A Growing Defense: Living Seawalls and Shorelines

Coastal erosion and sea level rise have led to habitat reduction for aquatic plants and animals. These phenomena have also increased the flood risk for coastal property owners. Now is the time to erect defenses. However, while artificial defenses like concrete barriers and retaining walls are vital contributors to the solution for flooding, you may want to add additional features.

Not only should you have a seawall to protect your property but also to help local habitats by creating either a living seawall, a living shoreline, or both. These break up wave energy and help stop the undersea erosion that can cause seawalls to collapse.

Habitat Restoration

A living seawall is a concrete seawall with modifications made on the seaward side. These modifications allow aquatic life to attach to the wall, be they plants or small animals that need a nesting site. The seawall can be a traditional wall-like structure or an artificial reef.

When sea life once again sets up homes on the wall, this encourages the growth of aquatic plants like seagrasses.
A living shoreline is more extensive. People have modified a patch of natural shoreline to grow into a marshlike area, complete with shrubs and trees. The living shoreline is not a manicured garden, though the plants may need human-powered care like a garden might. The shoreline helps stop a lot of the powerful wave energy that can be so destructive to houses.

Energy Diffusion

The biggest advantage to having a living shoreline or seawall in front of your other defenses is that the landforms and sea life help redistribute the energy of an incoming wave. Whether you deal with only the small but frequent wakes from jet skis or the stronger impacts of tropical system swells, the plant life in these shorelines and walls breaks up much of the energy pushing the water toward your property.

In fact, in areas that experience coastal monsoons, mangrove swamps help prevent flooding. Without the groves, coastal regions flood substantially more during these storms.

However, you don't need an extensive mangrove forest planted in front of your boat dock. A typical setup might be a concrete seawall that has a living layer planted on the seaward side, with a living shoreline in front of that.

For gentler areas — for example, those Jet Ski wakes that aren't severe, but that can erode sand — a living seawall with a layer of seagrass may be more appropriate, with no living shoreline in front of that.

Under-Wall Erosion

Make no mistake — a hard seawall or similar defense is necessary for areas where you have a lot of wave energy crashing toward a structure. But by combining the hard defenses with a living defense, you increase the ability of the entire structure to diffuse energy both above and below the waterline.

Sometimes the energy of a wave that crashes against a hard wall doesn't really go away — the energy goes elsewhere. That can be around a wall or under it.

The force of the moving water can erode silt and sediment on the floor of the sea too. That means the sediment holding the seawall in place can start to wash away, leading to a collapsed wall. Living defenses that diffuse the energy help stop that from happening.

If you want to erect a concrete barrier on your property, work with the land and plant life that are already in place. Contact Edgewater Marine Construction, Inc., to discuss integrating a seawall or bulkhead into existing marshes or other natural formations. Adequate and diverse waterfront construction techniques offer protection for your property and for surrounding sea life.