19970330 Ver 1_Mitigation Plans_20010712

DETAILED WETLAND MITIGATION PLAN
RANDLEMAN RESERVOIR WATER SUPPLY
RICHLAND CREEK MITIGATION SITE
GUILFORD COUNTY, NORTH CAROLINA
Prepared for:
PIEDMONT TRIAD REGIONAL WATER AUTHORITY
Prepared by:
EcoScience
EcoScience Corporation
612 Wade Avenue, Suite 200
Raleigh, North Carolina 27605
October 2000
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TABLE OF CONTENTS
Page
LIST OF FIGURES ................................................ iii
LIST OF TABLES ................................................ iv
1.0 INTRODUCTION ............................................ 1
1.1 Purpose ............................................. 1
1.2 Objectives of Wetland Restoration .......................... 1
1.3 Primary Methods for Wetland Restoration 3
1.4 Mitigation Site Selection ................................. 4
2.0 METHODS ................................................ 8
3.0 EXISTING CONDITIONS ...................................... 11
3.1 Physiography, Topography, and Land Use ..................... 11
3.2 Soils ...............................................15
3.3 Plant Communities ..................................... 17
3.4 Hydrology ........................................... 19
3.5 Water Quality ......................................... 23
3.6 Wildlife .............................................24
3.7 Unique Natural Areas and Protected Species ................... 25
3.8 Jurisdictional Wetlands .................................. 26
4.0 WETLAND RESTORATION STUDIES .............................. 29
4.1 Restoration Alternatives Analyses ........................... 29
4.2 Reservoir Pool Level and Sedimentation Analysis ................ 31
4.3 Surface Water Analyses ................................. 36
4.4 Groundwater Modeling .................................. 41
4.5 Reference Plant Communities .............................. 45
4.6 Reference Physiography and Surface Topography ................ 49
5.0 WETLAND RESTORATION PLAN ................................
5.1 Passive Saturation / Inundation from the Reservoir Pool ........... 51
51
5.2 Constructed Levee Removal ............................... 51
5.3
5.4 In-Stream Weir Construction ..............................
Surface Scarification .................................... 53
55
5.5 Woody Debris Deposition ................................ 55
5.6 Wetland Community Restoration ........................... 55

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6.0 MONITORING PLAN ......................................... 62
6.1 Hydrology ........................................... 62
6.2 Hydrology Success Criteria ............................... 62
6.3 Soil ................................................ 64
6.4 Soil Success Criteria .................................... 64
6.5 Vegetation ........................................... 64
6.6 Vegetation Success Criteria ............................... 65
6.7 Report Submittal ...................................... 66
7.0 IMPLEMENTATION SCHEDULE ................................. 67
8.0 DISPENSATION OF PROPERTY ................................. 68
9.0 WETLAND FUNCTIONAL EVALUATION ........................... 69
9.1 Existing Conditions ..................................... 69
9.2 Projected Post-Restoration Conditions ........................ 69
10.0 REFERENCES ..............................................71
LIST OF FIGURES
Page
Figure 1: Site Location: Randleman Reservoir ......................... 2
Figure 2: Site Location: Richland Creek Mitigation Site ................... 7
Figure 3: Aerial Photograph (1999) ................................. 9
Figure 4: Physiography, Topography, and Land Use ..................... 12
Figure 5: Soil Map Units: Hydric / Non-Hydric Soil Boundaries .............. 16
Figure 6: Plant Communities ..................................... 18
Figure 7: Flood Frequency Analyses ................................ 21
Figure 8: Jurisdictional Wetlands .................................. 27
Figure 9: Pool Level and Sedimentation: Reference Site 1 ................. 34
Figure 10: Pool Level and Sedimentation: Reference Site 2 ................. 35
Figure 11: Pool Level and Sedimentation: Randleman Reservoir .............. 37
Figure 12: DRAINMOD Estimates: Post Project Conditions ................. 44
Figure 13: Reference Site: Plan View and Cross Sections .................. 50
Figure 14: Hydrology Restoration ................................... 52
Figure 15: Conceptual Channel Profile: Post-Project Conditions .............. 54
Figure 16: Target Landscape Ecosystems: Richland Creek Mitigation Site ....... 56
Figure 17: Target Landscape Ecosystems: Richland Creek Mitigation Site ...... 57
Figure 18: Planting Plan ......................................... 59
Figure 19: Monitoring Plan / Mitigation Design Units ..................... 63
LIST OF TABLES
Paqe
Table 1: Estimated Acreage of Mitigation Design Units Based on Preliminary Studies
for 10 Potential Mitigation Sites Associated with the Randleman Reservoir
.................................................. 5
Table 2: Water Surface Elevation Estimates for Various Flood Frequencies ..... 39
Table 3: Modeled Groundwater Discharge Zone of Influence
on Wetland Hydroperiods: Chewacla / Wehadkee Soils ............ 43
Table 4: Reference Forest Ecosystem Plot Summary .................... 47
Table 5: Reference Forest Ecosystem Plot Summary .................... 48
Table 6: Planting Plan ......................................... 60
IV
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DETAILED WETLAND MITIGATION PLAN
RANDLEMAN WATER SUPPLY RESERVOIR
RICHLAND CREEK MITIGATION SITE
GUILFORD COUNTY, NORTH CAROLINA
1.0 INTRODUCTION
1.1 PURPOSE
The Piedmont Triad Regional Water Authority (PTRWA) proposes development of the
Randleman Reservoir in Randolph and Guilford Counties, North Carolina (Figure 1). The
purpose of this project is to develop a safe and dependable water supply source for North
Carolina's Piedmont Triad region that will satisfy the projected water demand for a period
of 50 years. The proposed 3,000-acre reservoir will unavoidably impact approximately 121
acres of wetlands through impoundment and establishment of an open water system.
These jurisdictional wetlands are subject to regulation under Section 404 of the Clean
Water Act (CWA) (33 U.S.C. § 1344).
For unavoidable wetland impacts, compensatory mitigation is required to facilitate no net
loss of wetland functions in the region. Compensatory mitigation is typically performed
to replace similar wetland types and wetland functions as those impacted (ex: forested,
stream-side wetlands). Wetland restoration, creation, enhancement, or preservation
represent typical methods designed to offset wetland impacts. The North Carolina
Division of Water Quality (DWQ) has instituted a policy that prefers a minimum of 1 acre
of wetland be restored or created for every acre of wetland impacted. Subsequently,
remaining wetland functional replacement needs may then be off-set through wetland
enhancement and/or preservation.
1.2 OBJECTIVES OF WETLAND RESTORATION
The primary objectives for wetland restoration include:
1) Restore or create 121 acres of wetlands as required under regulatory
guidance.
2) Assist in protecting the drinking water supply from pollutants discharged
from the developing watersheds. Excess nutrients, fecal coliform,
sediments, and chemical contaminants (metals, etc.) represent the primary
water quality concerns for the reservoir.
3) Maximize benefits to water quality through establishment of functioning
wetlands above the reservoir pool.
4) Replace habitat for wetland dependent wildlife displaced by establishment
of open water.
5) Maximize the acreage of wetland restoration or creation achieved at the
Richland Creek mitigation site.

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Water quality benefits are maximized by reducing the capacity for sediment to reach open
water within the reservoir pool. Entrenched streams in the region have abandoned
adjacent floodplains and tend to discharge large quantities of sediment within water
supply reservoirs (Section 4.3). Therefore, wetland restoration for water quality should
be designed to reduce sediment transport capacity of streams immediately above the
reservoir and to entrap sediment within vegetated wetland surfaces. As a result, sediment
would be deposited on floodplain surfaces that periodically dry out in areas outside of the
reservoir pool. Wetland vegetation would serve to provide nutrient uptake and recycling
functions within deposited sediment. Using this rationale, entrenched stream and terrace
systems would be converted into alluvial wetland fans. A highly sinuous (E) to braided
(D) stream system would be developed within the alluvial deposition area (Rosgen 1996).
Wetland vegetation would be established on the alluvial deposition to stabilize the
sediment and provide for pollutant recycling through oxidation (drying) and reduction
(wetting) processes. Within the reservoir immediately downstream of entrenched streams,
sediment from the watershed is deposited directly into the water supply, in a permanently
inundated, reducing environment. Without periodic oxidation processes, pollutants
generally dissolve within the water column and consequently reduce drinking water
quality.
Establishment of the reservoir will effectively stop sediment transport capacity within each
tributary that flows into the lake. The primary objective of mitigation is to extend the
sediment deposition wedge in the upstream direction of each valley, prior to confluence
with the lake. The reservoir will passively develop wetlands within a certain area in each
valley, immediately above the reservoir pool. This project is intended to assist that
process through active measures, including extension of wetlands in the up-valley
direction and establishment of wetland vegetation on active alluvial surfaces.
1.3 PRIMARY METHODS FOR WETLAND RESTORATION
Two primary methods for wetland restoration have been proposed to extend the sediment
wedge into design wetlands above the reservoir, restore 121 acres of riverine wetlands,
and to provide suitable habitat for wetland dependent wildlife. Primary methods include:
1) in-stream structures designed to reduce sediment transport capacity; and 2) greentree
impoundments designed to allow management of water levels and sediment deposition
patterns.
In-Stream Structures
In-stream structures are proposed primarily along dredged or entrenched stream corridors
on relatively low-slope valley floors (<0.009 rise/run) supporting forest vegetation.
Adjacent floodplains have been abandoned by the incised stream and converted to
elevated terraces not regularly exposed to overbank flooding or wetland hydrodynamics.
Properly designed in-stream structures are expected to reduce the degree of channel
incision, reduce the rate of groundwater discharge from the floodplain into the channel,
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increase overbank flooding from the channel onto the floodplain, reduce sediment
transport capacity, and provide greater sediment deposition within vegetated wetlands.
Greentree Impoundments
Greentree impoundments are proposed on more steeply sloped floodplains and stream
terraces (>0.008 rise/run) or pastured sites where relatively severe stream channel
degradation and steepening has occurred above the reservoir pool. In general, a greentree
impoundment comprises a floodplain levee and controllable outlet structure that is
modified periodically to promote the development of forested wetlands. Functioning
greentree impoundments above the lake reservoir are expected to provide for significant
nutrient uptake, recycling, and management benefits.
The elevation of the outlet is typically raised during winter months to promote ponding,
sediment deposition, and waterfowl habitat. Subsequently, the elevation of the outlet
is lowered in early spring to allow for vegetation growth, nutrient uptake, and seedling
establishment. Levee systems are typically constructed to provide for less than 2 to 3 feet
of inundation during winter months, to prevent over-topping, and to allow for survival of
tree seedlings. The winter depth is generally dependent upon the height of seedlings.
The raising and lowering of outlet structures requires regular monitoring and maintenance
by qualified personnel to facilitate the growth and survival of tree species. The time for
outlet adjustment may vary annually and is dependent upon localized conditions within
the watershed. Seedling mortality should be tracked on an annual basis, and the date of
spring lowering of water levels is modified to maximize the rate of forest regeneration.
Tree or shrub species selected for planting will vary based on expected hydrologic regimes
and other site-specific conditions. In general, sites lacking substantial forest vegetation
and primarily used as pasture land were targeted for this mitigation option.
1.4 MITIGATION SITE SELECTION
During the environmental impact assessment, project planners identified and evaluated a
total of 25 potential mitigation sites within stream corridors extending above the reservoir
pool. A description of mitigation potential for each of these sites was prepared in
previous documents (ESC 1998a, ESC 1998b, ESC 1999).
Of these 25 sites, 10 sites were determined to support wetland restoration potential on
floodplains encompassing up to 121 acres of restorable land area. Table 1 and Figure 1
depict the location of each site and projected acreages potentially available for wetland
restoration use.

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This document details restoration and enhancement procedures for riverine and lake
shoreline wetland restoration and creation along Richland Creek, one of the 10 mitigation
sites (Figure 2). The Richland Creek mitigation site (Site) includes 70.5 acres that
encompass the stream and adjacent floodplain servicing a watershed of approximately
14.5 square miles immediately above the reservoir. In-stream structures are proposed
along the dredged and entrenched Richland Creek corridor to reduce the rate of
groundwater discharge from the floodplain into the channel, increase overbank flooding
from the channel onto the floodplain, and increase deposition of sediment on vegetated
wetland surfaces above the reservoir pool.
This summary document includes the following: 1) descriptions of existing conditions; 2)
surface and groundwater hydraulic analyses; 3) reference lake shoreline line studies; and
4) reference soil and forest ecosystem investigations. Subsequently, detailed plans are
provided for in-stream structures, wetland restoration/creation, vegetation planting, site
monitoring, and success criteria. Remaining mitigation sites that follow the format of this
mitigation plan (utilizing in-stream structures above the reservoir pool) will be attached as
appendix documents to this summary mitigation plan.

