When Engineering Meets Ecology: Why Coastal Land Managers May Want to Consider Hybrid Living Shorelines for Their Projects

As a coastal land manager, you may find yourself facing challenging questions about how to best protect and restore your shoreline and the nearby assets. Roadways, marshes, public recreational areas, and other infrastructure in proximity to shorelines are all vulnerable to changing climate conditions.

Traditional approaches to protecting these areas, including bulkheads, revetments, and seawalls, are not always feasible due to regulatory or practical constraints. In contrast, vegetative living shorelines use natural approaches to stabilize coastal areas. This may include marsh restoration, beach nourishment, and dune creation.

However, these approaches may not be entirely successful in moderate to high energy environments. One alternative approach is a hybrid living shoreline. This approach combines both engineered elements and ecological components. Keep reading to learn how this approach can benefit your coastal projects and goals.

Hybrid Shoreline Techniques

Let’s first examine what constitutes a hybrid living shoreline. Hybrid living shorelines combine elements of traditional coastal infrastructure with ecological restoration. Hybrid living shoreline techniques may include

• offshore breakwaters
• beach nourishment
• oyster reef structures
• marsh restoration
• living revetments
• crib walls
• brush mattresses
• bluff and dune stabilization
• coir logs,
• and other similar features and techniques.

To meet project goals, hybrid living shoreline projects will feature a combination of several of these techniques. Hybrid structures are ideal in several scenarios because they provide continued protection to fixed assets along the coast while providing an ecological benefit.

For example, a shoreline experiencing erosion and marsh loss that is situated near a highly developed area could benefit from breakwaters to slow sediment and marsh loss, nourishment landward of the breakwaters, and planting of the nourished area with native marsh plants to expand the marsh, all without having to move existing roads or buildings.

Hybrid History

Hybrid shorelines have become more prevalent as an approach in the last ten to twenty years, as more project owners are looking to incorporate ecological value to their projects while continuing to protect upland structures. Traditionally, hard structures, such as seawalls, bulkheads, and revetments, were the standard for protecting shorelines.

As time went on, the disruption that these engineered structures caused to natural systems became more evident, and a more natural approach to shoreline stabilization became favored.

While natural shoreline stabilization provides the most ecological benefit, these are often difficult to successfully implement in environments which are highly developed and/or have high wind and wave action. This is where the hybrid approach was born – from the need for the ecological benefits in combination with stabilizing and restoring shorelines in more challenging environments.

Protecting the Coast with Hybrid Living Shorelines

Hybrid living shorelines help mimic natural processes that retain sediment in the nearshore area, allowing for slowed erosion, sediment accretion, and eventually the establishment of native marshes.

Historically, in areas where armored shorelines (bulkheads, seawalls, revetments) were installed, a source of sediment was removed from the natural transport processes that occur along the coast. With the lack of natural sediment into the system, water and waves could only remove sediment that was seaward of the hard structures or in other unprotected areas.

This often resulted in loss of natural marshes, erosion, land loss at the end of hard structures, and changes to the natural sediment transport along the coast overall. With a hybrid living shoreline, you can replenish sediment, slow the sediment loss to the larger waterbody, mitigate erosion, and reestablish the ecological benefits that marshes or other natural shoreline features provide.

Is a Hybrid Living Shoreline Right for Your Project?

You have plenty to consider when thinking about how best to move forward with your coastal project.  A few key questions can help guide you in determining the best solution for your goals. Your answers will help determine if a hybrid living shoreline might be a good fit. These include:

• How much of the shoreline surrounding my project is developed versus natural?
• What is the width of the waterway perpendicular to my shoreline?
• Are there any land ownership challenges that limit what can be implemented?
• Is there or was there marsh previously located at my project site?
• Was the site previously significantly disturbed (e.g., fill brought in, previous structures which failed over time, marsh ditching, etc.)?
• Do I have support and/or funding for initial maintenance and adaptive management?

If you are unsure how to best answer these questions, you may want to consider engaging a consultant, who can help you sort through options and decide on a path forward for your coastal project.

These questions (and answers) in conjunction with your overall project goals can aid in directing you to the most practical solution for your site. In general, if your site is in a highly developed area, experiences high wind and wave energy, and you’re looking to enhance the ecological benefits the site provides, a hybrid living shoreline may be the right option.

If you’re planning a coastal restoration project and you’d like to explore hybrid living shorelines further, please feel free to reach out to me at lpomiurbat@geiconsultants.com. Our team is available to assist with your project from planning to design, and through construction.