Drains/Canals can be differentiated from Roads as they do not provide connectivity to the existing road network.
In Figure: 2.3.2.2b note that the upper part of the drain near the water source gives off a light blue signature, indicating presence of water. The drain terminates at the water tank which also shows the same water signature.
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, Water Tank or Sea.
Drains follow the topography of the land whereas roads may traverse hills and valleys.
The use of mulitspectral imagery band combinations can aid in the interpretation and differentiation of water.
