The streams may be classified into the following types

There are stream which have their courses determined by the initial slope. Their courses are directly controlled by the initial topography.

On the other hand, there are other types of streams which are not depended on the original topography, but are guided by the differential erosion of the bed rocks. In other words, the valleys of such streams are excavated on the lines of the softer or less resistant rocks.

Their courses, therefore, are in direct response to rock structures. So the streams may be classified on the basis of the slope as well as rock structures. The streams may be classified into the following types:

(i) Consequent streams (iv) Obsequent streams

(ii) Subsequent streams (v) Braided streams

(iii) Resequent streams (vi) Antecedent streams

(i) Consequent streams:

Such streams whose courses are the direct consequence of the initial topography are called consequent streams. So any stream whose course is controlled by the initial slope of a land surface is called a consequent stream.

They occur on many landforms, such as, fault block, volcanoes, or beds of drained lakes. Most of the streams flowing on the land surface are of this type, and often their courses are due to crystal deformation of one kind or the other.

Consequent streams are definitely controlled by the slopes of the surrounding land. The valley of a consequent stream is progressively lengthened by head ward erosion.

As the consequent streams erode their valleys by down cutting, the valley sides provide secondary slopes down which tributaries can flow. The consequent streams along with their tributaries of different orders establish a tree-like drainage pattern called dendritic.

A consequent river may even capture the head waters of a river on the other side of the main watershed.

Insequent streams:

Streams that develop their valleys on flat-lying sedimentary rocks, or on massive rocks like granite which have no struc­tural features, are called insequent streams.

As tributaries of the consequent streams the drainage pattern produced by them is called dendritic. These streams generally make an acute angle with the upstream part of the consequent river. This stream develops its own tributary.

(ii) Subsequent streams:

Many stream courses are not dependent on the original topo­graphy. They develop their valleys along an out­crop of less-resistant rocks or a regional fault or joint pattern, at right angles to the drainage conse­quent upon the slope of the land.

Since these streams develop along weak structures, they leng­then their valleys mainly by head ward erosion. The ridges composed of resistant rocks that are found between two parallel strike valleys are called hogbacks or Cuestas.

(iii) Resequent streams:

A resequent stream flows in the same direction as that of the initial consequent stream, but which develops in response to a new base level.

(iv) Obsequent streams:

These steams have developed in certain positions by adjustment to rock structures. After the valley development of consequent and subsequent streams, obsequent streams may form at right angles to the subsequent streams and flow opposite to the direction of flow of the original consequent stream.

Such obsequent streams are found in regions of tilted strata where escarpments form by the erosion of the land surface. Obsequent streams develop on such escarpments.

(v) Braided streams:

Braided streams are characterized by a network of interconnected channels. These channels look like the strands of a braid. The whole river system is shallow and loaded with alluvial materials which are exposed at low water.

Braided streams are common in a delta region when the main stream crosses it. Because of deposition in the stream channel, it is divided into numerous channels which diverge and then reunite with each other.

Braid­ing is also the characteristic feature of streams crossing the glaciofluvial deposits after emer­ging from the snout of a glacier.

(vii) Antecedent river:

If a river has been able to maintain its direction of flow in spite of the tectonic uplift of land across its course, then it is called as antecedent or inconsequent river.

Sometimes, after the course of a river has been firmly established, the tectonic movements, intrusion or extrusions of igneous rock may occur which ordinarily would divert the course.

But if the rate of uplift of a barrier is lower than the rate of down-cutting by the river, the river is successful in maintaining its original course. In the Himalayan region, for example, there are several fine examples of antecedent rivers.

The Indus and its tributary the Sutlej, and the Brahmaputra are pre-Himalayan in origin, for they rise in Tibet well to the north of the highest peaks. The Indus River, when it leaves Kashmir near Nanga Parbat (8,737 m) with precipitous wall on both sides, has cut through 5,600 m of rock keeping pace with the uplift of the mountain range.

Besides, there are other rivers such as, the Ganga, Ghagra, Chenab in India, and the Colorado River in U.S.A. which have crossed the uplifted mountains and plateau by means of deep, rather exceptionally deep gorges. One of the most remarkable examples of Antecedent River is the Arun River of Nepal.