Living Shorelines and Structural Shoreline Practices

hardening shorelines reduces habitat and populations of forage fish such as the bay anchovy (Anchoa mitchilli), the most abundant fish in the Chesapeake Bay
hardening shorelines reduces habitat and populations of forage fish such as the bay anchovy (Anchoa mitchilli), the most abundant fish in the Chesapeake Bay
Source: Chesapeake Bay Program, Bay Anchovy

Owners of shoreline property threatened by erosion have traditionally installed bulkheads, seawalls, revetments, breakwaters, groins, and jetties. The hardened shoreline eliminates the habitat at the edge of water and land, reducing the food and shelter needed by juvenile fish, crabs, and other species.

By 2016, over 15% of the Chesapeake Bay shoreline had been transformed by traditional "grey infrastructure." Around Hampton Roads, that percentage exceeded 50%. Roughly 25% of the shoreline on major Chesapake Bay tributaries had been hardened.

Hardened shorelines create a rigid shoreline that can not migrate. Blocking the natural migration of tidal marshes will gradually reduce the acreage along the Chesapeake Bay of that highly-productive ecosystem:1

Tidal wetlands can keep pace with up to about 2.5 millimeters (mm) of sea-level rise per year, by trapping sediments and forming peat. But sea level is currently rising by about 3 mm per year, and the rate is expected to accelerate to 5 to 10 mm per year in the coming decades. Under those conditions, tidal wetlands could only survive by migrating landward with the rising seas. Construction of bulkheads or similar protective structures prohibits this migration, essentially drowning the wetlands in place.

where bulkheads block natural migration, tidal marshes disappear as sea level rises faster than 2.5 millimeters (mm) per year
where bulkheads block natural migration, tidal marshes disappear as sea level rises faster than 2.5 millimeters (mm) per year
Source: College of William and Mary, Study reveals threat to tidal wetlands

When shoreline habitat is reduced, there is a reduction in the population of forage species such as marine worms (polychaetes), blue crabs, and bay anchovy (Anchoa mitchilli) - the most abundant fish in the Chesapeake Bay. Less forage results in a corresponding reduction in the number of predators at the top of the food chain, such as striped bass (Morone saxatilis) and summer flounder (Paralichthys dentatus).2

Living shorelines are now a "green infrastructure" option that minimizes the impact of altering shorelines. Low rock sills are built in the water near a shoreline to protect it from erosion by currents and wind-driven waves. The rock sill slows the flow of water, but permits it to wash over the top and even through the loosely-packed rocks. Typically sand/mud accumulates and a waterfront marsh develops between the rock sill and the shoreline, creating shallow water habitat. Unlike shorelines hardened with bulkheads and seawalls, the new marsh attracts invertebrates, polychaetes, insects, juvenile fish, and birds.

In 2020, the General Assembly mandated that the Virginia Marine Resources Commission (VMRC) prioritize living shorelines for stabilizing land:3

The Commission shall permit only living shoreline approaches to shoreline management unless the best available science shows that such approaches are not suitable. If the best available science shows that a living shoreline approach is not suitable, the Commission shall require the applicant to incorporate, to the maximum extent possible, elements of living shoreline approaches into permitted projects.

some owners of riverfront property cut grass to the shoreline
some owners of riverfront property cut grass to the shoreline
Source: Virginia Department of Transportation, Dorian - September 07, 2019

In developed areas, a high percentage of the shoreline is armored by bulkheads, breakwaters, and other physical barriers to protect infrastructure from inundation. A lawyer focused on waterfront legal cases calculated that by May 2022, the Virginia Marine Resources Commission had approved 5,983 feet of living shoreline and 6,581 feet of hardened shoreline:4

There are over 7,000 miles of coastline in Virginia (over three times the distance between Virginia Beach and San Diego). About 18% of the Chesapeake Bay coastline is armored, with higher values (45-50%) along urban shores in many areas.

As sea level rises, the remaining marshes in such areas will be squeezed. Rising water will flood the marsh near the water, and human barriers will block migration inland.

In contrast, elevation maps of the Chesapeake Bay show that in rural areas the low-lying fields and forests will be transformed into new wetlands. In particular, forested wetlands are at risk of conversion into tidal marsh.5

The US Navy planned the largest living shoreline project on the East Coast in 2022. On the York River, Naval Weapons Station Yorktown prepared to construct about 2,900 feet of living shoreline by stimulating production of "oyster castles." Concrete and granite forms, used as an artificial reef foundation, would lead to a new reef intended to absorb wave energy that eroded the shoreline.6

Wind farms may have benefits like living shorelines, in addition to reducing the need for fossil fuels. The underwater structures that support the towers become artificial reefs, as the seafloor recovers from the disruption of construction. Marine animals that require hard surfaces, such as mussels, grow on the foundations and attract other animals. A new ecosystem develops where habitat has been significantly altered, due to the addition of metal and concrete surfaces to areas formerly dominated by mud and sand.7

And in theory, wind farms in the Atlantic Ocean could absorb energy from storms and reduce the impacts onshore of high winds and storm surges.

A massive number of turbines (over 400,000) along the East Coast could redirect the power of a storm, reducing wind speeds by over 80mph and protecting urbanized areas such as Norfolk. No one has proposed building that many turbines - the expected number in the Outer Continental Shelf Offshore Virginia block was just 200 - but offshore structures offer an alternative to investing billions of dollars for hardening the shoreline:8

Unlike sea walls, offshore wind turbines would reduce both wind speed and storm surge and would generate electricity year-round.

