Living Shoreline Concept Designs: What needs to be considered?

Karen Duhring

Virginia Institute of Marine Science College of William & Mary

March 17, 2016

Delaware Living Shoreline Training Workshop Lewes, Delaware

Acknowledgments Thank You for contributions to this presentation

DNREC & CIB Staff

Jon Miller et al., Stevens Institute

Partnership for the Delaware Estuary

Joe Reiger, Elizabeth River Project, Virginia

Jim Cahoon, Bay Environmental, Virginia

Molly Mitchell, VIMS

Scott Hardaway, VIMS

Walter Priest, III VIMS-NOAA-Wetland Design

Bobbie Burton, Longwood University

Pat Menichino, James City County Virginia

Bhaskar Subramanian, Maryland DNR

David Burke, Burke Environmental Associates

Rob Schnabel, Chesapeake Bay Foundation

Living Shoreline Concept Designs

• Review of basic considerations

• Explore design parameters

– Why they are important

– How to get site-specific information

• Project types & lessons learned

• Putting the pieces together for concept designs

Shoreline Management Decision Process Review

1. Risk assessment & decision to act

Erosion history & forecast not tolerable?

Can upland land use adjustments solve problem?

If not, TAKE SHORELINE ACTION

2. Basic location & land use suitability considerations

3. Can adverse environmental harm be avoided?

Stabilization Alternatives Simplistic Order of Preference

from least to most environmental impact

Minor erosion with low risk

Minor erosion with some risk

Major erosion with some risk, natural buffers present or feasible to create

Major erosion with high risk, natural buffers absent or not feasible

Maintain / enhance vegetation

Non-Structural Living Shoreline

Hybrid Living Shoreline

Traditional Structures

e.g. revetment, offshore breakwaters

Non-Structural

Planted Marshes

Fiber Logs & Mats

Sand Fill

Slope Changes

Beach Nourishment

Hybrid

Rock Sills

Pre-Fabricated Concrete

Biogenic Reefs

Living Shoreline Project Categories

Is there a simple formula to know which approach to use?

Parameters Typically Used in the Design of Living Shorelines Source: Living Shorelines Engineering Guidelines 2015

System Parameters Erosion History

Tidal Range Sea Level Rise

Ecological Parameters Water Quality

Soil Type Sunlight Exposure

Hydrodynamic Parameters Wind Waves Boat Wakes

Currents Ice

Storm Surge

Terrestrial Parameters Upland Slope

Shoreline Slope Width

Nearshore Slope Offshore Depth

Soil Bearing Capacity Forces acting on the shoreline

short term Affect how shoreline

responds to forces

Large scale - long term Local scale for natural elements

Parameters Typically Used in the Design of Living Shorelines Source: Living Shorelines Engineering Guidelines 2015

Additional Parameters Permits/Regulatory

End Effects Constructability

Native/Invasive Species Debris Impact

Project Monitoring

Property Owner Interest

Multiple parameters are not equally weighted Just one alone might make a difference Some may be more critical than others

Site Evaluation Parameters

Desktop - Map Parameters

• Existing information available from maps or Internet resources

• Not readily visible or measurable at ground level

• Data availability may be limited for some parameters

Site Visit Parameters

• Not easily captured by remote sensing

• Site-specific characteristics

• Local setting

• Local knowledge

SYSTEM & HYDRODYNAMIC PARAMETERS

Erosion History

• Have shoreline erosion trends been measured for Delaware?

• If not, look for physical evidence & local knowledge – Slumped marsh edges, fallen trees, decreasing width of

land between shoreline & permanent features, etc.

