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31/08/2021

Ten ideas to make UK towns and cities more flood resilient

Shoeburyness scheme after (c) Stolon Studio.png

One of the most tangible effects of climate change so far has been an increase in extreme flood events which necessitates improvements in planning and design to make developments more flood resilient. Robert Barker considers potential approaches

Many experts are claiming that the recent floods in western Europe were worse than predicted due to climate change. When it comes to climate change, the only certainty is that the climate will change and the effects are uncertain. It is not to say that we don’t have predictions in the UK; we just have many different predictions, different outcomes and then sensitivity.

It is time for a radical rethink, if the UK is to start seriously making towns and cities more resilient to flooding.

Currently the UK has world leading flood modelling, positive flood-risk policies, useful guidance on flood resilience, an improving approach to flood insurance and an emerging awareness of flood risk. As is evident from this statement, the UK is not world leading in all fields and there is a failure in connecting these strands together to the same standard.

Whilst there have been improvements made to some of these areas over the last 15 years, it has not been nearly enough. Having worked in this field for many years, I have drawn up a virtuous circle for flood risk management in an effort to not only reduce risk, but also to reduce the consequences of flooding. This circle is one in which the improvements in modelling are reflected by revised planning policies emphasising reducing risk, supported by building regulations, performance certificates, building management plans and insurance, improving livelihoods, and returning to improving flood ‘risk’ modelling.

Below are a few suggestions that could help lead to this virtuous circle, even if they were implemented one stage at a time.

 

Ten ways to increase flood resilience

 

1. Change planning policy.

Make a flood-risk assessment mandatory for all planning applications, regardless of whether a site is in a flood zone (which only considers rivers and seas) and, as such, include an assessment of all forms of flooding. Furthermore, include a drainage calculation, demonstrating how run-off will be reduced to greenfield rates in all but exceptional circumstances, where there should still be an obligation to reduce run-off rates. Currently, an applicant or their agent could prepare a flood risk assessment (FRA) without clear and comprehensive understanding of the issues or relevant policy. In order to make these important assessments worthwhile, an FRA should need to be completed by a suitably qualified and regulated person.

2. Make all changes to surfaces subject to planning and building regulations.

Omit the installation of artificial grass, patios and other impermeable surfaces from permitted development. Whilst this may increase the work required for planning authorities, a simple questions and answer process could fast-track these simple applications. The benefit of doing this would help to raise awareness of limiting the extent of impermeable surfaces, and would provide a means to redress inappropriate development, through enforcement, within the existing system.

3. Make highways more absorbent.

Introduce policy to ensure highways and landscaping work must make improvements to absorb water. Roads and carparks could be made using porous asphalt combined with a permeable gravel base instead of conventional non-porous asphalt. There are almost 250,000 miles of roads in Great Britain and in London 80 per cent of all public space are streets (source: London Play). These currently account for an awful lot of impermeable surfaces.

4. Make changes to permitted development rules to require extensions and garden buildings to have greenfield run-off rates.

This can be done with simple pre-approved details for either green roofs or hard roofs combined with attenuation, rather than the need for calculations to be provided.

5. Integrate surface water flooding into combined flood-maps.

Land-use planning is based on flood zones. Whilst it may be difficult to accurately predict the extent of flooding from surface water, to have surface water (and reservoir) flooding separated from zonal mapping can lead to misunderstanding. Currently, it is possible to download a report stating that a location is at low risk of flooding (from river and seas) and yet be at high risk of surface water flooding. This only becomes apparent upon further scrutiny of the information. If assessment isn’t carried out thoroughly, this can be easily missed. Whilst surface water flooding is highly influenced by local factors, if the extents were drawn more broadly than the current maps, this would at least give some indication of the potential for risk to a location.

6. Provide water companies with powers to incentivise reducing run-off rates.

If the water companies rewarded those customers who reduce run-off and waste water, using measures such as permeable paving, green-roofs, attenuation, landscaping, grey water recycling, against the cost of their supply, attitudes would change. There is presently no incentive to reduce the amount of waste-water and run off. The emphasis has been to reduce water use, but there needs to be consideration of waste water too.

