Living Shorelines Definitions & Descriptions
Living Shorelines Definitions & Descriptions Karen Duhring Virginia Institute of Marine Science College of William & Mary June 10, 2015 Living Shoreline Contractor Training Workshop Camden County College, New Jersey
Living Shorelines Definitions & Descriptions
• Common Definitions • Project type examples with site-specific considerations – Non-structural or Bio-Based
– Hybrid
• Common Contractor Concerns
What’s the Difference? Habitat Restoration Wetland Mitigation Primary purpose is to create & replace lost natural habitat for its intrinsic value Human presence minimal if not absent
Living Shorelines Primary purpose is to solve a problem
Reduce erosion risk, site remediation, beneficial use of dredged material
Human presence normal
What are Living Shorelines for Erosion Protection? Alternatives for bulkheads & revetments Where erosion cannot be tolerated & some type of action is necessary Mimic or protect existing native habitats Riparian buffers + tidal marshes + sand beaches + Shellfish reefs + SAV?
Common Elements in Living Shorelines Definitions • Erosion risk reduction – unacceptable erosion risk is present and some type of shoreline management action is deemed necessary
• Wave attenuation – rough surfaces to reduce wave height and energy of approaching waves
• Habitat heterogeneity – Diverse habitats similar to natural shorelines in local area
• Habitat continuum – unimpeded migration of fish and wildlife along the shoreline and between aquatic and terrestrial habitats, plus the import and export of organic matter between habitats
• Habitat migration allowance – habitat features can shift in response to sea level rise, vertical sediment accretion is possible Source: Bilkovic, Mitchell, Mason & Duhring, 2015 in press
Living Shoreline Project Categories Non-Structural ‘Bio-Based’
Hybrid
Adequate protection provided with vegetative stabilization + gradual slopes
Engineered structures required to achieve desired level of protection
Suitable sites: Very Low - Low energy
Suitable sites: Low-moderate energy
Non-Structural Approaches Enhance Existing Marsh &/or Riparian Buffer
Grade Bank & Restore Riparian Buffer
J. Scalf
Planted Marshes & Fiber Logs
Beach Nourishment & Dune Creation
Planted Marshes – important considerations • Good summary of design criteria – Walter I. Priest, III 2006 Living Shoreline Summit Proceedings
• Tidal benchmarks are critical, local tide range & extreme tide levels (both low & high) • Patience & due diligence required – Wave attenuation provided by “well-established” marsh which takes at least 1 growing season ( 3-4 months) – More habitat benefits achieved after 5 years, especially benthic community due to lag time for organic matter accumulation & processing
Planted marsh must be sloped so it is completely exposed at low tide; plant failure may be caused by standing water
Low marsh
High marsh
Salt Bushes
S. alterniflora
S. patens
I. Frutescens &
B. halimifolia
Regular high tide line
Birdsong Wetland Norfolk, VA
Typical Grass Species Used for Salt Marsh Low Marsh
High Marsh
Salt grass Distichlis spicata
Saltmarsh cord grass Spartina alterniflora
Saltmeadow hay Spartina patens
More species possible for low salinity or fresh water, select those that remain above ground during winter e.g. Spartina cynosuroides, Juncus effusus
