Drainage Systems in India

With steep slope and uplift a river cuts downward. Exam tip: connect gorges with vertical erosion.

Dendritic pattern forms on uniform rock resistance and general slope. Exam tip: remember it through tree branches.

Trellis pattern develops in structurally controlled areas. Exam tip: remember bands of hard and soft rocks.

Radial pattern shows outward flow from a central highland. Exam tip: connect Amarkantak with radial example.

Rectangular pattern may be controlled by rock joints and fractures. Exam tip: identify right-angled bends.

In parallel pattern streams flow almost in one direction. Exam tip: connect it with steep uniform slope.

A water divide is highland and a basin is the drained area. Exam tip: remember the difference between boundary and area.

Himalayan rivers are affected by young terrain and heavy sediments. Exam tip: connect course change with slope and sediments.

In old hard plateau river courses remain relatively stable. Exam tip: connect Peninsular plateau with mature rivers.

The general Deccan slope is eastward but Narmada and Tapi flow westward. Exam tip: remember them as exceptions.

Narmada is a major west-flowing river in a rift valley. Exam tip: connect Narmada with rift valley.

East-flowing rivers travel long distances and deposit sediments. Exam tip: connect Mahanadi Godavari Krishna Kaveri with deltas.

The western coast is narrow and steep so deposition spreads less. Exam tip: remember estuaries with west-flowing rivers.

Godavari is among the most extensive river systems of Peninsular India. Exam tip: connect Dakshin Ganga with Godavari.

The eastward slope of Deccan Plateau leads many rivers to the Bay of Bengal. Exam tip: study slope and river direction together.

In plains a river slows and forms winding courses. Exam tip: connect meanders with lateral erosion and deposition.

Kosi can bring heavy sediments shift course and cause floods. Exam tip: remember Kosi with course shifting.

In Assam the Brahmaputra forms a wide channel with high water and sediments. Exam tip: connect it with floods and river islands.

In delta areas the main stream divides into many distributaries. Exam tip: connect distributary with the final part of a river.

The Sundarbans is a vast deltaic and mangrove region formed mainly by the Ganga and Brahmaputra river systems. These rivers carry sediment from the land and deposit it where their channels approach the Bay of Bengal. The channels divide repeatedly into distributaries, while tidal water, mudflats, and low-lying islands shape the landscape. Mangrove vegetation grows well in this muddy, saline, regularly flooded environment.

Option A correctly combines sediment deposition with the development of distributaries by the Ganga and Brahmaputra. The Narmada is associated with a rift valley, not the Sundarbans. The Luni belongs to the arid western region, and the Indus does not explain this eastern deltaic mangrove system. Therefore the supplied answer is correct, and the useful association is “Sundarbans—Ganga-Brahmaputra delta—mangroves.”

Direct answer: B, some rivers end in inland basins. Drainage means the way river water flows and where it finally ends. Many Indian rivers flow to the sea, but this is not true for every river. The Luni flows through the dry region of Rajasthan. Much of its water is lost by evaporation or enters inland depressions and salt marshes such as the Rann of Kachchh rather than forming a permanent route to the sea. Therefore it shows that India also has inland drainage. Option A is wrong because “all” is too absolute. Option B is correct because it describes inland drainage. Option C is wrong because Luni does not rise in the Himalayas; it rises in the Aravalli region. Option D is wrong because not every river forms a delta. Memory cue: Luni means limited inland drainage.

The direct answer is A: heavy rainfall combined with a steep slope makes fast-flowing erosion and flash flooding more likely. Heavy rain supplies a large amount of water to the catchment in a short time. A steep slope gives that water a strong downhill pull, so it moves rapidly through channels. Fast water has greater erosive power and can carry more soil and sediment. If the amount of water rises quickly, river levels can suddenly exceed the channel capacity, producing a flash flood. Option A correctly combines both likely effects. Option B is wrong because heavy rain normally increases streamflow, although a river can dry later under different conditions. Option C is wrong because a river does not automatically become completely underground; that depends on special geology such as karst rocks. Option D is wrong because a delta is a depositional feature and cannot simply turn into a mountain because of rainfall and slope. The fact chain is heavy rain + steep slope → rapid runoff → high river energy → erosion and sudden flooding. In an exam, link steep slopes with quick runoff, not with slow infiltration.

Khadar is newer alluvium renewed by flood deposits. Exam tip: connect Khadar with fertile new alluvium.

Bhangar is older alluvium and Khadar is newer alluvium. Exam tip: connect both with river deposition in the Ganga plain.

Jhelum Chenab Ravi Beas and Sutlej belong to the Indus system. Exam tip: remember the five rivers of Punjab.