On the basis of their characteristics and patterns, streams are classified into a number of groups each of which implies something of the origin and history of stream. They are described below.
Consequent Streams: On any newly uplifted land surface the first streams will have their own characters determined by the original slope and natural irregularities of the surface. Such streams are, therefore, consequent of the original relief features. They may not only lengthen by head erosion and deepen and widen their valleys but also they may have tributaries developed as a direct consequence of the initial topography. All such streams whose pattern is determined solely by the direction of the slope of the land or consequent on the initial topography, are called Consequent streams. These occur generally in massive and flatlying rocks and commonly have dendritic patterns.
Subsequent Streams: These are streams that occupy a belt of weak rocks and these pattern is determined by the nature of the weak rocks. They originate independently of the original topography and are determined and regulated by erosion proceeding differ ently upon bed rock according to differences in hardness, structure and resistance to erosion. Since they originate and develop independently and subsequent to the original relief of the land they are appropriately called Subsequent streams in contradiction with the streams that are more commonly the tributaries of the main consequent streams. Usually subsequent tributaries develop at nearly right angles to a consequent main stream. This angular pattern of stream courses is known as trellis patterns. Streams in which no adjustment of rock structure takes place since they develop in a large area of massive rock formation as granite, never have subsequent tributaries. This is because the adjustment is complete from the beginning. This in sequent stream pattern is often tree like and hence designated as dendritic.
Obsequent Streams : A subsequent stream that develops as a tributary at about right angles to the main consequent stream may, in turn have tributaries which often flow in the opposite direction to the original course, of consequent stream and hence called Obsequent streams. Condition particularly favourable for the development of obseqeunt streams are to be found in regions of tilted strata where escarpments such as cuestas form the land surface which is worn down by erosion,
Antecedent Streams : These are streams that have maintained their courses across a local uplift of the crust that rose by folding or faulting in their paths. The name antecedent stream arises due to the fact that the stream is antecedent to or older than the uplift.
Super imposed Streams : Super imposed stream is one that let down or SUPerposed from overlying strata on to a buried surface underneath them. The stream’s path was not controlled in any way by the surface on which it is now flowing. Most superposed Streams began as consequents of the surface of the covering rocks.