Switch grass Panicum virgatum
Salt Bushes planted at landward side of high marsh
Not as flood tolerant, use at upland edge
Groundsel Bush Baccharis halimifolia
Marsh Elder Iva frutescens
Wax myrtle / Bayberry Morella cerifera M. pennsylvanica
Nursery Stock
Cell Pack 72 or 96 = # cell packs per flat
4. Pack well to remove air pockets
2. Slow-release fertilizer in hole 1. Dig hole
3. Insert plant at least 4 inches deep Can’t plant too deep!
Planting Process New Gosport Wetland, Portsmouth
Plant Spacing & Growth Pattern
Closer spacing for more rapid cover Wider spacing to cover large area with limited budget
Marsh grasses will spread underground by rhizomes Eventually space between plants will fill in naturally
Planted rows not visible over time
If it’s done correctly….. Planting Day
4 Months Later
Successful establishment indicated by flowering grasses
Planted Freshwater Marsh
Photo Courtesy NC Coastal Federation
How wide should the marsh be? • The answer depends on the energy regime at project site & the erosion problem—the bigger the waves, the wider the marsh
• Adjacent development & navigation interests may limit marsh width • Allow for landward migration & expansion with connected riparian buffer zone
Embayed or “Pocket” Marsh Alternative design to fringe marsh Tidal connection
More complex planting zones Low marsh
Upland excavation areas High marsh
VIMS Teaching Marsh Gloucester Pt, VA
Grazing Exclusion Devices Single row of staked netting for narrow fringe
String network to cover wide fringe
Mute Swans & Canada Geese can pull new plants out of the ground, but not established well-rooted plants; exclusion device can be removed after 1 growing season
Fiber Logs & Mats The use of manufactured, bio-degradable fiber products to provide temporary support for planted tidal marshes and/or riparian buffer restoration May also be effective for trapping sediment
P. Menichino
P. Menichino
Fiber Logs – important considerations • Easily lifted out of place by the force of water – Most suitable sites are low flow velocity – Staking & anchoring essential if they are in the water – Full contact with ground should be maintained
• Temporary, biodegradable – May or may not need to be replaced
• Planting into logs has mixed results – Saturation is important for plants – Adjacent planted marsh usually grows into them
• Some reported fiber log project ‘failures’ due to unrealistic expectations or incorrect applications – Cannot stand alone, usually combined with another element
Fiber log project example - Before
Undercut trees
J. Scalf
Fiber logs & sand fill to match adjacent marsh Construction access from water
J. Scalf
Planted tidal marsh with goose exclusion fence
J. Scalf
Fiber logs decay over time leaving just the planted marsh
Beach Nourishment & Dune Restoration • Addition of sand to a beach to raise its elevation and increase its width • Reshaping and stabilizing with dune plants
Beach & Dune Vegetation
American beach grass Ammophila breviligulata Cool-season grass for northern Mid-Atlantic Winter planting
Bitter panicum Panicum amarum
Saltmeadow hay Spartina patens
Sea oats Uniola paniculata
ANY QUESTIONS ABOUT NON-STRUCTURAL LIVING SHORELINE PROJECTS?
Hybrid Approach Where wind-waves & boat wakes are too extreme for non-structural methods Strategically placed structures to: • contain sand fill & support vegetation growth • allow tidal ebb & flood • maintain connections between upland & wetland habitats
Hybrid Project Types Marsh Toe Revetment
Marsh Sill
Living Reef
Offshore Breakwater w/ Beach Nourishment
Marsh Toe Revetment • Low-profile placed along eroding marsh edge • Placed against marsh or offset • Sediment accretion may occur
Marsh with Sill A low-profile revetment backfilled with sand to create & support a tidal marsh that otherwise could not occur
Typical Marsh Sill Construction Sequence
1. Filter cloth placed
2. Sand fill & stone sill
3. Settling period – check grade & tides
4. Plant tidal marsh vegetation
Marsh sills are submerged during storm events During a severe storm, the wave height reaching the upland bank is reduced by the “roughness” of the sill and wide planted marsh
Same well-established marsh 3 yrs after planting the day after Hurricane Irene
Marsh with Sill
Important Considerations 1. Is a Planted Marsh feasible if no marsh is present? Full sun Sandy soil Shallow nearshore 2. Are intertidal and nearshore slopes shallow & gradual? Minimize fill needed to achieve target elevations
Marsh with Sill
Important Considerations 3. Will sediment support equipment & weight of stone + sand?