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RANDLEMAN RESERVOIR MITIGATION PROJECT
RICHLAND CREEK SITE
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2.0 METHODS
Natural resource information for the Site was obtained from available sources, including
U. S. Geological Survey (USGS) topographic mapping (USGS High Point East and High
Point West 7.5 minute quadrangles), U. S. Fish and Wildlife Service (USFWS) National
Wetlands Inventory (NWI) mapping, and Natural Resource Conservation Service (NRCS)
soil survey (USDA 1977). These resources were utilized for base mapping and evaluation
of existing landscape and soil information prior to on-site inspection. Current (1999) aerial
photography was obtained and utilized to map relevant environmental features (Figure 3).
Characteristic and target natural community patterns were classified according to
constructs outlined in Schafale and Weakley's, Classification of the Natural Communities
of North Carolina (1990). North Carolina Natural Heritage Program (NCNHP) data bases
were evaluated for the presence of protected species and designated natural areas which
may serve as reference (relatively undisturbed) wetlands for restoration design.
On-site reference (relatively undisturbed) stream and wetland sites were selected to orient
restoration design and to provide baseline information on target (post-restoration) wetland
conditions. A regional vegetation reference data base and on-site inventory were used to
characterize target, post-restoration species composition. Topographic maps of the basin
floor were also prepared to show the gradation from permanently to semi-permanently
inundated conditions throughout the lower half of the site. A concurrent pool elevation
and sedimentation study provided information on sedimentation and wetland development
around the point of stream inflow and conservation pool levels. Topographic data were
overlaid on wetland restoration areas to establish methods for construction and restoration
of wetland communities within the Site.
Detailed topographic mapping to 1-foot contour intervals was developed by ground survey
paneling and aerial photogrametric methods. Additional land surveys were performed to
establish channel cross-sections and measure reference wetland surface topography.
Field investigations were performed in the spring of 2000 including soil surveys, on-site
resource mapping, land surveys, and landscape ecosystem classifications. Existing plant
communities and jurisdictional wetlands were described and mapped according to
landscape position, structure, composition, and groundwater analyses.
Wetland boundaries were obtained from a delineation performed in 1998. NRCS soil map
units were ground truthed by licenced soil scientists to verify units and to map inclusions
and taxadjunct areas. The revised soils maps were used as additional evidence for
predicting natural community patterns and wetland limits prior to human disturbances.

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Groundwater conditions were modeled using DRAINMOD, a computer model for
simulating withdrawal rates for shallow soils with high water tables. The model was
utilized to predict historic hydroperiods, the extent of wetland degradation due to
dredging and ditching, and the potential for wetland restoration through stream
modification.
Surface water analyses for the Richland Creek site were completed using standard study
methods of the U.S. Army Corps of Engineers (USACE) and NRCS. Flood events of a
magnitude which are expected to be equaled or exceeded once on average every 1-, 2-,
5-, 10-, or 100-year period were selected for use. These flood events are commonly called
the 2-, 5-, 10-, and 100-year floods. Floods with a return frequency of less than 2 years
are usually not studied in engineering applications. These analyses reflect either existing
or proposed conditions at the Site. The projected frequency and extent of overbank
flooding were used to determine potential for riverine wetland restoration in floodplain
portions of the Site.
This Site has been selected for wetland restoration use to promote a reduction in
sediment, nutrients, and pollutants flowing into Randleman Reservoir. Mitigation
activities are intended to provide sediment deposition, and pollutant and nutrient cycling
from surface waters within created and restored wetland areas. Recycling functions are
designed to reduce elevated nitrogen and phosphorus loads from the watershed towards
I background (forest) levels, prior to discharge into the reservoir.
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3.0 EXISTING CONDITIONS
3.1 PHYSIOGRAPHY, TOPOGRAPHY, AND LAND USE
The Site is located in the Piedmont Physiographic Province of North Carolina within the
Cape Fear River Basin. Physiography is characterized by moderately hilly terrain with
interstream divides intermixed with steeper slopes along well-defined drainage ways. The
Site is situated in the Richland Creek floodplain within the Cape Fear River Basin
(Hydrologic Unit #03030003 [USGS 1974]). The Site is located approximately 3.5 miles
southeast of High Point and approximately-5 miles southwest of Greensboro. Annual
precipitation in the region averages 42 inches per year with June and August representing
the months that support the highest average rainfall (4.21 inches and 4.36 inches
respectively) (USDA 1977).
The Site contains an approximately 5450-foot reach of Richland Creek (Figure 4).
Richland Creek supports a primary watershed of approximately 14.5 square miles and
flows into the Deep River 0.8 miles downstream. The Site is also dissected by five
unnamed tributaries from auxiliary watersheds flowing directly into the project reach of
Richland Creek (Figure 4, labeled site infalls).

The primary watershed associated with Richland Creek extends primarily through suburban
and urban areas associated with the City of High Point, the Interstate 85 (1-85) business
corridor, and developments associated with Melbourne Heights, Bakertown, and
Springfield. Land use within headwaters is dominated by commercial, industrial, and
infrastructural development with relatively high density residential development and
abandoned pastures in many remaining areas. Changes in water quality and runoff
characteristics due to development has been further altered by systematic dredging and
straightening of the channel within major sections of the 6 mile reach of Richland Creek.
Land uses in the auxiliary watersheds and within the Site are dominated by rural and
transitional suburban uses including forest, agriculture, horse and cattle farms, residential
homes, and state roads with limited commercial development occurring in the vicinity of
crossroad communities in the area. Increased industrial and commercial development is
occurring within the auxiliary watersheds with population expansion anticipated in the
next several decades. Therefore, the area surrounding the Site is expected to undergo
land use changes to more urban, residential, infrastructural, and commercial conditions.
The Site encompasses approximately 70.5 acres, including 62 acres of disturbed
bottomland forest and 4.5 acres of pastoral land. A power line utility easement extends
along the eastern Site boundary. An elevated sewer line extends north of the Site
boundary before reaching the High Point Sewage Disposal Plant located along the
northwestern portion of the Site (Figure 4).
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The acreage has been subdivided into three primary physiographic units for restoration
planning purposes: 1) stream levee; 2) primary floodplain; and 3) secondary floodplain
(backwater slough) (Figure 4). The primary variables utilized to segregate wetland
landscape units include land slope, river flood elevations from Richland Creek (Section
4.3), and the rate and direction of groundwater flow (Section 4.4).
Stream Levee
Stream levees are represented by an approximately 5-acre, linear margin along the banks
of Richland Creek. The physiographic area currently extends approximately 3200 linear
feet along both sides of Richland Creek, averaging approximately 35 feet in width. Under
historic conditions, the river levee represented slightly elevated, upland habitat influenced
by the frequent deposition of coarse, sandy alluvium during river floods. Groundwater
flow is characterized by relatively rapid, lateral to radial interflow towards the river
channel, inducing well drained conditions throughout a large majority of the year. Based
on reference stream reaches, natural stream levees are elevated approximately 1 to 2 feet
above the adjacent floodplain, with intermittent openings residing at lower elevations.
To allow foragricultural use of the stream flood lain approximately
p 2800 linear feet of
Richland Creek was dredged, straightened, and the low-lying levees buried under spoil
material. The elevated levees constructed along the banks of the river typically range from
2 to 6 feet above the floodplain, providing additional confinement of stream flows in
these areas. River dredging, levee construction, and subsequent channel degradation have
lowered the channel bottom up to 12 feet below the top of the constructed levee. Under
historic conditions, the stream levee is expected to have supported Piedmont levee forest
communities (Schafale and Weakley 1990). Currently, the constructed levee primarily
supports an access road to adjacent agricultural lands in the primary floodplain.
t Primary Floodplain
The primary river floodplain encompasses approximately 43 acres located along both sides
of the stream channel outside of the stream levee. (Figure 4). The floodplain historically
supported frequent overbank flooding (estimated at an approximate, 1.15-year return
interval for hydraulic models) and was periodically re-worked by alluvial processes and
periodic, long term inundation/saturation. Groundwater flow is dominated by semi-radial
to radial discharge towards the stream channel with episodic lateral discharge and surficial
expression of groundwater occurring within seepage areas. The physiographic area
continues to support isolated, low lying areas and undulating terrain where stained,
undecomposed organic matter remains on the soil surface, suggesting that long term
water storage functions were historically provided by the system.
During dredging programs along Richland Creek, a majority of the primary floodplain was
converted for agricultural use. However, a number of these agricultural tracts have been
abandoned over the last 2 decades, allowing re-development of disturbance adapted,
13

C
successional communities. Under historic conditions, natural communities are expected
to include Piedmont bottomland hardwood forest and oval to linear pockets of riverine
® swamp forest in the vicinity of low lying areas (Schafale and Weakley 1990).
Dredging along the stream has reduced the frequency of overbank flooding within the
primary floodplain from an estimated 1-year return interval to a 10- to 25-year return
interval that overtops the constructed levee. (Section 4.3). Therefore, the primary
floodplain and associated riverine wetland functions (sediment retention, nutrient cycling,
energy dissipation, etc.) have been effectively eliminated from the physiographic area by
stream alterations. Accelerated drainage is evident throughout the primary floodplain
physiographic area due to dredging activities and secondary stream diversions.
Secondarv Floodnlain
The secondary floodplain, encompassing approximately 23 acres, represents relatively flat
to gently-sloping areas situated along the toe of adjacent valley walls and braided (alluvial
fan), backwater, or anastomosed features at the confluence of the small tributaries with
the larger Richland Creek floodplain. Land slopes in this area vary significantly across
localized portions of the landscape but typically remain less than .005 rise/run. The area
includes numerous seeps, convex hummocks, and relatively long term ponding within
depressional backwater sloughs. Groundwater flow is expected to range from vertical
recharge in sloughs to lateral discharge along convex slopes adjacent to the primary
floodplain. Discharge from adjacent groundwater slopes into the floodplain floor provides
sustained surface water expression throughout the year, potentially supporting various
intermittent and perennial channels and ponded areas. Under historic conditions, the area
was likely dominated by riverine swamp forest and shrub-marsh communities.
The secondary floodplain is dissected by numerous unnamed tributaries and historically
supported auxiliary overbank flow. However, several of these tributaries have been
diverted around current and former agriculture fields and have degraded to equilibrate with
incised bed elevations in the Richland Creek channel. The ditches were diverted and
deepened to facilitate agricultural production and to convey drainage from upslope areas
through the Site. This constructed drainage network provides direct connectivity of
surface waters to Richland Creek, effectively bypassing land surfaces and potential
floodplain functions on the Site.
Upland groundwater slopes are not included within the Site boundary. However,
groundwater slopes are found immediately adjacent to the secondary floodplain on
relatively steep upland slopes. The physiographic area includes escarpments that rise 30
to 80 feet above the floodplain floor. These groundwater slopes constitute an important
component in support of wetland hydrodynamics within backwater areas of the Site.
These slopes are expected to exhibit unidirectional overland flow and accelerated radial
to lateral flow, providing for groundwater recharge along the outer floodplain periphery.
Mesic hardwood to dry oak-hickory forests persist within the physiographic area in
portions of the slopes not converted to crop land.
14
c
3.2 SOILS
Surficial soils have been mapped by NRCS (USDA 1977). Soils were verified in the
summer of 1999 by licenced soil scientists to refine soil map units and locate inclusions
and taxadjunct areas. Systematic transects were established and sampled to ensure
proper coverage. Refined soil mapping is depicted in Figure 5. Primary soil types include
the Chewacla series, Udorthents series, and Wehadkee series.
The floodplains and stream terraces primarily support alluvial, Chewacla soils (Fiuvaquentic
Dystrochrepts), encompassing approximately 50.5 acres (72%) of the 70.5-acre Site.
Chewacla soils are somewhat poorly drained, nonhydric soils which have been formed
primarily by fluvial activity. Chewacla soils, located in the broad, relatively flat valley
floor, contain numerous inclusions of hydric soils (i.e. Wehadkee [Typic Fiuvaquents]) in
depressions, ephemeral channels, and swales which are more likely to support wetland .
hydrology. Chewacla soils generally exhibit broad, inter-layered variability in texture and
permeability dependent upon energy dissipation and sediment deposition patterns
associated with each stream overbank flood event. Soil texture generally ranges from
coarse sandy loam to silt loam of moderate to moderately rapid infiltration. Important
factors in the formation and maintenance of wetland systems as hydric inclusions in the
Chewacla map units include: 1) microtopography and variability in fluvial deposition
across the landscape; 2) groundwater and surface water movement from adjacent uplands
along the outer edge of the floodplain; and 3) groundwater discharge rates from the
interior floodplain into the stream channel. Stream dredging, straightening, and
conversion to agricultural lands has likely increased the extent of Chewacla (nonhydric)
soils and concurrently decreased the extent of Wehadkee (hydric) map units in the Site.
Hydric soils are defined as "soils that are saturated, flooded, or ponded long enough
during the growing season to develop anaerobic conditions in the upper soil layer" (USDA
1987). Hydric soils comprise the Wehadkee series (Typic Fiuvaquents), located primarily
within relict backwater sloughs, depressions, ephemeral channels, and swales which
remain within the secondary floodplain. Under existing conditions, the Wehadkee series
comprises approximately 13.5 acres (19%) of the Site.
The Udorthents series represent earthen spoil deposition areas that occur intermittently
throughout the Site. Material excavated from dredged stream channels was used to
construct flood control levees, build roads adjacent to canals, and to fill swales and
depressions within agricultural use areas. Udorthents map units occupy approximately 2.5
acres (4%) of the Site.

