Nature-based Solutions: Harnessing the power of nature and knowledge
Photo Credit: Natuurmonumenten (Peter Leenen)
Nature-based Solutions (NbS) are enjoying a renaissance across multiple industries, including dredging, as environmental and sustainability concerns take centre stage. For dredging in particular, NbS has gained traction as maritime’s diverse stakeholders ramp up efforts to conserve habitats, restore biodiversity, and increase the resilience of coastal areas. The process relies on the application of scientific knowledge and novel use of technology to enable long term sustainable operations where possible.
A green approach
NbS facilitates cost-effective and sustainable approaches for managing water resources and disaster risk, enhancing the environmental and societal benefits of dredging projects. The process of employing natural systems to provide critical services is already being utilised to great effect — for example, wetlands have been shown to enable flood mitigation in Mozambique or mangroves have been used to reduce coastal erosion in Jamaica.
While NbS itself is a fairly broad umbrella term for a range of interrelated disciplines, two concepts are of particular relevance to the dredging industry:
Building with Nature: Utilising a design-based approach, building with nature (BwN) seeks to harness naturally-occurring processes to achieve desired outcomes, such as safe navigation, sustainable coastal development, and effective flood protection. A notable example is the ongoing Marker Wadden project in The Netherlands which includes the construction of multiple artificial islands with sand and silt dredged from the Markermeer ecosystem. Hybrid solutions of this nature, which integrate natural features and processes (green infrastructure) with traditional hard engineering (grey infrastructure) techniques, are considered to be more sustainable, reliable, and cost-effective than engineered solutions alone.
Ecosystem-based adaptation: Ecosystem-based adaptation seeks to conserve, restore, and manage ecosystems. An example is the Lower Otter Restoration Project (LORP) in the UK which aims to adapt and enhance the Lower Otter by breaching an existing 200-year old embankment and restoring the area to more natural conditions. After a decade of planning and field work, the project is nearing completion. Environment Agency Project Manager Dan Boswell, said: "Undertaking landscape change of this scale is a huge challenge in terms of engineering, the environment and communication. We are already seeing the positive impact for people and wildlife and that will only increase with time."
Other Initiatives, such as protecting mangroves and planting trees to regulate water flow, can reduce the vulnerability of coastal communities and the natural environment to erosion and climate change. Restoring coastal wetlands also has the added benefit of increasing carbon sequestration.
Emerging technologies and approaches
However, despite the potential of NbS, concerns persist. There remains a lack of consensus on whether these solutions are effective, with critics pointing to ongoing maintenance and management requirements, the time required for some solutions to yield quantifiable benefits, and the challenge of scaling-up a location-specific scheme to address global challenges.
To combat these concerns, proponents of NbS have increasingly embraced advanced technological innovation, novel methodologies, and empirical data to shape marine spatial planning, improve outcomes and galvanise stakeholder support.
For example, 3D-printing is already being used to construct artificial coral reefs, and geospatial technologies, including Geographic Information System (GIS), GPS, and geofencing, are increasingly used to collect, analyse, and store information.
Additionally, drones are being utilised effectively to rapidly map habitats, survey coastal areas and monitor coastal species. As noted by Drone Survey Services’ James Leslie, "Drone technology, equipped with sonar payloads and sensors, allows us to precisely map sediment buildup across marine habitats.” This, he said, enables their clients to carry out “precision dredging” to help minimise unnecessary ecosystem disruption. “Our drones allow for continuous monitoring to assess dredging impact and habitat recovery over time,” he continued. “This real-time data provides our clients with an efficient means of maintaining waterways and storage areas while upholding sustainability standards."
Big data can also play an important role in addressing concerns with NbS. Remote sensor technologies paired with sophisticated data analytics can provide decision-makers with unparalleled real-time information. This may include water temperature, turbidity, salinity, acidity and depth, and the impact of natural and human activity upon the marine environment. In turn, this knowledge can be used to improve the design, implementation, and monitoring of traditional and NbS projects. For example, The Netherlands integrates data from various sources — including sensors, satellites, and monitoring stations — to inform decisions regarding coastal protection, land use planning, and flood risk management.
Artificial intelligence (AI) and machine learning are also being used to crunch large swathes of data. This has allowed for more accurate impact modelling of NbS projects, as well as the optimisation of project performance to minimise financial and environmental risks. AI algorithms can analyse imagery to track changes in water quality and detect events of note, such as algal blooms or coral bleaching. Predictive analytics allows us to interrogate historical weather data, tide patterns, and coastal conditions to predict flood risks.
Preliminary studies on Ocean alkalinity enhancement (OAE) suggest that the deposit of silicate rock into global shelf seas and coastal areas by dredging companies - where wave action and tides can disperse them - can help increase the alkalinity of seawater and slow ocean acidification. Dubbed Coastal Carbon Capture by the team at Project Vesta, they calculate that depositing silicate in 0.1%-0.25% of global shelf seas could remove 1 billion tonnes of CO2 from the atmosphere. The approach is currently being evaluated for environmental impact and economic viability, with the aim of launching pilot field studies if modelling and laboratory tests prove positive.
Emerging industry solutions
Nature-based agitation dredging is increasingly perceived as a more sustainable and environmentally-friendly alternative to traditional dredging practices. Instead of mechanically removing sediments and transporting them to an offshore disposal site, nature-based agitation dredging encourages sediment mobility — for example by water injection — and then harnesses the power of waves and currents to redistribute it.
This technique can mitigate shoreline erosion by naturally redistributing sediment to eroded areas, helping to safeguard shore-based infrastructure and strengthen coastal resilience against sea-level rise and increased storm intensity. Nature-based agitation dredging also enhances natural habitats such as seagrass beds, oyster reefs, and wetlands. This process can contribute to habitat restoration projects, thereby improving biodiversity and overall ecosystem health.
A recently published case study offered useful insights into the potential utility of nature-based agitation dredging during its evaluation of the recently launched Tiamat dredger at Harwich Harbour in the UK. Using monitoring data and validated numerical modelling, the case study found that the net productivity (in tonnes of dry solids) by the Tiamat was equivalent to a medium-sized trailing suction hopper dredger (TSHD), but at a much reduced economic and energy cost. This will have significant benefits for the ongoing maintenance dredging in the region which is conducted five times a year to maintain the harbour’s deepwater channel at a minimum 14.5 metres below chart datum.
Additionally, the study estimated that the method increased (designated) intertidal habitat by around 0.6 ha/year, which could be increased by coinciding dredging with the flood and ebb tides. This offers significant benefits to the Stour/ Orwell intertidal areas. Chief Executive Officer and Executive Board Director at Harwich Haven Authority, Sarah West said, “We are committed to working with nature, for nature. We are confident Tiamat will deliver a more sustainable and much more effective method of dredging for port authorities and dredging companies across the globe.”
However, despite these recent positive developments, nature-based agitation dredging is still in its infancy. The solution is also not without its challenges, including the need for careful site selection, modelling and monitoring, and the potential for unintended consequences on sediment dynamics and water quality. More research is needed to evaluate its potential for different use cases and there is room to further refine existing techniques. If such issues can be overcome, nature-based agitation dredging could represent a transformative solution to sustainably managing coastal areas.
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