Highly suitable for sill Not as suitable
Marsh with Sill
Site-Specific Considerations 5. Is Submerged Aquatic Vegetation (SAV) habitat present? Look at previous 5 years VIMS SAV inventory for habitat potential
6. Will local navigation be affected? Submerged stone structure hazard potential Sediment trapping in channels
Design Criteria to Maintain Coastal Processes
• Crest height in relation to Mean High Water • Tidal gaps – windows – openings • Stone size & interstitial spaces
Tidal Openings
When should they be included? • Sill crest height > MHW • Sill length > 100 Ft ?? – No definitive standard – May need more or less
• Site-specific – Tidal ponds – Natural or created channels – Open ends – Recreation access
Tidal openings allow access for marine wildlife, but they also introduce wave energy into the planted marsh. Stable embayments eventually form
Tidal Openings
Design Challenge – too much energy • “Straight” tidal openings allow access for marine wildlife, but also introduce wave energy into the planted marsh. • Stable embayments eventually form • Shoaling may occur that blocks access & tides
Tidal Openings
Other Types
Weir Opening or Vented Sill
Straight gap with cobblestone
Gap covered with stone at lower elevation
Reduces sand deposits How is biological activity altered?
Tidal Openings
Other Types
Gapped offset sections at pocket marsh Taper ends toward wave energy
Living Reefs • Oysters & ribbed mussels being used • Colonizing on fiber logs & marsh sills
• Enhance or replace stone material • Increase habitat diversity
Living Reefs Important Considerations
1. Are there any natural reefs in vicinity to mimic? 2. What is the local tide range & extreme tide potential? Will the reef remain submerged or be exposed ? 3. Is the wave climate low enough for loose shell or is some type of containment needed? 4. Are there any navigation or public health concerns?
Living Reefs • Structure material substitute Loose or bagged shell Pre-cast concrete structures Other engineered wave attenuation devices
Loose Shell Good for habitat value Not usually effective for wave attenuation
Bagged Shell Similar structural integrity as stone sills, but easier to install Long-term reef evolution still under investigation
Plastic mesh having incidental impacts, e.g. entrapment, microplastic pollution? Are wire gabions better?
Reef Balls Pre-cast concrete with embedded oyster shell Pre-soaked for spat settlement Requires crane to lift on and off boats
Oyster Castles Smaller, interlocking units with embedded oyster shell
‘Ready Reef’ just one of several new products on market
Source: http://readyreef.com/index.html
How Well Do Living Reefs Work for Erosion Protection? • Loose shell - usually not much wave attenuation • Bagged shell - more structural integrity for wave reduction, unknown oyster habitat value over time • Pre-cast concrete structures • Maybe best combined with other design elements Planted marsh Sand beach
Living Reefs combined with other elements • Increase habitat diversity Combination of multiple habitats has greater ecosystem services VIMS Teaching Marsh
Tidal marsh Mud flat Loose shell oyster reef Shallow water
Increase habitat diversity within projects
Loose shell & reef balls in the lee of gapped sills
ANY QUESTIONS ABOUT HYBRID LIVING SHORELINE PROJECTS?
UNIQUE CONCERNS FOR LIVING SHORELINE CONTRACTORS Note: This last section was not presented at the June 10 workshop for the sake of time. They are included here for information.
Constructability must be determined EARLY in planning process
B. Burton
J. Scalf
• Construction access from land or water? • Any marsh crossings required? May need to use mats • Machine size? • Excavator reach • Bobcat • Wheelbarrows for hand placement • Soft substrates – machines can get stuck
Construction equipment operators might need to work together…..
…..to avoid costly errors with liability & environmental harm
Common Contractor Concerns • Erosion & Sediment controls – Use silt fences & booms as required
• Stormwater runoff interruptions – Know where outfalls are
Common Contractor Concerns • Working with non-traditional clients & volunteers – Volunteer coordinators very useful
• Customer satisfaction & liability – Includes post-construction site restoration
Common Contractor Concerns • Living shoreline projects must be designed for site-specific conditions – No ‘cook book’ standards – Seek technical advice & support from LS partners
• Engineering ‘comfort level’ – Try not to ‘over-design’ just for assurance – Try to deal with uncertainty – Be flexible, adaptive
Living Shorelines Definitions & Descriptions
Summary • Increasing wave attenuation & stabilization using native habitats is the main objective Create gradual slopes Native plants & shellfish dominate
• Site-specific suitability for different actions must be determined • Contractors may need to work with unfamiliar clients & partners, there is a lot of help available • Include construction access & post-construction restoration in the planning process
Questions?
