Indian Drainage System_ Its Features & Patterns.

Himalayan Drainage vs Peninsular Drainage

Himalayan Drainage

Antecedent drainage i.e. Himalayan rivers are older than lesser Himalayas and Shiwaliks Himalayan rivers are older than the structures they cut across Perennial flowing River → fed by rain and melting glaciers Geologically young with long course of flow Flow through lose alluvial soils of northern plains Form deep valley and gorges due to intensive erosion Generate large quantities of sediment & cause annual flooding & form Deltas Nature of river course is quiet changing, meandering , forming ox-bow lakes & high waterfalls Have deeper basins and large catchment areas

Peninsular Drainage

Super-imposed drainage i.e. regional structures are older than the river valleys that cut through them. Nature of flow is seasonal i.e. majorly during south west monsoon Geologically older with shorter course of flow Flow through hard granitic soils of peninsular India Shallow graded valleys with little erosion. Forms shallow valleys, small waterfalls, deltas and estuaries

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West Flowing Rivers vs East Flowing Rivers of Peninsular India

West Flowing Rivers	Flow into Arabian sea Flow through rift valley in straight linear course Do not have extensive network of tributaries Geologically young Generally form estuaries and not deltas Their valley floors are much above the sea level Flow swiftly into the sea
East Flowing Rivers	Flow into bay of Bengal Have extensive network of tributaries Geologically old Have large catchment areas and form deltas Their valley floors are at sea level Flow sluggishly into the sea

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Watershed

• Geographic area through which water flows across the land and drains into a common body of water, whether a stream, river, lake, or ocean
• Watershed boundary will more or less follow the highest ridgeline around the stream channels and meet at the bottom or lowest point of the land where water flows out of the watershed, the mouth of the waterway

Drainage basin

• Also known as catchment basin
• An area of land where surface water from rain, melting snow, or ice converges to a single point at a lower elevation
• Usually converses at the exit of the basin, where the waters join another water body viz.  river, lake, reservoir, estuary, wetland, or sea
• Hence it is an area drained by tributary streams that coalesce into a main channel

Watershed Divide

• The line, which divides the surface runoff between two adjacent river basins, is called the topographic water divide, or the watershed divide.
• It marks the highest points between the basins, but isolated peaks within a basin may reach higher elevations than any point on the divide.

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Stream or Flowing River Patterns

• The combined effects of climate and geology on the catchment topography yield an erosion pattern, which is characterized by a network of streams.
• Some of the frequently observed stream patterns are as follows -

Dendritic River Pattern

• River channel follows the slope of the terrain
• Homogeneous beds of uniform resistance to erosion
• Streams run in all directions without definite preference to any one particular region
• Example → Indo – Gangetic Plains

Rectangular River Pattern

• Regions that have undergone faulting
• Provide uniform resistance to erosion
• Streams Meet at right angle approx.
• Develops on strongly joined rocky terrain
• Example → Vindhya Mountains of India

Trellis River Pattern

• River joined by tributaries at approx. right angle
• Develops in folded topography; alternate layers of hard & soft rocks
• Longer streams have preference to one direction
• Tributaries have preference to right angle to the main stream
• Example → Appalachian Mountains of North America & Singhbhum (Chotanagpur Plateau)

Radial River Pattern

• Streams flow in different directions from central peak
• Outflowing rivers, away from a central point, analogous with the spokes of a wheel
• Generally referred to rivers flowing through dome Mountains and volcanoes
• Example → Rivers Narmada, Son and Mahanadi originating from Amarkantak Hills; Girnar Hills (Kathiwar, Gujarat), and Mikir Hills of Assam

Pinnate River Pattern

• Main stream runs in one direction
• Tributaries join it at oblique angle

Parallel River Pattern

• Main stream runs in one direction
• Tributaries also join it running in the same direction