Evaluating the Condition of Seawalls/Bulkheads
Seawalls and bulkheads (walls) provide shoreline stabilization
for many coastal and waterfront properties throughout Florida
and the Caribbean.The walls provide an economical approach for
vertical shoreline stabilization, allowing owners to maximize
upland property area, as opposed to other shoreline stabilization
methods such as revetments or natural wetlands/mangroves. Existing
walls were constructed of many different structural configurations,
and at various time periods. Coastal and waterfront properties
are in high demand in Southern Florida and the Caribbean with
an increasing coastal population. Developers and property owners
are looking to rehabilitate existing properties, and the condition
of a coastal seawall or waterfront bulkhead can significantly
impact the total cost of property development.Also, many waterfront
property owners may have experienced problems with their existing
structures, or have concerns regarding the structural integrity
of their walls.
- Difference between Seawall &
- Present Materials of Construction
with a Discussion of Material Performance
- Discuss Wall Structural Evaluation
- Seawalls and Bulkheads
Introduce Elements of Wall Design
- Address Special Regulatory Issues
- Present Frequently Asked Questions
Seawall vs .Bulkhead?
Many people refer to all vertical shoreline structures as
“seawalls,” but there is a difference between
a seawall and a bulkhead.
Seawall: structure that provides
shoreline protection from waves but also retains soil.
Bulkhead: vertical shoreline
stabilization structure that primarily retains soil, and provides
minimal protection from waves.
Seawalls are typically located on the coast fronting
beaches, and are subject to storm surges with pounding surf,
eroding shorelines and wave overtopping from coastal storm
events. Some localized waterfront properties may be subject
to significant wave activity, even though they are not exposed
to ocean waves. A coastal engineering study can provide seawall
design information to ensure that they are designed properly
to withstand the dynamic loading and overtopping effects of
waves. The “rule of thumb” in bulkhead design
is to account for wave impacts if the significant wave height
at a project site is expected to be in excess of three feet
(1 meter). Unfortunately, many existing walls on the coast
were simply designed as bulkheads, and did not account for
coastal storm impacts.
Elements of Wall Design
Prior to evaluating a bulkhead or seawall, the
following design considerations need to be addressed to be
able to properly assess the condition.
unit weight of soil, clay vs. sand, etc.
depth of wall for stability
Water Table: differential
water levels behind and in front of walls can introduce additional
loading on the wall.
Wall Material Properties:
strength and performance in the marine environment.
loads behind the wall such as vehicles.
These additional design considerations need to be addressed
If a wall is damaged or deteriorated, the original design may
not have accounted for the above-listed design considerations.
Original or “as-built” plans can provide a wealth
of information including the age of the structure and many of
the design elements listed in the above paragraphs. The deteriorated
condition of a wall may also be an indication that the wall
is in need of maintenance, or that it has fulfilled its service
Materials of Construction
Seawalls and bulkheads are constructed of similar materials.
The material of the wall must be properly identified prior
to assessing the condition. The following table presents common
wall construction materials with comments regarding availability,
construction issues, and general performance in the marine
|Pile/panel and sheet piling configurations
common in South Florida. Most common wall material in
South Florida due to the locally available aggregate;
provides service life of 30+ years if correct mix design
and proper marine structural design implemented.
Steel sheet piling commonly used for bulkheads/seawalls.
Material provides excellent strength characteristics
for high wall exposure applications. Provides interlocking
seal, and generally easy to install, even in harder
substrate. Must be properly coated and maintained for
long service life of 25+ years.
|Sheet piling provides good corrosion resistance,
but lighter sections allow for minimal exposed wall height.
Recognize corrosion potential of dissimilar metal hardware,
do not use in waters with low Ph or backfill with clay-mucky
soils. Difficult to install in hard substrates.
Not often used in South Florida, but occasionally
seen on inland waterways. Timber pile/wale/sheet system
is common structural configuration. Generally economical
material, but limited strength characteristics for high
wall heights. Preservative treatment is essential for
marine organisms. Difficult to install in hard substrates.
|Relatively new economical product with service
life of 50+ years. Available in different colors. Limited
strength characteristics for wall heights. Difficult to
install in hard substrates.
Seawalls on the coast of Florida come under the jurisdiction
of the Florida Department of Environmental Protection (DEP).
