulators and stakeholders, through to publishing your final plan.

Once your plan is published you must review it each year.

You should publish your draft DWMP by 1 November 2027, allowing for a 12 week public consultation.

You should publish your final DWMP by 31 August 2028.

1. Define boundaries

Your DWMP must focus on drainage and wastewater assets owned by you, the sewerage undertaker, but should consider interactions with other drainage and waterborne-pollutant systems and pathways, irrespective of organisational boundaries.

Your DWMP should be structured at a minimum of 3 levels for collaboration, analysis studies and reporting. These levels are:

1. Level 1 – Company level.
2. Level 2 – River catchment or local authority level.
3. Level 3 – Sewerage catchments level.
4. Aspects of the plan could also be published at level 4 – local solution level.

The selected boundaries should be documented and published as soon as possible to facilitate engagement with other stakeholders in the preparation of your plan.

1.1 Level 1 – company level

Level 1 covers the whole area of operation of the sewerage undertaker. It is primarily used for collating all of the Level 3 detailed plans into a company-wide report.

1.2 Level 2 – River catchment or local authority boundary level

This is the main level for establishing collaboration between organisations and for assessing the environmental condition of water bodies. It is a grouping of Level 3 areas into larger strategic planning areas.

Level 2 areas should normally align with the river basin district management catchments used by RBMPs for receiving water quality management. There are 117 management catchments in England as defined on the Environment Agency Catchment Data Explorer website. There are 3 RBMPs in Wales, which are available on the NRW website.

An alternative grouping may be required for local authority areas that are served by several drainage catchments draining to different treatment works. 

It may be necessary to have two overlapping definitions of level 2 areas with different stakeholders involved in each. This is illustrated in figure 1 below.

Figure 1: Relationship of DWMP levels

Figure 1 displays the different boundaries that your DWMP should conduct analysis studies, report and collaborate at, spanning from your whole area of operation to smaller local areas, as shown by the key. The figure shows individual level 3 study catchments and how they are grouped into level 2 river catchments and local authority areas. An individual level 3 catchment can be in both a level 2 river catchment and a local authority area and so will need consultation with both level 2 stakeholder groups.

1.3 Level 3 – sewerage catchments level

This is the main level for carrying out a planning study and developing the plan. The default study boundary should be the catchment of a wastewater treatment works including surface water drainage systems serving the same catchment.

Small catchments, such as those with under 2,000 population equivalent – consistent with the Urban Waste Water Treatment Regulations – may be considered as part of the study of an adjacent larger catchment or may be grouped together with other small catchments into one study, particularly if potential options may include flow transfers between catchments.

1.4 Level 4 – local solution level

Smaller local areas could be defined to report flood risks or overflow discharges which you and your stakeholders have deemed unsatisfactory (with reference to the latest storm overflow guidance) and to develop solutions to those risks, which could include local community partnership interventions (see 2.3.3 below). These boundaries can be defined as clusters of problems, as pre-defined sections of the drainage system, or as fixed geographic areas.

Wherever possible these local area boundaries should not cross strategic boundaries to simplify the collation of organisational plans.

2. Stakeholder engagement

Stakeholder engagement is key to developing a robust plan that meets the needs of your customers, the environment and the communities that you serve. You should engage with a wide range of stakeholders throughout the formation of your DWMP. Future regulations will set out any statutory consultees required in the DWMP process.

Your stakeholders should be regularly engaged in developing the plan through to publication. Regular engagement with stakeholders and regulators during the plan development process will help ensure a final plan consistent with expectations. Good stakeholder engagement should lead to less challenge of your draft plan as it should help identify and resolve concerns early in the process.

Each component of your published DWMP should document how stakeholders and communities have been engaged and how that engagement has influenced the development of your plan.

The arrangements for stakeholder engagement will be different for each of the different planning levels.

Welsh companies should engage with stakeholders proactively and extensively and as a minimum should do so in accordance with this guidance.

2.1 Consultees

You should engage with stakeholders early and regularly in the DWMP process.

Government intend to set out in secondary legislation a requirement for you to undertake a public consultation on your draft DWMP. Under the proposed secondary legislation, you will be required to circulate the plan to specified stakeholders, likely to include:

1. Department for Environment, Food and Rural Affairs (Defra).
2. For companies wholly or partially in England, environmental regulators (Environment Agency (EA), Natural England (NE)).
3. Ofwat.
4. Consumer Council for Water (CCW).
5. For companies wholly or partly in Wales, Welsh Government and Natural Resources Wales (NRW).

Wholly or partly in your area:

1. New Appointments and Variations (NAVs).
2. All local authorities (including parish or community council where appropriate).
3. Highways authorities.
4. Internal drainage boards (IDBs).
5. Any national park authorities.
6. The Broads authority (if applicable).
7. The Historic Buildings and Monuments Commission for England.
8. Cadw in Wales.
9. Any inland navigation or canal navigation authority.
10. Any other sewerage undertaker you identify for potential partnership in the development of drainage and sewerage solutions.

You should also engage as early as possible with relevant statutory consultees for the Strategic Environmental Assessment (SEA) and Habitats Regulations Assessment (HRA) where appropriate. Separate guidance is available on these processes.

You could also engage with appropriate environmental groups, consultants, academics, local governments, industry associations, catchment coastal partnerships or committees, as well as other interested groups. You could also engage with flood partnerships and regional flood and coastal committees.

2.2 Level 1 – company-wide

You should establish a company-wide group including economic and environmental regulators, representatives of key local authorities and the existing sewerage undertaker customer challenge group (CCG) to help set the strategic direction for the plan and the value of impacts on customers, the environment, recreation and local economy. More detail on developing the value framework is given in section 10.

2.3 Level 2 – river catchments or conurbations

The key level of collaboration between water companies, local authorities, environmental stakeholders and other RMAs will be the level 2 area plans (typically river management catchments or combined local authority areas).

For each level 2 area, you should take ownership of engagement, leading a collaborative group through the process to develop your DWMP. This should have a formal remit and governance structure, reporting directly to the company-wide group and CCG to inform, escalating level 2 issues identified.

These groups should, where possible, build on and enhance your existing partnership arrangements (for example catchment partnerships, flood partnerships, regional flood and coastal committees and others) so as not to introduce another set of interfaces. The group should be chaired by an appropriate representative of your company. The group should comprise all key stakeholders relevant to the area.

This should include (where relevant):

1. Sewerage undertakers.
2. Environmental regulators (EA, Natural England, NRW, Cadw).
3. Regional Flood and Coastal Committees (RFCCs).
4. Your Customer Challenge Group (CCG)
5. Consumer Council for Water (CCW).
6. Combined local authorities.
7. Lead Local Flood Authorities (LLFAs).
8. Local planning authorities (LPAs).
9. National and local highways authorities (such as National Highways).
10. Heritage organisations such as English Heritage and Historic England.
11. Agricultural bodies.
12. Major businesses.
13. IDBs.

You should also include relevant non-government organisations such as environment groups, river trusts, flood action groups, or catchment partnerships.

The group should aim to facilitate:

• agreement with local authorities and other flood RMAs on strategic context and the options toolkit
• sharing of data information and plans
• sharing of planning activities across organisations such as risk assessments and consultations
• alignment and linkage of stakeholder plans and the resultant delivery programmes
• defining ownership of interventions and the means of resourcing them

2.4 Level 3 – catchment groups

The assessment of risks and planning of interventions is carried out at level 3.  Collaboration here could be through a sub-group of the level 2 strategic planning group potentially with the addition of local interested parties such as community action groups.

There could also be collaboration for all detailed level 4 assessment areas. This would be the main point to engage with the local community and action groups.

3. Progress report

You should aim to publish an on-line data table, and update it at least every year, to track progress on the production of the DWMP ahead of the publication of the draft plan.

Each level 3 area should have one line in your table. This should aim to include:

• catchment name
• current and forecast population
• whether a detailed planning study is required
• whether a water quality impact study is planned
• date of most recent revision of the full plan including dates from earlier cycles
• date of most recent revision of the short-term plan including dates from earlier cycles
• whether a revision is required due to performance or trend changes
• the current stage of study

You should also aim to publish a Level 1 summary table showing, against each of the study stages, the percentage of the total population served by the sewerage undertaker for which that stage is planned and for which it has been delivered in the last 5 years.

4. Write a draft plan

Your DWMP should be easily accessible and transparent, with both the plan and the reasons for the characteristics of the plan open to government, regulators, stakeholders and the public. Your DWMP should also be accessible for different user needs. 

You should consider the wide range of people and organisations who need to understand your DWMP. You should map the relevant stakeholders during preparation of your DWMP and include this map in your published plan.

Your outputs should be easy to understand and relevant for the different audiences. The different versions of reporting should reference common information on system performance, proposed actions, costs and benefits. 

If your plan affects sites in Wales, then you must ensure that all publications comply with the requirements of the Welsh Language (Wales) Measure 2011.

The plan should be reported at levels matching those of the structure of the planning process.

When writing your plan, you should also consider the reporting requirements for completing the stages (if applicable) of the SEA and HRA.

There should be a separate report for each level 3 study area, and these should be summarised into level 2 and level 1 reports.

4.1 Level 3 study reports

The reporting at Level 3 should aim to use a combination of written documents and maps to explain the plan. The maps should define what (and where) the plan will deliver, and the written documents explain why as concisely and clearly as possible.

Written documents

The written report for each Level 3 area should aim to include:

1. A brief outline of the DWMP planning methodology and reference to the Level 1 report for more detail.
2. Details of the stakeholder engagement that you have carried out for this area including the stakeholders involved, the degree of involvement and their feedback.
3. A summary of future trends for the local area including population growth, development, local impact of climate change and impact of future statutory and regulatory changes.
4. A description of major individual investment schemes and initiatives in the local area including the benefits that they will bring and likely impact on communities, the environment and the local economy during implementation.
5. A summary of all current and future impacts on recognised habitats and heritage sites to provide an SEA.
6. Actions required by other organisations to support the delivery of the plan such as investment in drainage assets and other sources of impact which are not the responsibility of the sewerage undertaker.
7. Actions required by local residents to support the delivery of the plan including removal of runoff, remedying misconnections and reduction in sewer misuse.

Map data

You should provide an accessible visual spatial portal, such as a geographic information system (GIS), that is searchable by catchment and by postcode and can select each planning horizon. This should aim to show:

1. Major land use changes (e.g. new towns), where known, within your areas.
2. Location of proposed major investment into the drainage and wastewater system, including associated investment by other stakeholders.
3. Areas where customer action is required; for example, to disconnect surface water, remedy misconnections and reduce sewer misuse.
4. Discharges that will fail to meet discharge criteria or that pose a risk to river quality, bathing water or shellfish water status.
5. Location of nature recovery opportunities and sensitivities as informed by Local Nature Recovery Strategies (LNRS) as well as highlighting all sites with statutory protections, such as Sites of Special Scientific Interest (SSSI).

4.2 Level 2 reports

Written documents

You should produce the content for a level 2 report. It should include the following sections:

1. Scope and objectives: an introduction to the DWMP, what it covers and what it will achieve.
2. The DWMP planning process: how the collaborative plan was developed, which organisations were involved and how they contributed.
3. Strategic context: the strategic objectives including the value framework developed at level 1, alignment with other strategic plans.
4. Option toolkit: the generic options, those rejected and the assessment criteria, benefits and constraints for those considered. It is not necessary to include details of the cost model for options.
5. A summary of your SEA.
6. Summary results: a summary of the overall benefits and investment costs of the plan within the level 2 boundary including benefits and costs to other organisations and stakeholders within the boundary.
7. Major projects: details of planned major investment projects and likely impact on communities, the environment and the local economy during construction.

Data tables

You should provide your own format of data tables for the level 2 report where this is helpful to explain specific collaborative elements of your plan. These supplementary tables should be consulted with the relevant stakeholders.

4.3 Level 1 report

Written documents

You should produce an overview report for your operating area. Much of the content will be common to the level 2 reports. It should include the following sections:

1. Scope and objectives: an introduction to the drainage planning process, what it covers and what it will achieve.
2. The planning process: how the collaborative plan was developed, which organisations were involved and how they contributed.
3. Strategy: the strategic objectives including the value framework, alignment with other strategic plans.
4. Option toolkit: the generic options, those rejected and the assessment criteria, benefits and constraints for those considered. It is not necessary to include details of the cost model for options.
5. A summary of your SEA.
6. Summary results: a summary of the overall benefits and costs of the plan within the Level 2 lead stakeholder organisation boundary including potential benefits and costs to other organisations and stakeholders within the boundary.
7. Major projects: details of planned major investment projects and likely impact on communities, the environment and the local economy during construction.

Data tables

Data tables are required to capture the key metrics and costs of the proposed solutions in your DWMP to address identified risks. Your data table will help demonstrate the actions you propose to take or continue under section 94A(3)(d) and (e) of the Water Industry Act 1991.

