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Marine and coastal environments are under pressure from increasingly violent weather events, which continue to escalate in frequency and force. At the same time, coastal cities, ports and marine infrastructures are growing in both number and scale. Biodiversity is also under threat from human activities and pressures, such as pollution, overexploitation and invasive species. Together with climate change impacts, these factors challenge both the natural and built environments. Coastal solutions must therefore be flexible and adapted to work in harmony with nature – not against it.
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Nature-based solutions from start to finish
Marine and coastal environments are dynamic, continuously reshaped by the natural forces of waves, tides and surges. To ensure long-term functionality, sustainability and cost-effectiveness, developments in these areas must be designed and implemented with a clear understanding and respect for local, natural physical and biological processes. This is also DHI’s approach: working with nature from start to finish.&nbsp;
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DHI partners with clients in the public and private sectors – including governments, non-profits, insurance, real estate developers and the shipping industry, for example – to protect shorelines from coastal hazards, support coastal development and safeguard ecosystems with nature-based solutions (NbS). We support all phases of NbS implementation by providing specialised and science-based advisory services, tailored to the scale and needs of each project throughout its entire life cycle.
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Locally relevant solutions for complex environments
As leaders in nature-based solutions, we help our clients address social and environmental challenges by leveraging natural features and processes tailored to the local environment. Our local presence and global experience, commitment to R&amp;D and advanced technologies enable us to develop sustainable solutions to address future climate and development challenges – with nature in focus.

Solutions

Marine infrastructure

There is increasing political and public focus on the impact major marine infrastructure projects such as bridges, artificial islands and tunnels can have on local ecosystems. DHI provides solutions for all aspects of the infrastructure lifecycle from design, construction and operations to ensure that the new structures work with nature, not against it. We help ensure that the infrastructure complies with strict environmental legislation and can cope with even the harshest environmental conditions.

Coastal development

Safeguarding against coastal flooding and adapting to climate change has never been more important. By implementing sustainable mitigation measures, it is possible to achieve cost-efficient and resilient design and development of new land, islands and waterfront projects while protecting the surrounding environment. 

Biodiversity Management

Balancing the protection of nature with economic development is an ongoing challenge, especially as infrastructure projects – such as constructing offshore wind farms, building railways and bridges and expanding ports – can potentially disrupt fragile ecosystems. This is why it is important to monitor, assess and mitigate biodiversity loss no matter the scale of your project. By integrating effective biodiversity management into your development plans, we can work together to create a sustainable future for both industry and the environment.

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See how we can help you in aquaculture, environment and ecosystems management.

Tsleil-Waututh Nation shoreline adaptation and restoration

Novel methods to protect and restore an eroding First Nation shoreline using nature-based solutions and traditional ecological knowledge and stewardship
 
The Tsleil-Waututh Nation (TWN, Indigenous name səlilwətaɬ, meaning ‘People of the Inlet’) is one of many Coast Salish peoples whose traditional territories span the Pacific Northwest, including parts of British Columbia, Washington and Oregon. In response to decades of shoreline degradation from erosion, vessel wake, wave action and loss of upland sediment, TWN initiated the Reserve Shoreline Adaptation and Restoration Project to protect and restore their foreshore along səl̓ilw̓ət (Burrard Inlet). The shoreline is a culturally significant and ecologically vital space for TWN, and the project reflects the Nation’s commitment to stewarding this land and water for present and future generations. Together with project partners, DHI supported TWN in developing shoreline designs using advanced modelling and physical testing. The initiative is Indigenous-led and emphasises the integration of nature-based solutions and TWN marine stewardship technologies to enhance resilience, restore ecological health and reconnect the community to the shoreline.
 
Challenge
TWN needed to address long-standing shoreline issues while embracing opportunities for ecological and cultural renewal. One key challenge was ongoing shoreline erosion — some areas had already experienced land loss of up to 13 metres, placing pressure on community lands, access points and important archaeological sites. Previous attempts to manage erosion through the installation of hard infrastructure (e.g., rip-rap) offered limited success and in some cases has contributed to habitat degradation and loss of intertidal connectivity. Additionally, coastal flooding, erosion and ‘coastal squeeze’ (the compression of habitats between rising seas and fixed infrastructure) are expected to intensify with future sea level rise and climate change.
The degradation of marine habitat has also impacted local biodiversity and the availability of traditionally harvested species such as shellfish, crabs, and seaweeds. The loss of shoreline integrity has both cultural and environmental impacts, highlighting the urgent need for innovative solutions that restore habitat and build long-term resilience.
 
