The DWMP blog – 27. Encouraging SuDS retrofit

Everyone agrees that the best way forward for drainage and wastewater management is to adopt Sustainable Drainage Systems (SuDS).?That is systems that store rainwater or infiltrate it to the ground to stop or slow runoff.?This reduces the discharge to sewers so reducing flooding, storm overflows and overloading of treatment works.?However, the first cycle of DWMPs generally showed that conventional grey solutions such as concrete detention tanks were cheaper than retrofitting SuDS for the same level of performance.?This shouldn’t be the case as half of the effort to retrofit SuDS is the responsibility of homeowners – if we can get them to do it.

The challenge therefore is to drive down the cost of SuDS retrofit so that it becomes the best value option and is widely used.

I raised this as an issue in my recent paper to the CIWEM Urban Drainage Group conference and was going to leave it at that until I read two related news items within a couple of days and remembering some slightly related work from a few years ago.

The first news item was research from the USA looking at attitudes of different stakeholders to household level SuDS.

??https://www.tandfonline.com/doi/full/10.1080/09640568.2022.2133687

The research identified three attitudes amongst stakeholders (I paraphrase):

1.????Market decentralists believe private landowners should be responsible for managing stormwater on their property but with financial incentives for SuDS and charges for discharge to sewer.

2.????Anti-market decentralists strongly oppose incentives and charges as they are unfair for low-income communities. ?They favour community engagement to encourage implementation.

3.????Technocratic opportunists favour technological innovations to exploit stormwater for beneficial use like irrigation.

Homeowners tended to be in group 2 with other stakeholders across all three groups.

I must confess that I haven’t read the full paper and so may not understand the detail, but I don’t see why financial incentives and charges are unfair for low-income communities whereas persuading homeowners to spend their own money on implementation would not be.

I then remembered work done by WSP a few years ago researching how to influence homeowners to reduce their water consumption.?See the details at https://www.wsp.com/en-gb/campaigns/value-of-water.? The table below shows the percentage of people influenced by different factors.

The results show that doing something for the environment was as much of a driver as financial incentives.

So, what might influence homeowners to install SuDS and how might we use these to encourage uptake?

·???????Do something good for the environment.?Everyone is concerned about storm overflow discharges, but I have yet to see any messaging from water companies that part of the cause is homeowners discharging runoff to combined sewers and the solution is literally in their own backyard.?Why are we not pushing this message?

• Keep water bills low.?There are two potential savings: the reduced water supply charge by reusing rainwater for garden watering or toilet flushing and the reduced surface water charge if no runoff is discharged to sewer.?The latter doesn’t seem to be enough to incentivise disconnection and maybe the cost estimates from DWMPs give us a new basis to calculate the value that could be put on this.
• Investing in SuDS to reduce future bills may be attractive to people with money in the bank, but not for those without savings.?For these people we may need a lump sum reward or free supply and installation of measures.?Some water companies supply and install water efficiency measures for free; so why not SuDS.
• Is the equivalent of avoiding the infrequent problem of water scarcity, avoiding the infrequent problem of flooding.?If so, maybe it is not a strong influencer.
• Comparison of measures with other homes.?Why are water butts always made in black or dark green so that they don’t stand out??What if they were made in shocking pink or bright yellow, imagine the neighbours’ reaction.?“Ooh you’ve got a new water butt.?Like the colour.?Is it any good??I think we should get one.”?Peer pressure through school friends can be even more effective for families with children.

I was not aware of any similar research into what would influence household level SuDS until this morning when Ofwat announced a new research project.?

https://waterinnovation.challenges.org/winners/towards-incentivisation-for-community-centric-rainwater-management/

When it rains heavily, excess water runs off people’s homes and driveways and enters the sewer network which can contribute to the network being overwhelmed and lead to surface water flooding, sewer flooding and sewage discharges. ?The project will encourage the widespread adoption of rainwater capture methods at a grass roots level. It will test and measure how communities can be incentivised to take up these measures and help protect the environment.

The focus is on rainwater reuse rather than infiltration SuDS, so avoiding that being an awful pun about grass roots level infiltration systems.?The detail does mention the other benefit of the savings on water bills through water reuse.??However, maybe the lesson from the earlier WSP work is that doing good for the environment should be the first incentive as it is likely to be more powerful than reducing the infrequent issue of flooding or the future saving on water bills.

I look forward to seeing how the project progresses.