• The term “drainage” describes the river system of an area.
• The area drained by a single river system is called a “drainage basin” or river basin.
• Any higher ground, such as mountain or upland separates two adjoining drainage basins. Such upland is known as a water divide or a watershed.
• Depending upon the relief, geological structure and climatic conditions of the area, the streams form different patterns.
Drainage Pattern:
• Drainage of an area is concerned with the study of main rivers and their tributaries with respect to their size, number, direction of flow, drainage basin, slope of the valley.
• A drainage system refers to the origin and development of stream through time.
• Drainage pattern means spatial arrangement and form of drainage system in terms of different rock types, geological structure, climatic conditions and denudational history.
• 1. Trellis Pattern: in this system the tributaries can be seen meeting the main stream at right angles. This exists where hard and soft rocks exist parallel to each other.
• 2. Dendritic Patterns (Tree shaped pattern): is the most common and widespread pattern to be found on the earth’s surface. In this pattern, the tributaries come from all directions to meet the main river. Like the branches of a tree the small streams meet larger streams and the larger streams meet the much larger streams, in the end they meet the river. This develops where the river channel follows the slope of the terrain.
• 3. Parallel Drainage Patterns: comprises numerous rivers which are parallel to each other and follow the regional slope. This pattern is developed on uniformly sloping areas such as coastal plains.
• 4. Radial Drainage Pattern/Centrifugal Pattern: develops where streams flow in different directions from a central peak or dome like structure. Streams which diverge from a central higher point in all directions.
Drainage System of India:
On the Basis of origin, two broad drainage