Permeable surfaces

The complete description of the NWRM: 

Permeable paving is designed to allow rainwater to infiltrate through the surface, either into underlying layers (soils and aquifers), or be stored below ground and released at a controlled rate to surface water. Permeable paving is used as a general term, but two types can be distinguished:

-       Porous pavements, where water is infiltrated across the entire surface (e.g. reinforced grass or gravel, or porous concrete and cobblestones)

-       Permeable pavements, where materials such as bricks are laid to provide void space through to the sub-base, by use of expanded or porous seals (rather than mortar or other fine particles).

It is most commonly used on roads and car parks, but the measure can also apply to broader use of permeable areas to promote greater infiltration. It can be used in most ground conditions and can be sited on waste, uncontrolled or non-engineered fill, providing the degree of compaction of the foundation material is high enough to prevent significant differential settlement.   A liner may be required where infiltration is not appropriate, or where soil integrity would be compromised. 

CIRIA (2007) and the “Centre des recherches routières” (Road Research Centre) of Brussels (2008) describes three different types of porous/permeable pavements:

  1. All rainfall passes through sub-structure and in to soils beneath, with (normally) no surface discharge (i.e. fully infiltrating);
  2. Perforated pipes lie between the sub-base and underlying sub-soil, to convey rainfall that exceeds the capacity of the sub-soil to a receiving drainage system (i.e. partially infiltrating);
  3. Perforated pipes lie beneath the sub-base, over an impermeable membrane, so all rainfall, after filtering through the sub-base, is conveyed to the receiving drainage system (i.e. no infiltration).

All types provide attenuation of rainfall, and potentially can also store runoff from surrounding areas, if designed and sized appropriately. Types A and B provide infiltration to underlying groundwater, thereby contributing to increased groundwater levels and/or flows, and hence potentially to baseflow.  Type C does not interact with groundwater, but stores rainfall (and potentially runoff) and releases it at a controlled rate, hence still contributes to regulating the rate of rainfall-runoff.


Permeable paving

Source: Andras Kis’ presentation, NWRM Workshop 1


Possible benefits with level: 
Benefits Levelsort ascending
ES1 - Water storage Medium
ES6 - Groundwater/aquifer recharge Medium
BP1 - Store runoff Medium
BP2 - Slow runoff Medium
BP6 - Increase infiltration and/or groundwater recharge Medium
ES7 - Flood risk reduction Medium
ES5 - Climate change adaptation and mitigation Low
ES8 - Erosion/sediment control Low
PO2 - Improving status of physico-chemical quality elements Low
PO4 - Improving chemical status and priority substances Low
PO5 - Improving quantitative status Low
PO7 - Prevent surface water status deterioration Low
PO11 - Better protection for ecosystems and more use of Green Infrastructure Low
BP8 - Reduce pollutant sources Low
BP9 - Intercept pollution pathways Low
ES9 - Filtration of pollutants Low
PO9 - Take adequate and co-ordinated measures to reduce flood risks High
Last updated: 09 Jun 2015 | Top