How does building a groin affect longshore drift?

Building a groin interrupts the natural movement of sediment along the shoreline caused by longshore drift. By extending into the water, groins trap sand on one side, leading to beach accumulation, while the downdrift side may experience erosion due to a reduction in sediment supply. This alteration can disrupt local ecosystems and change coastal dynamics, potentially impacting nearby beaches and navigation. Over time, the effectiveness of groins may diminish as sediment patterns shift.