Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
ii Christina River Watershed Wetland Condition Report
Matthew A. Jennette
Alison B. Rogerson
Andy M. Howard
Delaware Department of Natural Resources and Environmental Control
Division of Watershed Stewardship
820 Silver Lake Blvd, Suite 220
Dover, DE 19904
LeeAnn Haaf
Angela Padeletti
Kurt Cheng
Jessie Buckner
Partnership for the Delaware Estuary
110 South Poplar Street, Suite 202
Wilmington, DE 19801
The citation for this document is:
Jennette, M.A., Haaf, L., A.B. Rogerson, A.M. Howard, A. Padeletti, K. Cheng, and J. Buckner.
2014. Condition of Wetlands in the Christiana River Watershed. Delaware Department of
Natural Resources and Environmental Control, Watershed Assessment and Management
Section, Dover, DE and the Partnership for the Delaware Estuary, Wilmington, DE.
Christina River Watershed Wetland Condition Report iii
ACKNOWLEDGEMENTS
Funding for this project was provided by EPA Region III Wetland Program Development
Grant Assistance # CD-96312201-0, EPA National Estuary Program, the Delaware Department
of Natural Resources, and the DuPont Clear into the Future program. Technical support and
field research was made possible by the contributions of many individuals. Tom Kincaid and
Tony Olsen with the EPA Office of Research and Development Lab, Corvallis, Oregon provided
the data frame for field sampling and statistical weights for interpretation. Kristen Kyler and
Rebecca Rothweiler participated in many field assessments under a myriad of conditions.
Maggie Pletta and Michelle Lepori-Bui were helpful with revisions on drafts of the report, as
well as producing the cover art for the final document.
iv Christina River Watershed Wetland Condition Report
CONTENTS
Executive Summary .........................................................................................................................1
Introduction ......................................................................................................................................3
Watershed Overview ........................................................................................................................5
2.1 Geology and Hydrogeomorphology ....................................................................................5
2.2 Watershed History and Land-use ........................................................................................6
2.3 Wetland Resources..............................................................................................................8
Section 1: Condition of Wetlands in the Christina River Watershed .....................................11
Methods..........................................................................................................................................11
3.1 Changes to Wetland Acreage ............................................................................................11
3.2 Field Site Selection ...........................................................................................................11
3.3 Data Collection .................................................................................................................12
3.3.1 Landowner Contact and Site Access....................................................................... 12
3.3.2 Assessing Tidal Wetlands ....................................................................................... 12
3.3.3 Assessing Non-tidal Wetland Condition ................................................................. 15
3.4 Presenting Wetland Condition ..........................................................................................18
Results ............................................................................................................................................20
4.1 Landscape Analysis of Changes in Wetland Acreage ......................................................20
4.2 Landowner Contact and Site Access.................................................................................21
4.3 Condition of Tidal Wetlands .............................................................................................22
4.4 Condition of Non-tidal Wetlands ......................................................................................24
4.4.1 Non-tidal Flat Wetland Condition .......................................................................... 24
4.4.2 Non-tidal Riverine Wetland Condition ................................................................... 27
4.4.3 Non-tidal Depression Wetland Condition ............................................................... 29
4.5 Overall Condition and Watershed Comparison ................................................................29
Management Recommendations ....................................................................................................30
Section 2: Establishment of a Permanent Intensive Monitoring Station in the Christina
River Watershed ..........................................................................................................................33
Summary ........................................................................................................................................33
Introduction ....................................................................................................................................33
Methods..........................................................................................................................................34
5.1 Components of Site Specific Intensive Monitoring Stations ............................................34
5.1.1 Surface Elevation Tables (SETs) and Marker Horizons (MH) ............................... 34
Christina River Watershed Wetland Condition Report v
5.1.2 Soil Quality and Biomass........................................................................................ 35
5.1.3 Vegetation Transects ............................................................................................... 35
5.1.4 Vegetation Data in Fixed Plots ............................................................................... 35
5.1.5 Water Quality .......................................................................................................... 36
Results ............................................................................................................................................36
5.2.1 Surface Elevation Tables (SETs) and Marker Horizons (MH) ............................... 36
5.2.2 Soil Quality and Biomass........................................................................................ 38
5.2.3 Vegetation Transects ............................................................................................... 38
5.2.4 Vegetation in Fixed Plots ........................................................................................ 39
5.2.5 Water Quality .......................................................................................................... 42
Intensive Monitoring Conclusions .................................................................................................42
Literature Cited ..............................................................................................................................44
Appendix A: Qualitative Disturbance Rating (QDR) Category Descriptions ...............................47
Appendix B: DERAP Stressor Codes and Definitions ..................................................................48
Appendix C: DERAP IWC Stressors and Weights........................................................................50
Appendix D: MidTRAM Raw Data and Metric Scores from Estuarine Sites in the Christina
River Watershed.............................................................................................................................52
Appendix E: DERAP Wetland Assessment Stressor Checklist for Non-tidal Flat Wetlands in the
Christina River Watershed .............................................................................................................55
Appendix F: DERAP Wetland Assessment Stressor Checklist for Non-tidal Riverine Wetlands in
the Christina River Watershed .......................................................................................................58
Appendix G: DERAP Wetland Assessment Stressor Checklist for Non-tidal Depression
Wetlands in the Christina River Watershed ...................................................................................61
Appendix H: Site Specific Intensive Monitoring plot Locations and Sampling Dates .................62
Appendix I: Vegetation Zone Dominance .....................................................................................65
vi Christina River Watershed Wetland Condition Report
FIGURES
Figure 1. Location of the Christina River Watershed and the major basins of Delaware.