Contact Information
Karen Duhring [email protected] 804-684-7159
Living Shorelines Definitions & Descriptions
• Common Definitions • Project type examples with site-specific considerations – Non-structural or Bio-Based
– Hybrid
• Common Contractor Concerns
What’s the Difference? Habitat Restoration Wetland Mitigation Primary purpose is to create & replace lost natural habitat for its intrinsic value Human presence minimal if not absent
Living Shorelines Primary purpose is to solve a problem
Reduce erosion risk, site remediation, beneficial use of dredged material
Human presence normal
What are Living Shorelines for Erosion Protection? Alternatives for bulkheads & revetments Where erosion cannot be tolerated & some type of action is necessary Mimic or protect existing native habitats Riparian buffers + tidal marshes + sand beaches + Shellfish reefs + SAV?
Common Elements in Living Shorelines Definitions • Erosion risk reduction – unacceptable erosion risk is present and some type of shoreline management action is deemed necessary
• Wave attenuation – rough surfaces to reduce wave height and energy of approaching waves
• Habitat heterogeneity – Diverse habitats similar to natural shorelines in local area
• Habitat continuum – unimpeded migration of fish and wildlife along the shoreline and between aquatic and terrestrial habitats, plus the import and export of organic matter between habitats
• Habitat migration allowance – habitat features can shift in response to sea level rise, vertical sediment accretion is possible Source: Bilkovic, Mitchell, Mason & Duhring, 2015 in press
Living Shoreline Project Categories Non-Structural ‘Bio-Based’
Hybrid
Adequate protection provided with vegetative stabilization + gradual slopes
Engineered structures required to achieve desired level of protection
Suitable sites: Very Low - Low energy
Suitable sites: Low-moderate energy
Non-Structural Approaches Enhance Existing Marsh &/or Riparian Buffer
Grade Bank & Restore Riparian Buffer
J. Scalf
Planted Marshes & Fiber Logs
Beach Nourishment & Dune Creation
Planted Marshes – important considerations • Good summary of design criteria – Walter I. Priest, III 2006 Living Shoreline Summit Proceedings
• Tidal benchmarks are critical, local tide range & extreme tide levels (both low & high) • Patience & due diligence required – Wave attenuation provided by “well-established” marsh which takes at least 1 growing season ( 3-4 months) – More habitat benefits achieved after 5 years, especially benthic community due to lag time for organic matter accumulation & processing
Planted marsh must be sloped so it is completely exposed at low tide; plant failure may be caused by standing water
Low marsh
High marsh
Salt Bushes
S. alterniflora
S. patens
I. Frutescens &
B. halimifolia
Regular high tide line
Birdsong Wetland Norfolk, VA
Typical Grass Species Used for Salt Marsh Low Marsh
High Marsh
Salt grass Distichlis spicata
Saltmarsh cord grass Spartina alterniflora
Saltmeadow hay Spartina patens
More species possible for low salinity or fresh water, select those that remain above ground during winter e.g. Spartina cynosuroides, Juncus effusus