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3.3 PLANT COMMUNITIES
Plant communities along Richland Creek are influenced, in part, by past land use practices.
Drainage, site preparation, agricultural conversion, and logging over the years have
substantially altered the natural communities. Four communities have been identified for
descriptive purposes, including: 1) bottomland forest, 2) swamp forest, 3) pasture, and
4) levee forest (Figure 6).
Bottomland Forest
Bottomland forest accounts for approximately 44.5 acres of the 70.5-acre Site. The
bottomland forest assemblage has experienced prolonged degradation from past logging,
watershed diversion, agricultural usage, and ditch networks. The forest canopy includes
box elder (Acer negundo), sycamore (Platanus occidentalis), green ash (Fraxinus
pennsylvanica), tulip poplar (Liriodendron tulipifera), American elm (Ulmus americana), and
black willow (Salix nigra). Under-story species distribution is variable along hydrologic
gradients and includes muscadine grape (Vitis rotundifolia), beggar's ticks (Desmodium
sp.), Japanese honeysuckle (Lonicera japonica), poison ivy (Toxicodendron radicans),
jewel-weed (Impatiens capensis), Chinese privet (Ligustrum sinense), Virginia creeper
(Parthenocissus quinquefolia), and blackberry (Rubus sp.).
Swamp Forest
Swamp forests persist within isolated, relict backwater areas found in depressional areas.
This community, covering approximately 12 acres, appears to have been affected by
reductions in drainage area, loss of surface hydrodynamics, reductions in hydroperiod, and
periodic timber harvest. The canopy includes species listed in bottomland hardwood
forest, with inclusion and increasing frequency of swamp chestnut oak (Quercus
michauxii), ironwood (Carpinus caroliniana), swamp cottonwood (Populus heterophyllus),
and sweetgum (Liquidambar styraciflua). The understory is dense to sparse, depending
on the openness of the overstory. Under open canopies, the understory is dominated by
a dense layer of graminoids and forbs, including sedges (Carex spp.), rushes (Juncus spp.),
lizard tail (Saururus cernuus), false nettle (Boehmeria cylindrica), seedbox (Ludwegia spp.),
and jewel-weed.
Levee Forest
Approximately 5 acres of levee forest are found in a narrow fringe, on the elevated
deposits (natural and man-made) along Richland Creek. These moderately well drained
areas support plant species characteristic of levee forest communities (Schafale and
Weakley 1990). Canopy species include box elder, sycamore, river birch (Betula nigra),
green ash, black walnut (Juglans nigra), sweetgum, ironwood, and red maple. The mid-
story is dominated by eastern cedar (Juniperus virginiana), black cherry (Prunus serotina),
Chinese privet, and honey locust (Gleditsia triacanthos). Understory species include virgin
bower (Clematis virginiana), Japanese honeysuckle, muscadine grape, mouse ear
chickweed (Cerastium glomeratum), common greenbrier (Smilax rotundifolia), and poison
ivy.
17

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Approximately 4.5 acres of pasture land is located in the central portion of the Site. Hay
was last harvested in June of 2000. Pasture land is dominated by a variety of grasses and
herbs. The predominant species is fescue (Festuca spp.). Other characteristic species
include asters (Aster spp.), goldenrods (So/idago spp.), horseweed (Erigeron canadensis),
pigweed (Chenopodium album), ragweed (Ambrosia artemisiifo/ia), common morning glory
Upomoea purpurea), clover (Trifo/ium spp.), crabgrass (Digitaria spp.), and love grass
(Erogrostis sp.).
Adjacent border and forest edge communities support young sweetgum, black cherry, box
elder, and red maple (Acer rubrum). Thickets containing blackberry, winged sumac,
Canada elder (Sambucus canadensis), switch cane (Arundinaria gigantea), muscadine
grape, and common greenbrier are also present.
3.4 HYDROLOGY
The Site is located within the Piedmont hydrophysiographic province, which encompasses
the entire drainage basin for the East and West Forks of the Deep River. The region is
characterized by moderately hilly terrain with interstream divides exhibiting dendritic
drainage patterns and moderately steep slopes along valley floors (0.005-0.015 rise/run).
The region is characterized by moderate rainfall. In Guilford County, precipitation
averages 42 inches per year with precipitation evenly distributed throughout the year
(USDA 1977). Large floods (20-100 year return interval) typically correspond to large
thunderstorms and tropical events in the region.
Bed load material supplied by the region consists primarily of silts, sands, and weathered
bedrock (very coarse sand and small gravel). Bedrock outcrops are considered common
within incised streams in more steeply sloped valleys. Suspended load consists primarily
of easily eroded clays and silts, which transport attached nutrients into downstream
waters. Erosion and suspended sediment loads have been linked to nutrification problems
within the Piedmont hydrophysiographic province, including the Randleman Reservoir
region (DWQ 2000).
The Site encompasses broad floodplains associated with a 5450-foot reach of Richland
Creek. At site outfall, the system supports a watershed of approximately 14.5 miles
(Figure 4). The floodplain ranges from approximately 1000 feet in width within upper
reaches of the Site to 400 feet in width at Site outfall immediately upstream of the
Interstate 85 corridor. The annual sediment load supplied by the watershed is estimated
at 44,000 cubic feet (1.0 acre-feet) (Simmons 1976).
19
F-1

