According to the configuration of the channels, drainage systems can fall into one of several categories known as drainage patterns. Drainage patterns depend on the
geology of the land.
Accordant drainage patterns
A drainage system is described as accordant if its pattern correlates to the structure and relief of the landscape over which it flows.
Dendritic drainage patterns
Dendritic drainage pattern
Dendritic drainage systems (from
Greek δενδρίτης, dendrites, "of or pertaining to a tree") are the most common form of drainage system. In a dendritic system, there are many contributing streams (analogous to the twigs of a tree), which are then joined together into the
tributaries of the main river (the branches and the trunk of the tree, respectively). They develop where the river channel follows the slope of the terrain. Dendritic systems form in
V-shaped valleys; as a result, the rock types must be impervious and non-porous.
Parallel drainage pattern
Parallel drainage pattern
A parallel drainage system is a pattern of rivers caused by steep slopes with some
relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction. This system forms on uniformly sloping surfaces, for example, rivers flowing southeast from the Aberdare Mountains in Kenya.
Parallel drainage patterns form where there is a pronounced slope to the surface. A parallel pattern also develops in regions of parallel, elongate landforms like outcropping resistant rock bands. Tributary streams tend to stretch out in a parallel-like fashion following the slope of the surface. A parallel pattern sometimes indicates the presence of a major fault that cuts across an area of steeply folded bedrock. All forms of transitions can occur between parallel, dendritic, and trellis patterns.
Trellis drainage pattern
The geometry of a trellis drainage system is similar to that of a common garden
trellis used to grow vines. As the river flows along a strike valley, smaller tributaries feed into it from the steep slopes on the sides of mountains. These tributaries enter the main river at approximately 90 degree angle, causing a trellis-like appearance of the drainage system. Trellis drainage is characteristic of folded mountains, such as the
Appalachian Mountains in North America and in the north part of Trinidad.
Rectangular drainage pattern
Rectangular drainage pattern
Rectangular drainage develops on rocks that are of approximately uniform resistance to erosion, but which have two directions of
joining at approximately right angles. The joints are usually less resistant to erosion than the bulk rock so erosion tends to preferentially open the joints and streams eventually develop along the joints. The result is a stream system in which streams consist mainly of straight line segments with right angle bends and tributaries join larger streams at right angles.
Radial drainage pattern
In a radial drainage system, the streams radiate outwards from a central high point.
Volcanoes usually display excellent radial drainage. Other geological features on which radial drainage commonly develops are
laccoliths. On these features the drainage may exhibit a combination of radial patterns.
Centripetal drainage pattern
The centripetal drainage system is similar to the radial drainage system, with the only exception that radial drainage flows out versus centripetal drainage flows in.
Deranged drainage pattern
A deranged drainage system is a drainage system in
drainage basins where there is no coherent pattern to the rivers and lakes. It happens in areas where there has been much geological disruption. The classic example is the
Canadian Shield. During the last
ice age, the topsoil was scraped off, leaving mostly bare rock. The melting of the glaciers left land with many irregularities of elevation, and a great deal of water to collect in the low points, explaining the large number of lakes which are found in Canada. The drainage basins are young and are still sorting themselves out. Eventually the system will stabilize.
Annular drainage pattern
In an annular drainage pattern streams follow a roughly circular or concentric path along a belt of weak rock, resembling in plan a ringlike pattern. It is best displayed by streams draining a maturely dissected
structural dome or
basin where erosion has exposed rimming sedimentary strata of greatly varying degrees of hardness, as in the
Red Valley, which nearly encircles the domal structure of the
Black Hills of
Angular drainage pattern
Angular drainage patterns form where bedrock joints and faults intersect at more acute angles than rectangular drainage patterns. Angles are both more and less than 90 degrees.
Discordant drainage patterns
A drainage pattern is described as discordant if it does not correlate to the topography and geology of the area. Discordant drainage patterns are classified into two main types:
antecedent and superimposed,
 while anteposition drainage patterns combine the two. In antecedent drainage, a river's vertical incision ability matches that of land uplift due to tectonic forces. Superimposed drainage develops differently: initially, a drainage system develops on a surface composed of 'younger' rocks, but due to denudative activities this surface of younger rocks is removed and the river continues to flow over a seemingly new surface, but one in fact made up of rocks of old geological formation.