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Classifying wetlands and assessing their functions:. Using the NC Wetlands Assessment Method (NCWAM) to analyze wetland mitigation sites in the coastal plain region. Emily R. Burton Environmental Studies Graduate Student University of North Carolina, Wilmington May 5, 2008. North Carolina.

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classifying wetlands and assessing their functions

Classifying wetlands and assessing their functions:

Using the NC Wetlands Assessment Method (NCWAM) to analyze wetland mitigation sites in the coastal plain region.

Emily R. Burton

Environmental Studies Graduate Student

University of North Carolina, Wilmington

May 5, 2008

north carolina
North Carolina


Wetland Assessment Method

geography of nc coastal plain
Geography of NC Coastal Plain
  • Inner and outer coastal plain


  • Broad interstream divides
  • Gentle-sloping plains
  • Mineral-based, poorly drained


  • Cape Fear, White Oak, Neuse,

Roanoke, Tar-Pamlico, and

Chowan River Basins

land use and wetland loss
Land Use and Wetland Loss
  • Once contained approximately 95% of the state’s 6 million acres of wetlands
  • About 51% of the original wetlands in North Carolina had been lost or altered in some way
  • Between 1950 – 1980, approx. 42.2% of this loss was caused by agricultural activities
converting wetlands to agriculture
Converting Wetlands to Agriculture
  • Removal of all vegetation and debris
  • Cutting drainage ditches 24-48” deep
  • Creating field crowns
prior converted pc cropland
Prior Converted (PC) Cropland
  • Compaction of soils creates a plow-pan
  • NRCS declared PC as those lands that converted wetlands prior to December 23, 1985:

1. Do not flood more than 14 days during the growing season

2. Agricultural commodity

3. Not since been abandoned

definition of wetlands
Definition of Wetlands
  • USACE 1987 Wetland Delineation Manual
  • 3 Parameters:

1. Hydrology – presence of water within the upper 12 in. for at least 5% of the growing season

2. Hydrophytic vegetation – > 50% wetland species.

3. Hydric Soils – formed under wet conditions long enough to develop anaerobic conditions in upper 12 in.

wetlands and their importance
Wetlands and their Importance
  • Swamps, marshes, bogs, pine flats, and floodplains
  • Water quality improvement, flood storage, groundwater recharge, shoreline erosion protection
  • Provide habitat for fish and wildlife
  • Opportunities for recreation and aesthetic appreciation
regulatory protections
Regulatory Protections
  • Clean Water Act, 1972
  • Army Corps of Engineers
  • Section 404(b)(1) Guidelines:

1. Avoid filling wetland resources

2. Minimize adverse impacts

3. Provide compensatory mitigation

no net loss of wetlands
No Net Loss of Wetlands
  • 1989, President George Bush Sr.
  • Reduce the amount of wetlands impacted
  • Restore and create new wetlands
  • Three ways to provide mitigation through the regulatory process:

1. Mitigation Banking

2. In-Lieu Fee Process

3. Permittee Process (on-site restoration, enhancement, and/or creation)

mitigation banking
Mitigation Banking
  • Early 1990s market-

based instrument

  • Sponsor creates a “bank”

of restored, enhanced, and

/or created wetlands

  • Made credits available to developers to “buy”
  • Provides compensatory mitigation in advance of authorized impacts
mitigation banking cont
Mitigation Banking (cont.)
  • Sponsor submits a prospectus to the Corps and Inter-agency Review Team
  • Detailed plan of the bank site and success criteria
  • Mitigation Banking Instrument (MBI) provides the legal framework
  • Sponsor becomes responsible for providing mitigation for Corps permits and the long-term management and ecological success of the site.
north carolina department of transportation
North Carolina Department of Transportation
  • 1990 ambitious road-

building initiative

  • NCDOT responsible for

compensating for an

increasing amount of

wetland losses

  • Increased project delays
  • Wetland mitigation needed to expand and become more pro-active
in lieu fee process
In-Lieu Fee Process
  • 1997 North Carolina Wetlands Restoration Program (WRP)
  • Allows permittee to provide funds to

an in-lieu-fee sponsor (WRP Fund)

  • First method of developing a per-acre cost of wetland restoration
  • Mitigating within the same river basin as impacts
  • Reporting and documenting of statewide wetland acreage losses and gains
nc ecosystem enhancement program eep
NC Ecosystem Enhancement Program (EEP)
  • 2003 MOA between the Corps,


  • More consistent and streamlined approach to mitigation
  • Implementation of large-scale watershed-based restoration efforts
  • 2004 accepted the transfer and responsibility of all of NCDOT’s off-site mitigation projects.
wetland functional assessment
Wetland Functional Assessment
  • Evaluating and tracking wetland


