Which of the following statements is/are correct?
- 1. Most rivers of north Bihar are antecedent rivers.
- 2. These rivers have a strong tendency towards lateral erosion.
Choose the correct option:
- AOnly 2
- BNeither 1 nor 2
- COnly 1
- DBoth 1 and 2
Show answer and explanation
Correct answers: (a) Only 2 or (d) Both 1 and 2
Explanation
The book's key accepts only statement 2.
- Statement 2 is correct: the rivers of north Bihar come down from the Himalaya onto a flat, soft alluvial plain with a very gentle slope. They carry huge loads of silt, so they shift their courses and erode their banks sideways. The Kosi has moved more than 100 km westward in about 200 years.
- Statement 1: the largest of these rivers, the Kosi, Gandak and Ghaghra, rise beyond the Great Himalaya and cut gorges across it, so they are antecedent. But many others, such as the Burhi Gandak, Bagmati, Kamla and Mahananda, rise in the lower ranges or the plains and are not.
The book's key is (a), Only 2: most rivers of north Bihar are counted, one by one, as not antecedent. Some books call the north Bihar rivers antecedent as a group, since the Kosi, Gandak and Ghaghra are, so (d) is also accepted.