– Property owner experience & documentation

– Third party observations

• Try to determine if erosion has been chronic or episodic, i.e. slow & gradual or major events

Important for determining success criteria

Local Tide Range & Extreme Tide Levels

• NOAA Tides and Currents – Benchmark Sheets

• Variable by region

~ 5.5 ft. at Delaware City ~ 4.1 ft. at Lewes

• Mean tide range and spring tide range

• May want to supplement with real time measurements made over 30 days

Important for any ‘living’ component e.g. planting zones, living reef

Also for submerged & low-crested hybrid structures

Tidal Datums for Lewes, DE Tidal Epoch 1983 - 2001

Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS: HIGHEST OBSERVED WATER LEVEL (03/06/1962) = 2.810 MEAN HIGHER HIGH WATER MHHW = 1.418 MEAN HIGH WATER MHW = 1.290 North American Vertical Datum NAVD88 = 0.801 MEAN SEA LEVEL MSL = 0.680 MEAN TIDE LEVEL MTL = 0.669 MEAN LOW WATER MLW = 0.048 MEAN LOWER LOW WATER MLLW = 0.000 LOWEST OBSERVED WATER LEVEL (01/10/1978) = -1.284

1.24 meters (4.07 ft.)

Supplement with local knowledge of storm events & other extreme tides

Sea Level Rise

• Living elements sensitive to rising sea level

• Uncertainty for appropriate LS designs

• Consider short term need vs. long term project lifespan

Stay Tuned!

Hours of inundation > MHHW have increased greatly

since 1990

Living shoreline projects should incorporate inundation areas

where possible

Traditional tide chart applications not always accurate

e.g. timing construction with low tide

Sea Level Rise & Inundation Frequency

Source: NOAA, M. Mitchell, VIMS 2015

Wind Waves

• Frequently encountered condition based on average & longest fetch

• Maximum expected or extreme wave may not matter as much if project will be submerged

• Refer to Living Shoreline Design Guidelines & US Army Corps of Engineers estimating methods for shallow water

• In situ wave data collection using simple low cost approaches

– Recording water level oscillations on a graduated staff

– Plaster cast approach

Longest Fetch black lines

Average Fetch

measure 5 green arrow vectors and

take an average

Measure Fetch Distances

Boat Wakes

• May be significant source of wave energy in sheltered waterways

• Large slow moving barges vs. smaller faster boats have different wakes

• No good archived data on wakes

• Look for presence or absence of docks, marinas, marked channels

• Simple observation techniques have been developed for the Hudson River

• Local knowledge and judgment calls are required to weigh this parameter

Currents

• Important consideration @ tidal inlets, meandering riverbanks, freshwater inflows

• Currents can uproot vegetation, dislodge fiber logs, scour the bank, transport debris & ice

• Little data available

• Measuring currents in sheltered estuaries tricky

Ice

• Vegetation & structure uplift

• Floating ice like debris with impact forces

• Rely on local records, additional monitoring of living shorelines needed to aid design factors

Storm Surge • Less significant for living shorelines compared to

bulkheads & revetments

• Important for riparian buffer vegetation zones

• FEMA flood maps provide estimates

• Local knowledge from storm events (winter & summer)

e.g. ‘How high did the water get here in Sandy?’

Living shoreline project submerged during Nor’easter

TERRESTRIAL PARAMETERS

Shore Morphology

Pocket or embayed shorelines tend to cause waves to diverge and spread wave energy out Straight and headland shorelines receive the full impact of the wave climate Irregular shorelines tend to break up wave crests

Nearshore Slope & Offshore Depth distance to 2m contour

2m (6 ft.) contour lines

Broad shallow nearshore has different wave

attenuation than narrow deep water

with same fetch

Bathymetric maps are usually too coarse for design purpose May need to supplement with bathymetric survey

Upland & Shoreline-Intertidal Slope

Graphic courtesy Burke Environmental Associates

Upland Slope Level to

Spring Tide

Shoreline Slope Spring Tide to

MLLW

Upland & Shoreline Slopes

• Vegetation grows best on gradual slopes

• Wave run-up with less erosion & scarps

• Vertical banks & existing bulkheads tricky due to vertical lift, but not impossible to work with

• Wading surveys at low tide to determine existing slope & estimate desired slope changes

• Developed, urban estuaries may have distinct vertical elevation changes ‘vertical lift’ – Possible to overcome for ‘greening’ existing bulkheads &

revetment shorelines

Width Horizontal space between upland & water’s edge

What to do if there is not enough space with natural slopes?

