What is a seawall?

A seawall is a wall built along a shoreline to hold back land and protect the area behind it from waves and erosion. Its face may be vertical, curved or stepped; protecting the land does not prevent the beach in front from eroding.

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By InstaBids editorial team with AI research agents. Updated 31 October 2026

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What are the main types of seawalls?

Oregon’s erosion-control guide groups seawalls into three face shapes: vertical, curved and stepped. Vertical faces reflect waves; curved faces change the reflection, while steps help break up wave energy. These are descriptions of the shapes, rather than a design for a particular property. “Most seawalls can be divided into three categories: vertical, curved, and stepped.” Source: Oregon Department of Land Conservation and Development, read 2026-10-31. “Vertical seawalls use a strong vertical face to reflect wave energy.” Source: Oregon Department of Land Conservation and Development, read 2026-10-31. “Curved seawalls are intended to reduce the amount of scour that occurs due to wave reflection.” Source: Oregon Department of Land Conservation and Development, read 2026-10-31. “Stepped seawalls are intended to break up and dissipate waves to better protect the upland and to prolong the life of the structure.” Source: Oregon Department of Land Conservation and Development, read 2026-10-31.

What is a seawall in Wisconsin DNR guidance?

Wisconsin DNR describes a seawall as a nearly upright shoreline structure that holds land in place and protects the upland from wave action. Its guidance names timber, concrete, steel and aluminum sheet piling as common materials. “Seawalls are near-vertical structures commonly constructed of timber, concrete, steel or aluminum sheet piling.” Source: Wisconsin Department of Natural Resources, read 2026-10-31. “The structure is installed parallel to the shore and is intended to retain or prevent the sliding and slumping of land while protecting the adjacent upland area from wave action.” Source: Wisconsin Department of Natural Resources, read 2026-10-31.

Why do seawalls need drainage and filter fabric?

Massachusetts coastal guidance treats drainage and filtration as working parts of a seawall. Drainage relieves water pressure from rain or overtopping waves; filter fabric helps keep the retained soil from escaping with that water. “Seawall repair or reconstruction projects should include improvements to the drainage system to prevent pressure from building up behind the wall due to wave overtopping or ponding of rainwater.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31. “This pressure is one potential cause for structural failure.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31. “The fabric holds the sediment in place, while the water drains.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31.

Why do seawalls fail?

A seawall can lose the ground supporting it. Massachusetts coastal guidance describes a cycle in which erosion exposes more of the structure, reflected waves increase erosion, and the wall becomes undermined until its ability to protect the shore is lost. “Over time, the structure can become undermined, reducing its shoreline protection capacity, increasing maintenance costs, and ultimately leading to total structure failure.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31.

How long does a seawall last?

The Massachusetts guidance supplies no single service-life figure for a seawall. It ties protection to design, exposure and site conditions, and says maintenance is needed. A wall’s age alone therefore does not establish how much useful life remains. “No shoreline stabilization option permanently stops all erosion or storm damage.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31. “The level of protection provided depends on the option chosen, project design, and site-specific conditions such as the exposure to storms.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31. “All options require maintenance, and many also require steps to address adverse impacts to the shoreline system, called mitigation.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31.

Do seawalls degrade beaches?

Yes, a seawall can contribute to beach erosion even while protecting the land behind it. Massachusetts coastal guidance explains that reflected waves can erode the fronting beach or neighboring properties, and that continued sediment loss can eventually remove the beach. “Seawalls and revetments themselves can also exacerbate erosion problems by reflecting waves onto the beach in front of them or onto neighboring properties.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31. “As natural erosive forces continue to remove sediment over time, beaches in front of the hard structures are diminished and can eventually be completely lost.” Source: Massachusetts Office of Coastal Zone Management, read 2026-10-31.

Sources

Shoreline Erosion: Causes, Prevention, and Control Options — Wisconsin Department of Natural Resources; read 2026-10-31.
Guidebook on Erosion Control Practices of the Oregon Coast, seawall section, page 49 — Oregon Department of Land Conservation and Development; read 2026-10-31.
StormSmart Properties Fact Sheet 7: Repair and Reconstruction of Seawalls and Revetments — Massachusetts Office of Coastal Zone Management; read 2026-10-31.