Switch grass Panicum virgatum
Salt Bushes planted at landward side of high marsh
Not as flood tolerant, use at upland edge
Groundsel Bush Baccharis halimifolia
Marsh Elder Iva frutescens
Wax myrtle / Bayberry Morella cerifera M. pennsylvanica
Nursery Stock
Cell Pack 72 or 96 = # cell packs per flat
4. Pack well to remove air pockets
2. Slow-release fertilizer in hole 1. Dig hole
3. Insert plant at least 4 inches deep Can’t plant too deep!
Planting Process New Gosport Wetland, Portsmouth
Plant Spacing & Growth Pattern
Closer spacing for more rapid cover Wider spacing to cover large area with limited budget
Marsh grasses will spread underground by rhizomes Eventually space between plants will fill in naturally
Planted rows not visible over time
If it’s done correctly….. Planting Day
4 Months Later
Successful establishment indicated by flowering grasses
Planted Freshwater Marsh
Photo Courtesy NC Coastal Federation
How wide should the marsh be? • The answer depends on the energy regime at project site & the erosion problem—the bigger the waves, the wider the marsh
• Adjacent development & navigation interests may limit marsh width • Allow for landward migration & expansion with connected riparian buffer zone
Embayed or “Pocket” Marsh Alternative design to fringe marsh Tidal connection
More complex planting zones Low marsh
Upland excavation areas High marsh
VIMS Teaching Marsh Gloucester Pt, VA
Grazing Exclusion Devices Single row of staked netting for narrow fringe
String network to cover wide fringe
Mute Swans & Canada Geese can pull new plants out of the ground, but not established well-rooted plants; exclusion device can be removed after 1 growing season
Fiber Logs & Mats The use of manufactured, bio-degradable fiber products to provide temporary support for planted tidal marshes and/or riparian buffer restoration May also be effective for trapping sediment
P. Menichino
P. Menichino
Fiber Logs – important considerations • Easily lifted out of place by the force of water – Most suitable sites are low flow velocity – Staking & anchoring essential if they are in the water – Full contact with ground should be maintained
• Temporary, biodegradable – May or may not need to be replaced
• Planting into logs has mixed results – Saturation is important for plants – Adjacent planted marsh usually grows into them
• Some reported fiber log project ‘failures’ due to unrealistic expectations or incorrect applications – Cannot stand alone, usually combined with another element
Fiber log project example - Before
Undercut trees
J. Scalf
Fiber logs & sand fill to match adjacent marsh Construction access from water
J. Scalf
Planted tidal marsh with goose exclusion fence
J. Scalf
Fiber logs decay over time leaving just the planted marsh
Beach Nourishment & Dune Restoration • Addition of sand to a beach to raise its elevation and increase its width • Reshaping and stabilizing with dune plants
Beach & Dune Vegetation
American beach grass Ammophila breviligulata Cool-season grass for northern Mid-Atlantic Winter planting
Bitter panicum Panicum amarum
Saltmeadow hay Spartina patens
Sea oats Uniola paniculata
ANY QUESTIONS ABOUT NON-STRUCTURAL LIVING SHORELINE PROJECTS?
Hybrid Approach Where wind-waves & boat wakes are too extreme for non-structural methods Strategically placed structures to: • contain sand fill & support vegetation growth • allow tidal ebb & flood • maintain connections between upland & wetland habitats
Hybrid Project Types Marsh Toe Revetment
Marsh Sill
Living Reef
Offshore Breakwater w/ Beach Nourishment
Marsh Toe Revetment • Low-profile placed along eroding marsh edge • Placed against marsh or offset • Sediment accretion may occur
Marsh with Sill A low-profile revetment backfilled with sand to create & support a tidal marsh that otherwise could not occur
Typical Marsh Sill Construction Sequence
1. Filter cloth placed
2. Sand fill & stone sill
3. Settling period – check grade & tides
4. Plant tidal marsh vegetation
Marsh sills are submerged during storm events During a severe storm, the wave height reaching the upland bank is reduced by the “roughness” of the sill and wide planted marsh
Same well-established marsh 3 yrs after planting the day after Hurricane Irene
Marsh with Sill
Important Considerations 1. Is a Planted Marsh feasible if no marsh is present? Full sun Sandy soil Shallow nearshore 2. Are intertidal and nearshore slopes shallow & gradual? Minimize fill needed to achieve target elevations
Marsh with Sill
Important Considerations 3. Will sediment support equipment & weight of stone + sand?
