The DWMP blog – 28. Reducing the risk of surface water flooding

On 29th November the UK National Infrastructure Commission published a report on “Reducing the risk of surface water flooding” (see the link here https://tinyurl.com/2ps5btmw)

There are obvious parallels of this topic with DWMPs but these were not emphasised in the report.?In fact, during the launch presentation, in response to a question on whether DWMPs and surface water plans should be combined, the authors seemed to show a misunderstanding of the role of DWMPs stating, “DWMPs operate at a much larger scale and serve a particular purpose.?What we are recommending here is a much more focussed approach.”?I don’t think that they appreciate the level of detail that DWMPs go into.?Maybe they haven’t been following this blog.

The recommendations

The report makes 9 recommendations.?These are:

1.???By the end of 2023, government should implement Schedule 3 of the Flood and Water Management Act 2010 and update its technical standards for sustainable drainage systems.

2.???Government should undertake a comprehensive review of the effectiveness of all available options to manage unplanned increases in impermeable (or hard) surfaces, and their costs and benefits. ?By the end of 2024, government should decide whether policy changes are required to reduce the impacts on surface water flooding or adjust investment levels for flood risk reduction accordingly.

3.???Government should:

• require the Environment Agency to use the results of the second National Flood Risk Assessment in 2024 to identify new flood risk areas
• from 2025, require upper tier local authorities, water and sewerage companies, and other relevant authorities in the new flood risk areas to, where necessary, develop detailed local risk maps that can be integrated into the Environment Agency’s national map, and models that can be used to plan future management of surface water flooding.

4.???By early 2025, government should set a long-term target for a percentage reduction in the number of properties at high and medium risk of surface water flooding.

5.???The government should require risk management authorities in the new flood risk areas to agree appropriate local targets by mid 2025.

6.???Government should clarify in its strategic priorities for Ofwat that it should enable water and sewerage companies to invest in solutions to manage surface water flooding including sustainable drainage.

7.???Government should require:

• upper tier local authorities, water and sewerage companies, and, where relevant, internal drainage boards in the new flood risk areas to produce and deliver costed, joint investment plans for managing surface water that achieve the agreed local objectives and follow the ‘solutions hierarchy’
• the Environment Agency to review and assure the final plans with input from Ofwat and support from Regional Flood and Coastal Committees, and publish data on progress against local and national targets
• joint plans to be completed by 2026 and revised every five years following the review of flood risk areas the year before, and to inform the following Ofwat Price Review.

8.???By the end of 2025, government should devolve public funding to upper tier local authorities in or containing new flood risk areas, based on the Environment Agency’s assessment of the levels of risk in each new flood risk area. ?The funding allocation should be reviewed every five years, in line with single joint plan cycles.

9.???By the end of 2024, government should explore options for funding property level measures for those properties that remain at high risk of surface water flooding because improving drainage infrastructure is not cost effective.

I strongly support most of these, but readers of my blog will realise that there are some that I (and many other urban drainage practitioners) would like to tweak.?I explain why below and provide suggested new wording.

Recommendation 3

I would take out the restriction that detailed plans are only needed for areas that have a significant number of properties at risk.?This means that householders can suffer a postcode lottery if they are at high risk but in an area that generally isn’t.?(See Episode 5 of the blog for more on this.)?Sewerage companies are preparing DWMPs for more than 95% of the population that they serve, there is no reason why surface water planning should do less.

I would also put the emphasis on local assessment of risk and development of plans.?The EA may need to collate the national picture, but the risk assessment and plans need to be local.

My revised wording would therefore be.

Government should:

• require the Environment Agency to provide the results of the second National Flood Risk Assessment in 2024 to upper tier local authorities to help to identify properties at risk of surface water flooding.
• from 2025, require upper tier local authorities, water and sewerage companies, and other relevant authorities to, where necessary, develop detailed local risk maps that can be used to plan future management of surface water flooding.

Recommendation 5

The report recommends a cost benefit approach: properties where benefits outweigh costs should be protected and those where they do not should not be.?This is not compatible with setting a local target for a percentage reduction in numbers of properties as the numbers come out of the assessment (Episode 5 again has more on this).?This might also mean that the national targets set under Recommendation 4 are also irrelevant.?Revised wording for this recommendation would be.

The government should require risk management authorities by 2025to set appropriate local criteria for assessing investment.

Recommendation 6

I am not sure that this has been thought through.?Enabling sewerage companies to invest to manage surface water does not achieve anything unless they also have a duty to manage surface water.?Their current duty is only to manage the runoff from property curtilages, it is the responsibility of highways authorities and lead local flood authorities to manage everything else.?For this recommendation to achieve anything it would require these responsibilities to transfer to sewerage companies.?This might be a good idea, but it is not a simple matter.?Do they take on responsibility for cleaning highway gullies??What about sweeping up autumn leaves to prevent blockages?

Recommendation 7

DWMPs are exactly the sort of detailed local flood risk management plans that the report is recommending and some companies already include consideration of surface water in them.?The requirement should therefore be to extend the scope of DWMPs.?This was supported by a vote by delegates at the recent CIWEM Urban Drainage Group conference.?I discussed ideas for this in Episode 24.?

The EA does not currently have any formal role in reviewing DWMPs although they are consulted.?I do not see that they need a larger role in the extended scope to cover surface water.?The revised wording should therefore be.

Government should require:

• upper tier local authorities, water and sewerage companies, and, where relevant, internal drainage boards to produce and deliver costed, joint investment plans for managing surface water that achieve the agreed local objectives and follow the ‘solutions hierarchy’
• the joint plans will be extensions to the scope of DWMPs and are to be completed as part of Cycle 2 by 2028 and revised every five years.

Recommendation 8

This again falls into the trap of focussing only on those areas with large numbers of properties at risk and so creating a postcode lottery.?The revised wording should be:

By the end of 2028, government should devolve public funding to upper tier local authorities based on the requirements of the joint plans.?The funding allocation should be reviewed every five years when the plans are updated.?

Recommendation 9

The provision of funding for property level protection is welcome, but it should not be restricted to just surface water flooding.?It should cover all forms of flooding including sewer flooding.?Is the requirement to “explore” sufficient, or should there be a requirement to implement but over a longer timescale.?

By the end of 2028, government should implement options for funding property level measures for those properties that remain at high risk of flooding because improving drainage systems is not cost effective.

Conclusions

I hope that the NIC will understand the purpose of these suggestions, which are intended to be constructive and to strengthen the outcome of their report.