Infiltration Trenches

Code: 
U08
Sector: 
Urban
The complete description of the NWRM: 
Summary: 

Infiltration trenches are shallow excavations filled with rubble or stone. They allow water to infiltrate into the surrounding soils from the bottom and sides of the trench, enhancing the natural ability of the soil to drain water.  Ideally they should receive lateral inflow from an adjacent impermeable surface, but point source inflows may be acceptable with some design adaptation (effectively they are a form of soakaway).

Infiltration trenches reduce runoff rates and volumes and can help replenish groundwater and preserve base flow in rivers. They treat runoff by filtration through the substrate in the trench and subsequently through soil. They are effective at removing pollutants and sediment through physical filtration, adsorption onto the material in the trench, or biochemical reactions in the fill or soil.  However they are not intended to function as sediment traps and must always be designed with an effective pre-treatment system where sediment loading is high (e.g. filter strip). Unless very effective pre-treatment is included in the design, they are best located adjacent to impermeable surfaces such as car parks or roads/highways where there levels of particulates in the runoff are low. They work best as part of a larger sustainable drainage treatment train. Infiltration trenches are easy to integrate into a site and can be used for draining residential and non-residential runoff. Due to their narrow shape, they can be adapted to different sites, and can be easily retrofitted into the margin, perimeter or other unused areas of developed sites. Infiltration trenches are also ideal for use around playing fields, recreational areas or public open space. They can be effectively incorporated into the landscape and designed to require minimal land take.

Illustration(s): 

Infiltration trenches with stones in urban area

Source: Andras Kis’ presentation, NWRM Workshop 1

Infiltration trenches in agriculture area

Source: UNDP 2008 (http://www.sswm.info/category/implementation-tools/water-sources/hardware/precipitation-harvesting/field-trenches)

Possible benefits with level: 
Benefits Levelsort descending
ES6 - Groundwater/aquifer recharge High
ES7 - Flood risk reduction High
PO9 - Take adequate and co-ordinated measures to reduce flood risks High
BP6 - Increase infiltration and/or groundwater recharge High
ES1 - Water storage Low
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
PO7 - Prevent surface water status deterioration Low
PO8 - Prevent groundwater status deterioration Low
PO11 - Better protection for ecosystems and more use of Green Infrastructure Low
PO12 - More sustainable agriculture and forestry Low
BP2 - Slow runoff Low
BP7 - Increase soil water retention Low
ES11 - Aesthetic/cultural value Low
ES9 - Filtration of pollutants Medium
PO5 - Improving quantitative status Medium
BP1 - Store runoff Medium
BP9 - Intercept pollution pathways Medium
BP10 - Reduce erosion and/or sediment delivery Medium
Case study(ies): 
Last updated: 09 Jun 2015 | Top