Solution
To address severe erosion and environmental degradation along the reserve shoreline, TWN partnered with DHI to lead a comprehensive, data-driven and community-centered coastal adaptation initiative — implementing nature-based designs, advanced modelling and collaborative planning to protect and restore the coastline.
 
Solution highlights:

Coastal process and resilience modellingDHI helped simulate the effects of tides, storms and rising sea levels to guide the design process and improve resilience. This included assessing how coastal conditions and vessel wakes impact the shoreline.
Nature-based design integrationTogether with TWN, DHI co-developed shoreline designs that incorporate ecological restoration and Indigenous stewardship. These designs aim to protect the environment while supporting cultural values, with features like beaches, marshes and habitat areas.
Physical modelling validationDHI tested the preferred design in a scaled 3D model to ensure it could withstand future coastal conditions like extreme waves and rising seas. Evaluated overtopping, flooding and stone stability under future sea states.
Future-proof design guidanceDHI defined material specifications, crest elevations and adaptive design pathways to support long-term shoreline protection, and provided resilient design thresholds based on projected sea level rise (0.49–1.15 m) and storm scenarios. Construction tolerances and freeboard allowances were included to allow for flexible implementation. 

 
By combining ecological restoration with cultural priorities, DHI helped develop a nature-based shoreline design that adapts to future climate conditions. Unlike conventional erosion control projects, this approach emphasised co-development, habitat restoration and long-term community access.
 
Results
DHI’s modelling-driven, nature-based approach offers multiple benefits, aligning with TWN values and fostering ecological resilience. Design modelling confirms that the preferred concept will reduce wave-driven erosion along 500 m of shoreline, protecting areas that have already lost up to 13 m of land. Crest elevations and structural features were designed to withstand 1-in-100-year (1% AEP) storm events, accounting for projected sea level rise to year 2100, to help protect the irreplaceable cultural and archaeological sites located on TWN lands. Once implemented, the nature-based features such as cobble beaches, marsh benches and habitat islands will enhance biodiversity and restore native plant and marine species.
 
The project will reconnect the community to the shoreline with accessible paths, gathering spaces and a new canoe launch, ensuring safe access for all ages. With future climate change in mind, the design accounts for sea level rise and ensures long-term resilience. This initiative will restore the environment, strengthen cultural ties and lay the foundation for a resilient future, benefiting both the community and the environment.

 Supporting sand management along Adelaide’s shoreline

Applying shoreline morphology modelling supported by 40+ years of coastal monitoring to evaluate management options
 
Since the 1970s, the Government of South Australia’s Department for Environment and Water (DEW) has actively managed Adelaide’s shoreline through renourishment efforts. Despite recent large annual backpass campaigns, the shoreline between Adelaide Shores boat harbour and the West Beach Surf Life Saving Club (SLSC) continues to experience localised erosion. To address this issue, DEW has commissioned DHI to conduct a coastal processes modelling study. This study aims to enhance understanding of the coastal dynamics at West Beach and to explore alternative long-term management strategies.
 
Challenge
The Adelaide Metropolitan coastline comprises a discrete littoral sediment cell that extends along 30 km of the semi-protected eastern shoreline of Gulf St Vincent in South Australia. Sediment within the littoral cell is moved in a net northward direction with no significant supply of sediment provided from the south or offshore to replenish the beaches. The chronic sediment supply deficit combined with the impacts of historical coastal developments pose an ongoing challenge to the management of Adelaide’s Metropolitan coastline.
 
Solution
Providing models to assess management options
 
A comprehensive assessment of the coastal processes and observed erosion in the West Beach sediment cell was undertaken. This evaluation combines analysis of existing data with a state-of-the-art numerical modelling framework to predict long-term shoreline evolution.
 