  • Quantified based on acreage, numbers

of planted trees survived, and hydrolo-

gical data

  • Quality measured by the regulator’s best professional judgment (BPJ)
  • A new method of assessing wetland function was needed to make better and more defensible permit decisions
north carolina wetland assessment method ncwam
North Carolina Wetland Assessment Method (NCWAM)
  • A team of experts gathered in 2003 to analyze approx 40 different existing methodologies
  • NCWAM Draft Manual was released in December of 2007
  • Provides an accurate, consistent, rapid, observational, and scientifically-based field method
dichotomous key to general north carolina wetland types
Dichotomous Key to General North Carolina Wetland Types
  • 16 general wetland types in NC
  • Account for impacts by wetland type
  • Account for the inherent differences in function for each wetland type
ncwam field form
NCWAM Field Form
  • Level of function of wetlands based on ratings of indicators of function rather than their actual measurements
  • Evaluation of 22 metrics using observation, measurement, and BPJ
  • NC WAM rating calculatorconverts data into “High”, “Medium”, or “Low” functional ratings
wetland functions
Wetland Functions
  • 11 Sub-functions
  • 3 Main functions:
    • Hydrology
    • Water Quality
    • Habitat
  • “High”, “Medium” and “Low” ratings – by separate function and overall
  • Surface storage and retention
  • Subsurface storage

and retention

water quality
Water Quality
  • Particulate change
  • Soluble change
  • Pathogen change
  • Physical change
  • Pollution Change (combination of the first three)
  • Physical structure
  • Vegetation composition
  • Landscape patch structure
  • Habitat Uniqueness
site selection for nc wam evaluation
Site Selection for NC WAM Evaluation
  • 12 mitigation sites selected based on:

1. Geographical area – Inner and Outer Coastal Plain

2. Age of site development – 1993 – 2003; “Closed out”

3. Prior land use – PC cropland

pc restoration
PC Restoration
  • The most “bang for your buck”
  • Historically supported hydric soils
  • Encompass larger areas
  • Minimal restoration design work and cost
  • Restored PC croplands = 2,176 acres
site restoration
Site Restoration
  • Drainage ditches plugged and/or filled
  • Discing, deep ripping, surface scarification
deep ripping
Deep Ripping
  • Help increase permeability rates, surface roughness, hydrological retention, and improve vegetation restoration efforts
vegetation planting
Vegetation Planting
  • Within one year of site construction
  • Wetland species selected

according to wetland type

  • Determined by a reference area
  • Saplings planted in rows
site monitoring
Site Monitoring
  • Installation of ground water monitoring gauges
  • Vegetation remediation in first 1-2 years
  • Hydrology and vegetation success monitored for 4 – 6 years
  • Annual reports submitted to the Corps
  • Site restoration plans and monitoring reports from NCDOT, the Corps, and EEP
  • 8 NCDOT-owned, 4 privately

owned mitigation banks

  • ArcView/ArcMap GIS mapping
tools for the field
Tools for the Field
  • NCWAM forms and Draft Manual
  • Soil auger
  • Hand-held Global Position System (GPS)
  • Digital camera
  • Pocket rod
  • Soil surveys
  • Munsell Soil Color Charts
  • Compass
identifying assessment areas
Identifying Assessment Areas
  • Maps showing where hydrology had been restored and wetland vegetation planted
  • Walked and observed for changes
  • Identified a favorable, homogenous representation of a particular wetland type
  • Keyed out using the Dichotomous Key
site evaluation
Site Evaluation
  • Completed NCWAM Form for

the Assessment Area

  • Digital Photo Documentation
  • GPS recording of Lat/Long


  • 2-5 community types per site
  • 37 evaluations total
ncwam results
NCWAM Results
  • 8/16 NC wetland community types represented:

11 Hardwood flats

9 Non-riverine swamp forests

6 Riverine swamp forests

4 Bottomland hardwood forests

4 Pine flats

1 Pine savanna

1 Floodplain pool

1 Non-tidal freshwater marsh

  • 4 out of 12 mitigation sites rated “High” overall for all assessment areas evaluated:

Scuppernong River Corridor

Dismal Swamp

Hidden Lake

Gurley Tract

  • One rated “Low” overall:


results cont
Results (cont.)
  • 3 other sites had “Low” overall ratings
  • Alterations due to beaver


  • Lack of wetland functions due to presence of stream channelization, man-made berms, or soil compaction
  • Negative effects on all three wetland functions
  • Identifying the type of wetland

community present

  • Different than what was originally


  • Post-restoration events substantially altered site conditions
  • For purposes of consistency  site identified as it appeared
  • NC WAM has the ability to determine wetland functionality accurately
  • Hydrology “High” (75.5%) – first function to be replaced after a site is constructed
  • Water Quality “High” (67%) – relative to inundation duration, vegetation structure, and opportunity (surrounding land use)
  • Habitat “Low” (56.5%) – can take decades to hundreds of years to re-establish
lack of opportunity
Lack of Opportunity
  • Nearby stormwater directed away from the wetland via ditches or storm drains
  • Stream channelization

minimizes opportunity

for over- bank flooding

restoration methods
Restoration Methods
  • Standard method of restoring PC croplands works best for hydrology and water quality functions
  • Recommend introducing coarse woody debris to improve habitat functionality
  • “Less is better”

(eg. ABC Site)

  • Creation is not preferred

(eg. Haws Runs Site)

nc wam a validation for success
NC WAM: A Validation for Success
  • Performance measures prior to NCWAM based on minimum standard:

1. Hydrology present at least 12.5% of GS

2. Coverage of hydrophytic vegetation at least 260 stems/acre

  • NCWAM examines a range of wetland functions covering a number of observable characteristics
  • Valuable and accurate tool for evaluating success of mitigated wetlands
tracking function of mitigation sites
Tracking Function of Mitigation Sites
  • Enhancement areas – evaluate before and after improvements to track functional uplift
  • Restoration areas – evaluate before restoration plan approval to determine goals; require as part of the mitigation monitoring requirement
  • “High” ratings required for true

functional replacement

final word
Final Word
  • Mitigation sites are constantly subject to change
  • Recommend further evaluation of mitigation sites using NCWAM
  • Future study for Regulatory Co-op??