Living Shorelines: Nature-Based Techniques — Reefs, Coir, and Beach Nourishment
Last Updated: April 19, 2026
Summary
This course covers three nature-based living shoreline techniques — living reef breakwaters, coir mats and logs, and beach and shoreface nourishment — examining the design parameters, constructability considerations, and adaptive management requirements for each approach. Drawing on New Jersey Coastal General Permit 24 guidance and current coastal engineering literature, the course addresses system, hydrodynamic, terrestrial, and ecological factors specific to each technique, including organism survival thresholds, wave attenuation performance, sediment behavior, and regulatory coordination. Students will gain the technical knowledge to evaluate site suitability and develop designs for nature-based shoreline stabilization using biological, fibrous, and sediment-based components.
Learning Objectives
Identify the site conditions and design constraints governing living reef breakwaters, including organism submergence requirements, tidal range considerations, wave attenuation targets, and the influence of sea level rise on long-term reef performance.
Describe the design parameters and limitations of coir mats and logs as temporary shoreline stabilization elements, including appropriate energy thresholds, tidal placement, anchoring methods, and known failure modes in moderate to high energy and ice-prone environments.
Explain the design process for shoreface and nearshore beach nourishment, including sediment sizing, placement geometry, cross-shore and longshore equilibration behavior, and ecological considerations such as habitat compatibility and invasive species management.
Apply adaptive management and monitoring principles across all three techniques, including post-storm assessment, beneficial reuse of dredged material, renourishment planning, and coordination with NJDEP regulatory frameworks.
Notice: Our courses do not yet qualify for PDH credit for engineers licensed in Florida, Indiana, Maryland, New Jersey, and New York. Check your state requirements for details.
Course Reading Material
Living Shorelines: Nature-Based Techniques — Reefs, Coir, and Beach Nourishment
BasePDH | Course No. 09 | 2 PDH
Source: NJDEP Living Shorelines Guidance
Publisher: New Jersey Department of Environmental Protection (NJDEP), Division of Land Resource Protection
Supporting references: USACE Coastal Engineering Manual (2002), Chesapeake Bay Foundation living shorelines guidance, NOAA Office for Coastal Management
Description
Naturally occurring living reefs have always served to protect fragile shorelines and marshes but unfortunately many of the natural beds have disappeared either through natural or anthropogenic causes. Living reef breakwaters and sills have recently become a popular method for protecting and stabilizing shorelines, creating habitat, and improving water quality in sheltered areas. More common in the southern United States, these submerged aquatic habitats function like constructed breakwaters or sills. Living breakwaters in the northeast are typically constructed with oysters or mussels and use an artificial substrate (Reef Ball, Oyster Castle, etc). The substrate is either placed with the intent of natural recruitment or seeded with organisms grown in a controlled environment (remote setting). When constructed in areas with strong natural recruitment, large reef structures can eventually form. Like constructed breakwaters and sills, sediment deposition can occur behind these living reefs, allowing vegetation to take root (Rella & Miller, 2012).
Design Guidance
System Parameters
Erosion History
Historically, mussel and oyster reefs provided protection for vast stretches of the New Jersey coastline. Living reef projects aim to restore some of the natural protective capacity that has been lost over time by encouraging the development of small low-crested mussel/oyster sills. Sills are appropriate at sites with a low-moderate erosion rate. The Chesapeake Bay Foundation suggests hybrid approaches such as living reefs are appropriate at sites with erosion rates of between 2 and 8 ft/yr (Chesapeake Bay Foundation, 2007). Based on the success of several New Jersey marsh sill projects along higher energy shorelines, the recommended limit for living reefs in New Jersey has been raised from 4 ft/yr to 6 ft/yr.
Sea Level Rise
Living reef breakwaters have some capacity to adapt to changing conditions; however, they are particularly sensitive to changes in water quality. If parameters such as water temperature, salinity, and turbidity remain within the range required by the constituent species, living reefs can adapt naturally to slow changes in water level through natural growth/migration. If the changes are rapid however, they may outpace the ability of the natural system to respond (Rella & Miller, 2012). If the increase in reef elevation lags the increase in sea level, the effectiveness of the reef in dissipating waves will be reduced over time as sea level reduces the freeboard. Marsh vegetation which may be included as a part of a living reef project, is also highly susceptible to changes associated with sea level rise, i.e. drowning of root systems and salt intrusion. It is recommended that the latest guidance provided by the NJDEP be used to design living reefs in New Jersey. At the time this guidance was written, NJDEP recommended using the STAP sea level rise estimates associated with the moderate emissions scenario. Depending on the project setting, values in the low-end to likely range are considered appropriate for living reefs.
Tidal Range
Knowing the expected daily tidal range, as well as the spring tide and storm surge related extremes, is vital when planning any living reef project. It is imperative that the oysters/mussels forming the reef remain submerged at all times if growth is to continue during periods of low tide. In colder climates like the northeast, it is essential to keep the oysters/mussels submerged to prevent them from freezing during the winter months. Oysters can survive dormant in cold water but will die if exposed to cold air, so it is important to ensure that the oysters remain completely submerged during low tide (NY/NJ Baykeeper, 2005). Typically, the crest height for living reefs should be set at or below mean low water as oysters/mussels can only remain out of the water for between 2 and 6 hours depending on the weather conditions (NY/NJ Baykeeper, 2005). In order for marsh plantings behind the living reef to grow successfully, it is imperative that the roots of the marsh plantings are under water during periods of high tide and dry during times of low tide. The dominant salt marsh plantings do not grow well in permanently standing water because their roots need to breathe in order to survive (Priest, 2006).
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