When designing marine infrastructure such as jetties, breakwaters, and pontoons, it’s crucial to understand the behaviour of waves and their interaction with structures.
Waves can generally be classified into three key phases:
- Unbroken
- Breaking
- Broken
Each of these phases presents unique challenges that directly impact the design, stability, and longevity of marine infrastructure.
1. Unbroken Waves
Unbroken waves, or deep-water waves, are waves that have yet to interact with the seabed, maintaining a smooth and continuous form. These waves are typically more predictable, with their energy concentrated below the surface and minimal frictional loss.
Impact on Design:
- Steady Dynamic Loads:
Unbroken waves exert uniform and continuous forces on jetties and other infrastructure. In deep-water conditions, these dynamic loads need to be accounted for to prevent fatigue over time. - Structural Design:
For structures exposed to unbroken waves, engineers focus on strength and durability to withstand long-term exposure to consistent wave action.
2. Breaking Waves
Breaking waves occur as waves approach shallow waters, interacting with the seabed. The bottom of the wave slows, while the top part continues at high velocity, causing it to curl and break. This phase releases a significant amount of energy and creates strong, concentrated forces on any structure in its path.
Impact on Design:
- High Impact Forces:
Breaking waves exert sudden and intense loads. Marine infrastructure must be designed to handle these high-pressure forces, which can be many times greater than those from unbroken waves. - Energy Dissipation Features:
Features such as breakwaters or wave deflectors may be necessary to reduce the energy of breaking waves, protecting key infrastructure. - Scour and Erosion:
Breaking waves can lead to scouring of the seabed around the foundations of structures, requiring deep footings and protective scour layers.
3. Broken Waves
Broken waves are the remnants of breaking waves, where much of the energy has been dissipated. However, these turbulent waves can still create powerful surges, particularly in confined areas, which must be considered in marine infrastructure design.
Impact on Design:
- Surge and Oscillation:
Broken waves produce surging forces that can cause oscillation, particularly in floating or flexible structures. Careful design is needed to ensure the structure can absorb and distribute these forces. - Wave Overtopping:
Broken waves can cause water to overtop structures such as jetties and seawalls. Proper drainage and structural height must be designed to manage overtopping risks.
Magryn’s Expertise in Marine Infrastructure Design
Magryn & Associates has extensive experience in the design of marine infrastructure, from jetties and pontoons to seawalls and breakwaters. We leverage the latest guidelines and available data to ensure our designs are robust, reliable, and cost-effective.
Our team collaborates with specialized numerical wave modelers to provide accurate wave predictions, ensuring the wave forces at each stage—unbroken, breaking, and broken—are correctly accounted for in the design.
By integrating empirical data with advanced numerical modeling, we create optimized designs that not only protect against the dynamic forces of waves but also balance cost and constructability.
Principle types of breaking waves, from the reference, Coastal Engineering: Processes, Theory and Design Practice, by Dominic Reeve
Wave phases at Encounter Bay, South Australia