Geomorphology – Sediment Transport The movement of particles by rolling, sliding, and shuffling along an eroded surface (river bed, desert floor, or coastal zone) is called:

Introduction / Context:
Sediment transport occurs in several distinct modes depending on grain size, flow velocity, and fluid properties. This question asks you to identify the term for coarse particles that move in direct contact with the bed through rolling, sliding, or shuffling—an essential concept in fluvial geomorphology and coastal processes.

Given Data / Assumptions:

• Particles are described as rolling, sliding, or shuffling along the surface.
• We are dealing with bedload movement, not grains fully carried by the flow.
• Terminology choices include saltation, suspension, traction, and solution.

Concept / Approach:
Traction is the term for the bedload movement of the largest grains, which maintain contact with the bed as they roll or slide. Saltation involves bouncing in short hops; Suspension refers to fine particles carried within the fluid column; Solution describes ions dissolved in the fluid, invisible as discrete grains. The described motion matches traction precisely.

Step-by-Step Solution:

Verification / Alternative check:
Bedload samplers and channel observations consistently show cobbles and boulders moving by traction during floods, while sands commonly saltate and silts/clays remain in suspension—confirming the classification scheme.

Why Other Options Are Wrong:

• Saltation: Involves intermittent contact and hopping, not continuous rolling/sliding.
• Suspension: Grains are supported by turbulence, not bed contact.
• Solution: Chemical ions; no particulate rolling/sliding occurs.

Common Pitfalls:
Confusing saltation with traction; remember saltation is “hopping,” traction is “rolling/sliding,” and both are bedload, while suspension is part of suspended load.

Final Answer:
traction