Baseline Risk and Vulnerability Assessment

The Baseline Risk and Vulnerability Assessment (BRAVA) is an important step in the development of our DWMP in order to understand current system performance and future vulnerabilities (risks).

We developed a risk assessment methodology for each of the six national planning objectives (POs) specified by Water UK (POs 1 to 6) and for the two bespoke POs (POs 7  & 8) that we identified as helpful to the DWMP process.

We worked with our experts and those from partner organisations to develop risk assessments for six additional objectives (POs 9 – 14).

A summary of the methodologies we developed for all the risk assessments are available below. They set out the data used, the process followed and the thresholds applied to produce the risk profile, or risk banding of Band 0 (not significant), Band 1 (moderately significant) or Band 2 (very significant).   

BRAVA Methodology – Internal Sewer Flooding Risk

BRAVA Methodology – Pollution Risk

BRAVA Methodology – Sewer Collapse Risk

BRAVA Methodology – Sewer Flooding 1 in 50 year storm

BRAVA Methodology – Storm Overflow Performance

BRAVA Methodology – Risk of WTW Compliance (Quality)

BRAVA Methodology – Annualised Flood Risk (Hydraulic overload)

BRAVA Methodology – Wastewater Treatment Works (WTW) Dry Weather Flow (DWF) Compliance

BRAVA Methodology – Achieve Good Ecological Status / Potential

BRAVA Methodology – Improve surface water management

BRAVA Methodology – Secure nutrient neutrality

BRAVA Methodology – Reduce groundwater pollution

BRAVA Methodology – Improve bathing water quality

BRAVA Methodology – Protect shellfish water quality


We applied the methodologies to the 335 wastewater systems that were flagged during the Risk Based Catchment Screening as needing to be considered in further in the BRAVA stage of the DWMP. The BRAVA provided us with an assessment of the current risks (baseline 2020) and of the risks for future (2050) planning horizons.

The outputs of the BRAVA provide an indicative risk score for each wastewater system for the base year of 2020. For 6 of the planning objectives we were also able to calculate a future predicted score for 2050. The 2050 scores assume that we continue with the current maintenance regime. The risk scores are either 0, 1 or 2 as described in the table below (based on the Water UK Guidance on DWMPs):

Score Description
Very Significant (Score = 2) The performance of the wastewater system is potentially below the minimum threshold set by a company, and indicates there is a risk that warrants more investigation in the Options Development & Appraisal stage of DWMP.
Moderately Significant (Score = 1) The performance of the wastewater system appears to be borderline and therefore needs further investigation in the Options Development & Appraisal stage of DWMP.
Not significant (Score = 0) The performance is not an issue or concern. Within a catchment there may be some localised issues which need to be addressed as part of ‘business as usual’ investment decisions. Priority does not need to be placed on this planning objective in the catchment.
Not Flagged Denotes that the catchment was not identified (flagged) for progression to the BRAVA stage.
Not Applicable Denotes that a planning objective is not relevant to the catchment (for example, where a catchment has no storm overflows).

A summary of the BRAVA outputs for each of the river basin catchments is available within the river basin sections of this website:

BRAVA for the Adur and Ouse catchment

BRAVA for the Arun and Western Streams catchment

BRAVA for the Cuckmere and Pevensey Levels catchment

BRAVA for the East Hampshire catchment

BRAVA for the Isle of Wight catchment

BRAVA for the Medway catchment

BRAVA for the New Forest catchment

BRAVA for the North Kent catchment

BRAVA for the Rother catchment

BRAVA for the Stour catchment

BRAVA for the Test and Itchen catchment


The risk assessments are an important stage of the DWMP. We used the best data and information available from 2020 to meet the timetable and expectations established by Ofwat for all water companies. We aim to further develop and improve the risk assessments for future DWMPs.