Protecting properties on coastal parcels is critical, especially as we start to see much of our nation’s coastal areas affected by rising sea levels. Higher sea levels are allowing the tides to carry away much of the natural defenses and sands that keep properties and beaches protected from the oceans, especially during heavy coastal storms. In fact, some coastal communities are running out of beach sand due to global warming.
What can coastal property owners do to protect themselves? The answer is installing or improving existing seawalls. A bulkhead, also known as a seawall, helps prevent erosion of land area or damage to structures by placing a barrier between the sea and land. Seawalls protect properties and beaches against damage from wind, wave and ice forces. They may feature curved or flat-facing surfaces, and can be comprised of gravity retaining walls, cantilever retaining walls, and pile-supported retaining walls. New seawalls are commonly constructed of concrete, but older seawalls included materials like stone, an excellent buffer against wave energy.
Some seawalls use a sheet pile cutoff in their foundations to protect against undermining and promote stability. In addition, in order to prevent overtopping of waves and problems with drainage, the structure can be designed to allow for seawater to return back to the ocean without causing damage to the seawall itself. This allows a reduction in water pressure behind or in front of the seawall during tidal cycles. These drainage features also prevent soil erosion behind the walls.
Our team has several seawall projects going along the California coast. These include both repairing and raising seawalls. Most of these projects involve property owners concerned about existing seawalls on their property, or in preparation for a sale of their property.
We start by examining the structure above ground, during low tide, along the mudline. We’ll investigate the bulkheads to make sure they are plumb and devoid of any component corrosion. We’ll also check for settlement or soil loss along the rear of the bulkhead. If the bulkhead contains wood, we’ll also look for burrowing fishes and worms that can eat away at the organic materials used for support of the seawall. In addition, we check for corrosion, including rusting or cracking.
The next phase of inspection includes an underwater inspection where we’ll investigate the sediment levels behind the seawall. This type of inspection can be very dangerous, so specialized techniques are used to ensure the safety of all parties performing the inspection.
Where armor stone was used, we’ll ensure the stone is correctly placed and that it has not been replaced with unplanned deposits. If pile foundations were used, we check to make sure they have not been exposed by scour or undermining.
Our teams also check to make sure that the alignment and settlement of the seawall is still in its original form, since movement of the structure means that it has failed and that could result in the loss of the structure. If repairs are needed, we suggest that the seawalls be reinforced with helical piers and that steel mesh be used behind the bulkheads. This prevents sand from leaking out.
If a seawall already exists and is structurally sound, but not performing adequately, it may be necessary to raise the seawall to combat the higher water levels. To ensure properties behind these bulkheads are properly protected, we asses existing wall structural conditions and then design a new seawall height extension appropriate for the increased level of seawater. This new extension will prevent overtopping of the seawall during high tide events.
Have you ever had to deal with repairing a seawall on your property? What was the result? Let us know in the comments, below.
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