The tables contain data fields that are important in setting out what your DWMP will deliver and when, allowing for the benchmarking of your plans on a consistent basis. The data presented in the tables should be consistent with information presented in your DWMP narrative itself. A data table template will be provided for you to refer to. 

Data should be provided at company level (level 1) showing forecast values for each future planning horizon, starting with the 5-year horizon for the forthcoming Price Review. Information to complete the tables should be available from your level 3 DWMP analysis, aggregated to level 1, and should have greater certainty around the current (baseline) and short-term data. 

The data will provide forecast performance against each common performance indicator (as set out in section 10) and any additional bespoke performance indicators. Nominally this will include performance metrics and expenditure requirements (capital expenditure (CAPEX) and operational expenditure (OPEX)) for the DWMP baseline position (taken as the end of the current price review period) and for future planning horizons, aligned to every subsequent 5-year AMP period. Data will indicate forecast performance with and without implementation of the interventions identified to address risks.

4.4 Statement of assurance

You should provide an assurance statement from your board to the minister that you are satisfied:

1. You have met your obligations in developing your plan.
2. Your plan is a best value plan for managing and developing your drainage and wastewater systems so that you are able to meet and continue to meet your obligations under the Water Industry Act 1991.
3. Is based on sound and robust evidence including evidence relating to costs.

Your assurance statement should be accompanied by a supporting statement to detail how the board has engaged, overseen and scrutinised all stages of development of your plan and the evidence it has considered in giving its assurance statement.

5. Publish and publicly consult on the draft plan

If your plan affects sites in England, you should send your draft plan to the Secretary of State for the Environment. If your plan affects sites in Wales, you should send your draft plan to the Welsh Ministers.

You should share your draft plan with the statutory consultees that will be set out in secondary legislation (expected consultees are as laid out in section 2.1), and you should also share it with all other stakeholders that you have engaged with and publish it on your website. Further requirements in relation to a statutory consultation will be set out in secondary legislation closer to the time.

You should consider encouraging response by:

1. Offering to explain the plan to established groups, known interested parties or companies within your area.
2. Including an engaging summary of your plan that clearly sets out your proposals to your customers in plain language.
3. Holding virtual events, road shows or exhibitions.
4. Conducting questionnaires to gain views on your proposals, using phone or in person surveys or other recognised survey techniques.
5. Using social media to highlight the consultation.
6. Using innovative web-based engagement.
7. Joint communications with other stakeholders.

If you receive a query from a consultee, you should respond with supporting evidence where required within 20 working days of the request. A longer response time can be requested if you can justify this. The query responses should be published on your website in support of the draft plan.

The specific requirements and timings for the publication of, and consultation on, your draft plan will be set out in due course. Guidance in relation to these matters will be updated at that time with the below setting the expectations for what will be required of you during these stages. Welsh companies should, so far as possible follow the requirement set out in this guidance, and if in doubt contact NRW.

In Wales there will be no Welsh Government direction on the publication of your plan. Ofwat and NRW will review your plan and discuss with you any concerns or suggestions prior to publication. You should publish your plan once these discussions have been concluded. NRW will prepare and publish a report, for information to the Welsh Ministers on your published plan. The Welsh Ministers have the powers to direct a new plan be prepared at any time.

6. Publish the final plan and a statement of response

Following consultation on your draft plan, you should publish a final plan which has been revised to consider the results of the consultation and any changes required by the ministers.

You should also provide a statement of response to the consultation that:

1. Shows that you have considered the representations you have received.
2. Sets out the changes you have made to the plan as a result of the representations and your reasons for making them.
3. Says if you have not made changes as a result of representations and explains why.
4. Describes anything that has changed during the consultation period.

English companies should provide an updated assurance statement from your board to the minister, and all companies should provide one to Ofwat, and the relevant environmental regulator (EA and NRW) that you are satisfied:

1. You have met your obligations in developing your plan.
2. Your plan is a best value plan for managing and developing your drainage and wastewater systems so that you are able to continue to meet your obligations under the Water Industry Act 1991 and is based on sound and robust evidence including evidence relating to costs.

You should provide a supporting statement to detail how the Board has engaged, overseen and scrutinised all stages of development of your plan and the evidence it has considered in giving its assurance statement.

7. Review and maintain the final plan

Section 94A of the Water Industry Act 1991 sets out that your DWMP must be reviewed annually on the anniversary of its publication.

Should a material change in circumstances be identified at the review, you must prepare and publish a new revised plan. In any event, a new plan must be submitted no later than five years after the publication of the previous plan.

7.1 Annual review

The annual review of your plan should cover 2 aspects.

You should include a review of the trends that will influence the future risks for your drainage and wastewater systems. This will indicate where the initial considerations and assumptions you made in developing some, or all, of the DWMP are now significantly out of date and where the plan needs to be revised with new assumptions.

Some changes, such as climate change or new statutory requirements may affect all catchments and require a revision, although this would normally be carried out at the next required 5-year interval unless significant new data is identified. Other changes such as new development plans may affect only one catchment, and the DWMP can therefore be revised as soon as the significance of the change is understood.

You should also review any relevant section 19 Flood investigations by local authorities should flooding have occurred within the plan period, to determine whether revisions to the plan are necessary.

You should also include a review of the system performance for each level 3 area against performance indicators. There is inherent variability from year to year in system performance, and poor performance in one year may require corrective operational or maintenance changes. However, more than one year of poor performance may be required to identify that there is a material change. For example, environmental performance is frequently assessed on a rolling three-year average rather than a single year.

The assessment should include:

1. Performance against all relevant measures from the most recent version of the Ofwat Water Company Performance Report including measures from the most recent Environmental Performance Assessment (EPA).
2. Asset health measures for both infrastructure and non-infrastructure assets.
3. Systems with excessive infiltration flows that impact on system performance or operating cost.
4. Assessment of any monitored data on wastewater system performance and impact.

The review of performance should follow a staged assessment to understand whether an update of the DWMP is required. Supplementary guidance for the annual review and statement of conclusions will be made available in due course.

7.2 Table of publications

It is expected that you should publish, as a minimum, the specific outputs listed in the table of publications below, at each of the publication stages throughout the DWMP cycle.

Table 1: Table of publications

Publications	Minimum output form, minimum expectations	Description
Draft DWMP	Level 1 written report	Company-wide risk and investment need, short- (5yr), medium- (15yr), long-(25yr +), applying adaptation pathways scenarios caveated with uncertainty and trigger points. Aggregating summaries from Level 3 + Level 2.
Draft DWMP	Data tables	Consistently reported data on risks and investment need to meet performance indicators. Format to be confirmed.
Draft DWMP	Data attributes shared spatially on Level 2 + Level 3 (+ Level 4 where appropriate)	Data (as within tables on risks, solutions, costs and benefits) as attributes on open access spatial (GIS) portals: Level 1 (company-wide) Level 2 (river basin or local authority) Level 3 (sewerage catchment scale) Level 4 (could be local community outputs).
Draft DWMP	Level 2 and Level 3 written summaries	Summary of risks, investment need options, with short text explanation of data in a publicly accessible, visual and spatial (GIS) portals, including costs and benefits.
Draft DWMP	Reporting threshold outputs	Mapped RAG coded outputs (could be shared on spatial portals). Red = 2, Amber = 1 and Green = 0.
Draft DWMP	Customer summary	Non-technical summary of company plan (in any form) on risks, investment need and potential impact on customer bills.
Draft DWMP	Technical methodologies	This could include, but not limited to engagement method, modelling approach, allowances used
Draft DWMP	SEA & HRA	HRA: Summary of outcomes from the appropriate assessment for each European site. SEA: If an SEA is required, an environmental report must be published alongside the draft DWMP.
Draft DWMP	Board statement of assurance	Board assurance DWMP meets guidelines and legal obligations
Final DWMP	Updates to the outputs above	As a result of the consultation and maturity in understanding of investment need, including updated board assurance statement
Final DWMP	Statement of Response	You Said, We Did – outlining the changes made to the final DWMP (and where to find it in the documents and data) based on the feedback during the public consultation. If feedback not addressed, explanation as to why.
Annual Review Statement of Conclusions	Statement of Conclusions	Companies should present: how is the risk changing and what is causing that change of risk? Has there been a “material change of circumstance” to warrant a revised plan?
Annual Review Statement of Conclusions	Revised DWMP (if a material change of circumstances or Minister Direction)	If a material change in circumstance has occurred – revise plan (mostly likely at Level 2 or Level 3) if needed.

8. Basis of planning

This section gives an overview of the planning process that you should follow when developing your DWMP. The process is set out in figure 2 below.

Figure 2: Overview of planning process

Figure 2 is a schematic providing a summary of how the planning process of DWMPs should be conducted at each level, and what sections of the plan should be reviewed annually and every 5 years. To note: sections in the first box represent processes to be conducted at level 1, and sections in the second box represent processes to be conducted at level 3. Reporting is to be presented across all levels.

The sections below give a brief description of each stage in the process and are explained in more detail in the rest of this guidance.

8.1 Collaboration

You should set the scope of the plan and boundaries of the component plans and your stakeholder engagement plan. Although this step is shown at the start of the process you should collaborate with stakeholders throughout the development of your DWMP. You should aim to engage on each stage of the process as soon as possible to reduce the risk of abortive effort or delays in the planning process.

8.2 Strategic context

This defines the performance indicators and their value framework and documents the future trends that are likely to affect your plan. You should engage with your key stakeholders on these aspects.

Details of this stage are defined in section 9.

8.3 Options toolkit

Your options toolkit (the toolkit) should consider the full range of intervention options including operations and maintenance, and asset health interventions, that you propose to use to address current or future system performance risks. You should define the constraints on the use of options and set out option cost-benefit models (including the wider benefits that the options can deliver such as community benefit and biodiversity benefit).

You should engage with your key stakeholders on this toolkit.

Details of this stage are defined in section 11.

8.4 Risk based planning

You should use this stage to define the scope of the approach you will take to the planning necessary for each Level 3 area. Your planning approach should establish where there is a need for interventions by considering long term strategic issues, future trends, and recent performance. You should also identify any overlaps with other relevant plans including your own asset maintenance plans and plans by other stakeholders. 

This part of the framework should also form a key part of your annual review to help you identify if there has been a material change in circumstances that requires your plan to be revised in line with section 94A of the Water Industry Act 1991.

Details of this stage are defined in section 12.

8.5 Preparing analysis tools

During this planning stage, you should define what monitoring and analysis tools you will need and use to assess the current and future performance of your drainage and wastewater system, and to identify best value options for reducing risks. It is likely that for most catchments, you will need to undertake some form of deterministic or data driven modelling.

You could consider the scope of:

1. Your monitoring strategy for your assets (for example information which underpins asset and service performance forecasting) and for the environment (for example for chemical, ecological and microbiological parameters).
2. Analysis of current asset and performance data and trends.
3. How you will represent and model rainfall.
4. Hydraulic modelling for your study areas.
5. Water quality modelling of systems and their receiving waters.
6. Modelling of the capacity of wastewater treatment works.
7. Modelling of the asset health of the system and its individual elements.

You should aim to document all the requirements and the planned approaches and use this information to define the programme and budget for developing the next stage of the plan.

Details of this stage are defined in section 13.

8.6 Risk assessment and option development

This stage combines risk assessment with option development and assessment. Combining them allows for an efficient and iterative approach to developing options for different future planning scenarios. As part of the process, you should consider likely current and future uncertainty and the use of adaptive planning approaches, in order that investment decisions are not locked-in unnecessarily and there is flexibility to modify interventions later.

Details of this stage are defined in section 14.

8.7 Preferred plan

At this stage of the planning process, you should consider and document how the proposed interventions are to be delivered over the life of the plan. This should include applying adaptation pathways principles to account for uncertainty for long-term investment decisions, the sources of funding, the resourcing of the programme delivery and the implications for future operations and maintenance activity requirements.

Details of this stage are defined in section 15.

8.8 Reporting

The final step in the preparation of your DWMP should be to report it in language and formats that are accessible to all stakeholders. The high-level report should be a collation of the individual catchment reports and should be kept live so that revisions for individual catchments are automatically included in the published version. Actions and evidence identified in your DWMP should be transparent, accessible and kept up to date.

Details of this stage have been set out in sections 1 to 7.

8.9 Review

Section 94A of the Water Industry Act 1991 requires you to undertake an annual review of your plan to keep your plan up-to-date and to reflect any material changes in circumstance which may require an updated plan, ahead of the 5-yearly revision. Details of the annual review process will be provided in due course.

9. Strategic context

You should develop and present the strategic context for your DWMP at an organisational level, prior to catchment level planning being undertaken. The strategic context should set out the:

• future trends that are likely to affect your systems
• value framework that you will use to assess the cost benefit of investment

9.1 Generic future trends

As part of setting out the strategic context for your plan, you should assess and define the trends that will affect the future performance of your drainage and wastewater systems and that, therefore, need to be considered when developing a long-term plan. 

