The environment and its protection are always priorities during dredging projects, but dredging can also be a pro-active tool to improve the environment.
Dredging is not a “one size fits all” activity. Each project must be carefully weighed and examined in the context of the environment in which it is taking place. Although dredging operations can cause disruptions, the community and project owner must determine:
- Are these impacts long-term or temporary?
- Do the benefits, economic and social, of the final project outweigh certain environmental impacts?
- Can impacts can be mitigated by sound dredging practices?
Environmental impacts of a dredging project almost always arouse interest, discussion and often controversy amongst stakeholders, contractors and project owners. The major dredging contractors make significant investments in research to work responsibly in environmentally sensitive marine environments. Environmental engineers at the companies continue to evaluate sediments as well as the impacts of turbidity and sound on marine flora and fauna. Monitoring before, during and after a project are often pre-requisites.
Building with Nature
Additionally, concepts such as Building with Nature provide knowledge on how to improve the environment that can be applied worldwide. The preservation of ecosystems and reuse of clean sediments are an integral part of the design of a dredging project.
Remediation dredging is work in which contaminated industrial sites are cleaned and often transformed into healthy living and working locations. Restoring these so-called ‘brownfields’ into usable urban properties is another way in which dredging contributes to the improvement of the environment.
Balancing environment & economics
Finding a balance between economic and environmental values is crucial to the acceptance and therefore success of a project. Ecosystems Services is a recent effort to evaluate the cost/ benefits of a project.
Ecosystem services is a method which weighs all known benefits of a project against all known impacts that may come from implementing the project. The services of an ecosystem have been assigned to four general categories. An ecosystem can:
a. Provide for the production of food and water;
b. Regulate, that is, control climate changes and disease;
c. Support nutrient cycles and crop pollination; and
d. Contribute to culture, for instance, giving spiritual and recreational benefits.
These services have a monetary value and are balanced against the economic value that a project may contribute to the general welfare of a community or country.
- Building with Nature
- Climate Change
- CO2 & Other Emissions / Greenhouse Gases
- Coastal Protection
- Confined Disposal Facilities
- Coral Reefs
- Ecosystem Services
- Environmental Impact Assessment
- Environmental Monitoring
- Environmental Monitoring and Management Plans
- Flood Defence
- Management Practices for the Environment
- Remediation dredging (Contaminated sediments)
- Underwater Sound
Over the past decades, there has been a growing interest in exploring innovative ways to minimise the environmental footprint of coastal developments and in nature-based approaches for shoreline protection. At Mubarraz Island near Abu Dhabi (UAE), an international oil company beneficially reused ~12 million m³ of dredged material to protect pipelines, construct a causeway and create mangrove habitat to manage coastal erosion. This ‘Working with Nature’ approach has provided a cost-effective nature-based solution for shoreline protection, with added benefits for biodiversity conservation.
At Deltares in the Netherlands, a research team is developing a portfolio of technologies dedicated to the management of the finest and most challenging fraction of soft sediments. These technologies may unambiguously be called nature based because they make use of natural processes to enhance dewatering and strengthening, induce flocculation and the settling of fines, and protect the muddy bed from erosion.
Managing sediments, especially from dredging, is important for the management of estuaries and coastal areas. When implemented in the right way, a sediment management strategy can be qualified as a nature-based solution as it uses the physical processes of erosion and sedimentation to create added value. There is a need for an evaluation of sediment strategies and the habitats that are created for a wider range of objectives than only biodiversity and nature conservation. The concept of ecosystem services provides this broader framework.
At present too little use is made of the opportunities that the design and construction of land reclamation offer for the underground storage and recovery of fresh water. The managed aquifer recharge systems in the coastal dunes of the Netherlands are a good example of successful subsurface water storage. And it is to be expected that the sandy deposits of land reclamations could serve a similar purpose. This in turn will contribute to a sustainable development of land reclamations.
Dredging is essential for the maintenance and development of ports, harbours and waterways to allow for safe navigation, remediation and flood management. The process, which relocates large volumes of sediment, can be accompanied by the release of suspended sediments into the water column referred to as sediment plumes.
ReefGuard, a mobile coral breeding facility provides a highly controlled environment to aid in integrating the breeding and outplanting of corals. This article gives a detailed look into how proven small-scale coral breeding techniques can be scaled-up and applied in practice to promote environmental gain around marine infrastructure projects.
Building with Nature is an innovative approach that combines natural processes with innovative engineering methods to realise sustainable projects. Permeable dams are being utilised as part of a Building with Nature solution to help restore the eroding mangrove-mud coast of the Demak district in central Java, Indonesia.
Underwater sound from anthropogenic sources and its potential adverse effects on the marine environment is a topic of much global interest. This article gives an overview of known sound source levels for various dredging equipment and activities and describes a method used to extrapolate source levels.
Dredging for a new port complex in a remarkable, protected marine environment required adherence to very specific thresholds and an intensive Environmental Management Plan (EMP) that included mobile monitoring as well as daily visual observations of turbidity levels around the dredging works and the disposal zone.