1. Landward design where possible gradual slopes & vegetation zones landward from MLW, including bank grading & upland-wetland integration

2. Channelward design may need to overcome low elevations, more frequent wave energy, navigation conflicts, submerged lands regulatory issues

• Design width for new tidal marshes depends on the energy

regime at project site, the erosion problem & available space – Protective fringe marshes with stable upland banks generally are 10-20

ft. wide from marsh edge to base of bank in Chesapeake Bay region

• Include both low marsh & high marsh zones

Soil Bearing Capacity

Important consideration for hybrid structures & sand fill

How much settling will occur?

Start with simple 200-lb man test walking the project site

Geotechnical investigations may be advisable

Firm vs. soft

ECOLOGICAL PARAMETERS

Water Quality • Dissolved oxygen

• Water temperature

• Salinity

• Turbidity

• Site-specific conditions determine plant choices for upland &

wetland areas – especially salinity (freshwater or brackish)

• More local WQ data now available

• These factors might explain why living components fail to thrive

• Engineers unfamiliar with these parameters encouraged to seek assistance from water quality monitors & ecologists for LS habitat choices & designs

Soil Type • Important for vegetation growth & strong root system Essential

for erosion resistance

• Most living shoreline marshes are planted in coarse sand fill or accretion material settled from water column

• Always take soil borings or dig test pits where fill is going to be removed, be ready for surprises & be flexible during excavation even with test results in hand – Legacy contamination, solid waste, etc.

Shoreline Orientation – Sunlight Exposure

Good lighting More shade

South North

• Important for upland bank erosion projects with shoreline trees not as important for wide open marsh edges except for piers

• South & east vs. north & west is rule of thumb, not always a determining factor

ADDITIONAL CONSIDERATIONS

Permits – Regulatory

End Effects

Constructability Native/Invasive Species Debris Impact

Project Monitoring

End Effects

1. From adjacent engineered structures on living shoreline site

2. From proposed living shoreline project on adjacent shorelines

• Reflected wave energy from hybrid structures • Sediment capture & interruption

Transitions into adjacent shorelines

may need to be considered

Constructability

J. Scalf B. Burton

• Construction access from land or water

• Hand placement &/or machine types & sizes

• Wetland crossings & weight distribution

• Project designers & contractors must communicate early in design process

Minimize & restore construction access impacts

• For upland access, minimize vegetation removal & protect large trees

• Limit number of access paths to shoreline

• Use construction mats to distribute weight of machinery crossing through forest buffers and tidal marshes

• Plan for access restoration as needed (e.g. re-seeding)

Try to avoid harming wetlands like this

Project Monitoring & Maintenance

• Needs to be included with design

– Document baseline conditions, problem being solved to determine success, access for monitoring & maintenance

• Does not have to be complicated or scientifically intense

• Troubleshooting not uncommon based on monitoring

• Data from multiple projects helps inform entire community of practice

– Adaptive Management Feedback

Different Monitoring Interests to Answer Specific Questions

• Industry performance, economics, satisfaction

• Regulatory habitat trade-offs, compliance, policy effectiveness

• Other local government TMDL & FEMA credits

• Academic ecosystem & protection effects

• NGO & Citizen Scientists demo sites, volunteer opportunities

PROJECT TYPES & LESSONS LEARNED

PROJECT TYPE DETAILS

Bank Grading & Riparian Buffer Planting Beach Nourishment & Dune Planting Planted Tidal Marshes Fiber Logs & Mats Marsh Sills Living Reefs

Bank Grading Potential sites include:

• High, eroding banks without trees or development near shoreline

• Failing or failed bulkheads with lawns

• Mean high water near bank toe, narrow intertidal zone

• Very effective yet not very popular

Riparian Buffer Planting

• Convert lawns to more effective storm surge buffers

• Plant or seed vegetation that intercepts runoff and stabilizes bank face

• Native shoreline plants are best suited to local soil, salt and wind conditions; Non-native plants should be adapted to similar conditions

