How Aggressive Does A Seawall Need To Be?
Posted on: 9 June 2021
When dealing with seawall design projects, property owners often worry about over- or under-engineering the structure. How aggressive does a seawall need to be? A seawall design engineer will consider these five factors.
Purpose
Not every seawall serves the same purpose. If you're trying to halt erosion but don't fret much about flooding, for example, you'll probably focus on building a seawall that breaks the incoming tide. Conversely, if the seawall is part of flood prevention or mitigation efforts, you may need to devise a highly engineered solution.
It's critical to think about what would be the least-tolerable possible outcome for the property. You can then start setting your goals based on that.
Types of Waves
The typical wave action at a site makes a major difference. If your site largely sees standing waves that don't change very much, such as you might see along a lakeshore, a flat wall may be ideal. Conversely, an oceanside location that gets pounded by plunging waves may require a curved seawall that dissipates the energy of the waves.
Potential for Undermining
Especially in very sandy areas, there is a risk that water pressure could undermine a seawall. If you're trying to control flooding, the water could find its way through the sand and into the protected area.
Generally, the more fear you have of seeing the undermining of a seawall, the more you'll need to engineer the solution. You may need to use piles ahead of the seawall to break some of the wave energy, for example.
Natural Barriers
Reefs, mangroves, trees, and even seaweed can all serve as natural barriers. On the flip side, regions bereft of these features may face more coastal flooding and erosion.
A seawall may have to account for the presence or absence of barriers. Notably, there are scenarios where a seawall can harm existing barriers, and you'll need to account for that scenario, too.
The Shape of the Body of Water
A body of water can induce many problems based on its shape. Some bays, for example, encourage massive influxes of water during high tides. It's important to think about what the peak tide is likely to be over the lifetime of a seawall. For instance, you should review studies of how the body of water performs. If there are no recent studies for the location, you may need to conduct one.
Bear in mind ecosystems change over decades, and major events like hurricanes or earthquakes can cause them to change within days. If something major has happened recently, it's probably wise to conduct a fresh study. For more information, contact a seawall design engineer.
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