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).


The BRAVA involves the assessment of the risks for each of the planning objectives for the 353 sewer catchments flagged during the Risk Based Catchment Screening (RBCS). The remaining 28 sewer catchments (out of our total of 381 sewer catchments) were screened during the previous stage as the risks in these catchments are ‘not significant’, and hence do not require further assessment in the BRAVA stage.

The BRAVA has been completed initially for the six planning objectives defined by Water UK. These are the objectives that all water companies are required to use in their DWMPs and report the results to Water UK in December 2020.

We have produced a summary of the method that we have used to produce the BRAVA assessment for each planning objective. These are available to download:

(i) Risk of sewer flooding

(ii) Storm overflow performance

(iii) WTWs compliance

(iv) Internal flooding

(v) Pollution

(vi) Sewer collapse


The outputs of the BRAVA are a risk score for each sewer catchment. For three of the planning objectives the score is for the 2020 base year, and for the other three we have both the 2020 base year and a forecast estimate for the risk score in 2050. The 2050 score is on the assumption that we continue with the current maintenance regime.

The risk scores are either 0, 1 or 2 as described in this extract from the table developed by Water UK in November 2020:

Water UK – BRAVA Scoring Table (Extract)


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


We reported our BRAVA outputs to Water UK in December 2020.

Southern Water
December 2020

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