Protecting natural landforms and habitats by nourishing an eroding estuarine beach

An important issue facing coastal managers is how natural coastal habitats can be protected against wave erosion by human action. An assessment is made of attempts to protect a rare maritime forest on the bay side of a barrier island at Fire Island, New York, USA using artificial beach fill. The sediment deficit is caused by human attempts to stabilize the island by restricting inlet formation, overwash, and dune migration, and it is exacerbated by a nearby marina bulkhead. A total of 1099 m³ of sand dredged from the navigation channel was placed near the bulkhead. Loss of fill was 5.54–7.87 m³ m⁻¹ in the first 6 months. The fill was gone 18 months after placement. Sediment moving out of the fill area caused almost 4 m of shoreline advance 40 m downdrift after 6 months (gain of 3.28 m³ m⁻¹), followed by retreat of about 5 m at that location over the next 12 months (loss of 5.51 m³ m⁻¹). These results reveal how small changes in volume of microtidal estuarine beaches can cause great shoreline displacement rates. The amount of fill from maintenance dredging is insufficient to replenish erosion losses. Placing additional fill sediment on the bayside to create artificial washover fans can mimic natural landforms and overcome loss of sediment inputs caused by stabilizing the ocean shore. Mechanical placement may be preferable to natural processes, which would deliver sediment across the island and through pre-existing stable habitat, eliminating some of the features that take long to form.