A living shoreline is a way of managing coastal areas to protect, restore, or enhance the habitat. This is done through the placement of plants, stone, sand, and other materials. Living shorelines do not interrupt natural relationships between land, wetlands, and bodies of water.
Wetlands around the world have been damaged by dredging (digging). Most dredging is done to develop urban areas or expand ports. Dredging and drying a wetland can create more land for homes, businesses, or agriculture. Dredging a wetland near a harbor can allow more ships to dock, increasing the economic activity of the area. Dredging a harbor can also deepen the port, which allows larger ships, with more cargo, to dock.
Wetlands play an important natural role in coastal ecosystems. They prevent erosion of the land. Plants and trees anchor the soil and prevent it from washing out to sea. A wetland barrier between developed inland regions and the coast can protect fertile soil for agriculture, as well as development and recreation.
Wetlands also protect coastal areas from powerful storm surges. Storm surges are the waves that follow a hurricane or typhoon as it makes landfall. Storm surges can be more than a meter (three feet) tall. Hurricane Katrina, which devastated the U.S. city of New Orleans, Louisiana, in 2005, had a storm surge of about 7.5 meters (25 feet). Wetlands, with their spongy soil, absorb the energy and water of a storm surge. They also slow the surge. This protects homes, businesses, and agricultural areas.
Wetland habitats help clean waterways. Oysters, for instance, live in coastal wetlands and bays. Oysters are filter feeders. As they absorb nutrients from the water, they also absorb runoff and pollutants.
Wetlands also provide a habitat for a wide variety of organisms. Some organisms are commercially important to people, such as fish or crabs. Others play an important role in the coastal food web, such as seagrass, snails, or wading birds.
When people develop coastlines, they often protect the shoreline—and their property—by constructing rock, wood, or plastic seawalls. A seawall is a large, sturdy structure built to prevent erosion and damage from ocean waves. It extends, sometimes for kilometers, along a shoreline.
Constructing a seawall usually involves removing coastal vegetation such as seagrass, mangrove trees, and cattails. Without these plants, the biodiversity of the region shrinks. Insects, snails, and shrimp no longer have a reliable source of food. Birds and fish that prey on the insects or snails migrate elsewhere. The population of larger predators, such as muskrats or alligators, may fall sharply.
Living shorelines protect against erosion without removing vegetation or damaging coastal ecosystems. Unlike seawalls, living shorelines can adjust their height and width to the season or weather. They can expand during wet seasons and reduce their fertility during dry seasons. Living shorelines can be constructed by individuals, communities, or the government.
Goose Creek Tidal Wetlands Bank in the U.S. city of Chesapeake, Virginia, is a 4.2-hectare (10.4-acre) wetland. It was created by the Virginia Department of Transportation in 1982. That year, the department planned to build a new highway. The Goose Creek Tidal Wetlands were created to make up for wetland losses that would occur during highway construction. The government planted five species of salt marsh plants in the area. These plants were mostly reeds and cordgrass. The government then protected the wetlands from development.
Attracted by the new salt marsh, coastal species migrated to Goose Creek. Scientists have now identified 21 species of fish, including bass and anchovy, using the marsh. Invertebrates, such as shrimp and clams, are also part of the wetland ecosystem.
Types of Living Shorelines
There are many types of living shorelines. The type depends on the reason for creating it and the type of ecosystem involved.
Sometimes, living shorelines are built along recreational beaches to prevent erosion of sand and preserve the beach. This type of living shoreline may involve simply adding sand to the beach. It may also involve planting beachgrass to stabilize the sand, or building stone breakwaters. Breakwaters are structures placed offshore to reduce the power of incoming waves. This protects the beach from erosion. Breakwaters have the added benefit of creating calm water for swimming.
A living shoreline may be created along a river for recreational and commercial use. This type of living shoreline may include adding large rocks to the river bank. Frogs, insects, and plants live around river rocks. Moss and grasses help anchor sediment to the river bank. Stable river banks help reduce flooding and create a healthy river environment, allowing for sport fishing and expanded freshwater fisheries.
Some coastal communities create living shorelines to support or expand ecosystems that are already in place. Fringe marshes are an example of this type of living shoreline. Fringe marshes expand the natural ecosystem of a tidal marsh or swamp.
Creating fringe marshes may involve planting marsh grasses on the existing shoreline. The existing shoreline may also be expanded by creating sandbars or coastal area. Then, plants such as cattails, mosses, and sedges are planted. These attract insects. Larger predators such as birds may follow, building their nests among the plants and creating a healthy wetland habitat.
Many living shorelines include permanent support structures. These include:
- revetments: sloping structures placed directly on the shoreline. Revetments are usually made of riprap, a collection of large rocks or concrete fragments. Revetments are heavy “armor” for the shoreline.
- breakwaters: freestanding structures made of stone, sand, or other material placed offshore to reduce the power of incoming waves.
- sills: similar to breakwaters, but placed closer to shore.
- spurs: similar to breakwaters and sills, but attached to the shoreline or another structure.
- groins: large structures that extend straight out from the shoreline. Unlike seawalls, groins are perpendicular to the shore. Groins are usually made of concrete, wood, or rock. They often look like piers, and people can walk or even fish on them. Groins are usually built in groups, designed to protect the groin fields, or shoreline between them.