Trends should include (but not be limited to) changes in:

• climate and other environmental factors
• development
• population
• statutory and regulatory priorities and challenges
• economic influences
• technological changes
• customer and stakeholder behaviours

These are described in more detail in the following sections.

You should engage and document the trends that you intend to consider as part of your planning process and the magnitude of those trends. The significance of these trends for each individual study area is considered in a later step.

9.2 Climate and environmental

You should take account of the impact of climate change on all elements of your DWMP.  Guidance on the scenarios available are provided by the Met Office in UKCP publications on the Met Office website, and the Climate Impacts Tool on Gov.uk. You should use a range of the latest recommended scenarios, particularly the 50th percentile of the Representative Concentration Pathway (RCP) 8.5 scenario.

When you are using different future flow projections compared to the Enhanced Future Flows and Groundwater (eFLaG) projections held on the UK Centre for Ecology and Hydrology (UK CEH) website, these outputs should be explained and justified. You could use a mean or median ensemble, but you should understand the uncertainty associated with the full range of ensembles.

These recommendations are likely to be updated as further climate research is carried out. You should use the latest available regulator-recommended climate change scenarios and derived impacts when you start or revise a level 3 plan. Methodologies used to assess the effects of climate change on the water environment and the water industry have been developed to support the water resource planning, regional planning and business planning processes.

You should take account of the inherent uncertainty in both the assumed climate projection and the associated impacts and build this into your adaptive plan.

You should assess the impact of all aspects of climate change including:

1. Rainfall intensity – climate change impacts should be defined as the expected percentage increase in intensities of short duration rainfall in design storms and timeseries. You should consider how likely future change may vary with region, duration, return period and planning horizon. See also UK Water Industry Research (UKWIR) report 25/CL/10/20 on the UKWIR website, and EA guidance on climate change allowances on the EA website.
2. High river flows – climate change impacts should be defined as the expected increase in river flows (and associated levels) that could impact on drainage systems. The impact of climate on river flows varies by region and planning horizon. See guidance published by the EA on the EA website and Welsh Government guidance on Gov.wales.
3. Low river flows – climate change impacts should be defined as the expected reduction in river flows in summer due to reduced summer rainfall. Current estimates are for a long-term median 33% reduction. This can impact the discharge permits for wastewater treatment works and storm overflows. See the eFLaG projections hosted by UK CEH on their website and relevant water resource projections.
4. Temperatures – climate change impacts should be defined as the expected increase in average and peak temperatures during summer months. Recently, monthly air temperature projections from the UKCP18 regional model were used in conjunction with other variables such as geology and land use to generate predictions of monthly mean river water temperature data for approximately 4000 sites in England and 200 sites in Wales up to 2080. The projections are based on the RCP 8.5 high emissions scenario and were developed for each of the 12 ensemble members. The storm overflows impact assessment will use projected mean water temperatures and standard deviations for 2050 from this dataset. UK climate projections may be found on the Met Office website.
5. Sea level – climate change impacts should be defined as the expected increase in sea level for each planning horizon. Any expected increase in storm surge levels should also be considered. See guidance published by the EA on Gov.uk and Welsh Government published on Gov.wales.
6. Groundwater level and quality changes and trends, where applicable. Climate change is likely to result in warmer, wetter winters and hotter, dryer summers (including prolonged dry weather and periods of drought) and these changes are likely to lead to a greater frequency of higher groundwater levels or extremely low groundwater levels.

9.3 Development and population

You should consider the impacts on drainage and wastewater system capacity and performance of:

1. All planned new residential, commercial and industrial development and changes in land use. This should be based on the range of values set out in the guidance for WRMPs (based on local authority LDPs), and any new or emerging evidence such as regional planning exercises or spatial development strategies.
2. Urban creep (that is, increased impermeable surfaces producing runoff). Urban creep estimates can be based on bespoke local assessments or UKWIR guidance.
3. Future changes associated with other drainage systems, for example increased flows from highway drainage or changes to culverted watercourses, where information is available.

9.4 Statutory and regulatory priorities and challenges

You should evaluate the likelihood and implications of potential changes, including:

1. Changing environmental regulatory requirements (for example, relating to pharmaceuticals, microplastics, disinfection, per-and poly fluoroalkyl substances (PFAS)).
2. Designation of additional bathing waters.
3. Designation of additional Drinking Water Protected Areas (for rivers).
4. Groundwater Safeguard Zones (for groundwater).
5. Designation of additional sensitive catchment areas for nutrients.
6. Any other regulatory developments.

In Wales, water companies should engage with local authorities to identify and include in the DWMP details of all adopted surface water outfall locations, the associated highway and parking drainage areas, and those likely to be contributing the most pollution. This does not constitute an assumption of responsibility for highway pollution within the water company asset; rather, it will support future planning by prioritising action on the most concerning outfalls. As the water company owns these assets and outfalls, it is reasonable to expect them to confirm their locations and the relevant catchments.

9.5 Economics

You should evaluate the sensitivity and take account of uncertainty of, and implications associated with, potential changes including

1. Changing economic conditions including discount rates/inflation, value of materials or natural resources.
2. Changing customer willingness to pay for drainage and wastewater service levels.
3. Changing benefit levels.
4. Changing values of carbon (currently based on the Marginal Abatement Costs) and potential imposition of carbon taxes.
5. Availability of funding from other sources.

9.6 Technological changes

You should evaluate the sensitivity and take account of uncertainty of, and implications associated with, potential changes including:

1. Increased use of online monitoring and control.
2. Innovative treatment options for wastewater and runoff.
3. Innovative sewer lining technology.
4. Low-carbon methods of construction.
5. Increasing overflow and water quality monitoring.

9.7 Customer and stakeholder behaviours

You should evaluate the likelihood of, and implications associated with, potential:

1. Per capita flow i.e. expected reductions in per capita flow due to the implementation of metering and water efficiency measures.
2. Changes in customer behaviour due to demographic trends, for example working from home.
3. Changes to water efficiency technologies which may impact domestic and industrial wastewater.
4. Reduced disposal of commonly flushed items (for example wet wipes, sanitary products) and fats, oils and greases (FOG).

10. Define your value framework

The principles you use for planning your DWMP should be in line with overall investment planning good practice, namely that investment should be assessed based on a ‘best value’ approach. 

You should define the value of the benefits that will be delivered by your proposed interventions. Performance Indicators are used to help to value the benefits of maintaining or improving performance outcomes so that the net value (benefit minus cost) of investment can be assessed and used to inform the selection of proposed intervention options.

You may find processes such as that outlined on the Construction Innovation Hub’s Value Toolkit website useful for guidance on engaging with multiple stakeholders. You should engage stakeholders on the valuations of benefits in their value framework.

This section of the guidance considers the principles of good practice in valuing changes in service performance. 

10.1 Define indicators

The term “Performance Indicators” is used in this guidance to differentiate from ‘Performance Measures’ that look backwards at recent ‘observed’ performance (these are discussed in section 12.1).

These indicators are designed to enable current performance commitments of your drainage and wastewater systems to be considered in the context of future asset management planning. Performance indicators should be consistently and measurably assessed from a reliable and consistent baseline to demonstrate how your drainage and sewerage system is able, and will continue to be able, to meet legal obligations.

A common set of indicators is defined in this guidance for use by all sewerage undertakers. All the performance indicators will be “common” and forecastable. You may define additional (bespoke) indicators, but only if they are materially different from the common indicators and have support from your Level 1 stakeholders.

10.2 Principles for Performance Indicators

The following principles have been adopted in defining the common Performance Indicators:

1. They should mostly indicate outcomes, including impacts on people, the environment (water and wider) and the local economy.
2. They should be forward-looking indicators that can be predicted with a consistent and repeatable approach.
3. They should be ‘continuous variables’ that allow even small changes in performance to be identified and acted upon.
4. They should identify unacceptable individual performance failures at specific locations as well as company-wide average performance.
5. It should be possible to relate them to existing backward-looking Performance Measures; specifically, those used by Ofwat and the EA in England and NRW in Wales.
6. They should include some indicators that are not solely associated with sewerage undertaker assets, but where the provision of new assets may be part of improving performance.
7. They should be predictable on a consistent basis so that they can be compared across different catchments and different companies.
8. There could be flexibility for a company to define additional (bespoke) indicators – but only if they are materially different from the common indicators.
9. They should not be excessively complex or expensive.
10. It should be possible to apply a monetary value to most indicators. Where the requirements are subject to a test of best technical knowledge not entailing excessive costs (BTKNEEC) then establishing the net value is helpful in informing what constitutes excessive or disproportionate costs.

The requirement for using ‘continuous variables’ is to allow for an approach which can establish the incremental value of improvements in performance rather than meeting a target. For example, if a measure of property flooding is set as a single threshold that no property shall flood more frequently than a 1/30 annual probability, a best value option that improves the protection of some properties from 1/10 to 1/20 might not be prioritised appropriately.

The requirement for being applicable to individual issues (performance failures) is so that improvements can be targeted at the worst performance. For example, in the context of storm overflow spills, assessing each overflow individually will ensure that poorly performing overflows are targeted for improvement, as opposed to assessing performance on a company-wide average which could result in poorly performing assets being individually missed.

10.3 Common Performance indicators

You should evaluate each of the common performance indicators set out in the table below for each future planning horizon.

Table 2: Performance indicators

Category	Metric	Details
Flooding	Internal flooding	Annual number of internal sewer flooding incidents normalised per 10,000 sewer connections, in line with the latest Ofwat Performance Commitment definition. The annualised figure is to be based on reported and forecast incidents based on 1/10, 1/20, 1/30 and 1/50 return periods.
Flooding	External (curtilage) flooding	Annual number of external sewer flooding incidents normalised per 10,000 sewer connections, in line with the latest Ofwat Performance Commitment definition. The annualised figure is to be based on reported and forecast incidents based on 1/10, 1/20, 1/30 and 1/50 return periods.
Water environment	Storm overflow performance (England)	Number of storm overflows predicted to be at risk of not meeting Storm Overflow Discharge Reduction Plan (SODRP) targets and/or permit non-compliance for the relevant planning horizon. Baseline of spills is based on a minimum of 10 years’ worth of time series rainfall data (2014-2024). 10-year dataset needs to be uplifted to recognise baseline and future pressures.
Water environment	Storm overflow performance (Wales)	GN066 and GN021 outlines the criteria, process and methodology that water and sewerage companies must meet for an overflow to be classified as satisfactory.
Water environment	Treatment works compliance (numeric)	Annual number of wastewater treatment works predicted to fail numeric effluent quality permit limits.
Water environment	Treatment works compliance (descriptive at numeric sites)	Annual number of wastewater treatment works predicted to fail to meet descriptive conditions at numeric permit sites.
Water environment	Treatment works compliance: DWF	Annual number of wastewater treatment works predicted to fail to meet discharge permit conditions for Dry Weather Flows.
Water environment	Treatment works compliance: FFT	Annual number of wastewater treatment works predicted to fail to meet discharge permit conditions for annual Flow to Full Treatment.
Water environment	Good Ecological and/or Chemical Status: Public sewerage	Number of RNAGS (Reasons for Not Achieving Good Status / Deterioration) associated with sewerage assets discharges (including surface water networks).
Water environment	Pollution incidents: serious	Annual number of serious (Category 1 and 2) pollution incidents from sewerage undertaker sewerage assets (including public surface water networks). Excludes sludge/biosolids incidents.
Water environment	Pollution incidents: total	Annual number of pollution incidents (Category 1-3) per 10,000 km of wastewater network from SU sewerage assets (including surface water networks). Excludes sludge/biosolids incidents.
Economy and community	Bathing water quality	Number of current and future (if known) inland and coastal bathing waters where predicted performance of sewerage assets discharges will pose a risk to compliance with “sufficient” quality classification and not deteriorating from current standards, with a view to increasing the number as “good” or “excellent”.
Economy and community	Shellfish water quality	Number of current and future (if known) designated shellfish waters where predicted performance of sewerage assets discharges will pose a risk to compliance with the microbial standard specified in the Shellfish Waters Protected Areas (England and Wales) Directions.

Further common performance indicators to trial in Cycle 2

There are several performance indicators which are emerging or complex risks which are difficult to forecast. You should develop and trial methods for assessing these indicators in DWMP Cycle 2, although you should still present outputs. These indicators are shown below.

