How to Build a Seawall

What is a Seawall?

A seawall or “sea wall” is a coastal defense made of hard and strong material constructed to reduce the effects of strong waves on the beaches and inland along the coast. This definition is expanded in the United Kingdom, due to their large coastline-to-inland ratio and their extensive experience with the sea, to include dikes, polders and artificial port and harbour facilities. Seawalls are commonly made out of reinforced concrete, boulders or steel. In certain instances, sea walls are created out of sand-filled boxes or cages called gabions. These seawalls are created when numerous gabions are stacked side-by-side or on top of one another.

Occasionally, you’ll see vinyl seawalls, wood seawalls or seawall constructions of aluminum or fiberglass. In most cases, seawall design includes a curved embankment facing the water, so the energy from the waves of the ocean are directed back out to sea.

How To Build a Seawall

Building a seawall is an expensive undertaking, with cost estimates ranging from around four-thousand to seven-thousand dollars per meter. This means that most larger seawalls are funded by public finances, either by the local municipality or the national government. Those building a seawall must be careful in their designs and construction, because a poorly-designed seawall will see the base erode quickly and require constant repairs and maintenance work.

How To Build a Seawall – Revetments

A “revetment” is the least-involved type of seawall, usually used in less dangerous or demanding inland settings. A revetment is a sloped mound made of either rubble, sandbags or geotextiles. For tougher waves, rubble is the better material for the revetment. In any case, these bulkheads are stacked to minimize the erosion on the shore and to break the waves from moving further inland. Revetments can be either watertight or porous.

Vertical or Curved Seawall Construction

Once again, when building a sea wall, one must consider whether to build a vertical wall or a curved wall. Vertical seawalls are typically built in the most exposed situations, often directly off the shore. These seawalls are built straight up, hoping to reflect waves and storm conditions, though piles or windbreaks are often placed between the vertical sea wall and the sea. If you need to protect the base of the seawall, or you want to prevent waves from topping the seawall, you are more likely to build curved seawalls (or stepped seawalls). The curve dissipates the energy of the wave, much like curved plate armor would deflect the energy of a weapon or a rounded helmet deflects some of the energy of falling debris.

What is a Seawall and Which Kind Should I Build?

Designing and building a seawall requires study of the particular situation you find yourself in. Also, construction costs might hinder your efforts to build the most elaborate kind of seawall. In either case, you should study the shoreline near you and determine the kind of challenges and dangers faced by the waves and storms coming off the sea near you. If you can build a sloped seawall made of sandbags or rubble that will do the trick, consider building your own seawall to protect the shoreline near your home. If you find that the ocean conditions near your beach or shore is more challenging or more dangerous and you don’t have large funds to build an elaborate seawall, then you might have to consider talking to city hall about building a sea wall with public funds. In this case, it’s likely that nearby neighbors or the community as a whole will be best served by a concrete seawall, so you might have to organize a civic group to pursue the construction of a public seawall.

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