13.1.1.Outfall drainage

All roads and tracks should be built with a cross-fall to shed water. This normally angles away from the hillside, except where a built-up bank is unstable or higher than 1.5 metres.
If outfall drainage isn’t enough to control runoff, crossbanks can be a good, cheap long-lasting solution. A cross-bank (also known as a ‘whoa boy’) is like a large speed hump built across the track. It is formed by digging a trench 20–30 cm deep on a slight slope across the track and using the excavated earth to form a bank on the downhill side.