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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.

 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.

Protecting coastal communities around San Francisco Bay

Using 2D modelling to assess flood risks and improve San Francisco Bay’s floodplain maps
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Flooding can significantly impact coastal homes and businesses. However, information on flood-prone areas around San Francisco Bay was outdated or lacking. The United States Federal Emergency Management Agency (FEMA) needed to assess flood risks for the entire Bay Area. DHI's coastal models provided reliable data for flood risk analysis, helping local governments improve their flood management and equipping local residents with the information needed to better protect themselves from floods.
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Challenge
Located on the West Coast of the United States, the shores of the San Francisco Bay are home to more than seven million people. With billions of dollars of infrastructure located adjacent to the hundreds of miles of shoreline, an accurate assessment of the flood risk is vital. Extreme water levels caused by storms and other factors can have serious implications for the people and businesses that call the Bay Area home.
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The Bay Area hasn't had a comprehensive study since the early 1980s. To better understand coastal flood hazards for the entire San Francisco Bay, FEMA requested a regional Flood Insurance Study (FIS) to assess flood risks in the area.
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Solution
Using MIKE 21, DHI developed a system of regional scale coastal models in order to predict the following for the entire San Francisco Bay:

Extreme tide (astronomical tide plus storm surge)
Swell entering from the Pacific Ocean
Sea waves generated from local winds in the Bay

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Normally, we would apply a highly detailed study to a focused study area. However, this project required the same level of detail for the entire 250 mile-long Bay Area shoreline. To allow us to identify the storms in advance, we operated the models in hindcast mode to produce continuous results of water levels and waves covering 31 years in the North and Central Bay and&nbsp;54 years in the South Bay.&nbsp;
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Following this, we used the regional model results to establish maximum 1% (100-year) and 0.2% (500-year) Still Water Levels (SWLs) – the maximum water level that will occur – and wave height conditions. The DHI team then calibrated and validated the models using National Oceanic and Atmospheric Administration (NOAA) tide gage measurements from around the bay as well as various wave measurements from inside and outside the bay.
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Results
The results of the regional modelling study were key components for the development of FIS floodplain maps for the entire Bay Area. FEMA and its study contractors are using the regional model results as boundary conditions for further detailed coastal hazard analysis. This will also be the basis for most future studies. The detailed coastal hazard analysis could have far reaching implications for the businesses and people who live and work around the Bay. The results could lead to a modification in flood risk designations for coastal communities, which could in turn lead to changes in flood insurance rates, land-use planning around the Bay and floodplain management practices.
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By having a clearer idea of where flooding is most likely to occur, communities surrounding the San Francisco Bay can take the appropriate measures to ensure their safety.

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