Streams are the body of water flowing on the surface depending upon the topography of the area. Many streams join the main river.
Streams are classified into four types depending on their origin:
- Consequent Streams: These are the first streams to have developed in accordance with the topography of any area. They generally follow the slope of initial land surface as they flow downslope and then gradually develop their channels along the available slopes.
- Subsequent Streams: These act as tributary streams to the consequent streams. Subsequent streams generally take their course along the weak and easily erodible zones such as rock boundaries, fault zones, joints etc. These weak zones are discovered and eroded after the development of the consequent streams.
- Obsequent Streams: The controlling factor for determining the course of the obsequent stream is the prevailing relief , in most cases the flow direction of this stream is opposite to the mainstream .They are general called the tributaries of the obsequent streams .
- Insequent streams: These are also called the irregular streams. These are found to flow in the channels that show no well-defined relationship with either the slope of the area or the character of the rocks.
Drainage Patterns associated with the above Stream Patterns
All the above described patterns contribute towards the removal and drainage of any water received by that region either from the precipitated water or from other sources. The relationship of all the streams with each other and with the region as a whole gives rise to the Drainage Patterns.
Drainage Patterns are of many types and these are as follows:
- Trellis Pattern: Trellis pattern is said to develop when a consequent stream receives a number of subsequent streams from the right and left at approximately right angles to its direction of flow. This type of pattern develops in regions containing folded or tilted strata. Here the mainstream develops in the strike valleys cut into the soft rocks while tributaries flow down the resistant ridges.
- Dendritic Pattern: When the streams of different types(Consequent, Subsequent, Obsequent etc.) are all fairly common in a region and none appears to dominate other groups. The overall appearance of the water bodies in that region show a branching tree like arrangement. This pattern develops in terrains covered with uniform rock types, such as horizontal sedimentary rocks or massive igneous or metamorphic rocks.
- Radial Pattern: This type of drainage pattern develops in regions which are either elevated or depressed with reference to the surrounding topography i.e. streams may either flow out from a central elevated region or flow towards a common central region when it is depressed.
- Parallel Pattern: This type of drainage pattern develops in a terrain containing tilted rock beds and parallel faults. The Major stream occupies the fault while tributaries which are flowing parallel, meet the stream approximately at the same angle.