Coastal erosion threatens infrastructure, property, and natural habitats globally. Traditionally, this threat was met with “hard stabilization” structures, such as seawalls, revetments, and groynes, which are fixed, rigid barriers designed to resist the ocean’s energy. However, the environmental toll and limited long-term effectiveness of these structures have prompted coastal managers to seek more sustainable, flexible, and nature-aligned alternatives. These modern approaches focus on working with natural coastal processes to achieve resilience, moving away from concrete and steel.
The Consequences of Hard Structures
Hard structures often lead to unintended consequences for the beaches they are meant to protect. Seawalls, for example, reflect wave energy back onto the beach, scouring away sand at the base and causing the beach face to narrow or disappear completely over time, a process known as passive erosion. This loss of beach area eliminates the natural buffer zone that protects upland areas during storms.
Structures built perpendicular to the shore, like groynes and jetties, interrupt the natural flow of sand along the coast, called longshore transport. While sand builds up on the updrift side, the downdrift side is starved of sediment, leading to accelerated erosion in adjacent areas. This “end effect” shifts the problem down the coast, requiring more interventions elsewhere. These static barriers also destroy natural habitats, such as nesting grounds for sea turtles and shorebirds, and prevent the natural landward migration of beaches and dunes as sea levels rise.
Adding Sediment to the Shoreline
A primary alternative to hard armoring is beach nourishment, which involves mechanically adding large quantities of suitable sediment to an eroded beach. This “soft engineering” approach widens the beach profile, creating a larger buffer that dissipates wave energy before it reaches coastal infrastructure. The wider, gentler slope allows waves to break further offshore, reducing their destructive power during storms.
The process begins with detailed surveys to identify offshore “borrow sites” where sand closely matches the native beach material in grain size and composition. Specialized dredge vessels excavate this sand and pump it through pipelines directly onto the eroded shoreline. Since nourishment does not eliminate the forces causing erosion, the added sand is naturally redistributed by waves and currents, meaning the beach must be periodically replenished, often every two to ten years, to maintain its protective width.
Using Nature to Stabilize Coasts
Ecological engineering offers “living shorelines,” which integrates natural elements to stabilize the coast while enhancing habitat. Unlike static concrete structures, living shorelines are dynamic and adapt to changing environmental conditions, such as sea-level rise. These solutions involve planting specialized vegetation, such as marsh grasses or dune plants, whose root systems bind the sediment and stabilize the soil.
In calmer, sheltered waters, living shorelines may incorporate low-profile, wave-attenuating structures like oyster reefs or submerged sills made of rock or shell bags. These structures reduce wave energy, allowing the vegetation planted behind them to thrive and trap fine sediments, promoting natural land accretion. The restored habitats provide environmental benefits, including improved water quality through filtration and the creation of diverse ecosystems for marine life.
Moving Away from the Water
Non-structural alternatives focus on administrative and planning strategies that avoid placing property in harm’s way, rather than physically intervening in coastal processes. The concept of “managed retreat,” or planned relocation, involves deliberately moving buildings and infrastructure away from vulnerable shorelines. This strategy acknowledges that attempting to hold the line against the sea is unsustainable in highly erosive areas.
Regulatory tools like coastal setbacks and zoning restrictions prevent new development in high-risk zones or require construction to be placed inland based on projected erosion rates. A rolling setback line, for instance, adjusts the allowable building limit landward as the shoreline erodes, ensuring new investments are not subject to immediate coastal hazards. These planning measures allow natural coastal processes to continue unimpeded, preserving the beach and dune system as a natural defense for the ecosystem and inland communities.