Chesapeake Bay Geology and Sea Level Rise

Climate Change in Virginia

Will Norfolk (and the Rest of Hampton Roads) Drown?

Virginia and Submerged Lands

Who Owns Submerged Lands After They Emerge Through Accretion and Landfilling?

a living shoreline at Penniman Spit was designed to reduce erosion on the shoreline of Naval Weapons Station Yorktown
a living shoreline at Penniman Spit was designed to reduce erosion on the shoreline of Naval Weapons Station Yorktown
Source: ESRI, ArcGIS Online

concrete forms are placed below the low-water mark and oysters use the hard substrate to grow into castles
concrete forms are placed below the low-water mark and oysters use the hard substrate to grow into castles
Source: Virginia Institute of Marine Science (VIMS), Pre-Cast Reef Structures

Virginia Department of Transportation (VDOT) funded a living shoreline project at Belle Isle State Park
Virginia Department of Transportation (VDOT) funded a living shoreline project at Belle Isle State Park
Virginia Department of Transportation (VDOT) funded a living shoreline project at Belle Isle State Park
Virginia Department of Transportation (VDOT) funded a living shoreline project at Belle Isle State Park

Links

the Corps of Engineers placed rock on the York River shoreline in 2013 to counter erosion threatening the Colonial National Parkway

the Corps of Engineers placed rock on the York River shoreline in 2013 to counter erosion threatening the Colonial National Parkway
the Corps of Engineers placed rock on the York River shoreline in 2013 to counter erosion threatening the Colonial National Parkway
Source: US Army Corps of Engineers, Norfolk District Image Gallery

References

1. David Malmquist, "Study reveals threat to tidal wetlands," College of William and Mary, November 9, 2009, https://www.wm.edu/news/stories/2009/study-reveals-threat-to-tidal-wetlands-123.php; "Living shorelines gain ground around the Chesapeake Bay but face hurdles," Bay Journal, January 22, 2024, https://www.bayjournal.com/news/policy/living-shorelines-gain-ground-around-the-chesapeake-bay-but-face-hurdles/article_7e8fa37a-b934-11ee-b784-bfa4404808dc.html (last checked February 20, 2024)
2. "Bay Anchovy," Chesapeake Bay Program, https://www.chesapeakebay.net/discover/field-guide/entry/bay-anchovy; "Researchers map best conditions for forage fishes in the Chesapeake," Virginia Institute of Marine Science (VIMS), October 27, 2021, https://www.vims.edu/newsandevents/topstories/2021/forage_fishes.php; "Forage Status and Trends Report for the Chesapeake Bay," Chesapeake Bay Program Forage Action Team, November 2023, p.5, https://www.chesapeakebay.net/what/publications/forage-status-and-trends-report (last checked February 20, 2024)
3. "Section 28.2-104.1. Living shorelines; development of general permit; guidance," Title 28.2. Fisheries and Habitat of the Tidal Waters - Subtitle I. General Provisions Relating to Marine Resources Commission - Chapter 1. Administration - Article 1. Commission; Commissioner, Code of Virginia, https://law.lis.virginia.gov/vacode/title28.2/chapter1/section28.2-104.1/ (last checked July 26, 2022)
4. "Updates On Living Shorelines – Webinar Recap," Jim Lang - Waterfront Law, July 5, 2022, https://www.waterfrontpropertylaw.com/blog/posts/updates-on-living-shorelines-webinar-recap/ (last checked July 26, 2022)
5. Grace D. Molino, Joel A. Carr, Neil K. Ganju, Matthew L. Kirwan, "Variability in marsh migration potential determined by topographic rather than anthropogenic constraints in the Chesapeake Bay region," Limnology and Oceanography Letters, May 31, 2022, https://doi.org/10.1002/lol2.10262; "Rural areas will bear the brunt of U.S. sea-level rise," Virginia Institute of Marine Sciences, June 14, 2022, https://www.vims.edu/newsandevents/topstories/2022/rural_inundation.php (last checked July 1, 2022)
6. "Naval Weapons Station Yorktown building living shoreline to combat erosion, sea level rise," WHRO, July 14, 2022, https://whro.org/news/30676-naval-weapons-station-yorktown-building-living-shoreline-to-combat-erosion-sea-level-rise (last checked July 15, 2022)
7. "Where the wind blows, marine life will flock - Virginia's first offshore turbines become a haven for ocean creatures," The Virginian-Pilot, October 15, 2021, https://www.pilotonline.com/news/environment/vp-nw-offshore-wind-marine-life-20211014-npdjx4qzl5d37eiclokeah7q3q-story.html (last checked October 15, 2021)
8. Mark Z. Jacobson, Cristina L. Archer, Willett Kempton, "Taming hurricanes with arrays of offshore wind turbines," Nature Climate Change, February 26, 2014, http://doi.org/10.1038/NCLIMATE2120; "Wind turbines could weaken hurricanes, study shows," The Virginian-Pilot, February 28, 2014, http://hamptonroads.com/node/708371 (last checked February 28, 2014)

Colonial Beach before installation of sand retention structures
Colonial Beach before installation of sand retention structures
Source: National Archives, Colonial Beach (August 1949)

rock breakwaters, built parallel to the shore at Willoughby Bay Spit and East Ocean View in Norfolk, interrupt the natural migration of sand and maintain a beach
rock breakwaters, built parallel to the shore at Willoughby Bay Spit and East Ocean View in Norfolk, interrupt the natural migration of sand and maintain a beach
Source: US Army Corps of Engineers, Norfolk District Image Gallery


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