Component: Filter trench




Filter trenches are shallow excavations filled with rubble or stone that create temporary subsurface storage of stormwater runoff. These trenches can be used to filter and convey stormwater to downstream SuDS components.


Ideally they should receive lateral inflow from an adjacent impermeable surface, but point source inflows may be acceptable.


Advantages & disadvantages




  • Important hydraulic benefits are achieved

  • Can be incorporated easily into site landscaping and fits well beside roads.






  • High clogging potential without effective pre-treatment – not for sites with fine particled soils (clay/silts) in upstream catchment

  • Build-up of pollution/ blockages difficult to see

  • High historic failure rate due to poor maintenance, wrong siting or high debris input

  • Limited to relatively small catchments

  • High cost of replacing filter material should blockage occur.















Where component can be used SuDS filter trench

Residential:  Yes

Commercial/industrial:  Yes

High density:  Yes

Retrofit:  Yes

Contaminated sites:  Yes

Sites above vulnerable groundwater: Yes



Peak flow reduction:  Medium

Volume reduction:  Low

Water quality treatment: High

Amenity potential:  Low

Ecology potential:  Low



  • Regular inspection for signs of clogging

  • Removal of sediment from pre-treatment system

  • Removal and cleaning or replacement of stone.


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