Port expansions, and especially greenfield ports, often have the potential to result in direct damage to, or loss of, existing aquatic habitat and alterations to physical processes, such as waves and sediment transport, which may indirectly impact habitat through marine construction and shipping operations.
The loss can be offset by incorporating habitat features in the design or by restoring degraded habitat elsewhere. The requirements to redress habitat loss typically vary with the quality and size of the original habitat that is damaged or destroyed by the new development. As an increasing value is placed on actions for a more sustainable future, compensatory habitat creation is more likely to need to exceed the losses of high-quality habitats.
Successful design and implementation of habitat features, or “habitat compensation projects”, can be challenging and costly. WSP’s multidisciplinary team of geomorphologists, terrestrial and marine ecologists, coastal and geotechnical engineers, as well as construction and permitting specialists, work together to deliver successful and smart habitat compensation projects to port clients.
A “Design with Nature” Approach
A compensatory habitat project requires thoughtful consideration of the physical, chemical, and biological processes that sustain the natural habitat, the engineering necessary to bring the habitat to fruition, and the ecological objectives of the project’s stakeholders. Our team’s successful approach to habitat design and compensation projects follows a “design-with-nature” approach, which involves consideration of ecological principles, the chemical interplay between fresh water and salt water, as well as potential or legacy contaminants, and geomorphological principles as the main basis of design for marine or coastal habitats. This approach is generally referred to as “nature-based design” and allows for continued action of coastal processes and ecosystem functions, while also providing stable or dynamically stable habitat-enhancement measures.
Successful habitat enhancement projects typically require a demonstration of biological performance and physical stability in perpetuity as performance endpoints. Engineering a robust and static structure following traditional engineering principles may not provide a solution that preserves ecosystem functions, while also adapting and self-regulating in response to seasonal and inter-annual variability or trends in environmental conditions.
An example of this is the necessary evolution of a beach and salt marsh habitat that must respond and adapt to rising sea levels. As such, habitat designs are uniquely site specific and must incorporate existing site geomorphological conditions and ecological information, along with typical engineering design criteria to meet habitat objectives where appropriate. The ideal approach aims to achieve the required ecological performance without being physically restrictive to naturally occurring processes or creating undue environmental or human safety risk.
Designing with nature first starts with knowing the type of habitat that needs to be developed. This may include broad consideration of the primary plants, organisms, fish, and wildlife that will use the habitat either as residents or transients. Often the species considered are based on the anticipated losses from the port development, but also may be based on local needs. For example, indigenous traditional harvesting, filling a gap in a habitat niche to encourage a threatened species, or recreational values may all need to be considered and prioritized. This process relies not only on sound understanding of biological and ecological sciences, but also understanding the social, cultural, and economic values in the region.
Equally important to these considerations are the physical environment and morphological context for the new habitat. It is a bit like successful gardening, but often much more complicated and challenging. We do not have several thousand years of historical experience behind the design of natural habitats as we do with traditional agriculture. Also, the idea is not necessarily to control nature into producing a perfect crop of, say, tomatoes, it is to encourage a natural habitat that supports a diversity of species. You must consider the balance of fresh and salt water, shade and sunlight exposure, energy from tides, waves, and currents, and resistance as well as nutrient supply from soil and substrate for plant growth as well as landform shape and stability now and in future climatological conditions.
The physical components are like the skeleton or backbone that supports the ecosystem. Unlike planter boxes in your backyard, where you add a bit of fertilizer, diverse natural habitats in coastal and marine environments are typically not rigid and static but more often dynamic and flexible responding to wind, tides, waves, currents, and sea level change and other climate factors. They can also be subject to invasive species that can wreak havoc on the tender shoots of new plantings.
Using Natural Analogues for Success
Selecting a habitat type and a compensation site requires consideration of all the above ecological and physical relationships. To overcome many of the challenges involved, we often apply an approach that uses natural analogues (e.g., similar, representative sites) as a basis to select habitat types and choose sites where establishment of a similar or corresponding habitat has a high likelihood of success. If we apply what works for nature in a similar setting, the new habitat has a greater chance of success than if we force something to fit. The key to this way of thinking is to design the project to work with natural processes as much as possible.
For example, a project that takes advantage of longshore drift will function better, last longer and cost less than a project that interrupts longshore drift. Application of this principle requires a combination of geomorphological and ecological interpretation to first identify the relevant matching patterns in landforms and habitat, and then visualize the implementation of the concept at a potential compensation site. Fundamental considerations for coastal settings include the orientation of the shoreline relative to wave exposure, the composition and distribution of material sizes, and the elevations inhabited by resident plants and other living organisms.
A progressive series of desktop and field-based selection, screening, and survey efforts is needed, followed by detailed analysis of coastal processes, for successfully developing and implementing an equivalent concept at a new site through the design and construction phases. Some carefully considered coastal engineering may also be required to protect portions of the habitat. The use of reefs, breakwaters, or headlands, constructed with the rocky material known as “riprap” for example, may in some instances serve a dual purpose of providing a useful substrate for marine algae to become established, while also serving a sediment control or shore protection function for a spawning beach or salt marsh situated in the lee. Practical considerations include the accessibility of the new habitat site for construction equipment and the quantity of excavation and fill material that may need to be imported to the site to achieve the habitat substrate and protective framework.
Nature-based design requires a different mindset. While traditional engineering solutions tend towards stable/fixed structures with low habitat value, in contrast the biological needs of a habitat depend on a dynamic design allowing for habitat renewal through natural processes. In essence, the more fixed and permanent the habitat design (e.g., less likely to erode), the lower the habitat value. The more flexible and self-healing the design – by accommodating nature-based design principles – the more valuable and durable the resulting habitat.
ABOUT THE AUTHOR
Rowland Atkins, M.Sc., P.Geo, is a Senior Geomorphologist at WSP. He is a registered professional geoscientist in the Provinces of British Columbia, Ontario and Alberta, Canada. He has over twenty-five years of experience in coastal geomorphology, including assessment of sea level rise, coastal erosion and sedimentation, the impact of structures on littoral circulation, habitat restoration, and analysis of oceanographic parameters including tides, waves, and currents.
Phil Osborne, PhD, P.Geo, is a Senior Coastal Geomorphologist and Senior Practice Leader at WSP. Phil leads WSP’s global Coastal, Ports and Marine Engineering Technical Community, and provides strategic and technical leadership for a wide range of services in coastal, estuarine, and fluvial environments. He has led multiple nature-based shore protection and marine habitat restoration projects, applying geomorphological, ecological, and engineering principles.