7. Introduce flooding into the Building Regulations.

Presently the Building Regulations do not include flooding. Introducing a new part to the Building Regulations, “Resistance, Resilience and Means of Warning and Escape from Flooding”, supported by approved details (similar to Part L and Part E), could help to preserve lives, livelihoods and properties. Building Regulations apply to all new buildings and works to existing buildings. Flood-proofing property is complex and without adequate, robust guidance and testing, there is a risk that the same sort of fundamental failures seen with poorly installed fire protection will be repeated with flood-proofing.

8. Develop a Flood Performance Certificate (FPC) that is mandatory for every property, to encourage more resilient buildings and better insurance.

All property sold or let has information regarding energy performance in the Energy Performance Certificate (EPC). The same could be done flooding. If every property had an FPC, this would raise awareness of the risk and provide an indication of the work that could be done to reduce flood-risk. If work had been carried out and certified, this could then be used to demonstrate the reduction in flood-risk/increase of flood resilience. Insurance premiums (and/or excesses) could then be based on this information, instead of the blanket postcode system which currently prevails. This would need to be carefully developed, monitored, and assessed, and potentially creating a new technical monitoring role to check work/assess conditions.

9. Make a flood safety strategy mandatory for every building.

Whilst this may seem like overkill, it will expect every property owner to consider the risk of flooding to their property and the well-being of the occupants. This could be done as part of the health and safety documentation and building management plans for ALL buildings. This would need to consider all sources of flooding, including surface-water as well as fluvial and tidal flooding.

10. Change flood zones to be based on risk, not probability (or maybe, abolish zones).

Current flood zones are determined based on the probability of an area flooding not the risk posed by a flood. Flood risk is not only a factor of probability but also flood depth and velocity (as well as local contextual impacts). The principle of flood zones is to direct development away from areas of highest risk. This is sensible guidance, but the difficulty is that flooding doesn’t respect neatly drawn boundaries and sometimes extends beyond them. Much of the recent flooding has been from surface water in areas that are in flood zone 1 – low risk of flooding (from rivers and seas). These probability-based maps need to be regularly updated based on revised predictions to account for climate change, which is only as good as the assessment method. Given the number of properties flooded that are not in medium to high-risk areas, and the uncertainty in the predictions, are they still useful? With fire policy, each situation must be assessed for risk and an appropriate response proposed. In principle fire risk is deemed to increase based on the height of the building. The same principle broadly applies to flooding: the greater the depth of flooding, the more serious the risk. Yet flood policy is based on probability not depth.

Furthermore, flood zones don’t really help the millions of places and properties that are already within them. Flood zones also don’t assess risk, they only give an indication of the probability of flooding. This means that a location that could be at risk of ankle deep, slow flowing flood water could be in the same zone as another site that is at risk of 10 foot deep, fast flowing tidal water. If a site can be effectively protected from regular flooding, should this be lumped together with a site that is dangerous to lives and property? Replacing probability-based flood zones with risk-based flood maps could help policy makers and experts better plan for flood resilience in buildings and places when needed, whilst helping positively support communities at all other times.

And this leads back around to the beginning of the virtuous circle, in which we should revise the flood modelling to combine issues, mapping and update policy.

Four steps to managing flood risk

Stolon, with Lanpro planning consultants and Ardent Consulting, recently secured planning consent for Garrison Gardens, a flood resilient development of masterplan for 215 homes, commercial space and a new health centre in Shoeburyness. Stolon has designed various schemes incorporating flood resilience, resistance and SuDS, which are constructed or in construction.

Their approach follows a four-step strategy:

1. Land raising

2. Flood storage

3. Flood resilience, (with floodable garages and parking)

4. Sustainable drainage. ©Stolon Studio

Visualisations of Garrison Gardens before and after flooding:

Robert Barker is a director of Stolon Studio Architects and an RIBA fellow, recognised for his work on flooding and climate change. He is also an author of the RIBA published book Aquatecture, Buildings Designed to Live and Work with Water;  the Metric Handbook flood-aware chapter and wiki-buildings articles on flood resistance, resilience, elevated properties and amphibious construction.

Image credits | ©StolonStudio

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