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Planning objectives

Developing planning objectives is an important early step in the process for Drainage and Wastewater Management Plans (DWMPs). The planning objectives enable us to consider and identify the issues that we, and the organisations we are working with, care about in each river basin catchment, such as flooding and pollution.


Planning objectives are used in the DWMP process to assess the current and future performance of the drainage and wastewater systems and identify where action and/or future investment is required. The performance is considered as a risk where failure could have an impact on people and/or the environment.

Developing the Planning Objectives

The Planning Objectives (POs) were developed at the beginning of the DWMP during the strategic context stage and were used throughout each of the following stages, the Baseline Risk and Vulnerability Assessment (BRAVA), the Problem Characterisation, the Options Development and Programme Appraisal.

Six planning objectives were defined under the national DWMP guidance for all water companies to use within their DWMPs and report on nationally. The six common, national planning objectives are:

  • PO1: Risk of sewer flooding in a 1 in 50 year storm – this is a severe storm that is likely to occur once in every 50 years or, put another way, a 2% chance of happening in any 12 month period
  • PO2: Storm overflow performance – this is non-compliance of a storm overflow with the permit issued by the Environment Agency which specifies the amount, frequency and concentration allowed to be discharged into the receiving water
  • PO3: Risk of Wastewater Treatment Works quality compliance failure – this is non-compliance of a Wastewater Treatment Works (WTWs) with its permit
  • PO4: Internal sewer flooding risk – which is internal flooding of a domestic or business premises by wastewater
  • PO5: Pollution risk - pollution from any wastewater source on land or in water
  • PO6: Sewer collapses risk. We identified that amending two of the national planning objectives would improve our understanding and definition of the current and future risks. As a result, we developed two additional objectives. .
  • PO7: Annualised Flood Risk (Hydraulic Overload):. Storms are taking place with increasing frequency, different levels of severity and with many geographical variations, all of which affects where and how much rain water enters, and fills, our sewers causing them to overload and flood. As a company, and supported by partners including the Lead Local Flood Authorities and the Environment Agency, we introduced the Annualised Flood Risk objective so that we could understand and calculate a risk score for 1 in 2, 1 in 5, 1 in 10, 1 in 20 and 1 in 50 storm return periods. This would provide us with a more detailed understanding of the likelihood of sewer flooding during less severe but more frequent storms
  • PO8: WTW Compliance with the EA’s permit relating to the dry weather flow (DWF) arriving at the treatment works: The national planning objective for Wastewater Treatment Works Compliance combined both Water Quality and Dry Weather Flow components. We decided that dividing the objective into its two component parts would provide a more accurate risk definition for each. We therefore developed the objective for compliance with our permit for Dry Weather Flow and kept the original objective to cover compliance with our permit on effluent quality.

Importantly for the development of our DWMP, we held a workshop with partner organisations in each river basin catchment in September 2020. The purpose of the workshops was to discuss the need for any additional planning objectives to reflect concerns over and above those specified in the national guidance and the two further objectives we had identified. The table below sets out the additional planning objectives proposed for each catchment. These were colour coded to enable us to identify and simply group into general topic areas.

We completed an assessment of the objectives identified at the workshops to:

  • Understand which objectives are common across our entire region
  • Identify which objectives should be considered further for inclusion in the first round of the DWMPs.

We used the following criteria to make the assessment:

  1. The number of times the additional objective had been proposed as this would strengthen the case for inclusion in the first round of the DWMP
  2. Data was readily available and the method for the risk assessment would be relatively straightforward: These would be explored further for inclusion in round 1 of the DWMP
  3. Data was not readily available or the method for an assessment would be complex and take time to develop: These would be deferred to future rounds of the DWMP
  4. Whether the proposed objective is a generic aim rather than an indicator of current and future performance. These would not be included as a planning objective but will be reflected elsewhere in the DWMP
  5. Whether it is already included in the existing national planning objectives and the national objective could be easily modified to include the proposal.