Table 3: Performance Indicators for Cycle 2 Development

Category	Metric	Details
Flooding	Surface water flooding (Shared responsibility)	Annual number of properties per 10,000 properties indicated as at medium (3.3%AEP – 1%AEP) and/or high (greater than 3.3%AEP) areas of risk of surface water flooding estimated from reported incidents, local models from other RMAs and/or most recent EA surface water flood risk maps. In Wales, the flood risk maps can be found on the NRW website. This only covers surface water flooding within companies’ drainage and wastewater catchments.
Water environment	Good Ecological and/or Chemical Status: Urban and transport (Shared responsibility)	Number of RNAGS (Reasons for Not Achieving Good Status / Deterioration) attributed to discharges of urban or highway runoff and misconnections that will not be remedied through investment by you or other organisations. This only covers runoff or connections entering companies’ drainage and wastewater catchments.
Water environment	Emergency overflow performance	Number of emergency overflows that operate once or more per year.
Water environment	Treatment works compliance (descriptive)	Annual number of wastewater treatment works predicted to fail to meet descriptive permits.
Water environment	Groundwater pollution	Length (km) of sewer within Source Protection Zone (SPZ) 1s (and 2s in Groundwater Safeguard Zones (SGZ)) where there are likely risks to groundwater from sewer exfiltration.
Water environment	Groundwater infiltration	Annual number of discharges during ‘dry weather’ caused by increase in sewer flow from groundwater infiltration.

10.4 Define values

Sewerage undertakers have used monetised valuations of service levels in decision support processes and tools for many years. These have widened from considering only the ‘private’ costs incurred by the sewerage undertaker to including valuations of ‘service’ performance (for example river quality and sewer flooding) and socio-environmental costs (for example odour nuisance, traffic disruption, carbon). This was set out in the UKWIR Common Framework (2002) and its update, the Framework for Expenditure Decision Making (2014) found on UKWIR’s website. More recently, companies have aligned valuations with the Six Capitals categories of the International Financial Reporting Standards’ (IFRS’) integrated reporting requirements which may be found on this linked document.

Ofwat’s Public Value Principles should also inform the use of valuation frameworks.

A list of existing published guidance on this topic is provided in section 16.

You may already have value frameworks in place that have values assigned for most of the performance indicators or for similar indicators where the values can be adapted.

The values that you apply to the performance indicators to assess investment must allow for the expected values at future planning horizons, as well as the current values. This is achieved not just by applying the appropriate discount rates, but also by continually updating the build-up of valuations in the value framework (for example customer willingness to pay, biodiversity values, fines and penalties, energy costs and the value of carbon).

You should consult the Level 1 stakeholders’ group on the defined value framework.

Although methodologies and approaches may vary from company to company, the following approaches should be considered during the compilation and in the justification of the sewerage undertaker’s best value plan.

Flood risk

The definitive UK framework for valuing the impact of flooding is set out in the Multi Coloured Manual found online. This includes an approach based on typical property values and likelihood of flooding. Sewerage undertakers have also previously used a framework with a notional unit value for flooding inside a residential property, for flooding of the curtilage of a residential property, and optionally for flooding of highways and other public areas. As an RMA you may be eligible for grant-in-aid (GIA) funding for a flood and coastal erosion risk management (FCERM) project – guidance is available on the Gov.uk page for FCERM projects.

You should adopt a valuation framework that aligns the two approaches described above. ‘Willingness to pay’ surveys are useful to confirm the current value of intangible impacts of flooding such as stress and ill health, but you would need to extrapolate any values to future planning horizons. The framework should include the physical and economic damage of flooding of commercial premises as well as residential properties.

Water Quality

Definition of the value framework for impacts to the quality of receiving waters should consider the following factors:

1. Value of failing to achieve Good Ecological Status and by how much it is missed.
2. Information on contribution (source apportionment) of failing to achieve Good Quantitative and Good Chemical Status for Groundwater (where available).
3. Impact on protected sites such as SSSI, Special Areas of Conservation (SAC), Special Protection Areas (SPA), Ramsar etc.
4. Failure to achieve bacterial quality for designated bathing waters.
5. Failure to achieve bacterial quality for designated shellfish waters.
6. Failure to achieve bacterial quality for recreational use and the number of people impacted.
7. Public preference for limiting discharge of untreated sewage over and above any impact on the environment or recreational use.
8. The value of detriment of increased pollutant concentrations in the watercourse even if this would not affect the achievement of Good Ecological Status.
9. The value of a determinant from improving from one status to another.

Discharge permit compliance

Compliance with discharge permits is a statutory requirement. The DWMP should evidence how you will comply with your discharge permits and continue to comply with these permits, identify where and why investment is required and when this is planned for delivery. These schemes should be mandated using the best value option.

Reasons for Not Achieving Good Status

The number of Reasons for Not Achieving Good Status (RNAGS) assigned to a water company’s activities or discharges is a useful measure of performance as it is already assessed by environmental regulators and directly aligns with their expectations. You could develop a method of allocating a monetary value to RNAGS. You could endeavour to have a value appropriate to all RNAGS across the region, but it may be necessary to have different values for different river reaches.

The approach should be applied at the level of the elements impacted by the discharges – for instance phosphorous, invertebrates etc. It could recognise that an RNAG may cover the impact of multiple discharges or that a single discharge can be an RNAG for multiple reaches.

A suggested initial valuation method is:

1. You will already have a monetised value for improving a reach of river and/or water body – either specific to each or generic for all.
2. Divide this value by the number of RNAGS affecting the elements impacts by the discharges in each reach and/or water body to give a notional value per RNAG.
3. Consider averaging this value across different reaches and/or water bodies to give a standard value per RNAG.

Any developments from this initial approach should be clearly documented in the value framework section of your DWMP report.

10.5 Define discount rates

You should define the discount rates you use in your planning process for calculating whole life costs and benefits and how distributional factors will be applied for different socio-economic groups. Your selected discount rate should be based on the guidance in the HM Treasury “Green Book” found online.

Discount rates should be applied in line with the Spackman approach found on the Ofgem website, agreed by regulators in the UK Regulators Network.

11. Options toolkit

This preparatory task, to prepare standard information for the toolkit of options, should be carried out at strategic level to cover all the Level 3 plans. You should work with other stakeholder organisations to include options that they could deliver (or you could deliver collaboratively) to help you achieve the objectives of the DWMP.

11.1 Generic options

This defines the range of potential option types for consideration across all aspects of drainage and wastewater planning in any geographic area.

The options will include a range of operational and maintenance activities, asset improvements, green infrastructure, land management, markets and customer side actions.

You should work with other stakeholder organisations to include options that they could deliver (or you could deliver collaboratively) to help you achieve the objectives of the DWMP.

It is useful to characterise the options into types to guide adaptive planning in the risk assessment and option development stage. These types are Incremental options, Modular options and One-off options.

Incremental: Options such as Sustainable Drainage Systems (SuDS) retrofit or infiltration reduction, where one area can be addressed one year, then another area the following year, without incurring significant additional cost as a result of the phasing of the work. 

Modular: Options such as attenuation storage or treatment works units, where one module can be built in the short-term, allowing for connections so that further modules can easily be added in the future. There is some additional cost in constructing in phases, but by deferring part of the cost this can give the lowest net present cost and improve the net present value of the scheme.

One-off: Options such as upsizing a sewer or tunnelling a new interceptor, where it may be impractical or very expensive to expand or reconstruct the asset in the future. These schemes may include larger options subject to planning under the Town and Country Planning Act 1990, or projects requiring a Development Consent Order (DCO) under the Planning Act 2008. Additional Welsh legislation in also applicable particularly the Planning (Wales) Act 2015, Well-being of Future Generations (Wales) Act 2015 and the Environment (Wales) Act 2016. The lowest net present cost may be achieved by building for the highest long-term need rather than incur substantial additional cost to expand capacity at a later date.

Incremental and modular options are preferred when there is significant uncertainty in future requirements as they will give ‘least regrets’ investment, but one-off options may be preferred when they will give the lowest net present cost, and potentially increase net present value, for all potential future scenarios.

In accordance with the NIC Solutions Hierarchy found online, you should prioritise solutions that maintain and optimise the existing drainage and wastewater system prior to any potential enhancement options.

A suggested list of generic options is given for guidance in the table below, but this is not exhaustive.

Table 4: Suggested generic options

Group	Option name
Customer side	Water efficiency – domestic
Customer side	Water efficiency – commercial
Customer side	Rainwater harvesting – domestic
Customer side	Rainwater harvesting – commercial
Customer side	SuDS – domestic
Customer side	SuDS – commercial
Customer side	Customer education – domestic
Customer side	Customer education – commercial
Customer side	Greywater re-use – domestic
Customer side	Greywater re-use – commercial
Customer side	Property flood resilience – above ground
Customer side	Property flood resilience – below ground
Customer side	Treat / pre-treat trade effluent
Sewerage network	Proactive maintenance – cleansing
Sewerage network	Proactive maintenance – rehabilitation
Sewerage network	Proactive maintenance – non-infra
Sewerage network	Intelligent operation
Sewerage network	Increased conveyance – infra
Sewerage network	Increased conveyance – non-infra
Sewerage network	Increased storage capacity
Sewerage network	Transfer within catchment
Sewerage network	Transfer between catchments
Sewerage network	Reduce infiltration
Sewerage network	New foul sewerage
Sewerage network	New surface water sewerage
Sewerage network	Relocate and/or improve outfalls
SuDS	SuDS – public
SuDS	Surface water source control – rural
SuDS	Rainwater harvesting – public
SuDS	Exceedance pathways
SuDS	Exceedance storage
Treatment	Improved maintenance
Treatment	Process optimisation
Treatment	Increased capacity – new streams
Treatment	Increased capability – new process
Treatment	New treatment works
Treatment	Relocate and/or improve outfalls
Treatment	Effluent reuse – non-potable
Treatment	Effluent reuse – potable
Treatment	Smart permitting
Treatment	Catchment management – low flows
Treatment	Catchment management – quality
Treatment	Flood protection for your assets

Nature-based Solutions in Wales

In Wales, nature-based solutions are the preferred option of Welsh Government, except where it can be demonstrated they are not practicable or are excessively costly. Water companies in Wales should aim to address the root cause of problems, prioritising their effort on the greatest environmental impact and prioritising low carbon or nature-based solutions (where applicable).

11.2 Acceptable options

The list of generic options should be reduced by rejecting those that are not acceptable to the stakeholders, based on objective, repeatable and consistent appraisal criteria. These rejected options should be recorded indicating why they have not been taken forward. This could be because they are not currently technically feasible, because they are not currently expected to be best value or because they would have unacceptable impacts.

11.3 Constraints

For each of the generic options, a list of constraints should be derived to provide an initial filter on when it is appropriate to fully assess the use of an option in the option development stage.

The constraints assessment could consider issues including, but not limited to:

• impact on stakeholders
• impact on the environment
• cost
• feasibility
• time to deliver
• suitability for area characteristics
• potential environmental impacts as part of the Strategic Environmental Assessment

This step must also identify those options where detailed environmental assessment will be required for their application.

11.4 Habitats Regulation Assessment

Your plan, including any options within it, should support the achievement of favourable conservation status of habitats and species identified by the Conservation of Habitats and Species Regulations 2017, hereafter the Habitats Regulations. It should also not prevent the achievement of favourable condition of sites designated under the regulations. You should assess if there are any likely significant effects on European sites from any of your options before you consider them as acceptable options.

Where you cannot conclude ‘no likely significant effects’, an ‘appropriate assessment’ is required to establish if the option can be delivered without having an adverse effect on the integrity of a designated site.

HRA refers to the assessment of the likely or potential effects of a plan or project on one or more European sites, namely

1. SACs and SPAs.
2. Candidate SACs (those submitted formally but not yet adopted or designated).
3. Proposed SPAs and SACs (sites subject to consultation on whether they should be designated).
4. Proposed and designated Ramsar sites, which are not designated under the Habitats Regulations but under government policy should have the same level of protection as SACs and SPAs.

The main stages in the HRA process are the following.

1. Screening stage, to check if the proposal is likely to have a significant effect on the site’s conservation objectives. If not, you do not need to go through the appropriate assessment or derogation stages.
2. Appropriate Assessment stage, to assess the adverse effect on the integrity (AEOI) of the proposal in more detail and identify ways to avoid or minimise any effects.
3. Derogation, to consider if proposals that would have an adverse effect on a European site qualify for an exemption.

For further detail on how to deliver your HRA see Habitats regulations assessments guidance .

You must check if the draft plan could have a significant effect on a European site within your level 1 area that could affect its conservation objectives. You can find the conservation objectives for European sites on land and inshore in:

England – Natural England’s designated sites database.

Wales – NRW’s designated sites database.

You must assess the effects of the plan or project alone, or in combination with other plans or projects, for example, the effects of supply options on European sites. A plan or project cannot normally be enacted unless you can be confident beyond reasonable scientific doubt that it would not have an AEOI of a European site, with specific exceptions which are detailed in the guidance linked below.

