Which coastal structure is built perpendicular to the shoreline to trap sand on the updrift side?

Which coastal structure is built perpendicular to the shoreline to trap sand on the updrift side?

• A. Groin
• B. Breakwater
• C. Sea wall
• D. Jetty

Answer: (A)

Longshore drift moves sand along the coast as waves approach at an angle. A groin extends from the beach perpendicular to the shoreline, directly interrupting that along‑shore sand flow. This causes sediment to accumulate on the updrift side of the groin, widening the beach there, while the downdrift side can be starved of sand and erode. Breakwaters are built parallel to the shore to reduce wave action near harbors, sea walls stand along the landward edge to stop inland erosion, and jetties extend into the sea at harbor entrances to protect navigation; their primary roles aren’t to trap sand along the beach on the updrift side.

Longshore drift moves sand along the coast as waves approach at an angle. A groin extends from the beach perpendicular to the shoreline, directly interrupting that along‑shore sand flow. This causes sediment to accumulate on the updrift side of the groin, widening the beach there, while the downdrift side can be starved of sand and erode. Breakwaters are built parallel to the shore to reduce wave action near harbors, sea walls stand along the landward edge to stop inland erosion, and jetties extend into the sea at harbor entrances to protect navigation; their primary roles aren’t to trap sand along the beach on the updrift side.