05/02/2026
Time to restore ground permeability in our cities.
Why?
1. Flood risk reduction and stormwater management
Impermeable surfaces prevent rainwater from infiltrating the soil. Instead, water runs off rapidly into drains, often overwhelming systems during heavy rainfall.
Re-permeabilising the ground:
- Slows down runoff
- Allows water to infiltrate and recharge groundwater
- Reduces surface flooding and combined sewer overflows
This is increasingly critical as intense rainfall events become more frequent, a trend highlighted in global urban climate assessments .
2. Cooling cities and reducing urban heat islands
Sealed surfaces absorb and re-radiate heat, driving the urban heat island effect. Permeable and vegetated surfaces:
- Retain moisture, enabling evaporative cooling
- Lower surface and ambient air temperatures
- Improve thermal comfort in streets and public spaces
3. Restoring the urban water cycle and groundwater recharge
When cities are fully sealed:
- Groundwater levels drop
- Urban vegetation becomes dependent on irrigation
- Cities become more vulnerable to droughts
Permeable soils help reconnect rainfall with natural hydrological cycles, improving long-term water security - especially important in water-stressed cities .
4. Supporting urban biodiversity and soil health
Healthy soils host microorganisms, insects, and plant roots. De-sealing and permeable design:
- Improve soil respiration and fertility
- Enable urban trees to grow deeper, stronger roots
- Support pollinators and micro-habitats
5. Equity, livability, and informal settlements
In many cities:
- Informal settlements are located in flood-prone, poorly drained areas
- Hard engineering solutions can displace communities
Permeable, nature-based approaches (bioswales, vegetated drainage, de-sealed courtyards) are:
- Cheaper and more adaptable
- Easier to co-design with communities
- Less likely to trigger displacement or “green gentrification”
6. What “re-permeabilising” looks like in practice
- Permeable pavements and parking areas
- De-paving sidewalks, schoolyards, and underused spaces
- Rain gardens, bioswales, and infiltration trenches
- Urban trees with structural soils
- Restoring natural streams or seasonal waterways
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