Highly suitable for sill Not as suitable
Marsh with Sill
Site-Specific Considerations 5. Is Submerged Aquatic Vegetation (SAV) habitat present? Look at previous 5 years VIMS SAV inventory for habitat potential
6. Will local navigation be affected? Submerged stone structure hazard potential Sediment trapping in channels
Design Criteria to Maintain Coastal Processes
• Crest height in relation to Mean High Water • Tidal gaps – windows – openings • Stone size & interstitial spaces
Tidal Openings
When should they be included? • Sill crest height > MHW • Sill length > 100 Ft ?? – No definitive standard – May need more or less
• Site-specific – Tidal ponds – Natural or created channels – Open ends – Recreation access
Tidal openings allow access for marine wildlife, but they also introduce wave energy into the planted marsh. Stable embayments eventually form
Tidal Openings
Design Challenge – too much energy • “Straight” tidal openings allow access for marine wildlife, but also introduce wave energy into the planted marsh. • Stable embayments eventually form • Shoaling may occur that blocks access & tides
Tidal Openings
Other Types
Weir Opening or Vented Sill
Straight gap with cobblestone
Gap covered with stone at lower elevation
Reduces sand deposits How is biological activity altered?
Tidal Openings
Other Types
Gapped offset sections at pocket marsh Taper ends toward wave energy
Living Reefs • Oysters & ribbed mussels being used • Colonizing on fiber logs & marsh sills
• Enhance or replace stone material • Increase habitat diversity
Living Reefs Important Considerations
1. Are there any natural reefs in vicinity to mimic? 2. What is the local tide range & extreme tide potential? Will the reef remain submerged or be exposed ? 3. Is the wave climate low enough for loose shell or is some type of containment needed? 4. Are there any navigation or public health concerns?
Living Reefs • Structure material substitute Loose or bagged shell Pre-cast concrete structures Other engineered wave attenuation devices
Loose Shell Good for habitat value Not usually effective for wave attenuation
Bagged Shell Similar structural integrity as stone sills, but easier to install Long-term reef evolution still under investigation
Plastic mesh having incidental impacts, e.g. entrapment, microplastic pollution? Are wire gabions better?
Reef Balls Pre-cast concrete with embedded oyster shell Pre-soaked for spat settlement Requires crane to lift on and off boats
Oyster Castles Smaller, interlocking units with embedded oyster shell
‘Ready Reef’ just one of several new products on market
Source: http://readyreef.com/index.html
How Well Do Living Reefs Work for Erosion Protection? • Loose shell - usually not much wave attenuation • Bagged shell - more structural integrity for wave reduction, unknown oyster habitat value over time • Pre-cast concrete structures • Maybe best combined with other design elements Planted marsh Sand beach
Living Reefs combined with other elements • Increase habitat diversity Combination of multiple habitats has greater ecosystem services VIMS Teaching Marsh
Tidal marsh Mud flat Loose shell oyster reef Shallow water
Increase habitat diversity within projects
Loose shell & reef balls in the lee of gapped sills
ANY QUESTIONS ABOUT HYBRID LIVING SHORELINE PROJECTS?
UNIQUE CONCERNS FOR LIVING SHORELINE CONTRACTORS Note: This last section was not presented at the June 10 workshop for the sake of time. They are included here for information.
Constructability must be determined EARLY in planning process
B. Burton
J. Scalf
• Construction access from land or water? • Any marsh crossings required? May need to use mats • Machine size? • Excavator reach • Bobcat • Wheelbarrows for hand placement • Soft substrates – machines can get stuck
Construction equipment operators might need to work together…..
…..to avoid costly errors with liability & environmental harm
Common Contractor Concerns • Erosion & Sediment controls – Use silt fences & booms as required
• Stormwater runoff interruptions – Know where outfalls are
Common Contractor Concerns • Working with non-traditional clients & volunteers – Volunteer coordinators very useful
• Customer satisfaction & liability – Includes post-construction site restoration
Common Contractor Concerns • Living shoreline projects must be designed for site-specific conditions – No ‘cook book’ standards – Seek technical advice & support from LS partners
• Engineering ‘comfort level’ – Try not to ‘over-design’ just for assurance – Try to deal with uncertainty – Be flexible, adaptive
Living Shorelines Definitions & Descriptions
Summary • Increasing wave attenuation & stabilization using native habitats is the main objective Create gradual slopes Native plants & shellfish dominate
• Site-specific suitability for different actions must be determined • Contractors may need to work with unfamiliar clients & partners, there is a lot of help available • Include construction access & post-construction restoration in the planning process
Questions?
Contact Information
Karen Duhring [email protected] 804-684-7159
