How is a Seawall Constructed?

A seawall is a protective structure or embankment used in a coastal area to help mitigate damage and disturbance associated with waves, tides, tsunamis, hurricanes, and other natural disasters. Sea walls protect from overtopping waves and storm surges. They help coastal areas retain soil that would otherwise be lost or disturbed over time, ultimately preventing land from sliding. And they keep real estate and commercial properties as well as other coastal resources safe from water damage.

SEAWALL VS. BULKHEAD

You may have heard of seawalls referred to as bulkheads and vice versa, but true sea walls differ from true bulkheads in that they provide shelter from waves as well as retaining soil in an area. A bulkhead, on the other hand, primarily serves the purpose of providing stabilization at the shoreline in order to retain soil. Both seawalls and bulkheads help stop the land from sliding due to their soil retention capabilities, but seawalls are bigger and serve the dual purpose of interrupting waves and surges. Seawalls are frequently constructed using concrete, while bulkheads may be constructed using gravity structures or sheet piling.

MATERIALS

As mentioned, seawalls can be made of concrete, but they are also quite often made of steel. Many are made of concrete with steel reinforcements. They can also be constructed of timber, boulders, vinyl, or composites. Vinyl seawalls are a popular option when a seawall needs to be constructed easily and quickly, but they need to be replaced every 20 years or so. Wooden seawalls are an attractive choice, but they are the most easily damaged of all types. When seawalls are constructed, they can have seaward faces that are concave, vertical, or stepped. They are commonly built with defensive materials referred to as revetments, which are laid on their slopes. Additionally, they may include quays and landing platforms for unloading and loading vessels. They may also be engineered with jetties, groins, and offshore breakwater.

STEEL AND VINYL SHEET PILE

When constructed with steel, seawalls are often comprised steel sheet pile. Steel sheet pile is a great option for seawall construction because of their relative ease of installation, strength, and longevity. Although they can acquire damage and erosion from years of saltwater wear and tear, steel sheet pile is relatively long-lasting. Additionally, when steel sheet piles are not utilized, vinyl sheet piles are a great alternative. While vinyl sheet piles do not carry the same strength as steel sheet piles, vinyl sheets are less susceptible to corrosion than steel.

Engineering specs will differ based on the requirements of the particular area where a seawall is installed. Soil properties, topography conditions such as grading and elevation, embedment, and water levels should all be carefully assessed during the design process to ensure a high-quality build. Zoning restrictions as well as local ordinances must be considered in the construction process.

The frequency and scope of maintenance and repair after a seawall is constructed will differ based on the materials used in construction as well as coastal conditions, i.e. how many storms occur in a particular area at any given time. Seawalls that are failing can pose significant risk to coastal properties and other resources. Seawalls that do not adequately do their jobs may have erosion holes, settling soil, or long cracks that present issues. These vulnerabilities should be promptly addressed through repair or replacement of damaged seawalls.

EQUIPMENT

Types of equipment used in seawall construction include excavators to prepare an area for installation and for backfilling, pile driving equipment if piles are to be installed, barges for storage of equipment and materials, cranes, tiebacks, anchors, welding equipment, and other specialized equipment, depending on the particular seawall construction project.

In some areas where construction of a new seawall is being proposed, the pros and cons of construction must be carefully weighed. Seawalls do a lot of good, but they can also harden shorelines on coastal ecosystems and can otherwise disrupt the natural coastal exchange of sediment. This can result in damage to intertidal beaches and wetlands. Sea walls can also contribute to the dissipation of beaches due to how they modify the transport of sediments. If the need to protect an area from natural disasters and erosion is critical, though, a sea wall is a very viable choice.

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