A seawall is a coastal defense structure built parallel to the shoreline to protect inland areas from wave action and prevent coastal erosion.
Essentially, a seawall acts as a barrier between the ocean and the land. It is typically constructed from durable materials such as concrete, masonry, or sheet piles and is designed to withstand the constant pounding of waves and the erosive forces of the sea. The primary function of a seawall is to:
- Protect Land: Prevent waves from reaching and eroding the land behind it, safeguarding buildings, infrastructure, and natural habitats.
- Reduce Erosion: Minimize the loss of sediment and land due to wave action and currents.
- Stabilize Shoreline: Help maintain the existing shoreline position and prevent further landward retreat.
How Seawalls Work
Seawalls work by directly intercepting wave energy. When a wave strikes a seawall, some of the energy is reflected back into the ocean. The rest of the energy is either dissipated through turbulence and friction or transmitted to the structure itself.
Types of Seawalls
While seawalls share the same basic purpose, they come in various designs and materials, including:
- Vertical Seawalls: Straight, upright walls that reflect wave energy.
- Curved Seawalls: Designed with a curved face to redirect wave energy upwards and backwards, reducing overtopping.
- Rubble Mound Seawalls: Constructed from large rocks or boulders, which dissipate wave energy through friction and turbulence.
- Sheet Pile Seawalls: Made from interlocking steel sheets driven into the ground, often used in areas with soft soils.
Considerations
It's important to consider the potential environmental impacts of seawalls. While effective at protecting land, they can sometimes:
- Increase Erosion Elsewhere: By reflecting wave energy, seawalls can sometimes accelerate erosion on adjacent beaches.
- Disrupt Natural Processes: They can interfere with the natural movement of sediment and alter coastal ecosystems.
- Reduce Beach Access: They can sometimes limit public access to the beach.
Therefore, the decision to build a seawall should be made after careful consideration of its potential benefits and drawbacks. Alternatives like beach nourishment, dune restoration, and managed retreat should also be considered.
