The arrangement, in map view of a river and its tributaries is a drainage pattern. A drainage
pattern in many cases reveals the nature and structure of the rock underneath it. Most tributaries join
the main stream at an acute angle, forming a V or Y pointing downstream. If the pattern created by
the river as it cuts up the landscape resembles the branches of a tree or veins in a leaf, it is called a
DENDRITIC drainage. This word comes from the Greek word Dendron which means tree. The
main river is the ‘trunk’ and the tributaries are the ‘branches’ and ‘twigs.’This drainage pattern
develops in areas of uniform rock type and structure. It is the most common type of drainage
pattern.
Activity 1 . Draw and label the dendritic drainage pattern.
On the other hand if the rocks are made up of alternate bands of hard and soft rocks, the tributaries
tend to follow the pattern of the rock structure. If the outcrops of the rock occur at right angles to
the main valley, the tributaries will join it at right angles as subsequent streams. The drainage
pattern so developed will be rectangular in shape and is called TRELLISed drainage.
Activity 2. Draw and label the Trellis drainage pattern.
Rivers flowing outwards like spokes from a wheel and downhill from conical mountains, such as
composite volcanoes and dome, gives rise to a RADIAL drainage pattern.
Activity 3 . Draw and label a Radial drainage pattern.