In addition to evaluating the structural condition of a seawall,
the DEP has special requirements for seawalls at or near the
Erosion Control Line (ECL). A coastal engineering analysis
is required to determine if an existing seawall will be affected
by a 30-year coastal storm event. If the existing wall is
within the 30-year Erosion Projection, then the property owner
must “provide scientific and engineering evidence that
the armoring structure (seawall) has been designed, constructed,
and maintained to survive the effects of a 30-year storm and
provide protection to existing and proposed structures from
the erosion associated with that event.” The DEP requires
certification by a professional engineer that the seawall
was designed, constructed, and is in adequate condition to
meet the following criteria:
1. The top of the seawall must be at or above the predicted
maximum wave crest elevation, considering the eroded beach
profile, of the 30-year design storm.
2. The seawall must be stable under the 30-year design storm
including localized scour, with adequate penetration and toe
protection to avoid settlement, toe failure, or loss of material
from beneath or behind the armoring.
3. The seawall must have sufficient continuity or return
walls to prevent flanking under the design storm from impacting
the proposed construction.
4. The seawall must withstand the static and hydrodynamic
forces of the 30-year design storm.
The American Society of Civil Engineers (ASCE) Underwater
Investigations Standard Practice Manual was released in 2001
and provides guidance for the evaluation of walls. Procedures
are also applicable for above-water structures. Most bulkheads
are along the waterfront, and should be evaluated above and
below the water, whereas seawalls typically are not exposed
to water on a regular basis.
The following topics are covered related to structural bulkhead/seawall
- Qualifications of Inspection Personnel
- Types and methods of inspections
- Typical forms of deterioration
- CoFrequency of Inspection
A comprehensive report is essential to document a proper
bulkhead or seawall evaluation. All of the above items should
be included along with photographs and sketches of the observed
configuration with notes regarding deterioration. Comparison
of previous reports provides an indication of the rate of
Repair recommendations, along with construction cost estimates,
should be included to provide the property owner with sound
engineering advice so they can plan for maintenance or repairs
as necessary. The report should be sealed by a registered
professional engineer experienced in the evaluation of in-service
FAQ Regarding Bulkheads and Seawalls
Can I raise the grade of my property with the
The bulkhead must be evaluated by an engineer to determine
if the structure can withstand the additional loads from fill
and structural modifications. Deterioration can severely weaken
the structural capacity of the bulkhead, and the bulkhead
was most likely designed for the existing conditions.
What is the best material for bulkheads and
Material selection is site-specific and dependent on design
conditions. Concrete (if designed appropriately) generally
provides a long service life, but it is not favorable from
a first-cost basis. Vinyl sheet piling and other composite
materials, where applicable, should be considered due to their
resistance to the harsh marine environment and 50+ year service
How long can I expect my wall to last?
Answers to this question are generally subjective. An experienced
marine structural engineer can provide general assumptions
as to the “expected remaining service life” of
a marine structure. Comparisons with observed deterioration
over time can also provide an indication of material performance.
Certain non-destructive and/or partially destructive materials
testing can provide additional information for the assessment.
What regulatory permits are required?
Bulkheads typically require an environmental resource permit
from several agencies including the county environmental resource
management agency, the DEP, and the U.S. Army Corps of Engineers.
Depending on the jurisdiction, the local water management
district may also issue a permit. Seawalls require a permit
generally from the state agency such as the DEP.
How often should I inspect the wall?
The ASCE Manual provides guidance for the frequency of inspections.
Generally, seawalls and bulkheads should be evaluated every
5 to 6 years.
How do I repair my wall?
A qualified marine structural engineer should be consulted
to evaluate the existing wall and to determine if rehabilitation
or replacement is required. Options can generally be provided
to provide an economical approach to meet budget constraints.
Who can build a wall?
Marine structures are specialized structures,
often requiring water-based construction equipment and techniques.
The costs for waterfront construction are generally higher
than for upland structures such as buildings. Bulkhead or
seawall work should be reserved for a qualified and experienced
1. There is a difference between a bulkhead and a seawall.
2. Bulkhead and Seawall design
is site-specific and the design elements of a particular
structure should be understood prior to evaluation.
3. Bulkhead materials of construction exhibit
various forms of deterioration in the marine environment.
Proper material identification is essential to assess structural
4. Seawalls in Florida come under the jurisdiction
of the DEP, and require coastal engineering studies to assess
5. ASCE recently released a standard practice
manual to provide guidance for the above/below water assessment
of marine structures.
6. Bulkhead and seawall evaluations should be
conducted by qualified personnel under the supervision of
a licensed professional engineer.
By; Coastal Systems International, Inc.