It wouldn’t be a British summer without a crop of news platform articles about how hot, cold, wet or dry it is. And there’s more to hit the headlines than in the past, too. Britain’s summer weather patterns – so long associated with rain that jokes about a Bank Holiday correlating with a certain downpour are familiar to everyone – are changing. Indeed, so are the patterns throughout the year.
The new normal is effectively climate whiplash. Long, hot spells bake soils, after which the first proper downpour sheets off pavements and compacted verges, overwhelming drains that were already struggling. When that first storm hits, rainfall intensity outpaces what hardened, hydrophobic soils can absorb and what gullies can carry; water skims across hard surfaces, concentrates along kerb lines and cambered roads, pools at low spots, and in minutes puddles appear and grow as the local drainage network backs up. This flow simply overtops the kerb into shops and homes: a flash flood. Cue more click-worthy headlines (as well as lots of disruption for homes and businesses).
The answer isn’t to increase sewer capacity, and it’s not even solely to remediate aging infrastructure, it’s to take an entirely different approach to drainage infrastructure.
Sponge cities for climate change resilience
We need to redesign our streets to store, slow and soak. So-called ‘sponge cities’ use distributed green-blue systems – including tree pits, permeable paving and linked raingardens – that intercept runoff at the surface, hold and meter it, strip out first-flush pollutants, then pass only safe flows to the network. In dry spells some sponge city elements passively irrigate trees (which help cool pavements); in downpours the nature-based drainage provides staged overflows and clear exceedance routes. Modular, retrofit-friendly and easy to maintain, this is budget-friendly resilience you can build one block at a time.
The cost of doing nothing is very likely to be significant, as the scientific evidence for this problem to only increase is pretty unequivocal.
The Met Office now puts the chance of another 40°C UK day at roughly 50/50 within 12 years, and says temperatures several degrees higher than 2022’s record are now possible. Hotter spells don’t just test people; they desiccate soils and hard surfaces, priming them to resist water infiltration when rain returns. At the same time, attribution studies show human-driven global warming is already increasing the intensity of UK storm rainfall. Put those two trends together and the solution becomes clear: cool streets during drought; attenuate water during cloudbursts.
Policy is finally catching up. England’s National Standards for Sustainable Drainage (SuDS) – published in June and updated in July this year – set an outcomes-led bar: manage peak flows, treat water quality, deliver amenity and biodiversity, and prove the system can be maintained and (crucially) adopted. This is not a tick-box exercise, it’s a nudge in the right direction to re-cast approaches to drainage infrastructure that can handle both heat and cloudburst, solving both challenges with a single solution
Street trees to cool, store, release
Trees are central when they’re treated as infrastructure, not ornaments. Healthy urban trees cool through shade and evapotranspiration; the evidence base on their microclimate benefit is solid. Pair that biology with engineering – root-friendly soil volumes in structural cells, oxygenation, controlled inlets from kerb or slot drains, and a throttled outlet to the next SuDS stage – and a street tree becomes a discreet detention basin under the pavement. The usual objections don’t stand up when designs are competent, too. Root barriers manage conflict with utilities and paving, leaf guards and pre-treatment baskets keep inlets clear, and exceedance routes are a standard part of any credible drainage submission.
The key ingredients of the optimal design are practical, straightforward and repeatable:
- Bring runoff into the pit and distribute it within an uncompacted soil cell so the tree gets moisture in dry spells and the system holds water temporarily in wet ones.
- Size a modest detention volume for the local 1-in-30 design storm; return flows through a small orifice (or adjustable control) so downstream assets aren’t swamped.
- Provide a deliberate overflow to permeable paving or a raingarden chain for exceedance.
- Vent the soil, support the surface slabs, and specify mulch and wicking layers so roots don’t starve when heat lingers.
- Maintenance should be simple, visible and safe: inspection covers or baskets where debris accumulates; generous inlet apertures you can assess at a glance; seasonal checks with ‘eyes and hands’ not specialist kit (because if a design needs bespoke tools to keep working, it’s the wrong design).
That said, risk isn’t uniform, and neither should specifications be. The National Drought Group has branded England’s current water shortfall a ‘nationally significant incident’, with five areas officially in drought and six others on prolonged dry-weather status – even as intense, short-duration downpours trigger surface-water flooding in other towns. That mix now regularly appears in summer, not just autumn and winter. It’s important to design to local soils and rainfall profiles, document exceedance routes, and align with the Lead Local Flood Authority’s preferences. The point is to make the submission defendable and adoptable the first time.
One design, multiple SuDS benefits
There is a business case behind green-blue engineering, too. Cooler, shaded pavements reduce heat stress and complaints; better microclimate supports dwell time and high-street footfall. Distributed attenuation reduces ponding incidents that drive insurance claims and reactive call-outs. And because the components are modular, retrofit can be staged block by block – undertaken through night works where necessary – without turning a town centre into a building site for months.
Most of the cost sits in civil coordination, and the upside is reputational as well as hydraulic: visible amenity, clearer air, healthier canopy, and a smoother planning process when you can show one project meeting multiple SuDS outcomes.
Manufacturers who specialise in engineered tree pits and SuDS cells should make this type of strategy easy to procure and easy to approve. Expect BIM objects and cross-sections that show inlets, detention volumes, aeration, root management, orifice sizing and defined overflow paths.
Expect a short hydraulic note with per-pit storage and linkage to downstream SuDS, plus a maintenance plan that names access points and tasks in plain English. And expect a design-review call that pressure-tests the detail against the National SuDS Standards so planning officers and LLFAs have fewer reasons to delay. The aim is always the same: a street that still works the day after drought, when the rain finally comes.