Clearance and repair to reduce flood risk: local authority guidance

3. Visual Inspections

3.1 The nature of inspections

The need for and frequency of inspections of bodies of water are to be planned and programmed, but can also be contingent on certain weather conditions, as per the assessments of bodies of water described in Chapter 2.

Under the previous legislation thirty-two local authorities will have as many as 64 different methods by which watercourses in the past have been inspected and maintained. The regime to be followed by local authorities under the Flood Risk Management (Scotland) Act 2009 is to be risk-based and plan led.

Inspections should now be targeted at the areas of risk identified in the assessment of bodies of water. They can also form part of inspections for asset management planning purposes.

Historically, planned inspections and maintenance will principally fall into two categories: Trash Screens (see paragraph 3.1.1) or watercourses and culverts (see paragraph 3.1.2).

The assessment of bodies of water required under section 18 of the Act should clearly identify the locations of trash screens and the inspection frequency, with the works of clearance dependent on the screen condition at time of inspection. It is unlikely that clearance of a screen will be specifically scheduled, but structural defects found during inspection should be recorded for subsequent assessment. Any remedial works would be scheduled for clearance and repair.

3.1.1 Trash screens

In general, certain locations on the watercourse network will be inspected on a scheduled basis with works undertaken either by those inspecting or by a squad instructed to do so. The obvious example of this is trash screens on culverts.

Most local authorities will undertake a programme of screen inspection and clearance to manage flood risk at high risk locations. Through local knowledge and experience an inspection and clearance regime will have been developed. This may see, for example, weekly inspections in the winter with monthly inspections in the summer. As the inspection and clearance will often be undertaken by manual operatives it is important for Council flood officers to obtain feedback on issues. For example regular attendance at a screen that has accumulated no trash may allow a reduction in frequency of visits. Conversely a regularly blinded screen may require increased visits or possibly a new screen to current standards.

Councils should also be mindful of the opportunities to engage with local communities and flood groups for inspection, and if safe, clearance of screens. This approach has been adopted by Scottish Borders Council and Angus Council.

For particularly high risk locations, Councils may wish to consider the installation of automatic river level monitors that will trigger alarms (text message or email) when a set level is reached. This can ensure that a blocked screen is attended before rising water leads to flooding. CCTV cameras offer further resilience, at a price. Such planned works themselves may be considered for inclusion in the schedule of clearance and repair under section 18.

3.1.2 Watercourses and culverted watercourses

In terms of substantially reducing flood risk, it is much more probable that smaller watercourses, in urban areas will be the focus for local authorities. However, inspections of open watercourses, generally in urban areas, are likely to be undertaken on a less frequent basis than trash screen inspections. Depending on the issues identified at the assessment stage, this may be a once or twice a year inspection, or less frequently as detailed in paragraph 2.6.

These works of inspection should be recorded in a manner to allow scheduling of such clearance of repair works. Again the frequency of these inspections should be determined from assessment but flexibility should always remain, especially to undertake additional inspections prior / during / after high flow events.

Identifying "things" that are of "significant risk" of becoming an "obstruction" e.g. fallen trees or garden waste end-tipped on a river bank is as important as identifying obstructions in the watercourse itself. This potentially has the opportunity to undertake targeted campaigns promoting more appropriate disposal of garden waste thus reducing flood risk and local authority maintenance costs.

Much risk is posed by culverted watercourses where the need to install high screens to prevent debris passing into the culvert is the first risk location. Even with a trash screen in place issues with the culvert still remain. The build-up of smaller debris can lead to blockage, which may give rise to the structural failure of elements, e.g. loss of brickwork, partial collapse. Assessment in these situations is likely to direct a local authority to undertake CCTV inspections of culverts. The frequency will be dependent on the common risks, e.g. age, material construction, available resources, etc. There may also be a need to consider whether the culvert is a structure in terms of The Management of Highway Structures – A Code of Practice which may then require inspections on 2 yearly/6 yearly General and Principal Inspections basis or a move to a risk-based frequency.

A reasonable inspection frequency by CCTV or man entry would be every 6 years to coincide with a plan cycle but this could be increased if issues are identified as problems arise.

3.2 Recording inspections

Inspections inform assessments of bodies of water. This is either as part of the development of the assessment and identification of flood risk or the results of the inspection will allow for a risk-based assessment of actions required.

These actions may be:

• immediate, e.g. inspector clears trash screen debris;
• emergency, urgent or planned ordered works of clearance and repair based on onsite risk-based assessment;
• planned ordered works of clearance and repair based on office risk-based assessment;
• results of inspection, e.g. dimensions, condition, feeds into office risk-based assessment (or study if applicable).

In any event, the inspection and its findings need to be recorded and made available for assessment and future inspections. Any works of clearance and repair shall also be recorded in the section 18 schedule.

The initial pre- and post-condition of the watercourse should be noted and photographed on the inspection record.

Inspection records should include all relevant data required for an assessment of the body of water or the need for a specific clearance and repair works to be reviewed. This might include photographs, videos and other evidence to support written records.