Coastal areas are highly vulnerable to the effects of ocean waves, storms, and rising sea levels. As a result, coastal protection structures have become essential for safeguarding harbors, infrastructures, and natural shorelines. These structures not only protect against the devastating impacts of erosion and flooding, but they also alter currents and sand movements, and can even redirect rivers and streams. This article explores various coastal protection structures, their types, and the benefits they offer.
I. Introduction
Coastal protection structures are designed to mitigate the impacts of sea wave actions and protect the infrastructure along shorelines, such as harbors, piers, and waterfront buildings. These structures are essential in regions susceptible to erosion, flooding, and storm surges. Coastal protection systems can change the movement of currents, control sand migration, and prevent the damage that natural forces often impose on the coast. In addition, they may be used to redirect rivers and streams, ensuring the stability of the land and preserving the coastal ecosystem.
II. Types of Coastal Protection Structures
Several different types of coastal protection structures are utilized to safeguard shorelines. Below, we discuss the most commonly used structures: seawalls, bulkheads, groins, jetties, and breakwaters.
1. Seawalls
Seawalls are large, robust structures that protect coastal areas from wave actions and storm surges. Typically built along shorelines, these structures prevent erosion, flooding, and loss of coastal infrastructure. Seawalls can be constructed from a variety of materials, including rubble mounds, granite masonry, and reinforced concrete. Different configurations are used depending on the wave action and site conditions.
- Curved Face Seawall
The curved face seawall is designed to withstand the impact of high waves. A sheet pile cutoff wall is employed at the foundation to prevent erosion caused by scouring waves. Large stones are placed at the toe of the wall to further mitigate scouring. This design is effective at protecting areas that experience significant wave activity. - Stepped Face Seawall
This seawall type is used for locations that face moderate wave action. Constructed with reinforced concrete sheet piles and tongue-and-groove joints, the spaces between piles are often filled with grout or geotextile fabric. The geotextile allows water to seep through, preventing the accumulation of hydrostatic pressure behind the wall. - Rubble Mound Seawall
Rubble mound seawalls are more cost-effective and relatively easier to build. These seawalls consist of large quarry stones that can adjust to scouring and wave actions without failing structurally. The design is simple and flexible, making it an ideal choice for certain coastal environments.
2. Bulkheads
Bulkheads are vertical barriers constructed to prevent soil erosion and protect the land behind them. Typically built from concrete, steel, or timber, bulkheads are commonly used in areas that are not exposed to strong waves but require protection from tidal forces and erosion. There are two main types of bulkheads: gravity bulkheads and anchored sheet pile bulkheads.
- Gravity Bulkheads
These are simple structures that rely on their weight to resist the forces of water and soil. Gravity bulkheads are typically used where wave action is minimal, and their primary purpose is to retain earth behind the structure. - Anchored Sheet Pile Bulkheads
In areas with more severe conditions or where rock is close to the surface, anchored sheet pile bulkheads are used. These structures are reinforced to withstand hydrostatic pressure and bending moments caused by water forces. Cellular sheet pile bulkheads are particularly useful in environments where sufficient penetration for other types of bulkheads is not feasible.
3. Groins
Groins are shore protection structures designed to reduce erosion by altering wave and current patterns along the shoreline. Typically built from concrete, stone, steel, or timber, groins extend perpendicular to the shoreline and can be either impermeable or permeable. The structure of a groin traps sand moving along the shore, helping to build up beaches and prevent further erosion.
Groins are categorized based on their length, height, and permeability, with impermeable groins effectively trapping sand and permeable groins allowing water to flow through while still reducing erosion.
4. Jetties
Jetties are long structures built at the entrance to harbors or river estuaries. They are designed to extend into deeper water and prevent the formation of sandbars, which can obstruct navigation and limit the flow of water. Jetties also help in controlling currents. Commonly constructed from materials like concrete, steel, stone, timber, and asphalt, jetties are essential for maintaining safe access to ports and preventing sediment buildup in channels.
Jetties serve both functional and protective roles, ensuring smooth maritime operations and protecting the shoreline from the effects of strong currents.
5. Breakwaters
Breakwaters are large structures built offshore to reduce the impact of waves on coastal areas, harbors, and shorelines. These structures are particularly useful for creating calm and secure environments for ships, especially in ports or anchorages. Breakwaters can be classified into three main types: offshore, shore-connected, and rubble mound breakwaters.
- Offshore Breakwaters
Built further away from the shore, offshore breakwaters act as barriers to incoming waves, reducing wave heights before they reach the coastline. - Shore-Connected Breakwaters
These breakwaters are connected to the shore and are designed to protect a specific coastal area, such as a harbor or beach. - Rubble Mound Breakwaters
Constructed using large stones or other materials, rubble mound breakwaters are used in areas exposed to heavy wave action. They are flexible and cost-effective, making them a popular choice in many regions.
Breakwaters provide a crucial layer of protection, ensuring safe harbor conditions and reducing coastal erosion.
III. Conclusion
Coastal protection structures play a critical role in preserving shorelines, protecting infrastructure, and mitigating the impacts of storm surges and erosion. By understanding the various types of coastal protection structures—seawalls, bulkheads, groins, jetties, and breakwaters—engineers can select the most suitable solution based on site conditions, wave action, and other environmental factors. These structures help create safer, more stable coastal environments, ensuring the longevity and resilience of coastal communities and ecosystems.