Imagine a beach slowly eroding away, its golden sands being claimed by the relentless waves. Now, imagine a solution that not only slows this erosion but also rejuvenates the beach, making it more resilient to future climate change impacts. This isn't a dream; it's the effects of nearshore nourishment.
Coastal areas are more than just picturesque landscapes; they are also dynamic ecosystems that play an important part in the preservation of the world's natural resources. However, these regions are continuously threatened by a variety of factors, both natural and anthropogenic in origin. The practice of nearshore nourishment has emerged as a viable solution to these problems, and it helps to ensure that our coastlines will continue to be resilient and vibrant in the future.
The Genesis of Nearshore Nourishment
There is nothing novel about the concept of restoring beaches and other coastal areas. Communities all over the world have spent the better part of the last few decades looking into ways to protect their coastlines and put an end to erosion. The second half of the 20th century, on the other hand, saw the beginning of the systematic approach to nearshore nourishment being developed as a coastal erosion solution.
This transformation was significantly aided by the early developments of International Coastal Management. The pioneering spirit of the company's founder, Angus Jackson, was responsible for the development of a significant number of the approaches that are now commonly associated with nearshore nourishment. Jackson played a pivotal role in the initial trials that were conducted in the early 1980s on the Gold Coast, which established a standard for subsequent coastal management initiatives.
Check out this video about our involvement in developing nearshore nourishment on the Gold Coast and its success.
How does Nearshore Nourishment Work?
Nearshore nourishment involves the strategic placement of sediments in the nearshore zone to promote natural beach replenishment. By understanding the local wave dynamics, tidal patterns, and sediment transport, experts can develop nearshore nourishment placement strategies to allow the natural process of sand migration to work for the benefit of the beach and actually naturally shift sand closer to the shore over time.
Using a Trailing Suction Hopper Dredger for Nearshore Nourishment
When it comes to beach nourishment, one piece of equipment stands out: the Trailing Suction Hopper Dredger (TSHD). This remarkable vessel offers versatility, allowing it to operate in varying offshore wave climates and discharge loads in multiple ways.
A TSHD can perform beach nourishment through:
Bottom Dumping: The vessel can unload its load through bottom doors, ensuring precise placement.
Rainbowing: Using a nozzle on the bow or side, it can disperse material evenly across the shoreline.
Pumping: It can pump material through a floating pipeline for precise placement.
The TSHD operates on a fascinating principle:
The vessel, equipped with one or two suction pipes, trails along the seabed.
A powerful pump inside the vessel generates suction, dislodging and transporting a mixture of seabed materials and water.
A drag-head, attached to the suction pipe, liquefies the seabed with a water jet system.
As the vessel approaches the dredging area, it reduces speed and lowers the suction pipes overboard. Once in position, the dredge pumps start, and the material is sucked up through the drag-head into the hopper.
The cycle consists of loading, sailing with a full load, unloading, and sailing empty. The duration of each cycle depends on various factors, including soil characteristics and sailing conditions.
The Benefits of Nearshore Nourishment
Eco-friendly: Unlike hard engineering solutions, nearshore nourishment works in harmony with nature, ensuring minimal disruption to coastal process and therefore is considered a nature based solution.
Adaptive: As environmental conditions change, nearshore nourishment strategies can be adjusted to meet the evolving needs of the coastline.
Economic Boost: Healthy coastlines attract tourism, bolstering local economies.
Nature-Based Solutions: Embracing Sustainability
While TSHD technology is impressive, coastal engineering is also embracing nature-based solutions. These approaches harmonize with nature to protect and restore coastlines, offering long-term benefits.
Sand Placement includes:
Placement in the Nearshore Zone by Bottom Dumping: This method accurately places sand between -4.0m and -7.0m CD but tends to deposit sand farther from the surf zone.
Placement in the Nearshore Zone by Rainbowing: Sand is accurately placed between -3.0m and -5.0m CD, closer to the surf zone, offering visual appeal. However, it is a more time-consuming method.
Looking Ahead
With the looming threat of climate change and its impact on sea levels and storm frequencies, the importance of sustainable coastal management techniques like nearshore nourishment cannot be overstated. Thanks to pioneers like Angus Jackson and the efforts of International Coastal Management, we have a solid foundation to build upon and ensure the preservation of our invaluable coastlines.
Nearshore nourishment is just one of the ways in which we can reduce beach erosion, in combination of a coastal management plan that can include sand bypassing systems and artificial reefs, nourishment projects can be even more effective.
Learn More
For an in-depth review of the history of nearshore nourishment, the trials and monitoring over specific projects and more, check out the published works by Angus Jackson and Bobbie Corbett, which were presented at the Australasian Coast and Ports Conference in 2023.