Coastal protection involves strategies and measures designed to defend coastlines. These efforts aim to safeguard coastal communities, their economies, and diverse ecosystems from natural processes. Coastlines are dynamic environments, constantly shaped by forces like waves, tides, and currents. Understanding these dynamics is foundational to developing effective protection strategies.
Threats to Coastlines
Coastlines worldwide face ongoing challenges from natural processes, including coastal erosion and storm surges. Coastal erosion involves the wearing away of land along the shoreline by wave action, tides, and currents, leading to the loss of rocks, soils, and sands. Storm surges, characterized by an abnormal rise in seawater level during a storm, are primarily caused by a storm’s powerful winds pushing water onshore. These natural phenomena can cause rapid damage to buildings, infrastructure, and natural habitats.
The impacts of these natural processes are intensified by global climate change. Rising global temperatures contribute to accelerated sea-level rise, which directly increases the risk of coastal erosion and flooding. Global average sea level has risen approximately 8-9 inches (21-24 centimeters) since 1880, with the rate of rise accelerating. Warmer ocean temperatures are also linked to an increase in the intensity of tropical storms, potentially leading to more powerful hurricanes and heavier rainfall. These changes amplify the threats to coastal areas, making protective measures important.
Hard Structural Approaches
Hard structural approaches involve constructing engineered barriers to defend coastlines. These structures control or block natural coastal processes by intercepting and dissipating wave energy. While effective locally, they can alter natural sediment transport patterns, potentially causing unintended erosion in adjacent or downdrift areas.
Seawalls
Seawalls are linear structures built parallel to the shoreline to protect land and infrastructure from erosion and inundation. They can take various forms, including vertical or sloping designs, and are constructed from materials like rock, concrete, or timber. While seawalls provide direct protection, reflected wave energy can accelerate erosion at their base or on nearby beaches.
Groynes
Groynes are structures built perpendicular to the shoreline, extending into the water. Their function is to reduce longshore drift, the movement of sand along the coast, thereby trapping sediment and widening the beach on their updrift side. A series of groynes can protect a stretch of coast, but they can cause sediment starvation and increased erosion on the downdrift side.
Breakwaters
Breakwaters are structures built parallel to the shore but located offshore. These structures are designed to block or reduce incoming wave energy before it reaches the coastline, encouraging sediment deposition behind them. Breakwaters can be submerged or visible, and while they dissipate wave energy, they may also impede the natural longshore transportation of beach material.
Nature-Based Solutions
Nature-based solutions, often referred to as “soft” or “green” infrastructure, work with natural systems to provide coastal protection. These methods leverage ecological processes to dissipate wave energy, stabilize shorelines, and offer additional environmental benefits. They aim to enhance or recreate natural coastal features that historically provided defense against marine forces.
Beach nourishment
Beach nourishment involves adding sand to existing beaches to increase their elevation and width. This process enhances the beach’s capacity to absorb wave energy and buffer inland areas from wave action and inundation. Since beaches are dynamic, nourishment is often an ongoing expense.
Dune restoration and stabilization
Dune restoration and stabilization focus on rebuilding and strengthening natural sand dunes. This involves planting native dune vegetation, such as grasses, which helps reshape and anchor the dunes. Healthy dunes act as natural barriers, buffering inland areas from wave action and storm surges.
Living shorelines
Living shorelines utilize natural materials like plants, sand, or rock to stabilize shorelines, rather than relying on hard structures. Examples include the restoration or creation of salt marshes, mangrove forests, and oyster reefs. These habitats prevent erosion by dampening wave energy and trapping sediments, while also providing habitat for marine life and improving water quality through filtration.
Integrated Coastal Management
Modern coastal protection strategies recognize that no single solution is universally effective. Integrated Coastal Management (ICM) is a comprehensive approach that assesses a specific location’s unique needs to combine various protection tools. This framework aims to achieve a balanced and sustainable approach to coastal resource utilization, considering both environmental protection and socio-economic development.
This approach incorporates hybrid solutions, which combine traditional engineered structures with nature-based elements. For instance, a restored salt marsh might be fronted by a low breakwater or an artificial oyster reef to provide enhanced protection in higher energy environments. Such combinations can offer both risk reduction and the ecological benefits associated with natural solutions.
Long-term monitoring of coastal processes and the performance of implemented solutions is part of integrated management. This allows for adaptive planning, where strategies are adjusted based on observed changes and new data. Engaging local communities and stakeholders in planning and decision-making processes is also important, ensuring diverse perspectives are considered and fostering local support for coastal resilience efforts.