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Ecological SystemsMaintaining and Enhancing Natural Features and Minimizing Adverse Impacts of Infrastructure Projects
Module 6Restoring Ecological
Function
Learning Outcomes
• Understand the value of ecological restoration
• Learn to focus on restoring ecological function rather than appearance
• Become familiar with techniques employed in a variety of restoration contexts
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1. Know where you are
2. Avoid sensitive areas
3. Minimize infrastructure impacts
4. Mitigate unavoidable losses
5. Improve ecological function where possible
Ecologically-Sensitive Design Process
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Mitigation Banking
• When damage to a wetland, stream, or aquatic resource is unavoidable, impacts may be offset by restoring or preserving an equivalent resource off-site
• Mitigation Banks are areas set aside to create large-scale, intact ecosystems6-5
EPA
• Wetlands in mitigation banks are restored prior to the destruction of existing wetlands on-site, which allows verification of equivalent function
• Larger intact ecosystems are more stable than smaller, fragmented systems, and can support larger wildlife
Advantages of Mitigation Banking
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• Mitigation banking is well-established only for wetlands; other ecosystems, especially upland ecosystems are not included
• Some small wetlands, such as vernal pools, are critically important for amphibian breeding and migratory birds
Caveats
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1. Know where you are
2. Avoid sensitive areas
3. Minimize infrastructure impacts
4. Mitigate unavoidable losses
5. Improve ecological function where possible
Ecologically-Sensitive Design Process
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• Consult with experts
• Remove barriers to ecological function
• Establish key species to jump-start self-organization
• Provide connectivity to existing habitat
• Be patient!
Basic Principles of Ecological Restoration
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• Ecological restoration is a discipline in its own right
• A growing number of specialists around the country have expertise and experience with restoration projects
• Including experts on your team can help to ensure success and avoid unintended consequences
Consult with Experts
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• Energetic barriers• Altered hydrology
• Material barriers• Excessive nutrient inputs• Altered sediment deposition (too much or too little)• Contamination
• Species-specific barriers• Noise, light pollution, habitat requirements, connectivity
Remove Barriers to Ecological Function
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• Usually, this involves establishing an appropriate plant community
• The plant community provides a backbone for the ecosystem, allowing colonization by animals
Install Key Species
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• This promotes colonization by species adapted to site conditions as they disperse from adjacent habitats
Provide Connectivity to Existing Habitat
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• It is impossible to physically reconstruct a functioning ecosystem, as you would build a car
• Creating appropriate conditions, and providing as much biodiversity as possible will allow the ecosystem to self-organize
Using Succession and Self-Organization
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• Some ecological processes take place over very long time periods (e.g. topsoil development, peat bog formation)
• It may or may not be possible to hurry these processes along to meet human timetables
• Once energy and material flows are restored, ecological processes will take over, and will eventually establish a functioning, complex, ecosystem
Patience
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If you build it, they will come(provided they can get there)
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• Stream geomorphology (the size and shape of the stream bed and banks) is a direct response to the size of storm flows
Restoring Hydrology in Streams
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Morphology of a Stable Stream
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NEH 653
Morphological Changes Due to Urbanization
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Northern Virginia Soil and Water Conservation District
Disconnection from floodplain
Incised Stream
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• If in-stream structure and meanders are rebuilt without addressing underlying hydrologic issues, there is a strong likelihood that restoration efforts will fail
• Restored stream morphology must match the current energy signature
Match Morphology to Hydrology
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BEST OPTION: restore watershed hydrology, then rebuild in-stream physical features
Unfortunately, watershed hydrology is the cumulative result of actions on multiple sites, so this is not generally possible in the context of a single infrastructure project
Options to Restore Hydrology
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ALTERNATE STRATEGY:
1. If possible, use floodplain to detain and infiltrate stormwater runoff
2. Install energy dissipating structures to reduce erosive power of storm flows
Restoring Stream Hydrology
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Energy Dissipating Structures
Rock weirs
• Prevent scouring
• Dissipate energy
• Direct flows away from banks
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Northern Virginia Soil and Water Conservation District
• Where flow velocities permit, banks can be stabilized with vegetation
• Biodegradable reinforcements can be used while vegetation becomes established
• In highly erosive conditions, stone may be necessary
Bank Stabilization
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Restoring In-stream Habitat
• Tree trunks with root wads can be used to slow and direct flows and provide habitat
• Trunks must be firmly anchored in stabilized banks
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BLM
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• OPTIONS:
• Reduce fertilizer application in watershed
• Capture and treat runoff close to the source
• Capture and treat runoff at the point where it is discharged to the water body (end-of-pipe)
Reducing Nutrient Inputs
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• Wastewater Treatment: Tertiary treatment to remove nitrogen and phosphorus
• Agriculture: Use vegetated buffers between fields and surface waters
• Stormwater: Remove nutrients using Low Impact Development BMPs such as bioretention
Removing Nutrients Close to the Source
End-of-pipe Options
• Regenerative stormwater conveyance (RSC)
• Constructed wetlands
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DDOE
EPA
Install erosion control structures, either in-stream or within watershed
Reducing Sedimentation
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FWS
Live fascines and coir blanket
Restoring Wetland Hydrology
• Wetland hydrology is all about flooding depth and frequency
• These two parameters must be correct for a wetland restoration project to be successful
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FWS
The Importance of Wetland Hydrology
• Wetland plants are primarily responsible for maintaining wetland structure and function
• These plants have very specific hydrologic requirements6-32
NRCS
• Remove dams and levees where possible
• Install energy dissipating structures to reduce erosion and promote settling
• Install sediment diversion structures
• Trucking in sediment is a short-term fix, but may fail in the long run if erosive forces and subsidence are not balanced by ongoing deposition
Restoring Sedimentation
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Sediment Diversion
6-34 USACE
• Lake and pond deterioration is usually a result of excess nutrient loading
• In addition to methods previously discussed, nutrients can be removed using • Algal turf scrubbers, and• Floating islands.
