Additional types of shore protection alternatives for both high- and low-wave-energy coasts function by reducing the wave energy striking the shoreline. Reefs, wetlands, and sills can reduce storm damage and mitigate erosion using land substrate and biological organisms to absorb wave energy.
Coral reefs are massive calcareous rock structures found in tropical waters. Oyster and worm reefs are other biogenic reef structures found in the southern Atlantic and Gulf coasts. Reefs are biological wave dampers that can accommodate rising sea level as long as they are alive. Therefore, preservation of existing reefs is essential for shore protection.
Wetlands, such as salt marshes and mangroves trap sediment to extend the shore, and they provide wave energy absorption in the process. Replanting and restoration of wetlands can therefore increase shore protection.
Sills are typically low, small, continuous rock structures placed at mean low water with some sand fill in the lee to provide substrate for marsh growth. Sills can thus be used in higher wave energy regimes to establish intertidal marsh grasses that aid in shore protection. Periodic marsh replanting and maintenance may be necessary depending on wave energy conditions.