Driven by MIKE Powered by DHI software, we developed hydrodynamic, wave and shoreline morphology models and calibrated them based on available measurements. In total, six management scenarios comprising of combinations of soft management options (nourishment, backpass systems) and hard structures have been simulated. For each scenario, the morphological evolution of the entire West Beach shoreline has been simulated for 7.5 years providing comparative assessments of the pros and cons of each scenario.
 
Results
The solution provided the Government of South Australia with:

An updated description of coastal processesUtilising historic data and advanced modeling techniques, the solution provided a comprehensive understanding of coastal processes in the region, facilitating more accurate assessments of coastal behaviour over time.
Comparison of management options and associated morphological impactsThe solution offered valuable insights into how different management approaches might affect coastal morphology, enabling more informed decisions about which strategies are likely to be most effective in mitigating coastal erosion and other challenges.
Data to support future decision-making for coastal managementReliable data is now available to support ongoing and future decision-making processes related to coastal management.


River mouth training in the Bay of Plenty

Designing twin training walls for the dynamic Opotiki Harbour Entrance
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Opotiki is a township with a strong vision of increasing the social and economic well-being of its community. Researched initiatives have shown that Opotiki is perfectly positioned for a large-scale aquaculture venture—a success that can only be brought alive through a transformation of the harbour entrance. Once a well-used trading route, local authorities are looking to make the harbour easier to navigate by constructing two parallel river training walls at the entrance. To help Opotiki District Council (ODC) achieve this, DHI provided design expertise and also assessed many significant factors which could impact the components of the ambitious project.
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Challenge
The coastal township of Opotiki sits on New Zealand’s eastern coast, in the North Island’s Bay of Plenty. Prior to the mid 1960s, the Opotiki harbour entrance had a long history of use by coastal shipping vessels which visited the township primarily as a trading port. Since then, the ability to navigate through the entrance has been adversely affected as waves routinely transporting sediments into the entrance formed an unreliable and often unsafe passage between the river and the sea. The confluence of the Waioeka and Otara rivers, approximately 1.5 kilometres above the harbour entrance, adds further complexity to the dynamic nature of the unique coastal environment.
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The most serious incident to date was when the entrance was closed for 64 days in 2007. Regular users of the route found it challenging and dangerous to navigate the passage five days out of 30 in a month on average. The ODC rallied central and local government, iwi and community groups, and commissioned a series of investigations to improve access to the harbour. We were engaged to find a solution by providing a conceptual design for the river training works while assessing environmental impacts at the same time. After considering many alternatives, our findings concluded that twin training walls at the entrance would provide the most appropriate stabilisation. One of the most important elements involved determining whether the large scale infrastructure project would adversely affect flood levels on the township.
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Solution
Different training wall configurations were assessed for a range of river flows and coastal conditions. DHI studied many aspects of the walls, including their ability to maintain a&nbsp;navigable entrance, the expected navigation conditions and possible scour in their vicinity. Our team also assessed the impacts on salinity within the harbour, sedimentation elements and backwater effects. On mitigating flood impacts, our experts recommended a confluence realignment as a feasible solution.
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DHI's solution was to construct two short straight breakwater training walls with a new entrance to the east of the existing one. The walls, approximately 500 metres long and 120&nbsp;metres apart, will also have scour protection elements included, without which the walls could be undermined during a large flood when deep scour may occur in between.&nbsp;
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With the application of one-dimensional (1D) and two dimensional (2D) models utilising MIKE Powered by DHI software, our team successfully developed a robust solution for ODC.
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Results
Ensuring the safe navigation of the harbour entrance while avoiding upstream flooding was principal within the project, as was understanding the many various coastal morphological impacts at play.
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From our modelling, we established that a re-engineered harbour entrance could alleviate the vessel access issues, allowing for more stable and improved entrance conditions. Although long term morphological impacts for flooding mitigation required further investigation, a realignment channel would somewhat reduce flooding impacts. The project, when undertaken, will greatly open up opportunities for the coastal settlement of Opotiki, creating potential aquaculture ventures and raising the wellbeing of the local community on manylevels.

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