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Green Your Riprap: A Simple, Low-Cost Technique

to Retrofit Riprap Shorelines

Shoreline Hardening in the

Chesapeake Bay

Over 18% of the Chesapeake Bay has been

hardened, in many cases through riprap

revetments. When a tidal shoreline is hardened,

fringe marsh ecological benefits disappear.

Revetments do not filter out nutrients and

capture sediment, so these enter the Bay instead.

Organisms can no longer find food, shelter, or

refuge in the intertidal area. The terrestrial and

aquatic communities that are able to use riprap

for habitat are different than those in fringe tidal

marshes. Without marsh vegetation to shade the

shoreline, nearshore water temperatures

increase, harming the ability of aquatic organisms

to utilize the area. Replacement of fringe marsh

areas with riprap has serious consequences for

the ecology of shorelines.

If a landowner wants a simple and low cost

way to improve the ecological and

aesthetic value of their existing riprap

shoreline, Green Riprap is a viable option!

What is Green Riprap?

Green riprap is a small-scale, low-cost restoration

technique for improving existing riprap shorelines,

and involves planting riprap with tidal marsh

plants.

This guide is for river restoration experts and homeowners who want to improve the ecological and aesthetic

value of shorelines armored with riprap revetments. In 2013 and 2015, U.S. Fish and Wildlife’s Chesapeake Bay

Field Office experimented with a technique, Green Riprap, to establish marsh plants in the spaces between

rocks in existing revetments along tidal shorelines. Projects were completed on the Severn and Magothy Rivers

near Annapolis, MD.

Benefits of Green Riprap

Habitat, food, and refuge for aquatic and

terrestrial life

Shade to cool nearshore water temperatures

Filtration of nitrogen and phosphorus

Sediment capture

Absorption of wave energy and reduction of

scour

Aesthetic improvement of property

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Success Story: Round Bay Community Beach

BEFORE 4 YEARS LATER

Site Conditions

Unique Features: breakwater present

Wave energy: Fetch of 2 mi to the SSW.

Significant boat wake

Nearshore water: Some of area has exposed

beach off the rock, other areas have gently sloping

shallow water not exposed at normal low tide

Sediment: Less than 1” of sediment accreted.

Aspect and Shade: South facing. Full sun.

Existing plants: none

The community of Round Bay wanted to beautify

and improve the riprap that was present along

their community beach. With the help of the Chesa-

peake Bay Field Office of USFWS, they planted 600

marsh grasses along 300 feet of bare riprap shore-

line. Planting was done by wedging the grass plugs

(grown out in 3” coir pots) between the rocks. An

existing breakwater likely helped the grasses es-

tablish and spread further along the riprap by miti-

gating 2 miles of fetch and significant boat wake.

Community members were so pleased with the

success of the planting that they have since planted

more grasses on their beach. Landowners along

the beach are especially satisfied with the aesthetic

improvement upon the bare rock.

Immediately after planting, 2013

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Success Story: West Severna Park Marina

BEFORE

5 YEARS LATER

Site Conditions

Wave energy: Max fetch of 0.3 miles

to the SSW. Protected cove, no boat

wake

Nearshore water: Bottom is not

exposed at normal low tide

Sediment: Less than 1” of silty

sediment accretion in rock.

Aspect and Shade: South facing. Full

sun.

Existing plants: High tide bush,

Hibiscus Immediately after planting, 2013

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Learn more about the ecology of hardened

shorelines

Dugan, J. E. et al. (2011). Estuarine and coastal structures: environmental effects, a

focus on shore and nearshore structures. Treatise on estuarine and coastal science,

8, 17 -41.

Fischenich, J. C. (2003). Effects of riprap on riverine and riparian ecosystems (No.

ERDC/EL-TR-03-4). Engineer Research and Development Center—Vicksburg MS

Environmental Lab.

NOAA. (2017). Impacts of Hardened Shorelines on Aquatic Resources: Research

Summary. NOAA National Centers for Coastal Ocean Science . Retrieved from https://

chesapeakebay.noaa.gov/shorelines/shorelines.

Seitz, R. D., et al. (2006). Influence of shallow-water habitats and shoreline

development on abundance, biomass, and diversity of benthic prey and predators in

Chesapeake Bay. Marine Ecology Progress Series, 326, 11-27.

Questions? Contact Us!

Leah Franzluebbers

leah_franzluebbers@fws.gov

(410) 173-4181

Rich Mason

rich_mason@fws.gov

(410) 173-4184

Planting Tips

Grow plugs in 3” round coconut fiber coir pots for

approximately 4-6 weeks to establish a robust root system.

Plant grasses by moving the rocks and wedging the plants in

the voids of the rip rap. Successful wedging will ensure that the

plants do not wash away with the tides.

Ensure that the grasses are planted in the correct hydrologic

zones (see Figure 1). Remember that the plant roots will be at a

lower elevation compared to the rock surface. Use other marsh

plants growing nearby to locate the mid– and high-tide lines.

Planting should occur at low tide for ease of access. Because

planting in rocks can be difficult, it may be helpful to stand in

the water or kneel on a foam pad on the rocks.

Figure 1. Planting zones on rip rap shorelines.