The watershed is characterized by a mixture of rural, urban, and suburban land uses
associated with the City of High Point, the Interstate 85 business corridor, and
surrounding towns. The main-stem of Richland Creek extends for approximately 6 miles
with headwaters extending towards downtown High Point. The watershed includes over
17 miles of perennial tributaries in the watershed (USGS 1982). Land use cover includes
forest (58.4%), pasture (25.4%), as well as metropolitan areas (13.0%) which includes the
City of High Point and portions of Greensboro and Randleman (DWQ 2000). Commercial,
industrial, and residential development is expected to expand in the watershed over the
next several decades due to proximity to the greater Greensboro-High Point metropolitan
region (Section 3.1).
Surface Water
Topographic mapping and historic (1977) aerial photography indicate that Richland Creek
once meandered across former and present agricultural fields and within backwater areas
along the southern edge of the Richland Creek floodplain. Relict stream fragments have
been identified in several areas of the Site, demarcated by discontinuous, meandering
depressions. After 1977, Richland Creek was dredged, straightened, and corralled by
stream-side dikes. Where dredging and dike construction begins, the abandoned
floodplain resides at approximately 685.5 feet above MSL while constructed dikes extend,
on average, to 689 feet above MSL. As a result, river dredging, levee construction, and
subsequent channel degradation have lowered the channel bottom up to 12 feet below
the top of the constructed levee. The loss of meander geometry and steepening of the
water surface has induced further bed incision, resulting in area-wide stream-bank failure
and erosion.
Relative to the floodplain elevation, the dredged channel supports an average bank to
bank width of 30 feet, and average depth of 7.5 feet, and a cross-sectional area of
approximately 225 square feet (max depth 7.9 feet). The channel cross-section is
effectively enlarged to 330 square feet by the constructed dikes. Conversely, the historic
channel is projected to support a cross-sectional area of approximately 120 square feet
(Harman et. a/. 1999). The dredged channel supports a sinuosity (channel length/valley
length) of 1.0. Substrate within the channel is composed of unconsolidated sand and silt
sediments originating, in part, from localized bank erosion. The channel is classified as
a G5 (sand dominated gully) based on fluvial geomorphic features (Rosgen 1996).
Stream discharge and flood elevations under existing conditions have been predicted
based on hydraulic models (Section 4.2). Figure 7 provide model predictions for the 1-
(projected bankfull), 2-, and 100-year storm (Section 4.3). In diked areas, the study
indicates that dredging and dike construction have effectively eliminated the influence of
overbank flooding until events approaching the 10-year to 25-year storm. If constructed
dikes were lowered to the elevation of the adjacent floodplain, flooding from the river
would approach a 2-year return interval in support of riverine wetland formation.
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The flood elevation model suggests that, under historic (pre-dredged) conditions, the Site
exhibited potential to provide approximately 2,400,00 cubic feet (56 acre-feet) of flood
storage and sediment retention capacity. Based on flood frequency analysis, it appears
that restoring a 1-year return interval, flooding at an average depth of 1 foot, will provide
similar storage capacity within the Site (immediately above the water supply reservoir).
Under existing conditions, the incised and corralled channel has eliminated these
important flood and sediment recycling functions within the watershed.
Five unnamed tributaries dissect the Site and flow into the Richland Creek channel. These
tributaries support auxiliary watersheds encompassing approximately 3 square miles of
land area. Within the primary floodplain physiographic area (Figure 4), these channels
represent intermittent and perennial streams that have been largely diverted around current
and former agriculture fields. The ditches were diverted and deepened to facilitate
agricultural production and to convey drainage from upslope areas through the Site. As
a result, the channels have incised to equilibrate with bed elevations induced along
Richland Creek. The constructed drainage network provides direct connectivity of surface
waters to Richland Creek, effectively bypassing land surfaces and potential floodplain
functions on the Site.
Within the secondary floodplain (backwater areas), several of these unnamed tributaries
exhibit braided (alluvial fan), backwater, or anastomosed features at the confluence with
the larger stream floodplain. These sites exhibit high ground water tables, regular
overbank flooding, high deposition rates, and consequent development of open canopy
swamp forest and emergent communities.
Groundwater
Surface water hydrodynamics, such as periodic overbank floods, fluvial sediment
deposition, and hydraulic energy dissipation, represent important attributes of floodplains
and bottomland hardwood forest in the region. However, streams in the region typically
function as groundwater withdrawal features throughout most of the year. Therefore,
groundwater inputs from auxiliary watersheds and upland slopes abutting the floodplain
represent the primary hydrologic input resulting in the development and maintenance of
riverine wetlands at this Site.
Groundwater gradients in May 2000 include intermittent surface expression along the
outer floodplain periphery, immediately adjacent to upland buffers (groundwater recharge
features). The groundwater gradient deepens to more than 6 feet below the surface in
proximity to Richland Creek and several unnamed tributaries (groundwater discharge
features). Dredging of Richland Creek and the concurrent degradation of adjacent
unnamed tributaries has significantly lowered the groundwater table and steepened the
groundwater discharge gradient throughout pastoral and forested portions of the Site.
Restoration of a shallower (less incised) stream network will generate a flatter
r
22
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groundwater gradient, increase surficial expression of groundwater, and potentially extend
wetland conditions into primary floodplains within the Site.
3.5 WATER QUALITY
Richland Creek maintains a State best usage classification of WS-IV CA (Stream Index No.
17-22) (DWQ 2000). Class WS-IV waters are protected as water supplies which are in
moderate to highly developed watersheds. Point source discharges are generally required
to meet stringent pre-treatment standards, to maintain pre-treatment failure (spill
prevention) plans, and to perform point source monitoring for toxic substances. Local
programs to control nonpoint source and stormwater discharge of pollution are also
required. CA signifies a Critical Area designation for watershed areas within 0.5 miles of
a water supply intake for the reservoir.
The Site consists of bottomland hardwood forest and open pasture land adjacent to the
stream channel. Run-off from adjacent farmland, residential areas, and the sludge disposal
fields from the waste treatment plant enter the drainage network through sheet flow and
on-site collection points (i.e. ponds, drainage swales and ditches). Stream channels
connecting adjacent farm ponds and storm channels have direct connectivity with
Richland Creek and may have deleterious effects on water quality.
Restoration of wetland hydrology and diversion of auxiliary watersheds onto restored
wetland surfaces will provide local water quality benefits, including important functions
such as sediment deposition, removal of elements and compounds, and nutrient cycling.
Historically, the floodplain provided water quality benefits to the 14.5 square mile
watershed associated with Richland Creek. However, runoff from this land area
effectively bypasses wetland floodplains as the dredged canals transport flow directly
through the Site. Restoration of wetland hydrology and diversion of watersheds onto
restored wetland surfaces will provide for restoration of overbank flooding and associated
water quality benefits above the Randleman Reservoir.
Because the Site is located at the elevation of the reservoir conservation pool, sediment
transport capacity of the stream system will be generally stopped at elevations of 681 feet
above MSL. A sediment wedge will develop within the reservoir pool and incrementally
extend farther into the open water area. Research suggests that up to 440,000 cubic feet
(1.0 acre-foot) of sediment will be deposited annually within the reducing aquatic
environment (Simmons 1976). Associated pollutants will not generally be degraded,
a assimilated, or recycled through periodic wetting (reduction) and drying (oxidation).
Therefore, wetland restoration has been designed to reduce sediment transport capacity
within the 5,450-foot reach of Richland Creek. As a result, the sediment wedge will be
extended in the upstream direction outside of the reservoir pool (above elevation 682),
where wetland functions will potentially provide for greater pollutant processing.
0
23
0
0
3.6 WILDLIFE
Although forested tracts in the region have been impacted, isolated natural areas provide
necessary food, water, and cover for various species of wildlife. Forested floodplains
along lower reaches of the Site support wildlife species adapted to riparian forest habitat.
In addition, ephemeral drainageways and ponding within isolated wetland areas provide
interaction among riparian and non-riparian wildlife guilds in the region. Wetland/upland
ecotones provide additional habitat diversity near the Site. These ecotones are among the
most diverse and productive environments for wildlife (Brinson et al. 1981).
During field investigations, tracks or observations of the following primarily terrestrial
mammals were documented: Virginia opossum (Didelphis virginiana), raccoon (Procyon
lotor), and white-tailed deer (Odocoileus virginianus). Other mammals expected to occur
within the project area include: southeastern shrew (Sorex longirostris), gray squirrel
(Sciurus carolinensis), eastern chipmunk (Tamias striatus), eastern cottontail (Sylvilagus
floridanus), beaver (Castor canadensis), striped skunk (Mephitis mephitis), meadow vole
(Microtus pennsylvanicus), and gray fox (Urocyon cinereoargenteus).
Due to the presence of various habitat located within the Site, a high diversity of bird
species is expected. Species sighted during field studies are typically found in both
forested communities as well as associated creek-side communities. Bird species identified
in wooded portions of the Site include: blue jay (Cyanocitta cristata), Carolina wren
(Thryothorus /udovicianus), yellow-throated warbler (Dendroica dominica), Carolina
chickadee (Parus carolinensis), and northern cardinal (Cardinalis cardinalis). Bird species
identified in open areas include: northern bobwhite (Colinus virginianus), mourning dove
(Zenaida macroura), eastern kingbird (Tyrannus tyrannus), American crow (Corvus
brachyrhynchos), American robin (Turdus migratorius), northern mockingbird (Mimus
polyglottos), song sparrow (Melospiza melodia), and eastern bluebird (Sialia sialis).
Characteristic bird species that can be expected to utilize wetlands in the region include
great blue heron (Ardea herodias), black-crowned night heron (Nycticorax nycticorax),
mallard (Anas platyrhynchos), wood duck (Aix sponsa), and barred owl (Strix varia). In
addition, a high number of passerine birds, both permanent and summer resident species,
nest in bottomland hardwood forest. Among these are several neotropical migrants such
as Swainson's warbler (Limnothlypis swainsonii) and prothonotary warbler (Protonotaria
citrea), and other forest interior species such as the wood thrush (Hylocichla mustelina)
and Acadian flycatcher (Empidonax virescens) that require large tracts of contiguous forest
for survival (Keller et a/. 1993).
Isolated areas of standing water, ditches, and canals in the area provide marginal
conditions for species of fish, reptiles, and amphibians. Characteristic species include red-
bellied water snake (Nerodia erythrogaster), yellow-bellied turtle (Trachemys scripta),
spotted turtle (Clemmys guttata), southern leopard frog (Rana utricularia), and marbled
0
24
0
0
salamander (Ambystoma opacum). However, due to dredging, straightening, and diversion
of streams into linear ditches that lack riparian cover, functional in-stream habitat is
considered significantly reduced within Richland Creek and the unnamed tributaries
(Figure 4). Riffles, pools, and diagnostic in-stream habitats are generally lacking within
the on-site, linear dredged channels.
3.7 UNIQUE NATURAL AREAS AND PROTECTED SPECIES
No significant natural areas are expected to be impacted by mitigation activities at the
Site. On-site forest corridors have connectivity with forested communities primarily along
stream corridors both above and below the site. Proposed mitigation is expected to
enhance these natural areas. No North Carolina Natural Heritage Program (NCNHP)-
designated Significant Natural Heritage Area (SNHA) exists within the project corridor.
A SNHA designation is given to an area due to the presence of rare species, rare or high
quality natural communities, or geologic features. This designation does not confer
protection or regulatory status. The nearest SNHA is the Jamestown Meander Scar which
is located approximately 2.1 miles to the northwest. The proposed mitigation as well as
the associated construction activities will be limited to the margins of the project
boundaries; therefore, no impacts are anticipated to any rare and unique natural areas.
Species with Federal classifications of Endangered (E) or Threatened (T) are protected
under the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.). The
status of "Endangered" refers to "any species which is in danger of extinction throughout
all or a significant portion of its range", and the status of "Threatened" refers to "any
species which is likely to become an endangered species within the foreseeable future
throughout all or a significant portion of its range" (16 U.S.C. 1532). The US Fish and
Wildlife Service (FWS) has revised the list of Federal-protected species as of June 16,
2000 to include the following protected species for Guilford (G) and Randolph (R)
Counties.
Vertebrates Status County
Bald eagle (Haliaeetus leucocephalus) T G
Cape Fear shiner (Notropis mekistocholas) E R
Vascular Plants
Schweinitz's sunflower (Rhus michauxii) E R
The status of these species is described below. Based on NCNHP files, no documented
occurrences of Federally "Threatened" or "Endangered" species in the vicinity of the Site.
Bald Eagle (Haliaeetus leucocephalus) - The bald eagle occurs throughout North America,
primarily in association with large lakes and coastal bays and sounds where food is
plentiful. Eagles are opportunistic hunters and scavengers, feeding on a wide variety of
aquatic-dependent organisms including fish, snakes, small mammals, and large water
25
0
a
birds. Nest sites occur close to feeding grounds in large trees (predominately pine or
cypress), either living or dead.
The Randleman Reservoir is expected to provide increased habitat potential for bald eagles
in the region. Mitigation activities would be expected to increase the distribution of
aquatic-dependent organisms in the Site, a food source for the raptor.
Cape Fear shiner (Notropis mekistocholas) - The Cape Fear shiner is a small (to 2 inches),
moderately stocky minnow. Food items probably include bottom detritus, diatoms, and
other periphytes (USFWS 1988). Habitat of the Cape Fear shiner is generally clean streams
with pools, riffles, and shallow runs over gravel, cobble, and boulder substrate (Rohde et.
aL 1994). Little is known about the Cape Fear shiner's life history. Present distribution
(November 1988) includes portions of Randolph, Chatham, Lee, Moore, and Harnett
Counties (USFWS 1988). As of 20 December 2000, the N.C. Wildlife Resources
Commission has designated Critical Habitat for this species in the Deep River in portions
of Randolph and Moore Counties, approximately 30 miles below the Site. Because
Richland Creek has been dredged and substrate is dominated by unconsolidated sediment,
habitat for this species is not expected on the Site.
Schweinitz's Sunflower (Helianthus schweinitzii1 - Schweinitz's sunflower is an erect,
unbranched, rhizomatous, perennial herb that grows to approximately 6 feet in height.
The current range of this species is within 60 miles of Charlotte, North Carolina, occurring
on upland interstream flats or gentle slopes, in soils that are thin or clayey in texture. The
species needs open areas protected from shade or excessive competition, reminiscent of
Piedmont prairies. Disturbances such as fire maintenance or regular mowing help sustain
preferred habitat (USFWS 1994). Bottomland forest communities on the Site are not
considered suitable habitat for this species.
Plant and animal species which are on the North Carolina state list as Endangered (E),
Threatened (T), or Special Concern (SC) receive limited protection under the North
Carolina Endangered Species Act (G.S. 113-331 et seq.) and the North Carolina Plant
Protection Act of 1979 (G.S. 106-202 et seq.). NCNHP records indicate no documented
occurrence of state listed species in the vicinity of the project.
3.8 JURISDICTIONAL WETLANDS
Jurisdictional areas are defined using the criteria set forth in the U.S. Army Corps of
Engineers, Wetlands Delineation Manual (DOA 1987). Approximately 13.6 acres of
jurisdictional wetlands were delineated on-site and confirmed by the U.S. Army Corps of
Engineers. Figure 8 depicts the boundary location of existing jurisdictional wetland
systems.
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Jurisdictional wetlands are most prevalent at the mouth of the numerous small tributaries
entering the Site. Discharge from adjacent groundwater slopes and braided channel
streams into the floodplain floor provide sustained surface water expression throughout
much of the year. Additional wetland systems are found in association with abandoned
meander channels located primarily along the south central property boundary.
Approximately 1.9 acres of these jurisdictional wetlands will be inundated by the reservoir
conservation pool (11.7 net acres of jurisdictional wetlands will remain after filling of the
reservoir).
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4.0 WETLAND RESTORATION STUDIES
This section summarizes studies performed to orient restoration design. Studies include:
1) Restoration Alternatives Analyses: Alternatives for wetland restoration
relative to stream, floodplain, and reservoir functions were assessed.
2) Reservoir Pool Sedimentation and Wetland Vegetation Study: Sedimentation
patterns and extent of wetlands were assessed on existing reservoirs in the
region.
3) Surface Water Analyses: Overbank flooding frequency and extent was
estimated based on the selected wetland restoration method.
4) Groundwater Modeling: The effect of drainage features on groundwater
wetland hydroperiods was modeled.
5) Reference Plant Communities: Reference wetland communities were
® sampled to predict the target distribution of vegetation to be established in
restoration areas.
6) Reference Physiography and Surface Topography: Reference wetland
surfaces were measured within an existing alluvial fan and stream to
,i characterize long term, projected conditions at the Site.
4.1 RESTORATION ALTERNATIVES ANALYSES
The objectives of this project include:
1) Assist in protecting the drinking water supply from pollutants discharged
from the developing watersheds. Pollutants attached to sediment
represents the primary water quality concern for this project.
2) Maximize benefits to water quality through establishment of functioning
wetlands above the reservoir pool.
3) Replace habitat for wetland dependent wildlife displaced by establishment
of open water.
4) Maximize the area of wetland restoration achieved by the project.
Restoration alternatives suggested by project participants are briefly described below.
Stable Channel Construction
Reconstruction of a potentially stable stream system was assessed as a replacement for
the existing, dredged and incised channel. The new channel would be designed to mimic
referenced, stable attributes including the geomorphic dimension, pattern, and profile
needed to transport water and sediment produced by the watershed. The restored
channel would reduce the rate of groundwater withdrawal from adjacent floodplains,
potentially resulting in wetland hydrology restoration in certain areas.

