4. Risk-based Assessments
4.1 The nature of assessments
Assessments of bodies of water are initially likely to be at a catchment or local authority wide scale (see Chapter 2). As a result of these assessments, further or more detailed assessments of a body of water or part thereof may be required. This should be done in a risk-based way.
Whilst the assessments can and do inform the wider flood risk management planning activities, section 18 of the Act is clear in that the requirement to assess bodies of water is to establish if works of clearance and repair would substantially reduce the risk of flooding. If they will, the works are scheduled (see Chapter 5 - section 18 schedule). The schedule must also indicate when the next assessment of the body of water is to be undertaken.
In undertaking these assessments, as described in this guidance, a risk-based, plan led approach should therefore be applied. In doing so, the following should be noted:
- Not all bodies of water will require a detailed assessment – but all should have been considered in the initial assessment.
- Not all assessments will result in a need for visual inspections – they may only be required at pinch points or under certain weather conditions.
- Not all assessments will result in works of clearance and repair – only those considered to substantially reduce the flood risk shall be scheduled.
- All works of clearance and repair from the assessment of bodies of water shall be entered on the section 18 schedule.
- Each works of clearance and repair entered on the section 18 schedule should indicate a planned implementation date (except immediate works – see below).
- Reassessment dates shall be indicated in the section 18 schedule.
The process to be followed in undertaking assessment of bodies of water, which may lead to clearance and repair works or other actions is shown in the flowchart (Guidance Flow Chart fold-out – see appendix 9.6)
4.2 Assessing the need for works of clearance and repair
The need for works of clearance and repair is assessed by the local authority. The level of detail of the assessment should be based on the level of risk and the scale of the works.
For straightforward works that will clearly substantially reduce the risk of flooding, then such works should be prioritised as such on the section 18 schedule.
For example the clearance of a trash screen, may not be recorded on the section 18 schedule, but a record of such works should be recorded in each assessment. In this example, the nature of the debris or the frequency of the need to clear may be material considerations in the assessment of flood risk and possible identification of other works of clearance and repair.
Where the benefits are less clear, the works may be complex or the costs are significant, it is considered reasonable that further assessment would be required. Such an assessment might involve hydraulic modelling or benefit-cost analysis. Such assessment in itself would also merit inclusion on the section 18 schedule – see below paragraph 4.3 'Next assessment of bodies of water'.
In extremis an assessment that is moving towards a more formal study may also be considered as part of actions in subsequent Flood Risk Management Planning cycles, as well as or instead of the section 18 schedule.
There is a commitment from local authorities to works that are included in the section 18 schedule. Whilst there is no express requirement in the Act to indicate when the works are to be implemented, it is considered that appropriate details on when the works will be carried out should be included. Local authorities should consider the availability of resources as well as the degree of flood risk. In addition, the local authority shall consider if the works will contribute to the implementation of current measures described in the applicable Flood Risk Management Strategy and Local Flood Risk Management Plan, or will not affect the implementation of the measures (reference section 59).
Given the direct link to the Strategies and Plans, it is considered that the works of clearance and repair are a key addition to the armoury of the local authority in carrying out its duties under the Act.
The proactive application of sections 18 and 59 provides opportunities for local authorities to manage and be seen to be managing flood risk at a very practical level.
See Chapter 5 for further guidance on assessing works of clearance and repair.
4.3 Next assessment of bodies of water
Where an assessment identifies that there is a risk of flooding and that works of clearance and repair are required, there will be a need for a further assessment of flood risk following the works. Where these works are not to be undertaken for a period of time, the local authority should consider when another assessment of the flood risk from this body of water or part thereof is to be undertaken. Likewise, where works of clearance and repair are not defined, the local authority should consider when another assessment of the flood risk from this body of water or part thereof is to be undertaken. The outcomes of such considerations shall be recorded on the section 18 schedule.
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