Coastal currents and sediment transport: which option describes littoral drift (often associated with the longshore current) most appropriately?

Introduction / Context:
Littoral drift refers to alongshore sediment transport driven primarily by waves approaching the shoreline at an angle, which set up a nearshore current running parallel to the coast. Recognizing its driver and direction is fundamental for siting harbours, groynes, and nourishment projects.

Given Data / Assumptions:

• Oblique wave approach induces a longshore current in the surf zone.
• Wind indirectly contributes by generating waves and setup.
• Transport is predominantly parallel to shore (not perpendicular), moving sand along the coastline.

Concept / Approach:
The longshore (littoral) current arises from the component of wave momentum flux parallel to the shoreline. While wind is the ultimate energy source for most waves, it is the waves’ tangential component at breaking that directly drives sediment motion alongshore.

Step-by-Step Solution:
Eliminate perpendicular-current option: that corresponds to rip currents or cross-shore processes, not littoral drift.Eliminate the “raised line of sand” option: that describes a berm or beach ridge, not a process.Select the parallel-to-shore current option, acknowledging wind's role via wave generation.

Verification / Alternative check:
Shoreline change patterns (updrift accretion/downdrift erosion) confirm the presence of littoral drift aligned with the prevailing wave approach.

Why Other Options Are Wrong:

• Raised line of sand: a morphological feature, not the transport process.
• Slow wind-driven surface drift offshore: describes general ocean surface drift, not the surf-zone longshore current.

Common Pitfalls:

• Attributing littoral drift directly to wind direction without considering wave approach angle.

Final Answer:
is a current parallel to the shore, caused due to tangential component of the wind