29
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This alternative would facilitate transport of sediment generated by the watershed into
the Randleman Reservoir. Within the lower half of the Site, this capacity to transport
sediment would be unavoidably stopped by the conservation pool associated with the
reservoir. In addition, facilitating transport of sediment and pollutants into water supply
waters is considered contrary to water quality related, project objectives. Therefore, this
option was discarded.
Greentree Impoundments
Greentree impoundments comprise a series of floodplain levees and controllable outlet
structures that are modified periodically throughout the year to promote the development
of forested, shrub-scrub, and emergent wetlands. Greentree impoundments have been
constructed above other water supply reservoirs in the region for wetland, wildlife, and
sediment retention functions. These structures can be controlled to regulate the depth
and frequency of inundation based upon objectives of the system. In this case, the
structures would be used to establish vegetated wetlands and limit transport of pollutants
into the reservoir.
In general, the levee system is constructed to provide for less than 2 to 3 feet of
inundation during winter months, to prevent over-topping, and to allow for survival of tree
seedlings. The winter depth is generally dependent upon the height of seedlings. The
raising and lowering of outlet structures requires regular monitoring and maintenance by
qualified personnel to facilitate the growth of tree species. The actual date that the
outlet is modified may vary annually and is dependent upon localized conditions within
the watershed. Seedling mortality is tracked on an annual basis and the date of spring
lowering is modified to maximize the rate of forest regeneration. Tree species selected for
planting may also be modified based upon collected data. Greentree impoundments
designed for forested wetland restoration have failed in the past, due primarily to lack of
resources for monitoring, management, and manipulation.
Based on alternatives analyses, construction of greentree impoundments across the
Richland Creek floodplain represents a viable option for this project. Although
construction activities would induce disturbances within the existing forest, the structures
would allow pro-active control of wetland development and function behind each
impoundment. An option that reduces both controllability and disturbance to the existing
landscape involves passive development of an alluvial fan as described below.
Alluvial Wetland Fan Development
This alternative is similar to greentree impoundments as described above. Both options
are designed to elevate water tables and reduce sediment transport into the reservoir.
However, with this scenario, levees are not constructed across the floodplain. Alluvial fan
development entails placement of fixed, in-stream weirs within the dredged channel. The
in-stream modifications are expected to reduce the degree of channel incision, increase
overbank flooding, reduce stream sediment transport capacity, and provide greater
30
i.l
sediment deposition within vegetated wetlands. The system would progress towards an
alluvial wetland fan where the channel actively migrates across fluvial material. During
the interim period, in-stream structures will sustain significant energy during flood events;
therefore, the potential exists for development of channel by-passes (shoot cut-offs)
around the structures. As such, risk of wetland restoration failure exists. The structures
must be designed to avoid short-circuiting and provide for sediment deposition in the
incised channel. Over a relatively long period of time, the shallower channel would
invariably abandon the structures and begin to actively migrate across the restored
floodplain. At this point, the system would need to be monitored for evidence of head-
cutting immediately above the reservoir or migration bank into the abandoned, dredged
channel. Additional structural modifications may be required in the future, after the
migrating stream abandons the existing dredged channel.
Passive development of an alluvial fan immediately above the reservoir represents a viable
option for this Site. This option will reduce initial disturbance in the floodplain associated
with greentree impoundments, reduce implementation cost relative to greentree
impoundments, and will require less need for seasonal management of the structures.
Based on alternatives analyses, placement of in-stream structures and alluvial wetland
development has been selected as the preferred mitigation alternative.
4.2 RESERVOIR POOL LEVEL AND SEDIMENTATION ANALYSIS
Reservoir sediment quality is an important environmental concern because sediment may
act as both a sink and a source of water-quality constituents to the overlying water
column and biota. Sedimentation rates are dependant on existing land use, land use
modifications, soils, and basin topography. Alternatives for sedimentation reduction
potentially include up-stream land management techniques, sluicing of sediment through
the reservoir, or interception of the sediment prior to entry into the reservoir. Even with
strict land management techniques in an urbanizing watershed, a certain amount of
"background" sediment will continually be moved by erosion processes. In a stable river
bed, erosion, sediment transport and deposition are in equilibrium. Dam construction
disrupts this balance, raising the base level of streams above the reservoir, and
encouraging the deposition through reduction of the gradient. As a result, the stream
deposits sediment as a delta at the confluence with the conservation pool. The
deposition process, otherwise known as warping or shoaling, advances at varying rates
dependent on the site and rate of sediment supply. Slope angles and extension patterns
on the delta are dependent on the particle size of the prevailing sediment deposited, with
courser sediment associated with higher angle slopes.
The Richland Creek wetland restoration project resides immediately above the normal pool
elevation (i.e. conservation pool) for the Randleman reservoir (Elevation = 682 feet above
MSL). Currently, the stream channel is incised to depths which induce a groundwater
withdrawal gradient (rate) that does not allow for wetland presence on the adjacent
primary floodplain. After the reservoir is constructed, sediment accretion is likely to occur
31
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within the Site, immediately upstream and downstream of the conservation pool. This
accretion will form a "sediment wedge" within the floodplain, stream channel, and delta
area inducing passive wetland conditions for an unknown distance (or elevation) in both
the upstream and downstream direction.
Obiectives
The objective of this study is to collect the following information on existing reservoirs
in the region:
1) Determine the elevation range above the conservation pool that supports
relatively contiguous wetlands apparently resulting from the conservation
pool, groundwater mounding, and/or sediment accretion. The data reported
will include the elevation of the conservation pool, the average period that
the reservoir water surface resides at the conservation pool elevation, the
elevation range for relatively contiguous, forested wetland formation, and
elevation range for emergent wetland formation.
2) Determine the elevation range of the stream bed above the conservation
pool that has sustained sediment accretion to the extent that the channel
supports an average depth of 1 foot or less.
3) Determine the range of channel depths present in the wetland elevation
range.
4) Prepare a profile and plan view that depicts typical conditions relative to the
conservation pool.
®t Methods
?f Field reconnaissance of several reservoirs and impoundments in the central Piedmont was
conducted in order to establish baseline information on sedimentation and wetland
development around the point of stream inflow and conservation pool levels. Two sites
were chosen that best exhibited long term (> 10 years) sedimentation processes for large
and small watersheds. One site is located at the point of inflow of Little Briar Creek into
Crabtree Lake, Wake County. Little Briar Creek services a watershed of approximately
13.5 square miles. Land use for this sub-basin is predominantly forested, but is part of
a rapidly developing part of Research Triangle Park, including the Raleigh-Durham
International Airport. The second site is located at the inflow of an unnamed tributary
of Horse Creek into Falls Lake, Wake County. The tributary services a watershed of
approximately 0.3 square miles. Land use for this watershed is predominantly forested,
though residential development is encroaching upon the upper reaches of the area.
Soils are mapped as the Chewacla series throughout the Crabtree Lake site, similar to
conditions on the mitigation site (USDA 1970). On the Falls Lake site, soils are mapped
as the Wake soils, 10-25% slopes (Lithic Udipsamments).

32

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Topographic maps of the alluvial wetland fans were prepared to 0.5-foot contour intervals
by laser level and Global Positioning System (GPS) measurements. Embankments,
shorelines, and wetland boundaries were measured and surveyed relative to the reservoir
water surface elevations. For Falls Lake, conservation pool and daily water surface
elevations were obtained for a 16-year period from USACE (1984-1999). Pool elevation
for Crabtree Lake was obtained from the elevation of the low-flow spillway crest tied to
a local USGS benchmark. Cross-sections and profiles were generated for the local stream
reach and floodplain area. Sediment borings were sited at various points along the
boundary of wetlands to determine depth of groundwater table relative to reservoir
elevations.
Results
Figures 9 and 10 provide a plan view and cross section for the sites at Crabtree Lake and
Falls Lake, including the groundwater elevations along the wetland fringe. Within the
conservation pool, a majority of the sediment deposition area resides under approximately
0.5 feet of water. Sediment deposition is greatest below the pool elevation contour with
inundated sediment bars generally extending into the lake over time. As the deposition
wedge elevates within central reaches of the inundated floodplain, the channel tends to
migrate towards the toe of adjacent slopes, incrementally filling the inundated valley floor.
On average, emergent wetland vegetation is present on accreted sediment to within 1 foot
below the normal pool. Forested and shrub-scrub wetland vegetation is typically present
to 2 feet above the normal pool in the upstream direction. These wetlands appear be
induced by an up-welling in the down-valley migration of groundwater, prior to inflow
with the conservation pool.
A review of lake level data for these reservoirs suggests that the water surface that
induces these wetlands resides within 0.5 feet of the conservation pool elevation, on
average, for 66% of the year. In Falls Lake, data indicate that the sediment wedge is
generated by water surfaces within 2 feet of the conservation pool elevation for 82% of
the time over the 15-year monitoring period'.
The study suggests that sediment deposition is concentrated within inundated areas at
or just below the conservation pool elevation. As the sediment surface approaches the
elevation of the conservation pool, the wedge begins to extend further into the reservoir.
This accreting surface passively develops emergent wetland vegetation on surfaces within
1 foot of the conservation pool. This accreting wetland surface will continue to enlarge
over the life of the reservoir.
1 For Falls Lake, the conservation pool elevation has been held fixed at 250.1 feet above MSL
over the 15-year monitoring period.
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develop passively on floodplain surfaces that reside up to 2 feet above the conservation
pool. The area sustains sediment deposition in the active channel, including channel
migration across the developing delta over time.
Application
For this application, the water surface within the filled, Randleman Reservoir is assumed
to remain within 0.5 feet of the conservation pool (682 feet above MSL) for a minimum
of 66% of the year and within 2.0 feet of the conservation pool for a minimum 82% of
the time over a 15-year period. Figure 11 depicts mapping of resulting passive wetland
development projected to occur on the Site as a result of the Randleman Reservoir.
The Site includes approximately 13.0 acres of open water (below 681 elevation) that are
projected to support future accretion and development of emergent wetlands. The 13.0-
acre area includes backwater conditions from the reservoir that will extend up the entire
on-site reach of the Richland Creek channel.
Between elevations of 681 and 682 feet above MSL, emergent and submerged aquatic
vegetation is projected to develop. This area will be semi-permanently saturated or
inundated up to 1 foot in depth immediately after filling the reservoir. Based on reference
studies, the area is expected to support 7.0 acres of wetlands upon project completion.
In upper reaches of the lake effect area, shrub-scrub and forested wetland systems are
expected to be passively restored, encompassing approximately 9.0 acres on lands from
682 to 684 feet above MSL.
In total, approximately 24.0 acres are expected to support wetlands as a result of
hydrological modifications associated with the reservoir. Active wetland restoration
measures will include removal of dikes within the restoration area, planting of wetland
adapted vegetation, and placement of in-stream weirs designed to laterally extend the
sediment wedge and wetland extent in the up-valley direction.
4.3 SURFACE WATER ANALYSES
Surface drainage on the Site and surrounding area was analyzed to predict the effects of
diverting existing surface drainage into wetland restoration areas along the primary and
secondary floodplains. Several alternatives were evaluated to determine surface water
modifications that maximize wetland acreage and water quality benefits, while providing
for increased wetland habitat for dependent species.

36

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Hydrologic and hydraulic analyses were completed using standard study methods of
USACE and NRCS. Flood events of a magnitude which are expected to be equaled or
exceeded once on average every 1-, 2-, 5-, 10-, or 100-year period were selected to
characterize existing and proposed conditions at the Site.
Hydrologic Analyses
Hydrologic analyses were carried out using the USACE HEC-1 model to establish the peak
stream discharge for the 1-, 2-, 5-, 10-, and 100-year flood events.
Input for the HEC-1 model consisted of synthetic storm precipitation data, drainage area,
NRCS curve numbers, and drainage basin lag time. Table 2 summarizes the total, 24-hour
precipitation event for each storm that was analyzed. Precipitation data was obtained
from U.S. National Weather Service documents (NOAA TP-40 and Hydro-35). The
drainage area was delineated on 7.5-minute USGS topographic maps and then subdivided
into subbasins based on land use or location of tributaries. The drainage area for each
subbasin was estimated using a planimeter. The NRCS curve numbers were estimated
using methods described in the TR-55 model. The subbasin lag times were estimated
using Snyder's method.
Because there were no onsite gage data, the HEC-1 computer models could not be
calibrated. The models were validated by comparing the 100-year peak discharges
estimated from the HEC-1 models with peak discharges estimated by regional formulas for
the Piedmont region of North Carolina in the USGS Water-Resources Investigations Report
87-4096. NRCS curve numbers for the HEC-1 models were adjusted until the HEC-1 peak
discharges were within 25 - 30% of the regional formula values. Table 2 summarizes peak
discharges estimated by the validated HEC-1 model and the regional equations.
Hydraulic Analyses
Water-surface elevations of the 1-, 2-, 5-, 10-, and 100-year floods of Richland Creek were
estimated using the USACE HEC-2 computer program. Channel cross sections for the .
hydraulic analyses were obtained from the most currently available HEC-2 computer runs
completed for Federal Emergency Management Agency (FEMA) Flood Insurance Studies
(FIS). Additional cross-sections that were needed to model proposed structures were
taken from digital orthophoto maps with a contour interval of 1 foot.
38

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taken from the HEC-2 computer runs previously mentioned and verified with field
inspections of the sites. Roughness coefficients in the main channel were 0.06 and 0.12
for overbank areas.
Starting water surface elevations and energy slope for existing conditions were estimated
from the published flood insurance studies for Guilford County. The slope-area option
provided by the HEC-2 model was used to estimate the true value of the water surface
i elevation at the beginning cross-section. For future conditions, the starting water surface
elevation at the first cross-section was 688.21 feet (100-year reservoir pool elevation) for
the 100-year flood and 682 feet for the 1-, 2-, 5-, and 10-year floods (normal reservoir
pool elevation).
Tables 2 summarizes the water surface elevations for existing and proposed conditions.
Water surface elevation are approximately 2.6 - 3.2 feet higher for proposed conditions
in downstream reaches of the Site, which is the closest cross-section to the reservoir pool.
As the cross-sections progress upstream away from the reservoir, the difference between
proposed and existing conditions decreases.
Figure 7 (Section 3.0) depicts modeled flood elevations for the 1-, 2-, and 100-year, 24-
hour storm event. The model indicates that overbank flooding has been effectively
eliminated until the 10-year storm along diked sections of the Creek. For the more
frequent storm events in un-diked areas (1-year to 5-year return interval), the efficacy of
the model has been questioned based upon observations in the field. The model suggests
that overbank flooding occurs annually under existing conditions.
Contact with former land managers suggest that overbank flood events have not been
recalled since the early 1990s. This period includes 24-hour rainfall events of 2.95 inches
and 4 inches (City of Greensboro rainfall on 16 February 1998 and 9 September 1996
respectively). Visual observations of erosion, scour, and wrack lines indicate that the
water surface resided several feet below the bankfull channel during the period after a
2.97- inch and 2.98-inch, 24-hour event (19 March 1998 and 8 May 1998 respectively).
One overbank event was recalled by operators of the nearby sewage treatment plant in or
around 1990, possibly due, in part, to a 5.55-inch rain event in January 1990. If so, these
observations suggest that overbank flooding under existing conditions may not occur until
events approximated by the 10-year to 100-year return interval, contrary to the HEC2
estimates.
Restoration methods are designed to reduce the channel from 7.5 feet in depth below the
floodplain to 1-3 feet below the floodplain after restoration. The channel cross-sectional
area will decrease from an average of approximately 237 square feet under existing
conditions to 65 square feet after modifications (73% reduction in cross-sectional area).
Based on available information, the reduction in channel cross-sectional area is intended
40

to restore overbank flooding from the 10-year to 25-year return interval to the 1-year
return interval or less for riverine wetland restoration purposes. The flood waters and
suspended sediment would migrate as sheet flow or groundwater migration in the down-
valley direction, across restored forested floodplains within the Site.

