Sea walls are structures constructed at the interface between land and sea, designed to manage the dynamic marine environment. These engineered barriers serve to protect coastal areas from the powerful forces of ocean waves and tides. They provide a physical boundary against the advance of the sea, safeguarding human interests and existing landforms from the ocean’s influence.
Defining Sea Walls
A sea wall is a human-made, rigid structure built parallel to the coastline. These structures serve as a form of coastal defense, primarily designed to protect the land from erosion and the impact of ocean processes. They establish a fixed boundary between the marine environment and the land behind them. Sea walls are typically constructed from robust materials such as reinforced concrete, large boulders, or steel. Their design often involves considerable mass to withstand the intense forces exerted by waves and storm surges, providing a barrier against wave action.
Mechanisms of Coastal Protection
Sea walls protect coastal areas by directly interacting with incoming waves and controlling their energy. They function by either reflecting wave energy back into the sea or dissipating it, thereby reducing the force that could erode land. Vertical sea walls primarily reflect wave energy, while sloped, curved, or mound-type designs are more effective at dissipating wave forces. This action prevents direct wave impact on the land.
The structures also play a role in controlling wave run-up, which is the vertical height waves reach on the wall’s surface, and overtopping, where waves spill over the top. Properly designed sea walls minimize these occurrences, protecting inland areas from flooding. By absorbing and redirecting wave energy, sea walls reduce the intensity of wave action, which helps to prevent erosion and safeguard infrastructure and properties situated behind them.
Impacts of Sea Wall Construction
The construction of sea walls can lead to various consequences for the coastal environment. One impact is the alteration of natural sediment movement patterns. Sea walls disrupt the exchange of sediment between land and sea, leading to sediment starvation on adjacent beaches. This occurs because the wall blocks the natural flow of sand, causing erosion at the ends of the structure, a phenomenon called flanking erosion.
Sea walls also cause habitat disruption by replacing natural shorelines with hardened surfaces. This reduces the complexity and diversity of habitats, impacting marine and intertidal species. Studies indicate that areas with sea walls may have reduced numbers and sizes of intertidal species and fewer shorebirds compared to natural beaches. The smooth surfaces of many sea walls may not provide suitable attachment points or refuges for marine life, further limiting biodiversity.
Situations Requiring Sea Walls
Sea walls are constructed in specific contexts where land value or existing development necessitates robust coastal defense. They protect high-value assets such as urban areas, critical infrastructure, and densely populated coastal communities. This includes safeguarding roads, railways, power plants, and wastewater treatment facilities from coastal flooding and erosion.
These structures are implemented in locations where other methods of coastal protection, often termed “softer” solutions, are impractical due to space limitations or existing development. Sea walls prevent further erosion and secure the shoreline where human habitation or significant investments are present. Their ability to offer protection against coastal flooding and erosion makes them a solution for areas where land is scarce or highly developed.