Which of the following best explain why the lower course of a river is sometimes choked with sediments? 1. The valley of a river is widest in its lower course. 2. The velocity of a river in its lower course is low. 3. The delta sometimes develops in a rivers lower course. 4. Much of the river water is drawn for irrigation in the lower course. Select the correct answer using the code given below : Code :

The lower course of a river is characterized by a wide, flat valley where the gradient becomes very gentle. This reduction in slope leads to a significant decrease in river velocity [1]. As the river's energy drops, it can no longer transport its heavy load, leading to the deposition of fine sediments known as alluvium. This process often results in the formation of deltas and distributaries, which further divide and slow the flow, causing the channel to become 'choked' or braided [2]. Additionally, human interventions such as drawing water for irrigation significantly reduce the river's volume and discharge in the lower reaches. This loss of water further diminishes the river's capacity to carry sediment, accelerating deposition and channel blockage [3]. Thus, all four factors—valley width, low velocity, delta formation, and irrigation withdrawals—contribute to the choking of the lower course.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 16: Fluvial Landforms and Cycle of Erosion > Old Age > p. 199
2. [2] https://education.nationalgeographic.org/resource/delta/
3. [3] INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Drainage System > THE HIMALAYAN DRAINAGE > p. 20