What is the main problem associated with groins?

The problem with groins is that they trap sand that is flowing to a neighboring beach. Thus, if a groin is growing the topographic beach updrift, it must be causing downdrift beach loss.

What are the negative impacts of groynes?

Other adverse effects (especially for rivers) can be an increase in current velocity in the constricted flow area, with increasing bed erosion and a deepening of the bed level. Groynes can also be used in estuaries to decrease tidal flow velocities at the shoreline.

What is submerged groin?

External Websites. Groin, in coastal engineering, a long, narrow structure built out into the water from a beach in order to prevent beach erosion or to trap and accumulate sand that would otherwise drift along the beach face and nearshore zone under the influence of waves approaching the beach at an angle.

What are ocean groins?

Groins are shore perpendicular structures, used to maintain updrift beaches or to restrict longshore sediment transport. By design, these structures are meant to capture sand transported by the longshore current; this depletes the sand supply to the beach area immediately down-drift of the structure.

What are the negative impacts of groin erosion?

This deprives the ebb and flood tide deltas of sand and can cause substantial negative impacts to adjacent Islands. In a complex coastal system, the precise location, onset and scale of these negative impacts are very difficult to pinpoint. As with all erosion control structures, it may take years for groin impacts to become apparent.

How does the groin area affect the beach?

When a groin works as intended, sand moving along the beach in the so-called downdrift direction is trapped on the updrift side of the groin, causing a sand deficit and increasing erosion rates on the downdrift side. This well-documented and unquestioned impact is widely cited in the engineering and geologic literature.

What happens to the groins during a hurricane?

When big storms occur, groins direct strong currents that carry large amounts of sand seaward, in an offshore direction parallel to the groins. After Hurricane Hugo, for example, sidescan sonar studies showed gullies excavated on the continental shelf adjacent to each of the groins on Pawleys Island in South Carolina.

Is it legal to use groins in North Carolina?

The implication by those who are promoting the law to allow the use of groins on North Carolina ocean and inlet shorelines is that this is experimental and that if the groins don’t work they will be removed or altered. There is nothing experimental about groins.