In exceptional cases, a plan or project can be authorised or adopted despite having an adverse effect on the integrity of a European site, but only when the following apply:

• there are no alternative solutions to delivering the objectives of the plan or project
• there are imperative reasons of overriding public interest
• compensatory measures are secured to maintain the overall coherence of the national site network

Therefore, it is important that your HRA is started as early as possible during preparation of your plan to feed into the considerations of constraints for the generic options list. This will give the HRA the greatest opportunity to influence the plan and therefore avoid or minimise impacts on European sites. The HRA should be seen as an iterative process throughout the plan’s development. When impacts are identified you should consider how you can change your plan and projects, before reassessing them.

Natural England and NRW are statutory consultees for the Appropriate Assessment stage, making it a legal duty to have regard to their advice. You should consult with them (as appropriate) as early as possible. This could be done earlier during the screening stage. Although there is no statutory requirement to consult at the screening stage, early engagement could help ensure a robust HRA. Natural England and NRW provide a pre-application Discretionary Advice Service (DAS).

Guidance can be found on GOV.UK for England and for on the NRW website for Wales.

The need to complete a HRA should not be a reason on its own to screen out an option. This is because a HRA screening may conclude that there are ‘no likely significant effects’. Alternatively, an Appropriate Assessment may conclude ‘no AEOI’. Either of these may allow the option to be retained within the plan.

Due to the strategic nature of DWMP, deferring the Appropriate Assessment for options identified in the HRA as having a ’likely significant effect’ may be acceptable in a DWMP context only when all the following criteria have been satisfied:

1. Where, due to scientific uncertainty of a novel or complex process and a need for more research, information cannot reasonably be gathered at the draft Cycle 2 DWMP.
2. Options are proposed for delivery later in the plan (post-2033 to be accounted for in future DWMP cycles) ensuring that there is time to allow for assessment and delivery of alternatives if necessary.
3. Alternatives are included in the plan at company and/or catchment level where the avoidance of an AEOI of European sites is certain, and these are available, feasible and deliverable.
4. A commitment is made to pursue alternatives if an adverse effect on integrity of a European site cannot be avoided for the preferred options set.

You should ensure that any previous HRA completed for any options included in your preferred plan remains current or is updated to account for any material changes in circumstance. Any HRA needs to be available for review and assessment by Natural England in England and NRW in Wales, and other relevant parties. You should explain how you have considered advice from these bodies. You must take a precautionary approach with your decisions at each stage of the HRA process.

Additionally, the information provided by LNRS can be utilised to help highlight strategic areas for nature to be considered during the HRA screening process. This can be especially valuable with identifying areas of functionally linked land near or adjacent to European sites, and the actions required on these sites to mitigate risks to, or further enhance, the notified features of European site.

11.5 Strategic Environmental Assessment (SEA)

Under the Environmental Assessment of Plans and Programmes Regulations 2004 (the ‘SEA Regulations’), certain plans and programmes are required to be subject to a Strategic Environmental Assessment (SEA). The SEA is a process that contributes to the integration of environmental considerations into the preparation and adoption of plans and programmes with a view to promoting sustainable development.

You will need to assess if your DWMP requires an SEA under the SEA Regulations. Refer to practical guidance SEA guidance for further information. If an SEA is required, you should ensure your SEA meets the legal requirements as set out in the SEA Regulations and ensure your SEA informs your plan decision-making, clearly demonstrating within your plan and SEA Environmental Report how the SEA has influenced the options development stage of the DWMP. 

The stages of the SEA process are as follows: 

1. Determine if an SEA is required under the SEA Regulations (refer to the published Practical Guide to the Strategic Environmental Assessment Directive for further information).
2. Setting the context and objectives (determining the baseline and developing the scope of the SEA, including producing a scoping report to consult on with the relevant consultation bodies).
3. Developing and refining reasonable plan alternatives and assessing effects.
4. Preparing the SEA environmental report and publishing for public consultees and consultation bodies alongside the draft DWMP for consultation.
5. Publication of the final DWMP and Statement of Environmental Particulars, including how changes have been made to the plan as a result of consultation and details on monitoring the significant environmental impacts of implementing solutions on the environment as identified in the SEA.

Additional information may be found online at the following: 

1. Strategic Environmental Assessment and sustainability appraisal.
2. The Environmental Assessment of Plans and Programmes Regulations 2004.

Should your plan be subject to an SEA, you must consult with your statutory consultation bodies throughout this process, which for England are Natural England, Historic England and the EA. You should also consult with a range of other bodies such as relevant LPAs, LLFAs, and interested environmental groups, and any other consultees listed in section 2.1 of this guidance.

Where DWMPs are cross-border or have potential for cross-border effects, the relevant SEA statutory consultation bodies for Wales (NRW and Cadw) or Scotland (NatureScot, Historic Environment Scotland and the Scottish Environment Protection Agency) should also be consulted. Where a DWMP is likely to have significant effects on the environment in a member state of the European Union, transboundary consultation will also be required.

You must ensure that you have complied with any other statutory requirements in developing your DWMP. For example, you must ensure that your DWMP meets the requirements of the Conservation of Habitats and Species Regulations 2017 by undertaking an HRA screening. Refer to section 11.4 for more information.

Once more detailed project options come forward, solutions may be subject to an Environmental Impact Assessment (EIA) under the relevant EIA Regulations. 

11.6 Cost models

You should develop a high-level cost model that allows an initial estimate of cost based on readily available measures, often referred to in unit cost models as “yardsticks”. These could be:

• area of impermeable surface disconnected by SuDS
• length and diameter of sewer
• volume of storage
• flow rate of treatment

You could also provide guidance on likely site-specific additional costs. Examples include additional costs for work in dense urban areas, the cost of land purchases, or the impact of poor ground conditions.

You could document known existing unit cost models and on-cost multipliers for inclusion in your DWMP.

11.7 Wider benefits

The benefits that the implementation of options will bring to the defined performance indicators are assessed later when the options in the toolkit are applied to a particular location. Some potential options, particularly blue-green infrastructure options such as sustainable drainage, bring inherent wider benefits; spatial targeting of these measures can maximise additional benefits. LNRS may help identify suitable areas to deploy these options. These wider benefits could include biodiversity, flood risk management, carbon sequestration, enhanced community spaces, and aesthetic improvements. A value framework for quantifying and valuing these benefits will already exist as part of your investment planning and optioneering processes and will have been reviewed in the previous stage of your DWMP. 

As part of this step, you should score each option against your company’s value framework for the wider benefits that it would bring. Ideally these benefits should be given a monetary value so that they can be included directly in your DWMP cost benefit assessment.

Further guidance on determining best value is available on the Ofwat website. You could also draw on information from relevant LNRS to identify suitable locations for nature-based solutions. Other benefits you should account for include:

1. Embedded carbon (tCO2e) of all wastewater projects and operational carbon reduction in operational greenhouse gases (tCO2e) of the wastewater system.
2. Biodiversity benefit (England) delivered by wastewater projects on sewerage undertaker land or third-party land where the net gain is funded by the sewerage undertaker. In Wales, there is a focus on achieving Biodiversity New Benefit, with a focus on integration into broader sustainability and nature recovery objectives.

12. Risk based planning

In this stage, you should define the scope of your planning study for each of your Level 3 areas.

As required under section 94A of the Water Industry Act 1991, you must review your DWMP annually and in doing so you should review the risk-based planning stage to identify whether there is a relevant material change in circumstances that requires you to revise your plan. Details of the requirements for the annual review are given in section 7.1.

12.1 Assess recent performance

Your DWMP must address the current and future demand on your system.

You should assess the recent performance of the systems in each area against relevant performance measures. You should consider and document both the absolute score against each measure and any long-term trends of improvement or deterioration.

You should assess:

1. Performance against all relevant measures from the most recent version of the Ofwat Water Company Performance Report including measures from the most recent Environmental Performance Assessment (EPA).
2. Excessive infiltration flows that impact on system performance or operating cost.
3. Continuous river (and/or other) water quality monitoring data.
4. Performance against biological measures for inland watercourses and the use of continuous monitoring for biological indicators in all waters.

You should consider each of the different measures individually rather than integrating them into a single screening score. This will allow you to understand the cause of poor performance of your system against each measure.

12.2 Assess asset health

performance from sewer blockage, sewer collapse and failure of non-infrastructure assets in pumping stations and treatment works. Managing risk should not result in planned residual risk of environmental permit non-compliance. These risks are covered in more detail in the following sections.

Your company should already have a regionwide assessment of asset health that will drive your existing plans for immediate operational activities and capital maintenance including PIRPs, infiltration reduction plans, blockage reduction plans and sewerage rehabilitation programmes. You should integrate the outputs of these existing assessments into your DWMP to help inform the total future investment plan and integrate with other drivers for investment.

Additional guidance on asset health measures is given in the UKWIR report on future asset planning.

12.3 Sewer blockage

The probability of sewer blockage depends on the combination of sewer characteristics and condition and the discharge of inappropriate and unsuitable material into the sewer including wet-wipes and FOG.

You should analyse hotspots of previous blockage locations and combine with other data to predict the likely future number and impact of blockages in an area. 

You should use this risk assessment to define appropriate best value sewer blockage risk management measures (for example education campaigns and automated or proactive sewer cleansing) but also consider sewer rehabilitation to remove defects.

You should evidence the extent to which the current level of capital maintenance can address performance indicators.

Further guidance is given in the UKWIR report Economic level of service for sewer blockages.

12.4 Sewer collapse

The recommended approach to assessing and managing the risk of collapse of a gravity sewer is set out in the Sewerage Risk Management/Sewer Rehabilitation Manual (SRM) found online on the WRc website.

You should carry out an assessment for gravity and pumped sewers and use this risk assessment to define appropriate sewer collapse risk management measures, such as proactive sewerage rehabilitation, for high-risk sewers and rising mains. This should be integrated with any need to relocate sewers or to increase their capacity.

12.5 Non-infrastructure assets

You should assess the reliability of operation of pumping stations and treatment works and the impact of asset failure.

You should adopt an appropriate method to predict the probability of failure of mechanical and electrical assets (for example, based on the age of the asset adjusted for current asset condition using mortality models such as Weibull curves). 

You should forecast the failure of structural assets such as tanks and channels using structural deterioration models (see e.g. UKWIR Report 11/WM/13/2 ‘Deterioration rates of long life, low probability of failure assets’, found on the UKWIR website).

You should assess the probability that failure of the asset will cause the system that it is part of, to fail. This should involve consideration of standby assets and other mitigation measures.

You should assess the site-specific consequences of failure of the system and should include any impacts on flooding, pollution, breach of discharge permits and additional operating costs.

You should use this risk assessment to define appropriate asset failure risk management measures (for example, renovation or renewal of high-risk assets or through providing additional standby or mitigation measures). This should be integrated with other strategic needs. You may find additional guidance in UKWIR Report 12/RG/05/32 ‘When to repair, refurbish or replace non-infrastructure assets’, found on the UKWIR website.

12.6 Local future trends

You should document the impact for the individual Level 3 area of the generic trends that you have identified as part of the strategic context. This should consider the most-affected areas of the catchment rather than the average over the catchment, as if one area of the catchment is subject to a significant planned development or other change, then it is likely that a plan will be required for the whole catchment even if there is no change elsewhere.

You could consider the impact of future trends on your public surface water sewers as well as on your foul and combined sewers. Surface water sewers are also subject to climate change and can cause water quality impact resulting from highway runoff and misconnections.

Your DWMP must assess the current and future demands on your system, which would include any expected development projects or changes in land use in your areas. You should map these expected changes and demonstrate how your selected options will meet changes in demand. This should also show which areas of the catchment are subject to other generic trends.

12.7 Strategic issues

Your DWMP should look for opportunities to help deliver your and other stakeholders’ strategic plans that affect, or are affected by, your sewerage systems. This stage should identify those potential strategic opportunities for the study catchment, including:

1. Discharge constraints (treated effluent and overflows).
2. Flood and erosion risk.
3. Sewer diversions.
4. First time sewerage.
5. Measures to support recovery of biodiversity and protected sites for nature.
6. Community, social and heritage assets.

These are described in more detail in the following sections.

12.8 Discharge constraints

Your plan should aim to integrate with other strategic plans and legal obligations for the water environment that also address discharge constraints, including RBMPs. RBMPs generally look five to ten years ahead, and so your DWMP should also consider the longer-term strategy for discharges to the water environment beyond the view of the RBMP.

You could characterise each existing and potential future treated effluent and overflow discharge location by:

1. Status of receiving water: bathing, shellfish, transitional and coastal waters (TRAC), river, lake, SSSI, groundwater etc. The future status of inland waters as “healthy for recreation” should be included.
2. For intermittent discharges to rivers, the dilution - defined in EA consenting guidance as the ratio between 95%ile low river flow (Q95) and Average Dry Weather Flow in the sewer. This should be assessed for the current situation and for the long-term future with changes in population and climate change and other impacts on low river flows.
3. The results of the investigation under the PR24 storm overflow assessment framework and storm overflow discharge reduction plan Environment Act drivers.
4. Increased risk of downstream river flooding from increased discharges from sewerage outfalls.
5. For treatment works, the technically achievable permit limits for final effluent quality.

