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DRAINAGE PATTERNS





Geomorphologists and hydrologists often view streams as being part of a drainage pattern. Over time, a stream system will achieve a particular drainage pattern to its network of stream channels and tributaries as determined by local geologic factors. Drainage patterns are classified on the basis of their form and texture. Their shape or pattern develops in response to the local topography and subsurface geology. Drainage channels develop where surface runoff is enhanced and earth materials provide the least resistance to erosion. The texture is governed by soil infiltration, and the volume of water available in a given period of time to enter the surface.

Name Pattern Description
Annular annular-pattern A ring-shaped drainage system. Over circular underground rock structures such as batholiths, the drainage network may develop into a series of concentric rings.
Dendritic dendritic-pattern A branching, treelike drainage pattern. In areas of uniform rock, with little distortion by folding or faulting, the rivers develop a random branching network similar to a tree.
Trellised trellised-pattern A rectangular drainage pattern. It occurs when the rock structure steers streams into a parallel course, with tributaries joining at almost right angles. Sometimes, the joint pattern in the rocks creates a Rectangular drainage. This is similar to the Trellised drainage, but the pattern is less distinct.
Parallel parallel-pattern Terrain structure causes rivers to flow in virtually parallel course, perhaps by parallel folds.
Radial radial-pattern A spoke-like pattern of rivers. These tend to flow away from the summit of a dome or volcano in all directions.
Deranged deranged-pattern An irregular broken drainage system. When ice sheets melt, the drainage pattern left behind may be broken and irregular. Rivers have not had time to adapt to the underlying rock structure, and follow the irregularities of glacial deposits.


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