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4.4 GROUNDWATER MODELING
Groundwater modeling was performed to characterize water table elevations under historic
(reference), existing, and post-restoration conditions. The groundwater modeling software
selected for simulating shallow subsurface conditions and groundwater behavior at the
Site is DRAINMOD. This model was developed by R.W. Skaggs, Ph.D., P.E., of North
Carolina State University (NCSU) to simulate the performance of water table management
systems.
Model Description
DRAINMOD was originally developed to simulate the performance of agricultural drainage
networks on sites with shallow water table conditions. DRAINMOD predicts water
balances in the soil-water regime at the midpoint between two drains of equal elevation.
The model is capable of calculating hourly values for water table depth, surface runoff,
subsurface drainage, infiltration, and actual evapotranspiration over long periods
referenced to climatological data. The reliability of DRAINMOD has been tested for a wide
range of soil, crop, and climatological conditions. Results of tests in North Carolina
(Skaggs, 1982), Ohio (Skaggs et a/. 1981), Louisiana (Gayle et A 1985; Fouss et A
1987), Florida (Rogers 1985), Michigan (Belcher and Merva 1987), and Belgium (Susanto
et A 1987) indicate that the model can be used to reliably predict water table elevations
and drain flow rates. DRAINMOD has also been used to evaluate wetland hydrology by
Skaggs et a/. (1993). Methods for evaluating water balance equations and equation
variables are discussed in Skaggs et a/. (1993).
DRAINMOD has been modified for application to wetland studies by adding a counter that
accumulates the number of events wherein the water table rises above a specified depth
and remains above that threshold depth for a given duration during the growing season.
Wetland hydrology is defined as groundwater within 12 inches of the surface for 28
consecutive days (12.5% of the growing season), and 11 consecutive days (5% of the
growing season). Wetland hydrology is achieved in the model if target hydroperiods are
met for more than one-half of the number of years modeled (i.e., 16 out of 31).
Groundwater drainage contours are established on available mapping for various durations
of saturation within 1-foot of the soil surface (i.e. saturation contour for 0-5%, 5-12.5%,
and 12.5-20% of the growing season).
41
n
I
Model inputs for DRAINMOD simulations were obtained as follows: the United States
Department of Agriculture (USDA) soil texture classification, number of days in the
growing season (defined as March 26 - November 6), and hydraulic conductivity data
were obtained from the NRCS soil survey for Guilford County (USDA 1977). Inputs for
soil parameters such as the water table depth/volume, drained/upflux relationship, Green-
Ampt parameters, and water content/matric suction relationship were obtained utilizing
the MUUF computer software developed by NRCS. Precipitation and temperature files
were obtained for the years 1930 through 1980 for Charlotte, North Carolina.
DRAINMOD simulations were designed to predict the transition zone from Chewacla soils
to Wehadkee soils based on groundwater drainage conditions within a relatively flat
floodplain surface. Chewacla soils represent a nonhydric (nonwetland), somewhat poorly
drained soil that is common on primary floodplains immediately adjacent to streams. The
Wehadkee series comprises hydric (typically wetland), poorly drained soils that are typical
in backwater floodplain areas situated further from drainageways.
Forested conditions (evapotranspiration rates) and published hydraulic conductivity values
were assumed for Chewacla soils. The simulations were run for six channel inverts (0, 1,
2, 4, 6, and 8 feet) and at various target hydroperiods during the growing season. Table
3 provides a depiction of the groundwater discharge zone of influence by invert depth
(elevation below floodplain). For example, a stream channel invert 6 feet below the
floodplain elevation is modeled as reducing surface hydroperiods below 5% of the
growing season at a distance of 215 feet from the channel. A former floodplain surface
6 feet in elevation above the channel invert and greater than 215 feet from the channel
is projected to support wetlands.
The preliminary groundwater drainage model was interpreted based upon field verification
of NRCS soil map units, channel depth (based on measured cross-sections), and floodplain
elevation (based on topographic maps). Model parameters were set to predict the average
annual duration in which groundwater remains within 1-foot of the soil surface at
assigned elevations above a channel invert or in-stream structure. The floodplain
elevations outside of the groundwater drainage contour and at the modeled channel depth
were judged to have a hydroperiod greater than 5 percent. Mapping of areas potentially
supporting wetland hydrology was prepared based on available topographic mapping
(Figure 12).
Post-Restoration Model Applications and Results
For groundwater wetland restoration, the primary objectives of this project include: 1)
reduce channel incision along Richland Creek and associated tributaries; 2) elevate the
groundwater gradient into the rooting zone for developing vegetation; and 3) establish
minimum wetland hydroperiods encompassing 5% of the growing season, which are
typical for riverine wetlands in the Piedmont hydrophysiographic province. Therefore, the
effective post-project depths of the Richland Creek channel will be reduced from an
average of 7.5 feet under existing conditions to gradients between 1 to 3 feet below the
® floodplain.
42
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0
Table 3
Modeled Groundwater Discharge Zone of Influence on Wetland Hydroperiod
Chewacla / Wehadkee Soil
Hydroperiods
<5% of the
growing season) Hydroperiods <
12.5% of the
growing season)`
Forested Conditions
(relatively high surface water storage and rooting functions)
0 ----- 29/31 ----- 27/31
1 253 20/31 145 16/31
2 85 16/31 225 16/31
3 125 16/32 275 17/31
4 160 16/31 315 16/31
6 215 16/31 380 16/31
8 245 16/31 405 16/31
Floodplain Surface Groundwater Number of Groundwater Number of
Elevation Above Discharge Zone of Years Discharge Zone of Years
Channel Invert / Influence 2.1 Wetland Influence Wetland
Weir Height' (feet) Criteria Met (foet) Criteria Mot
(feet) (Surface (Surface
1: "Weir Height" is assumed to represent the effective depth (invert) of the drainage feature.
2: Soil hydraulic conductivities and drainage rates have been generalized based upon NRCS data and regional
averages.
3: Discharge Zone of Influence is equal to %: of the modeled ditch spacing
4: Based on field observations, soil types projected to support wetland hydroperiods for greater than 5% to
12.5% of the growing season are expected to exhibit characteristics more indicative of the Wehadkee
series, a poorly drained soil. Based on the model, these areas may occur on floodplains within 25 feet
to 200 feet of streams potentially lacking significant effluent (groundwater withdrawal) character, such
as very shallow channels. Conversely, the model suggests that the transition from Chewacla soils
(somewhat poorly drained) to Wehadkee soils (poorly drained) may be achieved adjacent to larger
(dredged) effluent channels at distances ranging from 300 feet to 400 feet from the drainage structure
(assuming a relatively flat floodplain surface).

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DRAINMOD simulations modeled the zone of influence of the post project channel on
wetland hydroperiods within the primary floodplain. The maximum zone of influence may
be used to predict the area of groundwater wetland hydrological influence that may result
due the elevation of stream flow within the channel. In addition, the model provides an
estimate of the area that may continue to be affected in perpetuity by the stream channel
at a depth of 1 to 3 feet below the floodplain elevation.
Based on these simulations, the post-restoration channel is expected to continue to
effectively drain groundwater from adjacent areas to a distance of approximately 25 feet
to 125 feet from the channel, dependent upon the effective channel depth (base-flow
water surface elevation). Based on the model, approximately 6.4 acres immediately
adjacent to the post-restoration channel will not support groundwater wetland
hydroperiods (< 5% of the growing season) (Figure 12). In order to establish wetlands
in these stream-side areas, overbank flooding (surface water inputs) need to be restored
to a 1-year (annual) return interval with surface and vegetation roughness preventing
return flow to the channel for a minimum of 5 % (11 days) of the growing season.
4.5 REFERENCE PLANT COMMUNITIES
In order to establish a forested wetland system for mitigation purposes, a reference
community needs to be established. According to Mitigation Site Classification (MIST)
guidelines (EPA 1990), the area of proposed restoration should attempt to emulate a
Reference Forest Ecosystem (RFE) in terms of soils, hydrology, and vegetation. In this
case, the target RFEs were composed of steady-state woodlands in the region that have
sustained loading of fluvial sediments on floodplains in the past. However, forest
canopies have developed on these reference sites which support soil, landform, and
hydrological characteristics that restoration will attempt to emulate.
All of the RFE sites have been impacted by sediment deposition, selective cutting or high-
grading, channel migration/disturbances, and relatively high energy flood events.
Therefore, the species composition of these plots should be considered as a guide only.
Reference forest data used in restoration was modified to emulate steady state community
structure as described in the Classification of the Natural Communities of North Carolina
(Schafale and Weakley 1990).
Two regional reference sites were selected within floodplains along the Rocky River in
Cabarrus County, North Carolina. Floodplains associated with this river system have
aggraded over the past century, inducing braided channel configurations and accelerated
sediment deposition within reference feeder tributaries. However, the 16 plots have been
placed within relatively mature bottomland hardwood/swamp forests that have developed
on accreted sediment.
45
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The reference vegetation samples are designed to characterize the plant communities
proposed for restoration. Circular, 0.1-acre plot sampling was utilized to establish base-line
vegetation composition and structure in reference areas. Species were recorded along
with individual tree diameters, canopy class, and dominance. From collected field data,
importance values (Brower et al. 1990) of dominant canopy and mid-story trees were
calculated. The composition of shrub/sapling and herb strata were recorded and identified
to species (Table 4 and Table 5).
At Site 1 (Table 4), the forest canopy is dominated by green ash, (Importance value [IV]
28%), sweetgum (IV 19%), American elm (U/mus americana) (IV 11 %), box elder (IV 8%)
and red maple (IV 7%). Canopy species with lesser importance include black willow,
slippery elm (U/mus alata), river birch, tulip poplar, and water oak (Quercus nigra).
Understory trees include flowering dogwood, ironwood, and sugarberry (Celtis laevigata).
A developed shrub layer is not generally present. Herbs include Nepal microstegium,
violets (Viola spp.), asters (Aster sp.), and river oats (Chasmanthium latifolium).
At Site 2 (Table 5), the forest canopy is dominated by green ash, (IV 39%), box elder (IV
22%), American elm (IV 12%), and swamp chestnut oak (IV 6%). Portions of the canopy
at RFE locations were also dominated by ironwood, overcup oak (Quercus lyrata),
sugarberry, sweet gum, red maple, black willow, slippery elm, water oak, and river birch.
The shrub/sapling layer is characterized by the non-native Chinese privet (Ligustrum
chinensis), paw-paw (Asimina triloba), and shade tolerant canopy species. Herbaceous
species include Japanese honeysuckle (Lonicera japonica), blackberry, muscadine, common
greenbriar, sedges (Carex spp.), and poison ivy.
Piedmont swamp forests are communities located in depressional areas, along toe slopes,
and at the confluence of alluvial valleys, where lateral flow is restricted. These sites are
hydrologically influenced by upland seeps and drainages, and by occasional riverine
flooding. Overstory species are dominated by flood-tolerant bottomland elements such
as sweetgum, American elm, willow oak (Quercus phellos), swamp chestnut oak, green
ash, overcup oak, and swamp cottonwood (Populus heterophylla). Wetter sites may
provide a broken to open canopy providing enough light for development of a dense
herbaceous/shrub layer. Species found on these sites may include button-bush
(Cephalanthus occidentalis), elderberry (Sambucus canadensis), silky dogwood, false
nettle (Boehmeria cylindrica), sedges (Carex spp), rushes (Juncus spp.), and lizard's tail
(Saururus cernuus). Giant cane (Arundinaria gigantea) is prevalent in places.
J

