Question

In which one of the following rivers does helical flow play an important role in controlling river dynamics and channel morphology?

• A. Meandering rivers
• B. Straight rivers
• C. Braided rivers
• D. Bedrock rivers

Hint:

Helical flow in meandering rivers helps to shape channel features like point bars and cut banks by influencing erosion and sediment deposition.

Answer 1

The Correct Option is A

Step 1: Understanding Helical Flow.
Helical flow describes the secondary circulation of water within a river bend, where surface water moves toward the outer bank while bottom water moves inward. This spiral pattern is critical in sediment transport and erosion processes.

This phenomenon is most prominent in meandering rivers, where the river's sinuous path promotes the development of centrifugal forces and secondary flow structures, like helical flow. The flow contributes to lateral erosion on the outer bend and deposition on the inner bend, helping form and evolve meanders.

Step 2: Evaluating the Options.
- Option (A): Meandering rivers — ✅ Correct. Helical flow is a defining process in meandering river systems.
- Option (B): Braided rivers — ❌ Incorrect. These rivers are dominated by multiple interweaving channels and high sediment load, not helical flow.
- Option (C): Straight rivers — ❌ Incorrect. These have minimal curvature, thus less influence from helical flow.
- Option (D): Anastomosing rivers — ❌ Incorrect. These consist of multiple stable channels separated by vegetated islands and are not primarily influenced by helical flow.

Conclusion:
Option (A) is correct — helical flow is a key mechanism in meandering rivers, influencing erosion, deposition, and channel migration.