Minimising the impact of dredging operations

11th Oct 2020
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MINIMISING THE IMPACT OF DREDGING OPERATIONS

A look at the measures being taken to mitigate the impact of dredging work on fragile coral reef ecosystems

Following on from a previous blog post in May this year, which focused on the response of corals to chronic turbidity, we now look at how contractors can provide proactive protection, minimising the impact of their dredging operations on surrounding coral ecosystems.

With sites around dredging locations frequently experiencing days in darkness and extended periods of low light, this can result in a range of physiological and biochemical shifts in the health of corals, with the most common effects being bleaching or lightening. In some instances, when there is high turbidity, partial mortality can occur. Of course, this can be devastating as coral reefs are crucial contributors to a healthy marine ecosystem, providing a breeding ground for several species of fish, while also serving as natural protective barriers to shorelines.

Dredging contractors are well aware of the delicacy of dredging in coral reef areas, and a report from the International Association of Dredging Companies (IADC) states that by adopting sound planning, impact assessment, monitoring and management practices, large benefits can be achieved in term of avoiding or minimising adverse effects on the coral reef environment from dredging.

“An initial risk assessment based on available secondary data, initial field surveys, preliminary numerical modelling, an understanding of local and regional coastal processes, and identification of areas designated for protection under national or international legislation should be conducted. Local stakeholders should be involved to determine the reef services used in the area. This will help to determine the type of impact assessment that will be required and to identify potential effects for early mitigation during the design phase,” the IADC report adds.

While some impact to coral reefs cannot be prevented, several mitigation measures are available. Most of these measures aim to minimise the release and spread of sediments, thus reducing the levels of turbidity and sedimentation.

Silt curtains are one such measure, as not only do they contain and guide turbidity, but they also prevent turbid waters from entering other protected areas, studies have shown. In fact, research has shown that turbidity levels outside a properly specified, deployed and maintained silt curtain, are reduced by 80 to 90 percent.

Dr Rusty Brainard TRSDC How contractors can provide proactive protection, minimising the impact of their dredging operations on surrounding coral ecosystems

Dr Rusty Brainard, Chief Environmental Sustainability Officer at The Red Sea Development Company (TRSDC), the developer behind the Saudi Arabia megaproject that aims to set new standards in sustainable development and exceed expectations to create a unique travel experience and unforgettable memories, says:

Silt curtains are indeed required for any dredging and filling operations near sensitive habitats, especially corals, or other operations that could cause siltation or other water quality impairments. I don’t want to imply that these efforts are perfect, but I can assure you that we try everything we can to minimise the negative impacts associated with development, and are actively conducting R&D to find ways to enhance our environment.

However, Dr Brainard is keen to point out that TRSDC believes the best way to protect its coral reefs is to remove them from danger before any dredging work is done, as he explains.

The Red Sea Project is proactively working to relocate any corals prior to any dredging or filling associated with our development. Ideally, we relocate the corals to nearby similar habitats and environments (depth, flow, light, temperature, etc.) to give the corals the highest likelihood of success. The corals are physically attached to either similar existing reef structures or attached to new hard substrates installed to optimise their survival.

Ideally, we try to use calcium carbonate substrates such as ancient fossil reefs. We then monitor the corals over time to see how they’re doing and to continually learn to improve the relocation process.

If you would like to know more about our Ecobarrier Silt Curtains, our work with key players around the world and how we can help you on your project, please speak to Prathyush Levakumar on [email protected] or +971 4 885 3944