Through our assessment, we identified six additional planning objectives that were included in the first round of the DWMPs:

  • PO9: Achieve Good Ecological Status or Good Ecological Potential (GES/GEP)
  • PO10: Improve surface water management and reduce surface water flooding
  • PO11: Secure nutrient neutrality
  • PO12: Reduce groundwater pollution
  • PO13: Improve bathing
  • PO14: Protect shellfish waters


We considered the remaining potential objectives and concluded that:

  1. Reducing CSO discharges and pollution risk are already included in the Water UK objectives and will be progressed in the first round of the DWMPs
  2. Increasing natural capital and water reuse and recycling, and achieving biodiversity net gain and carbon neutrality are among our long-term aims and will be considered in our DWMPs and business plans, especially when identifying investment choices.
  3. Reducing the failure of pumping stations is an ongoing activity for our operational teams, and future risks are identified as part of our DWMP resilience assessment.
  4. Increasing the separation of surface water from foul has been incorporated within ‘improve surface water management’ and adopted as an objective
  5. Understanding the impact of coastal erosion on our assets, pollution of Marine Conservation Zones, the cumulative impacts of discharges to the Estuaries and flooding due to tide locking have all been deferred to the next round of DWMPs. This will allow us to work with the Environment Agency and local councils to obtain the data required to develop robust methodologies to assess current and future risks.
  6. We need to gather more data on the impact of effluent on receiving water bodies before we can progress the proposed objective to improve effluent quality during dry weather so have deferred this until the data is available.
  7. We have deferred the objective to reduce the impact of plastics and chemicals until the UK Water Industry Research (UKWIR) programme reports its findings. It is a generic long-term objective for our industry.
  8. Reducing misconnections is already a key focus for us with a new Misconnections Team providing significant input to our Bathing Waters improvement programme. However, it is not an objective we can achieve alone and, as part of the DWMP process, we have identified local hotspots and will target these and work with partner organisations to run campaigns to improve our customers’ understanding of the issue and change behaviours.

There are a few other areas such as aligning the DWMP with Defra’s 25 year Environment Strategy objectives and finding innovative solutions that address multiple issues are generic aims. We cannot complete a BRAVA for these as set out in the Water UK guidance on DWMPs, so they are not included as planning objectives. However, we support the Government’s strategy and the need to find innovative solutions so we will look for opportunities to both these things as we develop the DWMPs.

Incorporating the Planning Objectives in the developing DWMP

All 14 Planning Objectives were progressed through the Baseline Risk and Vulnerability Assessment (BRAVA) using a BRAVA methodology for each to assess the risks. This identified if there were current (2020) and future (2050) risks where the performance of our wastewater systems would not achieve the objective. We completed a 2020 assessment for all POs and a 2050 assessment for 6 POs – 4, 5, 6, 7, 8 and 11. However, we could not complete a 2050 assessment for the remaining 8 POs:

  • PO1: Internal sewer flooding
  • PO2: Pollution risk
  • PO3: Sewer collapse risk
  • PO9: Good Ecological Status / Potential
  • PO12: Groundwater pollution
  • PO13: Bathing waters
  • PO14: Shellfish waters

There were a number of reasons why we could not complete a 2050 assessment for these POs. These include that we could not:

  • base forecasts on historic incidents as, for example in the case of groundwater pollution, there are none
  • forecast how climate change will impact local ground conditions at any given point in time in terms of sewer collapse
  • assume that the measures implemented between now and 2050 will reduce risks to zero or how climate scenarios will change these risks
  • accurately assess the future risk based on the data available at the current time or have the modelling capability to provide an accurate assessment.

We will consider future assessments on a case-by-case basis as more information becomes available.

DWMP Planning Objectives and regulatory drivers

All our Planning Objectives map against regulatory drivers or are an obligation under the 2010 Flood and Water Management Act, as set out below.

Mapping our Planning Objectives against regulatory drivers

  Planning Objective Primary Regulatory Driver
1 Internal Sewer Flooding Flood and Water Management Act 2010
2 Pollution Environment Act, 2021
3 Sewer collapse Water Industry Act, 1991
4 Flooding in a 1 in 50 year storm Resilience metric (obligation under the Flood and Water Management Act 2010)
5 Storm overflows Environment Act, 2021
6 Wastewater Treatment Works Quality Compliance The Urban Wastewater Treatment Regulations, 1994
7 Annualised flood risk Resilience metric (obligation under the Flood and Water Management Act 2010)
8 Wastewater Treatment Works Dry Weather Flow compliance The Urban Wastewater Treatment Regulations, 1994
9 Good Ecological Status / Potential EU Water Environment Regulations, 2017
10 Surface water management Resilience metric (obligation under the Flood and Water Management Act 2010)
11 Nutrient Neutrality Habitats Regulation, 1992
12 Groundwater pollution The Groundwater Regulations, 2009
13 Bathing Waters The Bathing Waters Regulations, 2013
14 Shellfish Waters Water Environment Regulations 2017


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