46

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4.6 REFERENCE PHYSIOGRAPHY AND SURFACE TOPOGRAPHY
Surface features were mapped within reference Piedmont swam p/bottomland hardwood
forest in order to establish base-line topographic conditions for restoration planning use.
This community lies within a seasonally to semi-permanently inundated area that has
supported sediment accretion in the past with inundation from stream flows occurring on
a frequent basis. The channel is actively migrating across alluvial fans developed within
the aggrading floodplain.
Topographic maps of the accretion area were prepared to 0.5-foot contour intervals by
laser level and tape measure. Abandoned stream channels were mapped along with
approximate jurisdictional wetland extent relative to the water surface within stream
channels. A plan view, cross-sections, and profiles were generated for the channel and
adjacent alluvial surface. The channel dimension, rate of channel migration, and slope of
the floodplain floor represent the primary features extrapolated for use in restoration
planning. The objective of restoration is to reduce the effective size of the Richland
channel to induce sediment deposition, channel migration, braiding, ponding, and/or
anastomosed stream types above the water supply reservoir.
Figure 13 depicts a plan view and cross-sections of the alluvial fan, including locations of
abandoned channels that have developed over the last several years. The channel exhibits
active migration across the valley floor as aggradation processes elevate isolated portions
of the floodplain. The active channel is classified as an E5 (highly sinuous) stream type
in upper reaches of the reference Site. Subsequently, the channel transitions into an
anastomosed (DA5-6) channel and subsequent braided (D6) channel immediately prior to
the confluence with a near-permanently inundated section of the reference reach. This
braided reach and near-permanently inundated area represents projected conditions within
the transition zone into the reservoir conservation pool. The floodplain throughout this
reference reach continues to support forest vegetation, including shrub-scrub dominated
communities within the potentially inundated areas.
r

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5.0 WETLAND RESTORATION PLAN
This wetland restoration plan has been designed to convert the dredged channel and
adjacent abandoned terrace into an alluvial wetland complex immediately above and
within the Randleman Reservoir conservation pool. Components of the plan have been
established based on reference wetland studies described in Section 4.0. This effort will
be performed by: 1) passively saturating/inundating surfaces associated with the
conservation pool; 2) removing constructed stream-side levees; 3) installing in-stream
weirs; 4) scarifying pastured surfaces for reforestation; 5) distributing woody debris into
formerly cleared and pastured areas; and 6) planting of target wetland tree species in the
area. Monitoring of wetland development will be performed to track successional
characteristics of the Site and to verify wetland restoration success.
5.1 PASSIVE SATURATION / INUNDATION FROM THE RESERVOIR POOL
Based on reference studies within existing water supply reservoirs in the region, wetlands
are projected to develop on surface elevations ranging from a minimum of 1 foot below,
to 2 feet above the conservation pool (681-684 feet above MSL). As depicted in Figure
11, shrub/scrub and submerged aquatic vegetation is projected to develop on surfaces
ranging between 681 and 682 feet above MSL, encompassing approximately 7 acres of
land area. This land area is expected to expand into open water portions of the Site over
time as sediment accretion occurs within the reservoir pool (below existing elevations of
681 feet above MSL). However, restoration plans are designed to delay this accretion in
favor of alluvial wetland development outside of the open water area.
Based on reference studies, elevations between 682 and 684 feet above MSL will passively
develop shrub-scrub, bottomland hardwood, and bottomland swamp forest wetlands.
This area encompasses approximately 17 acres within central portions of the Site (Figure
11). These areas will be planted with tree species likely to replace existing elements as
wetland hydrology begins to dominate the area (Section 5.6). Active wetland restoration
will be initiated immediately above wetlands passively restored by the conservation pool.
Because restoration design is dependent upon initial establishment of backwater
conditions in Richland Creek, construction activities associated with placement of in-
stream weirs (Section 5.3) must be performed concurrent with filling of the reservoir.
5.2 CONSTRUCTED LEVEE REMOVAL
The constructed levee adjacent to Richland Creek will be lowered to adjacent floodplain
elevations as depicted in Figure 14. Spoil material will be used to the extent possible for
backfill during construction of in-stream weirs. The remaining material will be hauled to
an appropriate off-site location.
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The levee removal will extend for approximately 2800 feet on both sides of Richland Creek
(1400 feet each side of channel). Based on aerial topographic mapping, the levee
averages approximately 20 feet in width and 3 feet in height, including approximately
170,000 cubic feet (6,000 cubic yards) of excavated material. Surfaces will be stabilized
within the 1 acre area through scarification, mulching, planting of temporary erosion
control elements, and planting of shrub-tree elements as described in Section 5.6.
5.3 IN-STREAM WEIR CONSTRUCTION
In-stream weirs will be installed in the channel at the locations depicted in Figure 14. The
purpose of the weir is to: 1) elevate the base-flow water surface elevations within 1 to 2
feet of the floodplain throughout a majority of the reach; 2) elevate the groundwater table
to within 1 foot of the primary floodplain during portions of the growing season; and 3)
decrease the effective channel cross-sectional area from 237 square feet to an average of
65 square feet under post-restoration conditions. The structures will further modify
1 energy distributions through decreases in channel slope, designed to increase overbank
flooding and induce sediment deposition onto the floodplain.
' Four weirs are proposed with weirs placed at each 2-foot rise in the valley floor. The first
weir has been placed on the valley floor at the 684-foot contour depicted on topographic
mapping. A more accurate placement of this structure can be achieved by observing
actual water surface elevations in the channel resulting from the established conservation
pool. Subsequently, the weir would be accurately placed two feet above the conservation
pool water surface. Figure 15 provides a depiction of the target water surface profile
relative to the conservation pool and channel bed.
The weirs will be constructed of concrete or comparable material large enough to prevent
collapse of the structure during peak flows. The engineering design will ensure that the
weirs are not bypassed until the existing channel has been effectively filled with sediment.
If a structure is abandoned during new channel formation, modifications will be performed
to ensure that return flow does not divert directly back into the channel immediately
1 below the weir. In the interim period, shoot cut-offs around the weir will steepen the
water surface gradient and potentially short-circuit wetland restoration efforts. The
design or placement of these weirs may be modified during the engineering design phase
1 based on potential stability, constructability, cost, or other constraints

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5.4 SURFACE SCARIFICATION
Before wetland community restoration is implemented, pasture lands will be scarified
(Figure 14). The scarification will be performed as linear bands directed perpendicular to
land slope (surface water flows). After scarification, the soil surface will exhibit complex
microtopography ranging to 1 foot in vertical asymmetry across local reaches of the
landscape. Restored microtopographic relief is considered critical to short term hydrology
restoration efforts. Therefore, multiple passes along each band is recommended to ensure
adequate surface roughing and surface water storage potential across the Site.
Subsequently, community restoration will be initiated on scarified wetland surfaces.
5.5 WOODY DEBRIS DEPOSITION
Re-introduction of woody debris represents an important component of wetland
restoration on pastoral lands. Woody debris, including downed trees, tip mounds, snags,
and decomposing material represents important habitat elements for wetland dependent
wildlife. However, the restoration areas on pasture land will not be capable of providing
coarse, woody habitat elements for up to 50 years after re-planting. Therefore, woody
material generated from levee removal, weir construction, or other activities will be
distributed across future wetland surfaces to the extent feasible. The material may be
lifted or pushed from adjacent windrows or forest areas as well.
5.6 WETLAND COMMUNITY RESTORATION
Restoration of wetland forested communities provides habitat for area wildlife and allows
for development and expansion of characteristic wetland dependent species across the
landscape. Ecotonal changes between community types contribute to diversity and
provide secondary benefits such as enhanced feeding and nesting opportunities for
mammals, birds, amphibians, and other wildlife.
RFE data, on-site observations, and ecosystem classification has been used to develop the
species associations promoted during community restoration activities. Target plant
community associations include: 1) Piedmont swamp/bottomland hardwood forest and
2) scrub-shrub/Piedmont swamp forest. Figure 16 provides a conceptual depiction of
potential communities projected within the influence of the conservation pool including
emergent, shrub, and forest communities. Figure 17 provides a depiction of projected
communities in upper reaches of the Site, where stream flows will continue to facilitate
establishment of more characteristic bottomland hardwood distributions.
Plantina Plan
Emphasis has been focused on developing a diverse plant assemblage. This is particularly
vital due to the limited distribution of mast-producing bottomland hardwood tree species
presently existing in the vicinity, as evidenced during the RFE search. Planting a variety
of mast-producing species will provide a food source for wildlife and will facilitate habitat
diversity on the Site.
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The planting plan consists of: 1) acquisition of available wetland species; 2)
implementation of proposed surface topography improvements; and 3) planting of
selected species on-site. Figure 18 depicts the locations targeted for planting,
encompassing 42.3 acres of land area. Planted species names by community are listed
below.

PiedmontSwamp/Bottomland Hardwood Forest
1. Cherrybark Oak (Quercus pagoda)
2. Overcup Oak (Quercus lyrata)
3. Willow Oak (Quercus phe/%s)
4.
5. Swamp Chestnut Oak (Quercus m/chaux/i)
Swamp Cottonwood (Popu/us heterophylla)
6. Shagbark Hickory (Carya ovata)
7. Bitternut Hickory (Carya cordiformis)
8. Green Ash (Fraxlnus pennsylvan/ca)
9 American Elm (U/mus amer/cana)
10 Winged Elm (U/mus a/ata)
11. Tulip Poplar (Ur/odendron tulipifera)
Scrub-Shrub/Piedmont Swamp Forest
1. Black Willow (Sa/ix n/gra)
2. Possum-haw (ilex decidua)
3. Carolina holly (//ex amb/gua)
4. River Birch (Betula n/gra)
5. American Sycamore (Platanus occidental/s)
6. Green Ash (Fraxinus pennsy/vanlca)
7. American Elm (U/mus amer/cana)
8. Swamp Cottonwood (Popu/us heterophylla)
9. Overcup Oak (Quercus lyrata)
10.
11. Swamp Chestnut Oak (Quercus mlchauxll)
Silky Dogwood (Corpus amomum)
12. Button-bush (Cephalanthus occidental/s)
13. Elderberry (Sambucus canadensis)

14. Tag Alder (A/pus serru/ata)
Species selected for planting will be dependent upon availability of local seedling sources.
Advanced notification to nurseries (1 year) may facilitate availability of various non-
commercial species. Bare-root seedlings of tree species will be planted within specified
areas at a density of 680 stems per acre (8-foot centers). The total number of stems and
species distribution within each planting association are depicted in Table 6.
1 58

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Planting Plan
Vegetation Association
(Planting area) Shrub-Scrub/
Swamp Forest Bottomland
Hardwood/
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PLANTED
Stem Target (trees/ac) 680 680
Area (acres) 9.5 32.8 42.3
SPECIES # planted
1% total) # planted
total) # planted
(% total)
River Birch 65000) 650
Silky Dogwood 65000) 650
Button-bush 650 (10) 650
Elderberry 650(10) 650
Tag Alder 650(10) 650
Black Willow 325 (5) 325
Possum-haw 325 (5) 325
Carolina Holly 325(5) 325
American Sycamore 325 (5) 325
Swamp Cottonwood 65000) 2250 (10) 2900
American Elm 325 (5) 1125 (5) 1450
Green Ash 325 (5) 1125 (5) 1450
Swamp Chestnut Oak 325 (5) 2250 (10) 2575
Overcup Oak 325 (5) 2250 (10) 2575
Cherrybark Oak 2250 (10) 2250
Willow Oak 2250 (10) 2250
Shagbark Hickory 2250 (10) 2250
Bitternut Hickory 2250 (10) 2250
Winged Elm 2250 (10) 2250
Tulip Poplar 2250(10) 2250
TOTAL 6500 22300 28800
1: Some non-commercial elements may not be locally available at the time of planting.
The stem count for unavailable species should be distributed among other target
elements based on the percent (%) distribution. One year of advance notice to forest
nurseries will promote availability of some non-commercial elements. However,
reproductive failure in the nursery may occur.
2: Scientific names for each species, required for nursery inventory, are listed in the
mitigation plan.
0
Planting will be performed between December 1 and March 15 to allow plants to stabilize
during the dormant period and set root during the following spring season. Opportunistic
species, which typically dominate early- to mid-successional forests have been excluded
from initial plantings on interior floodplains. Opportunistic species such as sweet gum,
red maple, and loblolly pine may become established. However, to the degree that long
term species diversity is not jeopardized, these species should be considered important
components of steady-state forest communities. Planting of opportunistic species such
as black willow will be targeted as stabilization elements in erosion control areas
immediately adjacent to the creek.
The planting plan is the blueprint for community restoration. The anticipated results
stated in the regulatory success criteria (Section 6.0) may reflect vegetative conditions
achieved after steady-state forests are established over many years. However, the natural
progression through early successional stages of floodplain forest development will prevail
regardless of human interventions over a 5-year monitoring period. In total, approximately
28,800 seedlings will be planted during wetland community restoration efforts.

