Green Your Riprap: A Simple, Low-Cost Technique to ...Chesapeake Bay Over 18% of the Chesapeake Bay...
Transcript of Green Your Riprap: A Simple, Low-Cost Technique to ...Chesapeake Bay Over 18% of the Chesapeake Bay...
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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
(410) 173-4181
Rich Mason
(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.