• Flood tolerant species may need to be included

• Planting times for woody trees & shrubs may be different than perennials & ground covers

• Temporary irrigation may be needed during dry spells until plants are established

Beach Nourishment & Dune Planting • Addition of sand to a beach to

raise its elevation and increase its width

• Reshaping and stabilizing with dune plants

• Mimic local beaches & dunes

– Planting zones based on wind removal & deposition areas

• Avoid creating sand beaches where they do not occur naturally

– For recreational purposes

Beach & Dune Vegetation

American beach grass

Ammophila breviligulata

Cool-season grass for

northern Mid-Atlantic

Winter planting

Saltmeadow hay

Spartina patens

Bitter panicum

Panicum amarum

Seek advice from USDA Cape May Plant Materials Center

Planting Tidal Marshes at Upland Banks

• Fringing marsh most common (parallel to shore)

• Plant selection & zones based on local tide range, salinity, look for biological benchmarks

• Overhanging trees may cast shade, but avoid removing healthy shoreline trees just to increase sunlight for new marsh

– Prune overhanging branches

– Consult with arborist on tree life expectancy & health

Biological Benchmarks – Target Elevations

• Elevation ranges of natural marshes & riparian buffers in vicinity

Regular Low Tides

Regular High Tides High Marsh

Low Marsh

Upland

Embayed or “Pocket” Marsh Upland excavation areas where elevation can be lowered

More complex planting zones

Mimic tidal ponds

Low marsh

High marsh

VIMS Teaching Marsh Gloucester Pt, VA

Tidal connection

Salt Bushes

I. Frutescens &

B. halimifolia

Birdsong Wetland Norfolk, VA

Regular

high tide

line

Planted marsh must be sloped so it is completely exposed at low tide; plant failure may be caused by standing water

Low marsh

S. alterniflora

High marsh

S. patens

Planting Tidal Marshes at Eroding Marsh Edges

• Fill in between more erosion resistant points

• Wave climate information very important

• In most cases, at least fiber logs are necessary to help raise elevation & provide toe protection

• Low crested stone sills if bottom type & water depth are suitable

Typical Grass Species Used for Salt Marsh

Saltmarsh cord grass Spartina alterniflora

Saltmeadow hay Spartina patens

Switch grass Panicum virgatum

Salt grass Distichlis spicata

Low Marsh High Marsh

Groundsel Bush Baccharis halimifolia

Marsh Elder Iva frutescens

Salt Marsh Bushes planted at landward side of high marsh

Bayberry M. pennsylvanica

Not as flood tolerant, use at

upland transition

Planted Freshwater Marsh

• Many more plant species possible in freshwater areas

• Mimic natural marshes in area

• Try to include plants that stay above ground during winter

– Or design for winter conditions with no aboveground stems & leaves for wave attenuation

– Backshore protection

DNREC

Blackbird Creek Preserve

Wetland Plant Sources

• Wild harvest from donor marshes nearby that can recover from harvest – for small projects

– Hard to dig out plants from natural marshes

– Eroded marsh edge clumps can be salvaged

• Nursery stock has greatest success

– Plants typically grown in freshwater, must be brought up to site salinity by grower before delivery

Planting Process

2. Slow-release fertilizer in hole 3. Insert

plant at least 4 inches

deep

Can’t plant too deep!

1. Dig hole

New Gosport Wetland, Portsmouth

4. Pack well to remove air

pockets

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

If it’s done correctly…..

