Water bar

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Water bars are used on unbound surfaces to prevent scouring. They are built across the path on slopes with a ‘shedding bar’ to catch running water and to divert it off the surface. However, by creating a raised bar across the path to intercept water you will be introducing a physical barrier for most people including cyclists, wheelchair users and people with visual impairments. For that reason, water bars should only be used as a 'last resort' but preferrably cut-off drains should be considered first. Water bars should be installed when the path is constructed or upgraded, but can be installed on existing paths as an erosion control measure.

For water bars to catch and disperse water effectively they must be carefully positioned on the path. This depends on where water is coming onto the path, expected water volume and good dispersal areas – where water will not flow back onto the path further down. A ‘liner’ - a row of level stones - should be installed on the uphill side to prevent undercutting of the shedding bar.

Water bar

  • Use water bars as a last resort as they introduce a raised step in the path surface which can cause a trip hazard but also puncture bicycle tyres

  • In locations, where water bars are not the best option for accessibility more suitable alternatives like cut-off drains should be used

  • Most water bars are built in rural locations from locally won stone obtained on site. When local stone of a suitable size is not available, water bars can be built from alternative materials – standard concrete kerbing, dressed stone, slate, sawn timber, sawn logs, recycled plastic lumber, and even conveyor belt rubber

  • A channel should be installed on the uphill side of the shedding bar to prevent water from scouring the path surface or undermining the bar. An outlet is also required to allow water to disperse easily

  • Frequency of water bars depends on the path gradient. For example on an 8% (1:12) path gradient the distance between water bars should be around 12 metres

 

Specification
Using local won stone of suitable sized dimensions construct a water bar between 45° and 60° to the path line
Shedding bar depth should be a minimum 50mm at upper path edge rising to approximately 100mm at lower path edge
The liner stone(s) should be flush with the path surface and match the crossfall of the path
Extend water bar by 300mm on each path side
If required, include a large flat stone splash plate at the outlet end if the ground drops steeply or install a silt trap to collect washed off surface material
Construct path above the water bar level with the top edge of the shedding bar and, below, the front edge of front liner

 

Maintenance
Annual inspection is required to ensure that the bar is functioning and in safe and good condition
A well constructed water bar should be solid, immoveable and ‘self-cleaning’ but it may need clearing if there is a build up of surfacing or debris (e.g. leaf litter)
If a silt trap is installed this should be emptied annually (or after heavy rainfall) – washed out surfacing could be reapplied to the path if it is relatively free from other debris

 

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© 2014 Paths for All - Registered Scottish Charity No: SC025535, Company Limited by Guarantee No: 168554 inc. 19 Sept 1996 at Companies House, Edinburgh