Drains/Canals can be differentiated from natural watercourses by their linear structure.
Natural Watercourses can be differentiated from Drain/Canals by remnant vegetation adjacent to stream path.
Drains/Canals can be differentiated from Roads as they do not provide connectivity to the existing road network.
If the Drain/Canal is completely dry it will appear lighter, similar to the surrounding soil and vegetation. The the edges will often appear much lighter, due to the excavated soil from construction.
Drains generally start at a water source and can end at a Reservoir, Dam or Sea.
Drains follow the topography of the land whereas roads may traverse hills and valleys.
The use of multispectral imagery band combinations can aid in the interpretation and differentiation of water.
Regional Considerations:
In areas where there is irrigated crop farming Canals/Drains appear as regular structured networks which show a water flow hierarchy diminishing from source. They are often aligned with paddocks and have access tracks or roads running parallel to them.
Figure: 2.3.2.5 Representation of Canals in association with surrounding features.