Lake and Pond Restoration
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Algal Turf Scrubber™ (ATS)
• Water is pumped down a chute seeded with filamentous algae
• Algae grows, taking up excess nutrients
• Algae is harvested periodically, preventing eutrophication related to die-off6-36
University of Maryland – NEED PERMISSION
Floating Islands
• Floating treatment wetlands
• Wetland plants are suspended on floating mats
• Remove excess nutrients from the water column
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Floating Islands InternationalNEED PERMISSION
• 3 points: Enhance one ecosystem function
• 6 points: Enhance two ecosystem functions
• 9 points: Enhance three ecosystem functions
• 15 points: Enhance four ecosystem functions
• 19 points: Restore full ecosystem function
NW3.4 Maintain Wetland and Surface Water Functions
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NW3.4 Maintain Wetland and Surface Water Functions (cont’d)
• Enhance hydrologic connections• Reconnect rivers to
their floodplains• Restore wetland
hydrology
• Enhance water quality• Disconnect surface
water discharges• Use BMPs to infiltrate
runoff
• Enhance habitat• Restore riffles, pools,
shoreline• Plant appropriate species
• Enhance sediment transport• Remove dams and other
impediments
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• Areas connected to intact habitat will tend to regenerate following disturbance
• Natural successional processes may take decades
• Invasive and exotic species may need to be controlled
Restoring Disturbed Lands
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• Controlled burns can help to restore fire-dependent ecosystems
• Manual removal of underbrush may be an acceptable substitute where burning is infeasible, but some functions of fire are difficult to replicate• Some seeds require high temperatures in order to
trigger germination
Fire-Dependent Ecosystems
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• Soils are an essential component of terrestrial ecosystems
• Soil restoration involves:• Removal of contaminants• Reversing soil compaction• Increasing soil organic matter• Restoring soil ecological function
Soil Restoration
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• 8 points: Restore all soils disturbed during construction in the site’s vegetated area
• 10 points: Restore all soils disturbed as a result of previous development
NW3.3 Restore Disturbed Soils
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• Prior to development, topsoil should be removed and stockpiled
• After development, topsoil is replaced on unpaved disturbed areas, and quickly vegetated to minimize erosion
• Restoring soils disturbed as a result of previous development may require amending and aerating soils
NW3.3 Restore Disturbed Soils (cont’d)
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OPTIONS:
• Capping
• Physical removal (dredging, soil removal)
• Bioremediation
• Phytoremediation
Repairing Contamination
Bioremediation
• Use of bacteria to break down or transform contaminants
• Involves creation of environmental conditions conducive to bacterial function
• May require bioaugmentation with specialized bacteria or catalysts
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Lawrence Berkeley National Laboratory
Phytoremediation
• Use of plants to bind or break down contaminants
• Hyperaccumulators translocate metals from soil into plant tissues, which can be harvested
• Hybrid poplars detoxify organic solvents
6-47NIH
Reducing Light Pollution
• Limit nighttime lighting to only what is necessary for safety
• Use lights that cast light downward rather than upward
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Reducing Noise Pollution
• Plant trees to dampen noise
• Construct noise barriers around highways
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FHWA
What issues might you encounter if you attempted to restore an abandoned farm to its predevelopment condition?
Discussion Questions
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How is it possible to restore streams, lakes, and wetlands if you have no control over what is happening in the watershed?
Discussion Questions
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• Mitigate unavoidable ecosystem losses
• Restore ecological function wherever possible• Consult with experts• Remove barriers to ecological function• Establish key species to jump-start self-organization• Provide connectivity to existing habitat• Be patient!
Review
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• Society of Wetland Scientists. SWS Position Paper: Wetland Mitigation Banking. http://www.sws.org/wetland_concerns/banking.mgi
• Society for Ecological Restoration, 2004. SER Primer on Ecological Restoration. http://www.ser.org/pdf/primer3.pdf
• NRCS Stream Restoration Portal. http://go.usa.gov/Ko0
• NRCS, 1992. Engineering Field Handbook, Chapter 18: Soil Bioengineering for Upland Slope Protection and Erosion Reduction ftp://ftp-nhq.sc.egov.usda.gov/NHQ/pub/outgoing/jbernard/CED-Directives/efh/EFH-Ch18.pdf
• USEPA. Principles for the Ecological Restoration of Aquatic Resources. http://www.epa.gov/owow/restore/principles.html
Recommended Resources
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