Drainage Systems in India

Antecedent rivers keep their course even after uplift. Exam tip: connect it with Himalayan gorges.

Himalayan rivers get water from both glaciers and rainfall. Exam tip: understand perennial flow through two water sources.

Peninsular rivers depend more on monsoon rainfall. Exam tip: connect them with rain-fed rivers.

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

Trellis pattern forms through structurally controlled flow. Exam tip: identify parallel valleys and angled tributaries.

In radial pattern streams flow outward from a central highland. Exam tip: connect Amarkantak with this pattern.

In rectangular pattern streams may follow joints and fractures. Exam tip: treat right-angled bends as a clue.

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

Jhelum Chenab Ravi Beas and Sutlej are linked with the Indus system. Exam tip: remember the five rivers of Punjab.

The Brahmaputra is known by different names in different regions. Exam tip: connect river names with its route.

Devprayag is the confluence of the Bhagirathi and the Alaknanda, after which the river is called the Ganga. At Prayagraj, the Yamuna joins the Ganga as its major tributary. Thus, the two confluences represent different events, not the same one. Exam tip: remember Devprayag for the naming of the Ganga and Prayagraj for the Ganga-Yamuna confluence.

Northern tributaries come from the Himalayas and many southern tributaries from Peninsular highlands. Exam tip: remember source regions.

The direct answer is C: heavy sediment can make the Kosi channel shallow and cause it to shift course. The Kosi carries a very large load of sediment from its mountainous catchment. When this sediment is deposited in the river channel, the bed rises and the channel becomes shallower. Water then seeks a lower or easier route and may break through its banks, creating a new channel. Because the new course can spread across a wide, flat alluvial plain, flooding affects many areas of Bihar. Option C correctly explains the physical mechanism and the connection with Kosi floods. Option A is wrong because an estuary at the sea does not explain the Kosi’s repeated course changes in Bihar. Option B is wrong because the Kosi does not rise in the Western Ghats; its catchment is associated with the Himalaya. Option D is wrong because the Kosi’s water is not completely saline; it is mainly a freshwater river, though its sediment load is high. The fact chain is Himalayan erosion → heavy sediment → channel aggradation and shallowing → bank overflow or course shift → floods. Remember the phrase ‘Kosi, the sorrow of Bihar,’ but understand that sediment and shifting channels are the reason, not merely the nickname.

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

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

Direct answer: B, the area formed by deposits and distributaries of the Ganga-Brahmaputra delta. The Sundarbans is not merely a forest; it is a deltaic region where rivers divide into distributaries and deposit fine sediment near the Bay of Bengal. Tidal water, mud, and salt-tolerant mangrove vegetation shape the landscape. Option B is correct because it connects the forest with the river system that built its land. Option A is wrong: the Narmada rift valley lies in central India and is not the Sundarbans. Option C is wrong: Luni has inland drainage and does not create the Sundarbans. Option D is wrong: the Western Ghats are far away, and the Sundarbans is not a waterfall. Memory cue: Sundarbans means mangroves on the Ganga-Brahmaputra delta.

East-flowing rivers form deltas and many west-flowing rivers form estuaries. Exam tip: remember coastal and slope difference.

Most large Peninsular rivers are east-flowing but Narmada and Tapi are west-flowing. Exam tip: remember them as exceptions.

Narmada is a major river flowing through a rift valley. Exam tip: remember Narmada with rift valley.

Godavari is one of the largest river systems of Peninsular India. Exam tip: connect Dakshin Ganga with Godavari.

Krishna and Kaveri flow eastward to the Bay of Bengal. Exam tip: study slope and flow direction together.

These rivers flow towards the Bay of Bengal and deposit sediments. Exam tip: keep them separate from Narmada and Tapi.

Mahi and Sabarmati belong to the west-flowing river group of India. They rise in the central-western part of the country and generally move toward the Arabian Sea, entering it through the western coastal region. They are therefore not part of the Ganga drainage system, whose rivers generally flow eastward toward the Ganga basin and the Bay of Bengal. A river system is identified by its drainage basin and outlet, not simply by the fact that a river is in India.

Option A is correct because the westward direction and Arabian Sea outlet separate these rivers from the Ganga system. They are not branches of the Yamuna, do not form distributaries in the Sundarbans, and are not formed by the Bhagirathi and Alaknanda. These features belong to other drainage relationships, so A provides the geographical reason for rejecting the classification.

Luni is a major example of inland drainage. Exam tip: connect it with Rajasthan and arid region.

The direct answer is C: low rainfall, sandy terrain and closed basins. Inland drainage means that a stream does not reach the sea; it ends in a lake, desert depression, or disappears through evaporation and seepage. The Thar is very dry, so evaporation is strong and rivers have little water. Its sandy surface absorbs water, while enclosed low areas do not provide an outward route. Therefore a seasonal stream such as the Luni may end inland instead of joining the sea. A is wrong because the Thar is not a region of dense glaciers or heavy snow. B is wrong because a deep sea gulf would provide an outlet, not inland drainage. D is wrong because an eastern-coast delta is a depositional coastal feature, not the cause of drainage in the Thar. Memory cue: dry desert plus closed basin means inland drainage.