61

0 6.0 MONITORING PLAN
The Monitoring Plan will entail analysis of the restoration area according to jurisdictional
wetland criteria (DOA 1987). Monitoring will include the observation and evaluation of
three primary parameters including hydrology, soil, and vegetation. Monitoring of
restoration efforts will be performed for 5 years or until success criteria are fulfilled.
6.1 HYDROLOGY
After hydrological modifications are performed, surficial monitoring wells will be designed
and placed in accordance with specifications in U.S. Corps of Engineers', Installing
Monitoring Wells/Piezometers in Wetlands (WRP Technical Note HY-IA-3.1, August 1993).
Monitoring wells will be set to a maximum depth of 24 inches below the soil surface. All
screened portions of the well will be buried in a sand screen, filter fabric, and/or a
bentonite cap to prevent siltation during floods. Recording devices (if used) will be placed
five feet above the ground elevation. Placement of recording devices at this height should
guard against over topping for a projected 50-year flood elevation. The well will be
stabilized from flood shear by reinforcing steel bar (re-bar).
Eight monitoring wells will be installed in restoration areas to provide representative
coverage throughout the site. Approximate well locations are depicted in Figure 19.
Hydrological sampling will be performed during the growing season (March 26 to
November 6) at intervals necessary to satisfy the hydrologic success. In general, the wells
will be sampled weekly through the spring and early summer and intermittently through
the remainder of the growing season, if needed to verify success.
6.2 HYDROLOGY SUCCESS CRITERIA
Target hydrological characteristics have been evaluated using regulatory wetland
hydrology criteria. The regulatory wetland hydrology criterion requires saturation (free
water) within one foot of the soil surface for 5% of the growing season under normal
climatic conditions.
Success Criteria
Under normal climatic conditions, hydrology success criteria comprises saturation (free
water) within 1 foot of the soil surface for a minimum of 5% of the growing season. This
hydroperiod translates to saturation for a minimum, 11-day (5%) consecutive period during
the growing season, which extends from March 26 through November 6 (USDA 1977).
If wetland parameters are marginal as indicated by vegetation and hydrology monitoring,
a jurisdictional determination will be performed in the questionable areas.
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62
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6.3 SOIL
Mitigation activities are expected to increase the deposition and transport of river and
stream sediments during overbank flood events. As a result, soils (Fluvaquents) are
continuously reworked by fluvial processes. Because iron reduction rates (gleying) are not
spatially or temporally uniform on recent alluvial deposits, soil color or other visual, hydric
soil properties are not considered suitable for quantitative wetland soil monitoring/success
criteria on active river floodplains.
Soil monitoring will entail measurement of sediment accretion/reduction (aggradation/
degradation) at the location of each monitoring well and other hydraulically active areas
as identified by Site managers. Mitigation activities are designed to provide for flood and
sediment storage from the watershed. Therefore, hydraulic and energy dissipation
patterns should be distributed throughout as much of the Site as possible. However, an
area of particularly accelerated sediment deposition may raise land surfaces above the
elevation of the primary wetland floodplain over a relatively short period of time.
Conversely, deep scour holes or head-cuts may form in locations where flow velocity or
sediment deficits exceed a "normal distribution." Soil monitoring is designed to provide
a cursory review to predict the need for additional levee openings or drainageways if
accelerated deposition or scour potentially jeopardizes wetland restoration efforts.
The re-bar used to support monitoring wells will be marked upon installation and in each
1 monitoring year at the elevation of the existing ground surface. In addition, the height
of silt lines will be recorded to predict the depth of inundation during the flood period.
Additional re-bar will be placed and measured in high energy areas identified by Site
managers, as needed. The change in elevation of the alluvial surface and deposition/scour
patterns relative to flood elevations will be recorded and compared to previous years.
1 6.4 SOIL SUCCESS CRITERIA
Success criteria require that the deposition/scour rate not exceed over 1 foot change in
surface elevations in any given year. Any areas affected by this excessive deposition/scour
will be mapped in the field. The area will be reviewed to determine modifications to
drainage patterns that should be implemented, if any. Changes in surface elevations of
1 less than 1 foot per year will meet regulatory success criteria; however, modifications to
deposition / scour patterns may also be considered in certain circumstances.
6.5 VEGETATION
Restoration monitoring procedures for vegetation are designed in accordance with EPA
guidelines presented in MiST documentation (EPA 1990) and Compensatory Hardwood
Mitigation Guidelines (DOA 1993). The following presents a general discussion of the
monitoring program.
1 64

L-i
Vegetation will receive cursory, visual evaluation during periodic reading of monitoring
wells to ascertain the general conditions and degree of competition or overtopping of
planted elements. Subsequently, quantitative sampling of vegetation will be performed
once annually during the fall (September/November) for 5 years or until vegetation success
criteria are achieved. Sampling dates may be modified to accommodate river flood events
and plot inundation, as needed.
During the first sample event, a visual survey will be performed in the reference wetlands
to identify all canopy tree species represented within target communities. These reference
tree species will be utilized to define "character tree species" as termed in the success
criteria.
Permanent (on each well head) or nonpermanent, randomly placed plots will be
established at representative locations in the restoration areas. Each plot will consist of
two, 300-foot transacts extending at a randomly selected compass bearing from a central
origin. The plot width along the transect will extend 4-feet on each side of the tape,
providing a 0.11 acre plot sample at the location (600 feet x 8 feet / 43560 square
feet/acre). Sixteen plots will be established to provide a 4% sample and a depiction of
tree species available for current and future seed sources within the restoration area. In
each plot, tree species and number of stems will be recorded and seedling/sapling/tree
height measured. Tree data from all plots will be combined into one database to calculate
® an average density, by species, represented in restoration areas of the Site.
In each plot, presence/absence of shrub and herbaceous species will be recorded. A
wetland data form (DOA 1987) will be completed to document the classification and
description of vegetation, soil, and hydrology.
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6.6 VEGETATION SUCCESS CRITERIA
Success criteria include the verification, per the wetland data form, that each plot
supports a species composition sufficient for a jurisdictional determination. Additional
success criteria are dependent upon density and growth of "Character Tree Species."
"Character Tree Species" are identified through visual inventory of reference wetland
communities used to orient the restoration project design. All canopy tree species
identified in the reference wetland will be utilized to define "Character Tree Species" as
termed in the success criteria (Character Tree Species are generally listed in Section 4.5
and Section 5.6).
An average density of 320 stems per acre of Character Tree Species must be surviving in
the first three monitoring years. Subsequently, 290 stems per acre of character tree
species must be surviving in year 4, and 260 stems per acre of Character Tree Species in
year 5. Each individual species is limited to representing up to 20% of the 320 stem per
65

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acre total. Additional stems of a particular species above the 20% threshold are discarded
from the statistical analysis. In essence, a minimum of five different character tree species
® must be present with each species representing up to 20% of the 320 stem per acre total.
If vegetation success criteria are not achieved based on average density calculations from
combined plots over the entire restoration area, those individual plots that do not support
the stem per acre requirement and the representative area will be identified. Supplemental
planting will be performed in the identified area as needed until vegetation success criteria
are achieved.
No quantitative sampling requirements are proposed for herb assemblages. Development
of a forest canopy over several decades and restoration of wetland hydrology will dictate
success in migration and establishment of desired wetland understory and groundcover
populations.
6.7 REPORT SUBMITTAL
An Annual Wetland Monitoring Report (AWMR) will be prepared at the end of each
monitoring year (growing season). The AWMR will depict the sample plot and quadrant
locations and include photographs which illustrate site conditions. Data compilations and
analyses will be presented as described in Sections 6.1 through 6.6 including graphic and
tabular format, where practicable. Raw data in paper or computer (EXCEL) file format will
be prepared and submitted as an appendix or attachment to the AWMR.

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7.0 IMPLEMENTATION SCHEDULE
Project implementation will include performance of restoration work in three primary
stages including: 1) levee removal, weir construction, and site preparation; 2) tree and
shrub planting; and 3) monitoring plan implementation. This mitigation plan or
implementation schedule may be modified based upon civil design specifications, permit
conditions, or contractor limitations.
Stage 1: Levee Removal, Weir Construction, and Site Preparation
Stage 1 will be performed concurrent with or subsequent to filling of the reservoir. Levees
will be excavated and weirs constructed along the dredged channel. This work will be
performed during late spring and/or early summer months to reduce erosion hazards
associated with saturated soil or large August storms. Site preparation will be performed
1 during the same summer period, prior to tree planting.
Stage 2: Tree Plantinq
Tree and shrub planting will be performed the first winter after stage 1 is complete. The
seedlings will be planted during the winter dormant period, prior to March 1.
I Stage 3: Monitoring Plan Implementation
Monitoring wells and permanent vegetation plots will be established immediately after
construction and planting activities are completed (prior to March 26, the start of the
growing season). The Site will be visited frequently to read monitoring wells and to
evaluate wetland development during the first growing season. Vegetation sampling and
hydrology monitoring will be completed by November 6 (the end of the growing season).
The first year of monitoring would be completed upon submittal of the Annual Wetland
Monitoring Report and fulfillment of success criteria. The monitoring sequence will be
repeated as described for four additional years or until success criteria are achieved.

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® 8.0 DISPENSATION OF PROPERTY
PTRWA will maintain ownership of the property until all mitigation activities are
completed or until the Site is determined to be successful. Although no plan for
dispensation of the Site has been developed, PTRWA may continue to manage the
property or may deed the property to a resource agency (public or private) acceptable to
the appropriate regulatory agencies. Covenants and/or restrictions on the deed will be
included that will ensure adequate management and protection of the Site in perpetuity.
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9.0 WETLAND FUNCTIONAL EVALUATIONS
Mitigation activities at the Richland Creek Mitigation Site should be determined based on
wetland functions generated and a comparison of restored functions to potentially
impacted wetland resources. Therefore, an evaluation of mitigation wetlands, by
physiographic area (Figure 4), is provided to evaluate site utility for mitigation in the
region.
9.1 EXISTING CONDITIONS
Under existing conditions, hydrodynamic functions have been degraded or effectively
eliminated due to stream dredging, levee construction, soil leveling/compacson in pasture
areas, and removal of characteristic vegetation. Features which depict performance of
hydrodynamic wetland functions such as surface microtopography, seasonal ponding,
meandering stream channels, and characteristic wetland vegetation have been reduced or
eliminated by alternative land uses on primary floodplains. Reduction or elimination of
wetland hydrology has also negated nutrient cycling and biological functions within the
complex. These former wetlands do not support natural communities adapted to wetlands
or the wetland dependent wildlife characteristic in the region.
The 70.5-acre site supports 13.6 acres of relict wetlands within backwater areas and 4.0
acres of open water within the dredged channel (17.6 total acres). Of the existing
wetlands, approximately 1.9 acres are included as wetland impacts under the 404 Permit
Application for this project. Therefore, 11.7 acres of existing wetlands will be preserved
or enhanced during mitigation activities (Figure 20).
9.2 PROJECTED, POST-RESTORATION CONDITIONS
Lake Effect Wetlands
Wetland restoration objectives have been adapted for this project due to location of the
Site relative to the Randleman Reservoir. The lower half of the Site will be directly
influenced by the reservoir conservation pool, including sediment deposition within stream
channels, development of accreting sediment bars, and establishment of wetlands on
saturated/inundated surfaces. Based on reference studies, these lake effect wetlands are
projected to support a mosaic of emergent, shrub-scrub, and forested wetland
communities on land surfaces from 1 foot below to 2 feet above the conservation pool.
This land area, comprising approximately 24.0 acres, will provide wetland functions such
as increased habitat for wetland dependent wildlife, sediment retention above the water
supply, and pollutant processing on vegetated wetland surfaces. Open water is also
projected to encompass approximately 13.0 acres that will provide for sediment storage
and accreting wetland shorelines (Figure 20).

69

Monitoring and management of these lake effect wetlands will assist in ensuring that land
• surfaces exposed to long-term sedimentation are not elevated above the water table, with
capacity to support wetland functions subsequently reduced or diminished over time. In
addition, efforts to maintain vegetation within rapid sedimentation areas will also be
employed during the monitoring period.
Alluvial Wetland Complex
The upper half of the Site will be used to extend the sediment deposition wedge
associated with the reservoir and to establish wetland communities capable of providing
wildlife habitat and water quality benefits. Overbank flooding is projected to occur at a
1-year return interval through levee removal and placement of in-stream weirs. Assuming
weir stability, the dredged channel is expected to fill in with sediment over time,
facilitating passive stream restoration and migration across the developing alluvial fan.
The primary and secondary floodplain areas are expected to support an array of forested
wetland communities, providing replacement of habitat for wetland dependent species
displaced by the reservoir. Water quality benefits are projected to include sediment
retention and pollutant processing of waters generated by the 14.5-square mile, urbanizing
watershed.
Pro-active mitigation within the alluvial wetland complex is projected to provide
approximately 21.8 acres of wetland restoration above the lake effect, wetland restoration
area (an additional 24.0 acres). Therefore, 45.8 acres of wetland restoration, 11.7 acres
of wetland preservation/enhancement, and 13 acres of open water are potentially provided
by the Site.

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1 10.0 REFERENCES
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Lil

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fl
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Schouwenaars, J.M. 1995. The selection of internal and external water management
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1 Hydrology. Wetlands (11), pp 399-416.
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for Assessing Wetland Functions Using Hydrogeomorphic Classification, Reference
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