This assessment will help to identify potential best value strategies for each discharge.

12.9 Flood and erosion risk

You should assess risk to sewerage and drainage assets from all sources of flooding, such as watercourse or coastal flooding and erosion. The new National Flood Risk Assessment (NaFRA2), updated National Coastal Erosion Risk Map (NCERM) and accompanying maps for river, sea and surface water flooding should be used to identify where discharges from drainage systems could be restricted by high flood levels, or where drainage and wastewater assets could be at risk from flooding or coastal erosion. Sewerage undertakers have an obligation to act in a manner consistent with the National FCERM Strategy to plan for their infrastructure to be resilient to flooding and coastal change, and have regard to local strategies.

12.10 Sewer diversions

You should consider any needs for strategic changes in the layout of the sewerage system by diverting existing sewers that could be integrated with options to reduce other risks.  These diversions could be to:

• remove sewers from unsuitable locations such as under buildings or major infrastructure
• remove constraints on future development sites
• reduce energy costs by relocating or modifying pumping systems

12.11 First time sewerage

You should identify those areas with populations that are not currently served by public sewerage and those areas where private wastewater discharges are identified as reasons for a watercourse not achieving good status. You could consider whether these areas may require the provision of first-time sewerage within the life of the DWMP.

12.12 Community, social and heritage assets and habitats

For each plan area, you could identify and publish (using publicly available mapping) key features that should be protected from current or future risks and from disruption from the implementation of planned improvements. The features should include:

1. Key community infrastructure including schools, healthcare, community spaces, key transport routes.
2. Social assets including public open space, footpaths and landscapes.
3. Heritage assets including listed buildings, archaeological sites, National Trust properties, tree preservation orders.
4. Locally, nationally or internationally recognised habitats that are subject to protection, such as SSSIs.

Any proposed option that affects these locations may need additional measures detailed as to how any impact may be mitigated.

12.13 Prioritisation of studies

Your investment need identified in your DWMP should be supported by observed data and evidence wherever possible and complemented by predictive modelling where necessary. You should work with stakeholders to draw up a list of the catchments that will need a predictive study in the long-term, and those that will not need a study. The methodology that you use, and the resulting output, should be documented to justify the approach and to show the number of catchments and the population served in each of the two groups.

You should collaborate with stakeholders to prioritise which catchments are to be studied in Cycle 2. You should publish this methodology and the proportion of the target catchments and the proportion of the target population where studies are being carried out.

The details of this method will be left to the companies, but the following principles should be followed for prioritisation. If a Level 3 catchment falls into any of these criteria, it should be studied in Cycle 2:

1. All catchments with regulatory obligations to be met in the first 10 years of the plan.
2. Catchments with treatment works currently failing permit conditions.
3. Catchments with treatment works at current technically achievable limits for final effluent quality.
4. Catchments that include local areas of current poor service such as properties with an annual probability of flooding of more than 1/20, pollution incidents, for England overflows discharging 20 or more times in an average year or have triggered a Storm Overflow Assessment Framework (SOAF) investigation, and for Wales overflows causing the greatest impact on the environment.

For level 3 catchments that do not fall into the above criteria for cycle 2, an estimate should be made of the future investment and performance based on current understanding of performance and that identified for similar catchments.

13. Prepare analysis tools

To understand and evaluate current and future performance and risks, and prepare solutions to address rainfall, hydraulic capacity, water quality impact and treatment works capacity and performance, you will need to identify, develop or improve suitable analysis and modelling tools.

You should appropriately verify all tools against recent system performance data to demonstrate that they are suitably accurate. You should document and justify the accuracy of your tools, and their robustness for extrapolation to future conditions.

This section provides guidance on the steps you should follow to ensure you have appropriate tools in place to evidence your DWMP.

13.1 Plan the analysis method

Requirement for Hydraulic Modelling

You will have defined which aspects of your system performance require assessment in the previous (risk-based planning) step. This is likely to require assessment of hydraulic performance for most systems.

You could use predictive hydraulic models for this because:

1. The rainfall runoff process is inherently random so that the situation or combination of situations that need to be assessed, such as large events causing extensive flooding, will not have historical data.
2. The future will be different from the past and so cannot be represented using historical data. Any system affected by climate change, significant development or increased paved area will probably need a predictive model.

There may be opportunities to simplify the modelling approach using data-driven models, but these should be able to represent future conditions.

Requirement for Water Quality Modelling

A full assessment of water quality impact requires water quality modelling which can be complex and time consuming. You should usually take a catchment approach to water quality modelling and follow the principles in the EA’s water quality modelling strategy, available on request. Fully integrated catchment modelling may not be required in all cases. Water quality modelling considers the impact, and future requirements, of continuous and intermittent discharges.

EA guidance on water quality modelling of the impacts of storm overflows should be followed around achievement of SODRP targets and those of the latest SOAF.

13.2 Develop your rainfall model

Rainfall is the key driver for flood risk and the environmental impact from drainage and wastewater systems (except separate foul systems). You should develop a robust approach to representing rainfall with your models. You should use different representations of rainfall for assessing flood risk and overflow spills. 

Guidance on modelling of rainfall is given in the CIWEM Urban Drainage Group (UDG) Rainfall Modelling Guide 2016 on the CIWEM website. Some notes are given here on additional issues not covered by the guide, in particular, climate change.

Rainfall for flood risk

Assessment of flood risk from sewers generally uses synthetic design storms – that is storms that have the correct statistical characteristics for the rainfall climate of the area but have an idealised shape. 

You should aim to model design rainfall for 1/10, 1/20, 1/30 and 1/50 annual probability events as a minimum. This does not imply that options should be designed to a 1/50 annual probability standard.

You could assess summer and winter storms separately to determine the worst-case scenario, taking into account the different rainfall depths and profile shape associated with each.

You should aim to adapt your design rainfall events to account for the effect of climate change on rainfall intensities for future planning horizons. The percentage increase will depend on the region of the country and may also depend on the season, storm duration and return period. The increase will also have a significant uncertainty, and you should take this into account when evaluating and developing options for future scenarios. The latest guidance is given in the UKWIR report 22/CL/10/19 on the UKWIR website.   

Rainfall for spill assessment

For assessing overflow discharges your baseline will need to be based on a minimum of 10 years’ worth of time series rainfall data (2014 to 2024). This 10-year dataset needs to be uplifted to recognise baseline and future pressures.

13.3 Develop or improve hydraulic models

Drainage system models

The majority of drainage and sewerage systems will require hydraulic models of their capacity for future planning. Further guidance is available in the CIWEM UDG Code of Practice for the Hydraulic Modelling of Urban Drainage Systems 2017 (UDG CoP) found on the CIWEM website. Models should meet the requirements of a Type II model as defined in the CoP.

Where you already have a hydraulic simulation model of the systems then you should aim to review this to check that it is up to date. Where a study is required on foul, combined or surface systems that do not have existing models, then you could build these using best available information and following best practice industry guidance.

Your modelling approach should aim to ensure that:

1. Your model is stable and runs reliably, and that it accurately reflects the performance of the area when compared to observed data (including recent flow and level data and historical verification).
2. All overflows and constraints on flow through the wastewater treatment works are represented.
3. External boundary conditions including inflow from natural catchments and outflow restrictions from river and sea levels are represented in an appropriate way including changes in boundary conditions with time (including due to climate and development) for future planning horizons.

For river boundaries, you could follow the guidance in the CIWEM CoP including use of an initial screening assessment for a worst case of river levels at bank full. If this shows a significant impact, you should make the appropriate selection from the three approaches to representing the river boundary depending on the relative times of concentration of the river and sewerage systems. Further guidance on representing the joint probability of rainfall and river and sea levels is given in section A2 of the CIWEM UDG Integrated urban drainage modelling guide 2021, on the CIWEM website.

Surface flood models

All flood risk assessments, mapping and modelling need the maximum interoperability between the different RMAs. This is important both at a local level to target action in high-risk surface water areas and at a national level to gather a national picture of the risk. You should define and justify the method that you will use to represent the impact of flooding from sewers on properties and other areas. This method may depend on the severity and extent of the flood risk and could vary for different parts of a study area. You could select the most appropriate method from those listed below as described in the CIWEM UDG Integrated urban drainage modelling guide 2021:

1. Flood cone model – where the radius of the flood extent around a manhole depends on the volume of flooding and all properties and other areas within that radius are assumed to be flooded.
2. 2D flow model (one way link) – where the flood volume from a manhole is routed across the ground surface using a 2D model to identify which properties and other areas it affects. The link with the 2D model is one-way so that the flood flow does not return to the system.
3. 2D flow model (integrated) – where the flood volume from a manhole is routed across the ground surface using a 2D model to identify which properties and other areas it affects. The link with the 2D model is two-way so that the flood flow can return to the system.

13.4 Develop or improve water quality models

You should define and justify the method that you will use for modelling the impact of your discharges on water quality and this method should be agreed with the environmental regulator. 

Guidance on modelling of the impact of intermittent sewage discharges on receiving water quality is given in several publications:

• the EA SOAF sets out the requirement in England: Storm overflow assessment framework 2025
• the Foundation for Water Research (FWR) Urban Pollution Management Manual on the FWR website sets out detailed guidance on modelling approaches
• the UKWIR Guide to Modelling Intermittent Discharges on the UKWIR website

Treatment works modelling

You will need to model treatment works performance if you are assessing the capacity and performance of the works against its permit conditions and if you are including the treatment works in an integrated water quality impact model.

For assessing treatment works’ discharges on receiving water quality within an integrated water quality model, you should use a data driven model of existing performance (adjusted for future conditions) that shows the variation of flow and pollutant discharge as statistical distributions. River Quality Planning (RQP) and Source Apportionment Geographical Information System (SAGIS) Simulation of catchments (SIMCAT) are the most commonly used stochastic water quality models. SAGIS SIMCAT models are already set up for all of England and Wales. The latest version of any SAGIS SIMCAT models should be used where these models are used to assess the impacts of wastewater treatment works.

You may select more advanced modelling approaches (such as detailed simulation modelling) to support decisions relating to process or performance optimisation or for more detailed assessment of water quality impact.

River modelling

You should select and justify an appropriate method of modelling the impact of discharges on receiving water quality.

For slow moving waterbodies you could consider modelling and monitoring deposition and erosion of sediment where this is a local concern.

Coastal modelling

For discharges to coastal waters the main concern is bacteriological quality, and you should consider the balance between a simple spill frequency assessment and a detailed pollution dispersion and decay model.

Highway runoff

Where your surface water systems discharge highway runoff, you could carry out a screening assessment using an appropriate methodology, agreed with stakeholders, such as Highways England Water Risk Assessment Tool (HEWRAT). This can be applied to groups of outfalls discharging to a single reach of a watercourse rather than to individual outfalls.

14. Risk assessment and option development

This section covers the characterisation of risks and the development and assessment of improvement options to manage those risks.

14.1 Methodology

Your DWMP must include the sequence and timing of implementation of the measures you propose to take to meet, and continue to be able to meet, your obligations. You will need to develop a plan for staged delivery of investment for a range of future scenarios, using adaptive planning approaches that allow revised decision-making at future points in time as the future uncertainty is resolved.

Your approach should minimise the required modelling and assessment effort while still delivering a robust plan. You should first decide on the required number of future planning scenarios and the order in which they will be addressed.

Definitions

This section uses these 2 terms as defined here.

Base year. The first year that is assessed for predicted performance. It is defined as the end of the current AMP.

Baseline. The situation for any future year if there is no additional investment or operational change other than those already planned in the current AMP. This is consistent with guidance on undertaking cost benefit analysis, using ‘do nothing different’ as the point from which benefit is estimated.

14.2 Planning scenarios

The initial planning scenarios should be based on 5-year, 15-year and 25+ year planning horizons. There will be significant uncertainty in population growth, development, urban creep, water consumption, climate change and other trends in the longer-term horizons. You should therefore consider a range of scenarios in your adaptive plan.

The magnitude of change should be based on the latest regulator recommended allowances and any other published guidance, including the UKWIR report on the Future of Asset planning found on the UKWIR website. For simplicity, the lowest scenario should be consistent on all the future trends, and the high scenario high on all trends.

The recommended approach reduces the number of future scenarios by changing from fixed planning horizons each of which has uncertain magnitude of change to three fixed change scenarios each of which has an uncertain time of occurrence.

You should use the 5-year Medium scenario as the lowest planning scenario to define the options required in the short-term.

