UPPSC 2019 Prelims GS Paper-I · Question 124 of 150

Correct — B, Damodar. A fault valley, or rift valley, is a trough that a river inherits from tectonics rather than carves for itself: a block of crust drops between two roughly parallel faults, and the river simply occupies the ready-made depression. The Damodar is the standard Indian example among the east-flowing rivers. It rises on the Chhotanagpur plateau in Jharkhand and runs east through a long, narrow, fault-bounded trough — a graben produced by the down-warping and faulting that accompanied the break-up of Gondwanaland — before turning south to join the Hooghly below Kolkata. Two consequences give the answer away. First, the trough subsided long enough to preserve thick Gondwana sedimentary beds that would otherwise have been stripped away, and those beds carry India's richest coal seams: Raniganj, Jharia, Bokaro, Karanpura, Ramgarh and Giridih all lie in this one valley. Second, the structural control shows in the river's plan — an unusually straight, east-west course cutting across the general grain of the plateau, quite unlike the meandering, purely erosional valleys of its neighbours. UPSC asked this same fact in almost the same words in 1998, calling it a rift valley formed by down-warping.

• (a)Chambal — The Chambal rises at Janapav in the Vindhyan hills of Madhya Pradesh and flows north to join the Yamuna. Its valley is famous for something quite different — the badlands or beehad, a maze of deep ravines gouged out of soft alluvium by gully erosion. That is erosion by running water on weak material, not a structural trough between faults.
• (c)Gandak — The Gandak is a Himalayan river, the Kali Gandaki and Narayani of Nepal, which enters Bihar and joins the Ganga near Sonepur and Hajipur. Its signature landform is the great alluvial megafan it has built across north Bihar — a depositional feature of the Himalayan foredeep. It flows in an alluvial and antecedent gorge setting, not in a fault-bounded rift.
• (d)Ramaganga — The Ramganga rises in the Dudhatoli range of Uttarakhand, emerges onto the plains at Kalagarh on the edge of Corbett, and joins the Ganga near Kannauj in Uttar Pradesh. It is an ordinary Himalayan tributary flowing in a valley cut by erosion; no rift or graben is associated with it.

Indian river valleys fall into two broad classes by origin. Most are erosional — the river cuts its own valley into the rock, so the valley's shape reflects the rock's resistance and the river's energy. A minority are structural: the depression already existed as a tectonic feature and the river merely took it over. Peninsular India carries several such rifts, formed when the Gondwana supercontinent began to break apart and long blocks of crust sank between parallel normal faults. The Narmada and the Tapi are the famous west-flowing examples, which is why they alone among the large peninsular rivers refuse to drain into the Bay of Bengal. The Damodar is the east-flowing counterpart — a Gondwana graben on the Chhotanagpur plateau. Because these sunken troughs protected the coal-bearing Gondwana strata from erosion, India's coal geography is essentially a map of its rift valleys: Damodar, Son, Mahanadi and Godavari.

The quickest route to the answer is to ask which of the four names you associate with coal, because coal and rift valleys are the same story in India. Damodar immediately brings up Jharia and Raniganj; Chambal brings up ravines; Gandak brings up floods in north Bihar; Ramganga brings up Corbett and a UP tributary of the Ganga. Only one of those associations is structural. The second route is directional. If a candidate has learned 'Narmada and Tapi occupy rift valleys' as a west-flowing fact, the natural follow-up question is which east-flowing river does the same, and the answer is the Damodar — which is precisely how UPSC framed it in 1998. Note also that the Damodar is called the Sorrow of Bengal for the floods of its lower course, and that taming it produced the Damodar Valley Corporation, set up in 1948 on the model of the Tennessee Valley Authority and generally described as independent India's first multipurpose river valley project.

• The Damodar rises on the Chhotanagpur plateau in Jharkhand, flows east through a fault-bounded Gondwana trough, and joins the Hooghly south of Kolkata; its main tributary is the Barakar.
• Subsidence of that trough preserved the Gondwana coal measures, making the Damodar valley India's richest coal belt — Raniganj, Jharia, Bokaro, Karanpura, Ramgarh and Giridih.
• Raniganj was the first coalfield worked in India, from the late eighteenth century, while Jharia is the country's principal source of prime coking coal.
• The Damodar's destructive lower-course floods earned it the name 'Sorrow of Bengal'; the Damodar Valley Corporation, created in 1948 on the Tennessee Valley Authority model, was independent India's first multipurpose river valley project, with dams at Tilaiya, Konar, Maithon and Panchet.
• Among the large peninsular rivers, the Narmada and the Tapi occupy west-flowing rift troughs; the Damodar is the standard east-flowing example of a fault-controlled valley.

• Answering 'Narmada' by reflex when a rift valley is mentioned; Narmada is the west-flowing example, and this question specifies neither direction but expects the east-flowing Damodar.
• Treating the Chambal's ravines as a structural feature; badlands are the product of gully erosion in soft alluvium, not of faulting.
• Confusing the Ramganga — which rises in the Dudhatoli range of Uttarakhand and joins the Ganga near Kannauj — with the Gandak of Bihar, or assuming either has a rift association. Neither does; the Damodar's fault valley is the rift case here.

UPSC has asked this directly as 'which east-flowing river has a rift valley due to down-warping' and has tested the structural logic through the Narmada, while UPPSC asks it in the shorter form seen here; in both cases the reliable trigger is the coal-plus-rift association of the Damodar valley.

• practice — not a real PYQ

  The Damodar Valley Corporation, generally described as independent India's first multipurpose river valley project, was modelled on which one of the following?

  • (a)The Hoover Dam Authority of the United States
  • (b)The Tennessee Valley Authority of the United States
  • (c)The Snowy Mountains Scheme of Australia
  • (d)The Aswan High Dam Authority of Egypt

  Answer(b) The Tennessee Valley Authority of the United States — the DVC was set up in 1948 on the TVA pattern, combining flood control, irrigation, navigation and power generation for a single river basin under one authority.

• practice — not a real PYQ

  The coal seams of the Jharia and Raniganj coalfields belong to which one of the following rock systems?

  • (a)Dharwar system
  • (b)Cuddapah system
  • (c)Gondwana system
  • (d)Vindhyan system

  Answer(c) Gondwana system — over ninety per cent of India's coal comes from Gondwana strata preserved in the fault-bounded troughs of the Damodar, Son, Mahanadi and Godavari valleys; the Dharwar, Cuddapah and Vindhyan systems are older and essentially coal-free.