Coastal protection of beaches, cities and communities located close to oceans and seas is a primary activity of the dredging industry.
According to the United Nations Environmental Programme (UNEP), half the world's population lives within 60 kilometres of the sea, and three-quarters of all large cities are located on the coast. With the risks of climate change and the pressure of pollution from urban areas, these communities are more and more vulnerable.
These densely populated coastal cities are economic hubs, often representing major ports with their related industrial businesses, such as shipping and commercial fishing. Coastal areas also support tourism with a focus on beaches, hotels and cruise harbours.
To complicate matters, these coastal areas are also home to rich and fragile natural habitats.
Causes of coastal erosion
Coastal protection provides defence against flooding and erosion, which can be caused by:
- waves and tides,
- currents and
- littoral drift, i.e., the transport of sediments along a coast at an angle to the shoreline in the littoral zone (the surf line).
Climate change, resulting in melting ice caps and more frequent and more severe storms, have aggravated these conditions.
Coastlines and their ecosystems vary considerably but all require some degree of maintenance and protection, for instance:
- Sandy beaches with dunes are subject to the waves, tides, winds, and currents which can drag sand out to sea and bring it back in places where it may not be needed. Maintenance dredging seeks to replenishment these beaches and restore their natural beauty as well as their function as a barrier against flooding.
- Wetlands provide essential ecosystem services including erosion and flood protection, protection of natural habitats with unique species of flora and fauna. Commercial fisheries as well as recreational facilities are often near wetlands.
- Coral reefs whether in warm or cold waters are unique natural barriers, protecting coastal cities, communities, and beaches from ocean waves and limiting the vulnerability of coasts to wave action and storm damage.
- Mangroves provide natural protection and can be part of coastal protection strategy against wave damage, storms, and erosion. Their dense roots bind and build soils and slow down the effects of wind and waves. Restoring and protecting them by careful dredging should be a part of an overall coastal defence scheme.
Dredging must always consider these assets and can play a key role in protecting and restoring them.
Dredging & coastal protection
A variety of dredging solutions may include:
soft engineering solutions including sand dune stabilisation and beach nourishment.
- construction of hard structures such as seawalls;
- breakwaters to protect exposed harbours;
- underwater bunds;
- fixed piers or open-piled jetties;
- sand traps such as groynes;
- coastal armouring with revetments, gabions, riprap and acropodes.
- 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
During his distinguished career as professor of Coastal Engineering at Delft University of Technology (TU Delft), Kees d’Angremond served as head of Hydraulic and Offshore Engineering, chair of the department of Hydraulic and Geotechnical Engineering, and dean of the faculty of Civil Engineering from 1989 to 2001. Now professor emeritus, he still works as an advisor and independent consultant. We invited Kees to a conversation with Stefan Aarninkhof, professor of Coastal Engineering and chair of the department of Hydraulic Engineering at TU Delft, to talk about their careers in the dredging industry and the role of academia in the industry today.
The use of nature and natural processes is an innovative way to increase water safety and create added value through nature development and recreation. This exploratory study provides an initial inventory of the impact and costs of existing Building with Nature projects in the Netherlands. It also includes an analysis of the decision-making process in choosing this type of project and identifies success factors. Building with Nature projects deliver added value but often also involve additional costs compared to traditional reinforcements. These costs give an indication of what we as a society are prepared to pay for the development of nature and recreation as part of hydraulic engineering projects.
The development of a new marine project demands a system approach in which all aspects, including technical, economic, environmental and social, are considered and integrated equally and at an early stage. While insufficient information may be available to make informed decisions, choices need to be made to progress a project, assess impacts and risks, and engage stakeholders. This article explores the case of a new port terminal in Amatique Bay, Guatemala. A method was developed to assess, at an early stage, the potential negative impacts on seagrass habitats from the disposal of dredged material at different locations, while having limited real-time and location-specific information at hand.
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.
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.
Presentation: ‘Hondsbossche and Pettemer Sea Defence an example of sustainable asset valuatio’ by Sven Kramer (Van Oord) − Director Sustainability
This presentation shows the practical implications of taking all externalities into consideration as early as possible in a project procedure. It is complex but asset valuation is gradually becoming more and more feasible for large infrastructure projects. The independent International Institute of Sustainable Development carried out a study on the benefits of “Nature Based” coastal Protection compared to traditional “Grey” solutions. Their report is expected to be published mid-November 2021.
Presentation: ‘Sand as a Resource’ by Jan Fordeyn (Jan De Nul) − Director Project Development & Conceptual Design
In our day to day lives most of us are not aware of how many industries rely on sand as a part of their working process. The amount of sand consumed has dramatically increased over the last few years and this can be largely contributed to the world wide construction boom. How is this going to affect us in the future?
Webinar (replay): The Multiple Benefits of the Hondsbossche and Pettemer sea dunes, valued by the SAVi methodology
This webinar is especially of interest for policymakers, infrastructure developers, investors and other stakeholders with an interest in green infrastructure. But also for both technical and non-technical professionals in dredging-related industries like consultants and advisors at port and harbour authorities, offshore companies and other organisations that execute dredging projects.