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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
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North Carolina WAM! Wetland Assessment Method
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Geography of NC Coastal Plain
Inner and outer coastal plain ecoregions Broad interstream divides Gentle-sloping plains Mineral-based, poorly drained soils Cape Fear, White Oak, Neuse, Roanoke, Tar-Pamlico, and Chowan River Basins
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Aerial Image of North Carolina
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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
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Converting Wetlands to Agriculture
Removal of all vegetation and debris Cutting drainage ditches 24-48” deep Creating field crowns
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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
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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.
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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
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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
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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)
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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
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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.
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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
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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
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NC Ecosystem Enhancement Program (EEP)
2003 MOA between the Corps, DOT, and DENR 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.
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Wetland Functional Assessment
Evaluating and tracking wetland function 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
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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
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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
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Bottomland Hardwood Forest
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Riverine Swamp Forest
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Non-Tidal Freshwater Marsh
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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 calculator converts data into “High”, “Medium”, or “Low” functional ratings
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Wetland Functions 11 Sub-functions 3 Main functions: Hydrology
Water Quality Habitat “High”, “Medium” and “Low” ratings – by separate function and overall
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Hydrology Surface storage and retention Subsurface storage
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Water Quality Particulate change Soluble change Pathogen change
Physical change Pollution Change (combination of the first three)
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Habitat Physical structure Vegetation composition
Landscape patch structure Habitat Uniqueness
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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
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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
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Site Restoration Drainage ditches plugged and/or filled
Discing, deep ripping, surface scarification
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Deep Ripping Help increase permeability rates, surface roughness, hydrological retention, and improve vegetation restoration efforts
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Vegetation Planting Within one year of site construction
Wetland species selected according to wetland type Determined by a reference area Saplings planted in rows
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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
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Methodology Site restoration plans and monitoring reports from NCDOT, the Corps, and EEP 8 NCDOT-owned, 4 privately owned mitigation banks ArcView/ArcMap GIS mapping
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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
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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
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Site Evaluation Completed NCWAM Form for the Assessment Area
Digital Photo Documentation GPS recording of Lat/Long coordinates 2-5 community types per site 37 evaluations total
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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
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Table 1: Functional Results of Wetland Mitigation Sites
Functional Rating Low Medium High Hydrology -- Condition 11% 13.5% 75.5% Water Quality -- Condition 19% 67.5% Water Quality -- Opportun 16% 73% Habitat -- Condition 56.5% 30% Overall Rating 65%
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Table 2: Results of Wetland Functions for Individual Assessment Sites
Site Name/Assessment Area (AA) Wetland Community Type Hydrol Cond. Water Qual Habitat Overall 1. Scuppernong River AA 1 Non-Riverine Swamp Forest High Medium AA 2 Hardwood Flat 2. Bull Farms Floodplain Pool Bottomland Hardwood Forest Low AA 3 Riverine Swamp Forest AA 4 AA 5 3. Mildred Woods Pine Flat
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Table 2: Results of Wetland Functions for Individual Assessment Sites
Site Name/Assessment Area (AA) Wetland Community Type Hydrology Cond. Water Qual Habitat Overall 4. Dismal Swamp AA 1 Riverine Swamp Forest High AA 2 Non-Riverine Swamp Forest Medium AA 3 5. Hidden Lake AA 1 (Woodward Tract) Hardwood Flat Low AA 2 (Morris Tract) 6. Gurley Tract Bottomland hardwood Forest 7. Barra Farms (P-I) Pine Flat AA 4
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Table 2: Results of Wetland Functions for Individual Assessment Sites
Site Name/Assessment Area (AA) Wetland Community Type Hydrology Cond. Water Qual Habitat Overall 8. Long Swamp AA 1 Hardwood Flat High Medium AA 2 Non-Riverine Swamp Forest Low 9. Haws Run Riverine S. Forest (created) Riverine Swamp Forest AA 3 AA 4 Pine Savanna 10. Dowd Dairy
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Table 2: Results of Wetland Functions for Individual Assessment Sites
Site Name/Assessment Area (AA) Wetland Community Type Hydrology Cond. Water Qual Habitat Overall 11. ABC Site AA 1 Bottomland Hardwood Forest Low AA 2 Hardwood Flat 12. Bear Creek Mill Branch Site Riverine Swamp Forest Non-Tidal Fresh Water Marsh High
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Results 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: ABC
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Results (cont.) 3 other sites had “Low” overall ratings
Alterations due to beaver activity Lack of wetland functions due to presence of stream channelization, man-made berms, or soil compaction Negative effects on all three wetland functions
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Discussion Identifying the type of wetland community present
Different than what was originally planned Post-restoration events substantially altered site conditions For purposes of consistency site identified as it appeared
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Conclusions 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
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Lack of Opportunity Nearby stormwater directed away from the wetland via ditches or storm drains Stream channelization minimizes opportunity for over- bank flooding
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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)
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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
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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
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Final Word Mitigation sites are constantly subject to change
Recommend further evaluation of mitigation sites using NCWAM Future study for Regulatory Co-op??
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Thanks for the good times!!
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