Spring Planting Day End of the Summer

Successful establishment indicated by flowering grasses

Grazing Exclusion Devices

Mute Swans & Canada Geese can pull new plants out of the ground, but not established

well-rooted plants

Exclusion devices typically removed after 1st

growing season

J. Scalf

Planted Marsh TLC During 1st Growing Season

• Regular inspections

• Monitor ebb & flood tides

• Look for & re-plant washed out plugs

– Pack in deep

– Keep grazers out Washed out plant plugs can be collected & re-planted

Main Reasons Planted Marsh Does Not ‘Take’ • Planted too low - below mid-tide elevation or in

wrong zones

• Washed out plugs

• Incomplete drainage & ponding at low tide

• Rapid sediment accretion

Other Reasons • Flow stresses – bottlenecks, runoff, waves

• Foot traffic & recreational uses

• Soil contamination

• Undetermined

Need monitoring & analysis of results

Don’t re-plant until cause of failure determined

Planted Marsh Maintenance – After Establishment

• Remove excessive tidal debris & trash periodically as needed

• Prune overhanging branches if shading leads to reduced cover

• Remove nuisance, invasive species that limit project success

• Inspect & document storm effects, storm tide levels

• Do not mow, install landscape design features to control adjacent mowing, e.g. split rail, timbers

• Avoid using lawn chemicals nearby

Coir 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

Evolution of Practices Fiber Logs

No elevation or slope changes Sand fill to raise planted marsh elevation Stacking rows of logs

Simple staking below MHW

More aggressive staking Higher elevation placement

J. Rigger P. Menichino

Using both mats & logs

Monitoring & Maintenance

Fiber Logs

• Inspect frequently

• Pound loose stakes back into ground ASAP

• Add more logs or blankets to repair sand ‘leaks’

Fiber Logs – Lessons Learned

• Staking & anchoring essential if they are in the water

• Full contact with ground should be maintained

– Install logs end-to-end, tying them tightly together & reinforcing the break

– Place stakes in X across top of log

– Use cotton based twine with breaking strength >800 lbs with every turn around the stake knotted

• Logs should not be tucked against vertical erosion scarps where waves are abruptly reflected

Fiber Logs – Lessons Learned (cont.)

• Premium logs are denser for higher energy sites

• The faster sediments fill in, the less likely installation will fail

– Include sand backfill if the local sediment supply is low or to increase likelihood for successful marsh establishment

Ecological Parameter – Turbidity may indicate local sediment supply

So does evidence of accretion against logs, beaches, sand overwash, sediment trapped at groins or jetties

Marsh with Sill

A low-profile revetment backfilled with sand to create & support a tidal marsh

where wave climate too extreme for fiber logs

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

Evolution of Practices

Wide straight gaps Erosion & loss of marsh

Narrow & offset gaps or few gaps at all for engineering certainty – not always good practice

Marsh toe revetments at existing marsh edges & accretion

Marsh sills with sand fill + planted marshes

Potentially Negative Effects of Marsh Sills

• Covering shallow water benthic fauna

• Hydrodynamic changes - altering tidal exchange,

wave height and wave direction

• Altering sediment transport along shoreline

• Altering habitat use along marsh edge

• Construction access & maintenance impacts

– Temporary road fill, compaction

Design Criteria to Maintain Coastal Processes & Do No Harm

• Crest height in relation to Mean High Water

• Tidal gaps – windows – openings

• Stone size & interstitial spaces

• Re-locate living resources in footprint

– e.g. horseshoe crabs, oysters

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

– To allow for recreation access

More monitoring needed

Straight Tidal Openings Design Challenge – too much energy

• “Straight” tidal openings allow access for marine wildlife, but also introduce wave energy into the planted marsh

• Shoaling may occur just inside gaps that blocks access & tides

• Stable embayments eventually form & can be included in design

Source: Maryland Department of the Environment

to address erosion inside straight gaps

Offset Tidal Openings

Gapped offset sections at pocket marsh Taper ends toward wave energy

Source: Maryland Department of the Environment

Weir Opening or Vented Sill

Gap covered with stone at lower elevation

Sediment deposition evident

with some marsh dieback

Narrow or “Pinched” Tidal Opening

Narrow & curved

Reduces sand deposits

Pinches flow & access

Marsh Sill Troubleshooting

• Not enough tidal drainage leads to marsh dieoff – Add more openings

– Check marsh elevation & slope, add sand & re-grade

• Too much tidal exchange at openings leads to marsh or bank erosion – Reduce width or add inner structure

