Forest Road Engineering Guidebook - Ministry of Forests
Forest Road Engineering Guidebook - Ministry of Forests
Forest Road Engineering Guidebook - Ministry of Forests
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Waterbars<br />
<strong>Forest</strong> <strong>Road</strong> <strong>Engineering</strong> <strong>Guidebook</strong><br />
For sites with no rock where lack <strong>of</strong> armour is a concern, the potential for<br />
erosion can be reduced by widening the base <strong>of</strong> the cross-ditch or stream<br />
channel, flattening the sideslopes to a gentle angle, creating wide flares at the<br />
outlet, and ensuring that the outlet grades evenly into the natural ground with<br />
no step.<br />
The purpose <strong>of</strong> a waterbar is to intercept surface water on the road and convey<br />
it across the road onto stable slopes below the road. Waterbars can also<br />
be used to reduce the flow energy along the grade. Reverse waterbars direct<br />
flow <strong>of</strong>f the road into the drainage ditch (Figure 24).<br />
Slope approaches<br />
gently as required<br />
for vehicle access<br />
Construct berm on<br />
downgrade side or<br />
excavate to necessary<br />
depth for expected flow<br />
Outlet to be<br />
unobstructed<br />
and protected<br />
from erosion<br />
as necessary<br />
Figure 24. Waterbar installation.<br />
Waterbars are installed to<br />
divert surface flows only;<br />
they are not intended to<br />
intercept ditchline<br />
Reverse waterbar<br />
(skew to direct<br />
water to ditch)<br />
Downgrade<br />
(favourable)<br />
Skew as required<br />
(30 degrees typical)<br />
139
Change language