Scour Protection Offshore: Alternatives to Concrete Mats for Erosion Control

kyowa rock bags instead of concrete mats for erosion control

Would you believe that the open ocean faces a threat as much as the land from erosion? Scientists have discovered that the seabed is losing sediment and depleting due to scour. As a consequence, this endangers marine ecosystems, offshore structures, and marine activities. Scour protection offshore should be one of our primary concerns.

What Is Offshore Erosion?

Offshore erosion is the loss of the sediment layer on the seafloor due to a combination of coastal dynamics and human-driven activities

Wave energy, high tides, heavy storms, strong currents, and wind-induced water force are all contributing factors for scouring.

Offshore scouring can displace the sediment and increase the depth of the ocean. In addition, coastal and naval activities that disrupt the seabed can also escalate the matter. Rock bags and concrete mats for erosion control are two major methods used to control or stop water erosion offshore.

What Are the Impacts of Offshore Erosion?

When the seabed loses its sediment layer, it poses a grave threat to marine ecosystems. It degrades coral reef structure and prevents its ability to protect the coast from floods and heavy waves. Moreover, offshore erosion also threatens marine life, as it destroys their habitat underwater. An increase in the depth of sea level can cause flooding. It can bring damage to properties in coastal areas, affecting the communities residing nearby.

More importantly, scouring around structures like offshore wind farms, oil production sites, and gas production sites can destabilise their foundation and cause them to malfunction. These sites provide crucial resources for economic activities like electricity and fuel. So, scour protection offshore is an urgent necessity.

Another problem that maritime authorities deal with is the corrosion or damage of subsea cables and pipelines due to harsh underwater conditions. It can lead to leakages of the substance transported through these pipelines. Damages can also be costly to repair.

Is There a Solution for Scour Protection Offshore?

Yes! A versatile product that can resist extreme underwater conditions and adapt to the surrounding environment. Based on our experience in multiple scour protection offshore projects, we recommend rock bags as the best solution. They are tested continuously worldwide to measure their efficacy in tackling scour underwater.

The Japan-engineered product consists of a large netted bag containing small rocks. Made from 100% recycled material, rock bags are a highly environmentally friendly and sustainable method to stop scouring. Moreover, their structure is extremely versatile – unlike concrete mats for erosion control, which are more rigid! 

By installing rock bags around offshore structures and wind turbine foundations, you can protect them from scouring and wave shock. 

They’ve been used to protect the base of Wave Swell Energy Unit and the Great Barrier Reef NavAids in Australia from scour damage.

Rock bags are also ideal for protecting subsea cables and pipelines from corrosion. Installing them at cable intersection points prevents damage and swaying. Placing rock bags underneath cables running over slopes provides support.

Another benefit of using rock bags for scour protection offshore is their adaptability to marine conditions really well. They act as a habitat for small fish, and marine plants cover the bags over time.

Conventional Solutions for Scour Protection Offshore

concrete mats for erosion control
CC BY-SA 2.0 Nigel Chadwick

Concrete Mats

Concrete mats for erosion control can resist temperature fluctuations and promise durability, longer lifespan, and adaptability. So, they are quite useful for protecting underwater cables, offshore structures, and the base of seawalls.

Although eco-friendly, the design of concrete erosion control mats doesn’t promote marine life growth. Also, the gaps between concrete erosion control blocks can allow sediment to escape, making the area vulnerable to erosion despite protection. Rock bags provide more coverage and can be built into flexible structures like walls and slopes and fix an uneven seabed. 


geotubes for offhosre erosion control
CC BY-SA 3.0 – Ph: Classenc

Geotubes are tubular-shaped containers made using geotextile material. They separate sediment from water and then drain the water through holes.

Geotubes can sustain damage from sharp shells, which can affect their efficacy. Installation is also costly, unlike rock bags that need minimal manpower. The leakage of filling materials can be harmful to marine species. On the contrary, rock bags are sturdier and provide a lifespan of up to 50 years.

Sand-filled Containers

Sand-filled containers or bags work to stabilise sediment and control seafloor abrasion. They contain fill materials like sand and other similar elements and are considered a cheap alternative for concrete mats for erosion control.

However, they are a ‘soft’ method of scour protection offshore and may not be very effective. 

If the outer material of the container degrades, sand will eventually get washed away. The netted bag of rock bags has undergone many tests, proving their strength to resist extreme pressure. Even if it breaks, it won’t be harmful to the environment.

Boulder Seawalls

boulder seawall for erosion control
CC BY-SA 2.0 – ph: Chris Downer

Boulder seawalls of granite or limestone are another choice for scour protection offshore. Built along the shoreline, they defend the coast against wave attacks, high tides, and strong currents.

Unlike concrete mats for erosion control, a boulder seawall is a permanent erosion solution and, therefore, construction and maintenance are expensive. Rock bags are a more cost-effective alternative that performs the same job.

Revetment Mattress

Revetment mattresses constructed using concrete erosion control blocks, sand, or rocks are ideal for sloping areas. They protect artificial islands housing offshore sites, breakwaters, and similar structures.

The drawbacks associated with concrete mats for erosion control persist in this case too. There could be failures if the mattress cannot withstand extreme wave pressure. With scour protection rock bags, it is easy to build a sloping structure by arranging one on top of another. The size or angle of the slope doesn’t matter. There also won’t be gaps for sediment to escape.

Rock Filter Bags: Changing the Game

Rock bags’ versatility, flexibility, durability, and many other impressive features make them the perfect solution for offshore scour protection works. We also use it to stop water erosion in many other scenarios. 

Bluemont is the leading supplier of rock bags in Australia, New Zealand, and the Pacific Islands. Contact us by calling +61 2 9091 0360, or email us at

We provide the best erosion protection, flood control, and fire extinguishing solutions. 

Learn more about rock bags!