The 25-year High scenario represents the largest predicted change, and you should use this as the worst-case long-term planning scenario. This may not actually occur within the 25-year planning horizon.

You should choose a mid-point scenario to represent the lowest scenario that is almost certain to occur within 25 years in all plausible futures. In practice this is likely to occur sooner than 25-years. This is the Core scenario where investment will be justified in the long-term with no regrets.

This table summarises the three potential planning scenarios.

Table 5: Future planning scenarios

Scenario	Description	Likely occurrence within
A	5-year Medium – most plausible for short-term planning	Approximately 5 years
B	Core scenario – high likelihood for long-term planning.	10 to 20 years
C	25-year High – conservative for long-term planning	Greater than 25 years

There will be uncertainty on when the implementation of risk management options will be required and you should define trigger points for values of growth, climate change and other trends that will indicate when to undertake detailed preparation and delivery of schemes.

You should document the selected scenarios and magnitude of change for each change parameter, for each Level 3 area being assessed.

14.3 Base year assessment

You should already have assessed the historical performance up to the current day as part of verification that the assessment tools adequately represent the performance of the system.

You should assess the system performance for the base year (the end of the current AMP – 2030) to give the benchmark from which you can report the change in performance over the life of the plan. You should account for the status of schemes and maintenance activities planned for delivery during the current AMP.

14.4 Assessing a scenario

You should develop and assess best value investment options, repeating the process for each future scenario, but with changes in the base system that you start from and the suite of preferred options that you consider.

To reduce the amount of more complex water quality modelling that is required, you could first develop options to meet hydraulic requirements for flooding and spill frequency and then carry out water quality modelling, if deemed necessary to (continue to) meet obligations, from a baseline incorporating the preferred options for the hydraulic issues.

The assessment process for each of the scenarios is shown in the diagram below and described in the following sections.

Figure 3: Process for risk assessment and option development.

Figure 3 shows the four stages you could consider when assessing and developing options for an individual scenario. This includes hydraulic assessment, hydraulic options, quality assessment and quality options.

14.5 Hydraulic risk assessment

Update model

You should update the assessment tools to the future scenario using the future trends already identified for the area including all aspects detailed in section 9.1.

You should include in the updated model any investment schemes including maintenance activities that are already committed to in the current AMP.

Assess hydraulic risks

You should account for the status of capital maintenance activities to solve current operational problems before assessing underlying hydraulic risks, reflecting if they have been resolved. Where these problems may involve major capital maintenance projects then overlaps with long-term performance should be considered during the option development process.

You should aim to assess flood impact on properties and spill frequency to watercourses using the methods that you have chosen.

Characterise problems

You should collate all identified performance issues to allow an overview of problems requiring investment. Collapse and blockage risks can often be managed in isolation from other problems using cleansing and rehabilitation programmes. However, you should also collate them here as they may influence the solutions selected for other risks.

You should then look for commonality of the cause between different risks. This could involve review of:

1. Long sections of sewerage model results to identify the hydraulic influences of flooding or spill.
2. Influence of infiltration on sewer capacity and treatment works compliance.
3. Load apportionment between discharges to identify influences on river water quality if a quality assessment will be required.

You could group the issues into geographic clusters (Level 4 areas) where required investment is likely to be common across the area. Any planned schemes already included in the base year model could be included in an area for review.

There may also be some investments required that cut across localised areas and these could be assessed before looking at individual areas.

You should prioritise the areas based on the impact against all performance risks in the cluster. This is likely to be a mixture of statutory targets for environmental standards and risk values for flood and other risks. You should integrate the risk values over the longest planning horizon to give a whole-life risk value.

You may set a minimum risk threshold for the whole-life risk value for an area, below which you will not develop options to address those risks; you should aim to agree these thresholds with stakeholders. Risks to statutory targets and not meeting legal obligations always require you to develop options.

14.6 Develop hydraulic options

This stage develops initial potential solutions to hydraulic problems.

You should use a funnelling approach, initially using simple scoring methods and then progressing to detailed modelling of the applicable options.

Applicable options

You should select from the generic option toolkit those options that could help address the performance indicators in a Level 3 area and that are likely to be appropriate and feasible for that area. You should base this on the generic characteristics and constraints set out in the options toolkit including cost, benefit, feasibility, disruption, time to deliver, wider benefits etc.

In accordance with the NIC Solutions Hierarchy, you should prioritise solutions that maintain and optimise the existing drainage and wastewater system prior to any potential enhancement options.

You should start with options to improve the operation and maintenance of existing assets and then consider incremental and modular options before large one-off options (see section 11).

You should take forward the applicable options for further assessment. For hydraulic problems, these are likely to be:

• removal of localised bottlenecks in the system
• reduction of inflow through surface water disconnection and SuDS
• controlled discharge to watercourse in extreme rainfall events
• overland flow of flood water in extreme events particularly for surface water sewers
• construction of detention storage

Effective options

You should identify a combination of applicable options that will address the risks in the area to meet statutory objectives, deliver cost beneficial performance improvements and avoid unacceptable detriment to existing service levels. Unless there is clear information on when a scheme will be implemented, the benefit cost assessment should normally assume that the scheme will be implemented at the midpoint between the two planning horizons.

You could identify the combination of options either by:

• starting with those that are likely to deliver best value and working through the list until options that deliver less benefit than their cost are reached or
• using an optimisation engine to help find the best value combination of options

Feasible options

You should draw up a shortlist of potential options considering the buildability and acceptability for the proposed location. You should adjust cost estimates adding markups to allow for site conditions (these may already be representable in your unit cost models). Where necessary a detailed environmental assessment should be carried out. This is likely to be only required for major infrastructure options or options in designated sites.

Preferred options

You should then select the preferred options and embed them into a future baseline model for assessing longer term scenarios or for water quality assessments.

14.7 Quality risk assessment

In many cases the preferred options to resolve hydraulic risks will also help resolve water quality risks. The assessment described in section 13.1 could now be carried out to identify if you need to assess water quality risk and develop water quality options.

Update models

You could update the models to the future scenario using the future trends already identified for the area. For climate change this could include changes in river flow and changes in water temperature.

You should include in the model the preferred options developed in the previous hydraulic option development step for the scenario.

Assess quality risks

You could assess the future performance in a similar way to the hydraulic risk assessment.

There is a challenge of defining the future conditions for the quality of the upstream river flow as this requires an assessment of changes made to other areas upstream and changes in farming practice and other discharges. You could use sensitivity testing to identify the impact of the uncertainty on this.

14.8 Develop water quality options

You should develop options following the same funnelling approach as for hydraulic options.

Applicable options

The most applicable options for water quality problems could be:

• reduce flows
• relocate discharges
• improve treatment
• storage

Effective options

You could follow the same strategy as set out for hydraulic options.

Feasible options

You could draw up a shortlist of potential options using the same approach as for hydraulic options.

Preferred options

You could then select the preferred options and embed them into a future baseline model for assessing longer term scenarios.

15. Define the preferred plan

This stage of the planning process considers how benefits are to be delivered over the life of the plan, including how adaptive plans are best phased, how long-term investment plans will be smoothed, the opportunities and risks associated with proposed collaborative projects, and the implications of the plan for future operations and maintenance activities.

15.1 Smoothing the level 3 plans

In the option development process, you will have developed preferred options that will deliver value for each level 3 area for each of the planning horizons (notionally 5 years, 15 years and 25+ years). Each option will have: a cost, a list of benefits, a net present value (NPV, defined as net present benefit minus net present cost) and a benefit cost ratio based on an assumed delivery at the mid-point of the planning period.

For each level 3 area, you should tabulate the average annual cost for each planning scenario and the target value of performance measures at the end of each scenario assessed. You should produce additional versions of the table, with the medium- and long-term plans each brought forward by 5 years or delayed by 5 years. 

You should smooth the level 3 programme to ensure continued satisfactory performance against the performance indicators during the plan. You may accomplish this by moving projects with a low NPV or benefit cost ratio to a later block or bringing projects with a high NPV or benefit cost ratio to an earlier block.

At level 3, priority should be given to ensuring smooth performance even if this expenditure to resolve peaks and troughs of local risks is uneven.

Smoothing performance at level 3 will also ensure that performance will be smoothed at level 2.

15.2 Smoothing the level 1 plan

Your level 3 programmes should then be collated at a company level (level 1) and further smoothing carried out. You should aim for a smooth trend in performance against all the performance indicators and a smooth overall expenditure profile.

You should take into account and report on the potential impact on customer bills and deliverability of your plan.

15.3 Funding for collaborative projects

Your preferred investment plan should include collaborative projects with other stakeholders where action needs to be taken in parallel with the sewerage undertaker to deliver benefits.

You should collate these collaborative actions for each stakeholder and identify the funding that they will require. You should work with those stakeholders to identify potential sources of funding and to make the case for the investment.

As an RMA you may be eligible for grant-in-aid (GIA) funding for a flood and coastal erosion risk management (FCERM) project – guidance is available on the Gov.uk page for FCERM projects.

You should consider the maturity of the collaborative relationships and the risks of the projects not going ahead because of lack of funding or other reasons. You should clearly document the actions required if the collaborative project does not go ahead. This part of the plan should be included in the annual review of the DWMP.

You should also identify where existing plans by other stakeholders could be adapted to deliver outcomes for the DWMP at little extra cost. For example, you could collaborate with relevant LNRS responsible authorities to identify suitable projects included in the strategies.

15.4 Operational plan

Your DWMP should also define the changes to operational and maintenance strategies and plans to ensure that they are adapted to suit the long-term plan. This could include:

1. Arrangements for ownership and maintenance of blue-green infrastructure.
2. Reducing capital maintenance on assets that are shortly to be replaced or abandoned.
3. Identify overlaps between assets to be upsized and assets requiring capital maintenance.
4. Identify any potential future problems of sedimentation and blockage in the drainage system and plan for changed maintenance.

15.5 Defining a Best Value Plan

Your “Best Value Plan” is your preferred plan based on a ‘best value’ appraisal process. A ‘best value’ appraisal approach should incorporate natural capital approaches and evidence to ensure impacts on natural assets and the flow of ecosystem services are considered in decision-making.

When undertaking your ‘best value’ appraisal, you should explore a range of solutions, such as operational, customer-led, nature-based solutions and traditional capital expenditure solutions. You should promote solutions which deliver best value for customers, communities and the environment over the long-term.  

Your ‘best value’ appraisal should consider wider environmental and social benefits (for example biodiversity, flood risk management, carbon sequestration, and health and wellbeing), and opportunities for co-creation and co-funding. You can use natural capital evidence and metrics to support the assessment of benefits within your ‘best value’ appraisal. 

Defra’s Enabling a Natural Capital Approach provides guidance to help consider the value of a natural capital approach and includes an ecosystem services databook with guidance and sources of biophysical and valuation evidence associated with environmental effects. Other guidance and methods are available. In England, the water industry Natural Capital Evidence and Metrics (NCEM) contains recommended metrics for use in your ‘best value’ planning.

The concept of ‘best value’ should inform your overall strategy or plan to achieve the long-term outcomes you aim to deliver, and how they will deliver them in a range of plausible futures.

You should present how you will sequence these activities to achieve performance indicators in a ‘best value’ approach over the long term. The strategies should identify, given future uncertainties, what activities are best undertaken in the short and medium term and what can be better addressed in future periods. Therefore, they can help clearly set out the choices being made around the timing, scale and type of activities over the long term, and explain why those choices can maximise value for customers, communities and the environment.

16. Other guidance

This guidance references existing industry standard technical guidance. A list of current guidance is given here, but the latest industry standard guidance should always be used as it evolves.

16.1 Stakeholder engagement

CIRIA – Communication and engagement in local flood risk management.

Environment Agency – Working with others.

Defra – Co-funding schemes: how best to align the funding processes with the various bodies involved in resolving flooding.

Environment Agency – River catchment boundaries Catchment Data Explorer.

16.2 Regulatory framework

Defra – Guiding Principles for non-statutory DWMPs.

Defra – Water Industry Strategic Environmental Requirements (WISER).

Defra - Storm overflows: policy and guidance.

Ofwat – Ofwat annual performance assessment.

EA – Environmental Performance Assessment. 

16.3 Value framework

UKWIR – ‘Review of Cost Benefit Analysis and Benefits Valuation’ (2010).

Ofwat – Public Value Principles.

International Financial Reporting Standards – Integrated Reporting, 2013.

CIRIA – Benefits Estimation Tool (B£ST).

Multi Coloured Manual – Multi Coloured Manual – valuation of flood risk.

HM Treasury – Green Book.

Construction Innovation Hub – Value Toolkit.

EA – FCERM Appraisal.

16.4 Asset management

UKWIR – Framework for Expenditure Decision Making (2014).

IAM – Asset Management – An Anatomy.

UKWIR – ‘When to repair, refurbish or replace non-infrastructure assets’ (2012).

