Erosion around a seawall is one of the most common—and most misunderstood—problems facing waterfront property owners. While seawalls are designed to protect land from wave action and fluctuating water levels, the forces they resist don’t disappear. Instead, those forces often reappear as soil loss at the base of the wall, behind it, or along adjacent shoreline. Left unaddressed, erosion can compromise the structural integrity of the seawall, reduce usable yard space, and lead to costly repairs or total replacement.
This guide explains why erosion occurs around seawalls, how to identify early warning signs, and the most effective strategies to control and prevent further damage. Whether you own property on a lake, river, or coastal shoreline, understanding erosion management is essential to protecting your investment.
Understanding Why Erosion Happens Around Seawalls
A seawall works by reflecting wave energy rather than absorbing it. When waves strike the wall, that energy is redirected downward and sideways, often scouring soil at the toe (the base of the wall) or pulling material out from behind it. Over time, this process creates voids, sinkholes, or washouts.
Several factors contribute to erosion around seawalls:
- Wave reflection and turbulence: Hard vertical walls reflect wave energy instead of dissipating it, increasing scour at the base.
- Water level fluctuations: Seasonal changes, storm surges, and drawdowns can expose soils to repeated wetting and drying cycles.
- Poor drainage behind the wall: Hydrostatic pressure forces fine soils out through joints, cracks, or weep holes.
- Inadequate original design: Older seawalls may lack proper toe protection, filter fabric, or backfill material.
- Adjacent shoreline conditions: Erosion doesn’t stop at property lines. If neighboring areas are unprotected, your seawall may experience flanking erosion.
Understanding the root cause is the first step toward selecting the right solution.
Early Warning Signs of Erosion
Catching erosion early can save thousands of dollars in repairs. Property owners should routinely inspect both the front and back of their seawall for warning signs such as:
- Depressions or sinkholes forming behind the wall
- Exposed tiebacks or anchors
- Cracks, leaning, or bulging sections of the wall
- Soil washing out through seams or weep holes
- Gaps developing between the wall and surrounding ground
- Increased turbidity (muddy water) near the base after wave action
If any of these signs are present, erosion is already occurring and should be addressed promptly.
Managing Erosion at the Base (Toe) of the Seawall
Toe erosion is one of the most serious threats to a seawall’s stability. When soil is removed from the base, the wall loses support and can begin to settle or rotate.
Stone Revetment
One of the most effective solutions is installing a stone revetment at the base of the seawall. Large, angular armor stone absorbs and dissipates wave energy, reducing scour and protecting the toe.
Key benefits include:
- Long-term durability
- Improved wave energy dissipation
- Reduced maintenance requirements
- Added aesthetic value
Properly sized stone and correct placement are critical. Undersized stone can be displaced during storms, while improper installation may fail to stop erosion.
Concrete Toe Caps
In some cases, a concrete toe cap may be installed to reinforce the base of the wall. This method is commonly used with steel or sheet pile seawalls where space is limited.
While effective, toe caps must be engineered correctly to avoid reflecting additional energy that could worsen erosion nearby.
Preventing Soil Loss Behind the Seawall
Erosion behind the wall often goes unnoticed until visible damage appears. This type of erosion is usually caused by water pressure forcing fine soils through openings in the wall.
Proper Drainage Systems
A well-designed seawall includes adequate drainage to relieve hydrostatic pressure. This may involve:
- Weep holes
- Drain tile systems
- Gravel drainage zones
If drainage systems are clogged or missing, water will find its own path—often carrying soil with it.
Filter Fabric and Backfill
Geotextile filter fabric placed behind the wall prevents fine soils from migrating while still allowing water to pass through. Combined with clean, angular stone backfill, this creates a stable zone that resists erosion.
For older seawalls, retrofitting filter fabric may require partial excavation and repair, but it can significantly extend the life of the structure.
Addressing Flanking and End-Around Erosion
Flanking erosion occurs when water moves around the ends of a seawall, undermining it from the side. This is especially common where seawalls end abruptly or where neighboring properties are unprotected.
Solutions include:
- Extending the seawall past the erosion zone
- Installing return walls at the ends
- Adding revetment or natural stabilization beyond the wall
Ignoring flanking erosion can render even a well-built seawall ineffective.
Incorporating Living Shoreline Elements
In some environments, combining traditional seawall protection with natural elements can reduce erosion while improving ecological health.
Vegetation and Bioengineering
Native shoreline plants help stabilize soils, reduce runoff, and absorb wave energy. While vegetation alone may not be sufficient in high-energy areas, it can complement hard structures.
Hybrid Solutions
Hybrid approaches—such as placing stone revetment with planted terraces—offer a balance between durability and environmental benefits. These solutions are increasingly popular where regulations encourage softer shoreline treatments.
Maintenance: The Key to Long-Term Erosion Control
Even the best erosion control system requires ongoing maintenance. Property owners should:
- Inspect seawalls seasonally and after major storms
- Replace displaced stone promptly
- Clear blocked drainage outlets
- Monitor changes in shoreline contours
Routine maintenance not only prevents erosion from worsening but also helps document compliance with local regulations and permits.
When to Call a Professional
While minor erosion issues may be manageable, significant or recurring erosion should be evaluated by a marine construction professional or coastal engineer. Warning signs that professional help is needed include:
- Rapid soil loss
- Structural movement of the seawall
- Repeated repairs that fail
- Regulatory or permitting concerns
Professionals can assess site-specific conditions, recommend engineered solutions, and ensure work complies with environmental and permitting requirements.
Final Thoughts
Erosion around a seawall is not a sign of failure—it is a natural response to powerful water forces interacting with a rigid structure. However, ignoring erosion can lead to severe structural damage, property loss, and expensive repairs.
By understanding why erosion occurs, recognizing early warning signs, and implementing proven solutions such as stone revetment, proper drainage, and routine maintenance, property owners can significantly extend the life of their seawall. Proactive erosion management protects not only the seawall itself but also the land, structures, and investment behind it.
When handled correctly, erosion control transforms a seawall from a reactive barrier into a resilient, long-term shoreline protection system.