Final answer:
The construction of breakwater jetties extending out more than one-half mile would disrupt the natural longshore drift, causing sand accumulation on the updrift side and increased erosion on the downdrift side due to reduced sand supply. This can lead to significant changes in coastal processes and may require additional management measures.
Step-by-step explanation:
If breakwater jetties are constructed extending out more than one-half mile on each side of an inlet, such as the proposed ones for Oregon Inlet in NC Outer Banks, they would significantly alter the movement of sand and sediment around the inlet. The jetties would act as a physical barrier, interrupting the natural process of longshore drift, where sand moves along the coast due to the action of waves and currents.
With the placement of jetties, the sand being transported by longshore drift would accumulate on the updrift side, leading to a build-up of sand, which could extend the beach. However, on the downdrift side, sand supply would be reduced, potentially resulting in increased erosion as the natural replenishment of sand is blocked. Therefore, while jetties can protect the inlet and structures within it by preventing the migration of sand into the channel, they can also cause significant changes to coastal processes and potentially lead to detrimental effects on adjacent shorelines unless properly managed.
When considering coastal engineering projects like the construction of jetties, careful consideration must be given to their impact on local ecosystems and the potential need for additional measures, such as beach nourishment, to address the altered sediment dynamics.