• Settling below target height in soft sediments – Add more stone to raise height

Tightly packed stone in gabions restricts water movement through sill Algae bloom in warmer, stagnant area indicates stressful conditions for fish & crabs

Potential Stone Sill Alternatives

• Mid-tide bulkheads – Narrow waterways

– Deep nearshore depths

– Not well studied, may or may not have same adverse effects as traditional bulkheads

• Bio-genic Reefs

Evolution of Practices Stone for sill material Oyster Reef Alternatives

Proprietary Concrete Products

Oyster Castles Reef Balls Ready Reef

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?

Loose Shell Good for habitat value

Not usually effective for wave attenuation

Bagged Shell

Incidental impacts of plastic mesh? e.g. entrapment, microplastic pollution Are biodegradable products available?

Similar structural integrity as stone sills, but easier to install

Long-term reef evolution still under investigation

Desirable 3-D growth splitting bag open

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

Living Reef Combined with Other Elements to increase habitat diversity & troubleshoot erosion problems

Loose shell & reef balls at wide sill gap

PUTTING THE PIECES TOGETHER (VERY BRIEFLY)

Planted Marsh Materials

• Low marsh & high marsh plants

– Nursery stock or salvaged plants

– Quantity based on desired spacing

• Dibble bars or power augers to drill holes

• Slow release fertilizer

• Buckets to carry plants & fertilizer to shoreline

• Grazing exclusion fencing, stakes, &/or strings

Fiber Log Materials

• 12”x 12” 16”x12” 20”x12” sizes available

• Wood stakes 7-20 per log depending on site energy

• Cotton based twine with breaking strength >800 lbs.

• Mallets

• Possibly sand fill from upland source

Marsh Sill Materials

• Filter cloth

• Quarry stone sized for wave climate

• Sand fill from upland source

• Material transport equipment

• Material placement equipment

Living Reef Materials

• Oyster shell or reef products

• Material transport equipment

Concept Design

1. Describe the location & the problem

2. Project goals – Establish success criteria, how will you know if the project ‘works’

3. Lay out existing site conditions

4. Determine project type & possible elements

5. Don’t underestimate site prep & demolition costs

6. Approximate structure sizes & locations

7. Depict planting zones & plant species

8. Show jurisdictional boundaries & tide range

9. Prepare plan view & profile (cross-section)

10. Talk to regulatory officials & other advisors

Lewes Ballpark Site Conceptual Plan with location & arrangement of

elements

Source: Partnership for the Delaware Estuary

Lewes Ballpark Site Conceptual Plan - Profile

With Existing & Proposed Slope relationship of different elements

Source: Partnership for the Delaware Estuary

Living Shoreline Professional Service Opportunities

Design & Construction

• Scouting out suitable sites

• Site evaluations & alternatives analysis

• Concept drawings

• Permit applications & coordination

• Construction management

– Sub-contractors for heavy lifting

– Horticulture industry partners (nurseries & installers)

• Post-construction as-built surveys

– To confirm design standards, permit compliance

Living Shoreline Professional Service Opportunities

Long-Term

• Routine inspection & maintenance contracts

– Provide assurance, document performance

• Debris removal

• Planted area enhancements – gardening, pruning

• Invasive species management

• Storm damage assessment & recovery

Living Shoreline Concept Designs

Summary

• Engineers & ecologists can work together to design-build-monitor-maintain living shoreline projects

• Take advantage of lessons learned from previous work – read reports & stay engaged with community of practice

• Good references & data are available to determine site-specific parameters – some parameters still uncertain

• Include monitoring, maintenance, site prep, demolition, construction access & post-construction restoration in the concept design

Thanks for your interest

in Living Shorelines!

Contact Information

Karen Duhring karend@vims.edu 804-684-7159