GFMAM – The Asset Management Landscape.

ISO 55000 – Asset Management ISO 55000 Vocabulary, overview and principles.

16.5 Asset health

WRc – Sewerage Risk Management (SRM).

UKWIR – Future asset planning - scenarios, frameworks and measures: final report.

UKWIR – Economic level of service for sewer blockages.

UKWIR – Deterioration rates of sewers.

UKWIR – Deterioration rates of long life, low probability of failure assets.

16.6 Climate change

Met Office – UKCP publications.

UKWIR – Guidance for applying a climate change rainfall tool for long term drainage and wastewater management in the water industry - 25/CL/10/20.

UK CEH – future river flows.

EA – Climate Change allowances guidance.

16.7 Risk assessment tools and models

UDG – Rainfall guide 2016.

UDG – Code of Practice for the Hydraulic Modelling of Urban Drainage Systems.

UKWIR – Modelling sewer inlet capacity restrictions.

UDG – Integrated urban drainage modelling guide 2021.

FWR – Urban Pollution Management (UPM) manual.

UDG – Guide to quality modelling of sewer systems 2006.

UKWIR – Guide to Modelling Intermittent Discharges.

UDG – River data collection guide 1998.

UDG – River modelling guide 1998.

EA - Storm overflow assessment framework 2025.

16.8 Implementation

CIRIA – The SuDS manual.

CIRIA – Designing for Exceedance in Urban Drainage - Good Practice.

16.9 Strategic Environmental Assessment

The Environmental Assessment of Plans and Programmes Regulations 2004 (legislation.gov.uk).

Strategic Environmental Assessment Directive: guidance.

Strategic Environmental Assessment Regulations requirements checklist.

Environmental Impact Assessment directive guidance.

16.10 Habitats Regulations Assessment

Developers: get environmental advice on your planning proposals.

Habitats regulations assessments: protecting a European site.

Natural England – Site Search (naturalengland.org.uk).

Natural Resources Wales – Natural Resources Wales / Find protected areas of land and sea.

17. Links with other plans

At present, different aspects of flood and water environmental planning are the responsibility of different bodies including water companies, the EA in England and NRW in Wales, and local authorities (flood, highways and planning teams). 

In addressing the matters set out in section 94A(3)(a-g) of the Water Industry Act 1991 when writing your DWMP, you should consider and, as appropriate, align with or reflect the additional plans and strategies listed below.

17.1 Natural Resources Policy (Wales)

Your DWMP should reflect the Natural Resource Policy holistic ambitions on sustainable management of natural resources in Wales aiming to enhance the well-being of current and future generations. You should aim to address:

• sustainable management of natural resources
• biodiversity enhancement
• water quality and availability
• climate change mitigation and adaption
• integrated management approaches including innovation and resilience
• community engagement and wellbeing

17.2 Well-being of Future Generations (Wales) Act 2015.

The Well-being of Future Generations (Wales) Act 2015 requires water companies to apply the principles of collaboration, integration, involvement, long-term thinking, and prevention in their DWMP, ensuring their actions contribute to sustainable development and the well-being of future generations.

17.3 Water Resources Management Plans (WRMPs)

Water Resource Management Plans are strategic plans produced by the water industry at regular intervals, setting out how the companies intend to achieve a secure supply of water for customers and a protected and enhanced environment. You should ensure that your long-term planning for wastewater and water resources are aligned. You should consider alignment in your growth forecasts (section 14.2), climate change scenarios, other future trends and assumptions, and timetable for delivering solutions.

17.4 River Basin Management Plans (RBMPs)

These are statutory plans prepared by the EA in England and NRW in Wales that are reviewed and updated every 6 years. The plans set out statutory environmental objectives for the water environment and the programmes of measures required to achieve those objectives. The plans establish an integrated approach for the protection and sustainable use of the water environment. Water companies have a legal duty to have regard to the relevant RBMP when carrying out current and future activities, such as abstraction or the return of treated wastewater, supporting the achievement of the environmental objectives, including preventing deterioration in water bodies.

17.5 Flood Risk Management Plans (FRMPs)

These were statutory plans prepared by the EA in England and NRW in Wales every 6 years that set out how organisations, stakeholders and communities should work together to manage flood risk in England. The EA and NRW and LLFAs liaise with other flood risk management bodies in developing FRMPs. Current plans cover the period 2021 to 2027. Future requirements to develop FRMPs no longer apply as a result of the Retained EU Law (Reform and Revocation) Act 2023.

17.6 National Flood and Coastal Erosion Risk Management Strategy for England

The National Flood and Coastal Erosion Risk Management Strategy for England (National FCERM) describes what needs to be done by all RMAs involved in flood and coastal erosion risk management for the benefit of people and places. It sets out the long-term delivery objectives the nation should take over the next 10 to 30 years as well as shorter term, practical measures RMAs should take now. You should adhere to the National FCERM Strategy when preparing your DWMP. 

17.7 National Flood and Coastal Erosion Risk Management Strategy in Wales

The National Flood and Coastal Erosion Risk Management Strategy in Wales (National FCERM) sets out, on one place, Welsh Government’s overarching measures required by RMAs and other partners over the next decade to reduce flood and coastal risk. You should adhere to the National FCERM Strategy when preparing your DWMP.

17.8 Local Flood Risk Management Strategies (LFRMSs)

LLFAs currently have a duty under section 9 in England and section 10 in Wales of the Flood and Water Management Act 2010 to “develop, maintain, apply and monitor a strategy for local flood risk management in its area (a “local flood risk management strategy”).” The guidance for preparing LFRMSs states that they should complement other plans and policies on flood risk in the authority area. Although there is no set timeframe for when these plans must be updated, they must be consistent with the National FCERM Strategy, and section 128 of the National Strategy for FCERM in Wales. Section 11 of this guidance covers the expected common principles between DWMP and flood risk planning in England.

17.9 Surface Water Management Plans (SWMPs)

These are non-statutory plans that some local authorities have developed to plan for managing surface water flooding. These plans potentially have strong overlaps and synergies with DWMPs in understanding and managing sources, pathways and receptors of surface water flooding; you could consider the content of any relevant SWMPs in your area when producing your DWMP.

17.10 Storm Overflow Discharge Reduction Plan (SODRP) (England)

The Storm Overflow Discharge Reduction Plan sets targets on the water industry to reduce the frequency and the adverse impact of overflow discharges on public health and the environment. The SODRP has been introduced to help ensure that industry infrastructure keeps pace with increasing external pressures such as urban growth and climate change.

When producing your DWMP you should have regard to the newest version of SODRP or any additional related guidance, and account for the targets in SODRP when conducting your optioneering. DWMP options that help to separate surface water from the combined sewer network will be especially key to meeting SODRP (Goal 2.5, “Achieving the targets”).

17.11 Storm Overflow Management (Wales)

In Wales storm overflow performance is to be monitored and based on reducing ecological harm. The priority for action should focus on identifying and addressing storm overflows causing the greatest impact on the environment.

17.12 Highways Asset Management Plans (HAMPs) (England)

These are drawn up by highway authorities to demonstrate to Department for Transport (DfT) that they are making the best use of highway assets through Asset Management Plans. This should include plans for highway drainage assets. You could consider the content of any HAMPs in your area relevant to drainage and interaction with your drainage and sewerage system.

In Wales Highways Asset Management strategies, Road Maintenance Plans, or Transport Asset Management Plans are adopted, with a focus on sustainability, long-term planning, and aligning with broader environmental and societal goals, as outlined in the Well-being of Future Generations (Wales) Act 2015.

17.13 National Highways Long Term Plan and Road Investment Strategy (England)

These documents set out the 25-year strategy and investment plan for the strategic road network that National Highways are responsible for. This should include plans for highway drainage. Highway runoff can have a significant impact on the quality of the water environment, so your DWMP could consider any strategic and local plans when evaluating risks and developing options.

17.14 Transport for Wales (TfW) Strategic Road Plans (Wales)

In Wales TfW is responsible for the trunk roads and motorways. These include the Wales Transport Strategy and the National Transport Finance Plan. They are underpinned by principles of sustainability, inclusivity, and climate resilience, which are central to the Well-being of Future Generations (Wales) Act 2015. Your DWMP could consider any strategic and local plans when evaluating risks and developing options.

17.15 Local Development Plans (LDPs)

These are developed by LPAs and set out a vision and a framework for the future development of an area. Once in place, Local Plans become part of the statutory development plan. They must be updated every 5 years. You should consider the content of relevant LDPs in your areas when accounting for future population growth and urban development, including impact on flood risk and treatment capacity.

17.16 Spatial Development Strategies/Plans (England)

Spatial Development Strategies or Spatial Development Plans are overarching development plans produced by some combined authorities in England. They provide strategic policies for the development and use of land in the area they cover. You should consider the content and objectives of any spatial plans in your areas within your DWMP. Spatial Development Strategies are not a statutory requirement in Wales.

17.17 Water Cycle Studies (WCSs)

These are not required by law but are recommended in planning guidance to help local authorities identify the impact that strategic plans and development proposals will have on water supply, wastewater, flood risk and coastal change. They therefore underpin the LDP, and outputs should inform your localised understanding of wastewater capacity at the Level 3 areas in your DWMP.

17.18 Water Industry National Environment Programme (WINEP) (England) and National Environment Programme (NEP) (Wales)

The WINEP in England and NEP in Wales is the programme of actions that water companies need to take to meet new or changing environmental requirements, both statutory and non-statutory. In England, the requirements are set out in the WISER. WISER is derived from the legislative environmental requirements set by the Government and sets the strategic ambition for the actions in the WINEP.

In Wales water companies must follow guidance issued by NRW which is tailored to the legislative framework and environmental policies specific to Wales. The WINEP in England and NEP in Wales sets the programme of environmental enhancement actions water companies need to take to meet these new or changing statutory environmental obligations and non-statutory environmental requirements within the next AMP. 

You should consider the latest version of the WISER or subsequent policy when preparing your DWMP, including whether options within the DWMP may provide cross-cutting outcomes for environmental benefit.

It is important to note that your environmental expenditure is greater than the WINEP and NEP. 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 WINEP and NEP, capital maintenance and wastewater supply-demand investment need elements of your business plans.

Based on the latest available understanding, your DWMP should evidence what will be genuine environment enhancement expenditure within your WINEP and NEP when meeting performance indicators at the time of publication, and what will be delivered through other areas of expenditure.

17.19 Local Nature Recovery Strategies (LNRS) (England)

These are locally led statutory strategies which set priorities for biodiversity and wider environmental improvement for the area that they cover and map proposals for specific land management actions in the locations which would be particularly effective in achieving those priorities. You should consider LNRS during your DWMP optioneering, especially at more granular levels of planning at Level 3 and potential Level 4 areas.

LNRS are not directly applicable in Wales. Wales has established its own approach to nature recovery through frameworks including Nature Recovery Action Plans, Nature Recovery Networks, and the National Nature Recovery Framework. These strategies are designed to enhance biodiversity, restore habitats, and ensure ecological connectivity across Wales.

17.20 Pollution Incident Reduction Plans (PIRPs) (England and Wales)

PIRPs are annual plans for how both water and sewerage undertakers intend to reduce the occurrence of pollution incidents (as defined from the previous calendar year) that are attributable to its assets, in the next calendar year. The Water (Special Measures) Act includes measures placing these plans onto a statutory footing. You should reflect the immediate (current – within AMP) actions planned and taken as part of your PIRPs within your DWMP. Your DWMP is the evidence base for all your drainage and sewerage investment need ahead of each Price Review, including reducing pollution incidents in the context of your short, medium and long-term investment need to address performance issues.

17.21 Adaptation Reporting Power (ARP) Plans (England)

Established under the Climate Change Act 2008, the ARP invites organisations, including water companies, to submit reports detailing their climate change adaptation strategies. The fourth round of ARP reporting, aligned with the National Adaptation Programme 3 (NAP3), emphasizes the importance of adaptive measures and continuous improvement in climate resilience. It also provides updated guidance, including clearer direction on the use of climate scenarios, helping organisations assess risks and plan effectively while allowing flexibility to tailor approaches to their specific circumstances. You could consider the relevant outputs of ARP plans and the NAP3 when conducting the scenario development within your DWMP.

In Wales, there is no direct central equivalent to the ARP. However, the Climate Change Act 2008 gives powers to the Welsh Ministers to direct Welsh reporting authorities to prepare reports assessing the current and predicted impacts of climate change, along with their proposals and policies for climate adaptation, and to provide an assessment of their progress in implementing the proposals and policies outlined in any previous reports.

To ensure that climate resilience is fully integrated into long-term infrastructure planning, these reporting requirements could be incorporated into the scenario development within the DWMP. This would ensure that the DWMPs reflect realistic and comprehensive forecasts, helping to guide effective and resilient infrastructure development in response to climate change.