DRAINAGE SYSTEM 

Drainage Systems are divided into two broad categories: 

Sequent Drainage System

System of streams which follow the regional slope and are well adjusted to the geological structure is called sequent drainage system. 

  • Consequent Streams: The initial steams that originate in a particu-lar region in accordance with the initial slope of the land are called consequent streams. 
  • Subsequent Streams: The streams originated after the consequent stream and joining the master consequent at right angles are called subsequent streams. 
  • Resequent Streams: Streams which flow in the direction of the initial consequent strcam but join the subsequent streams, thereby developing in response to a new base level. 
  • Obsequent Streams: Streams flowing in a direction opposite to that of the dip of the rock strata, i.e. opposite to the master consequent stream. 

Insequent Drainage System

The streams which do not follow the region-al slope and arc not adjusted to geological structure are called insequent streams. 

  • Antecedent Drainage: A river that has been able to maintain its direction of flow despite the tectonic uplift of land across its course is known as antecedent river. 
  • Superimposed Drainage: When the nature and characteristics of the valley and flow direction of a consequent stream developed on the upper geological formation and structure arc super imposed on the lower geological formation of entirely characteristics, it is called superimposed drainage. 
    i. The Son river flowing across the Rewa Plateau (M.P.) is a typical example of superimposed drainage.

Drainage Patterns 

  • Dendritic Pattern: In this, the network of the streams resembles the shape of a tree with its branches.
  • Trellis Pattern: In this pattern, the rivers form a net like system and the tributary stream of each class flows roughly parallel to each other, e.g. Appalachian reason of USA. 
  • Rectangular Pattern: Though resembles trellis pattern, it differs from the trellis in that confluence of the tributaries is determined by faults and joints of the underlying rocks and streams are widely spaced and are more irregular than the trellis. 
  • Radial Pattern: It is a pattern of outflowing riven away from a central higher point. Some structures, volcanic cones and isolated upland tend to develop this pattern, e.g. Sri Lanka, Hazaribagh plateau, Kathiwar penin-sula, Mikir range. etc. 
  • Annular Pattern: This pattern, also known as circular pattern, is formed over a mature and directed dome characterized by a series of alternate bunds of hard and soft rocks, guiding the tributaries to take a circular path. 
  • Parallel Pattern: Here the master and tributary streams are parallel to each other, guided by the pronounced slopes, parallel faults or parallel topographic features, e.g. streams of western coastal plain of India. 
  • Barbed Pattern: Generally developed due to river capture, this pat-tern comprises tributaries flowing in the opposite direction to the master stream.