Watersheds at the Hydrologic Unit Code 10 scale are outlined in gray. ........................................ 5
Figure 2. Land cover of the Christina River watershed based on 2005 (PA), 2007 (DE), and 2010
(MD) Land-use/Land-cover datasets. ............................................................................................. 6
Figure 3. Pre- and post-construction alignment of the Christina River following the completion
of Interstate 95. The pre-construction channel boundary is outlined in orange, and the current
alignment southeast of Newport is outlined in red. ........................................................................ 7
Figure 4. Distribution of wetlands in the Christina River watershed, based on 2007 mapping. .... 9
Figure 5. Standard assessment area, subplot locations, and buffer used to collect data for the
Mid-Atlantic Tidal Rapid Assessment Method Version 3.0. ........................................................ 12
Figure 6. Standard assessment area and buffer used to collect data for the Delaware Rapid
Assessment Procedure Version 6.0. .............................................................................................. 15
Figure 7. An example CDF showing wetland condition. The red line is the population estimate.
The orange and green dashed lines show the breakpoints between condition categories. ........... 19
Figure 8. Estimated historic and present wetland coverage in the Christina River watershed. .... 20
Figure 9. Ownership of sampled wetland sites in the Christina River watershed (left) and success
rates for sampling private wetland sites (right). ............................................................................ 21
Figure 10. Location of wetland assessments performed in the Christina River watershed in 2011.
....................................................................................................................................................... 22
Figure 11. Box and whisker plot of buffer, hydrology, and habitat attribute group scores from
tidal wetlands in the Christina River watershed. .......................................................................... 23
Figure 12. The cumulative distribution function for tidal wetlands in the Christina watershed.
The orange and green dashed lines signify the condition category breakpoints dividing severely
stressed from moderately and minimally stressed portions of the tidal wetland population. ....... 24
Figure 13. Cumulative distribution function for non-tidal flat wetlands in the Christina River
watershed. Condition scores for the wetland population are represented as the red line with 95%
confidence intervals (gray dashed lines). The orange and green dashed lines designate condition
category breakpoints dividing severely stressed, moderately stressed, and minimally stressed
wetlands. ....................................................................................................................................... 26
Figure 14. Cumulative distribution function for non-tidal riverine wetlands in the Christina River
watershed. Condition scores for the wetland population are represented as the red line with 95%
confidence intervals (gray dashed lines). The orange and green dashed lines designate condition
category breakpoints dividing severely stressed, moderately stressed, and minimally stressed
wetlands. ....................................................................................................................................... 28
Figure 15. Combined condition of non-tidal flat and riverine wetlands in the Christina River
watershed, compared to wetland condition in the St. Jones, Murderkill, Mispillion, Broadkill, and
Inland Bays watersheds................................................................................................................. 29
Christina River Watershed Wetland Condition Report vii
Figure 16. Example of Site Specific Intensive Monitoring sampling lay-out along the main
waterway. ...................................................................................................................................... 33
Figure 17. Site Specific Intensive Monitoring (SSIM) point locations at Christina River,
Wilmington, DE: permanent vegetation plots (PVs; groups of three) and random edge plots
(REs) distributed along shoreline of main water bodies. .............................................................. 34
Figure 18. Cumulative accretion height change for Christina River. Heights are given as the
difference in mean accretion height of all SETs between sampling dates, error bars are standard
error. Arrow marks the approximate date of the landfall of Hurricane Sandy in New Jersey
(October 29, 2012). Yearly SET height changes (mm) are 15.6, 12.5, 8.2 for SET 1, 2, and 3,
respectively, averaging 12.1 mm/yr. Linear models predict NS from slope =0. .......................... 37
Figure 19. Cumulative accretion height change for Christina River. Heights are given as the
difference in mean accretion height of all SETs between sampling dates, error bars are standard
error. Arrow marks the approximate date of the landfall of Hurricane Sandy in New Jersey
(October 29, 2012). Yearly accretion rate is 1.27 mm/yr. Slope NS from zero ........................... 37
Figure 20. Percentages of dominant vegetation type over all three RTK GPS transects in 2012. 38
Figure 21. Percentages of dominant vegetation type over all three RTK GPS transects in 2011. 38
Figure 22. Three year trend of Vegetation Zone Dominance (VZD) scores at PVs (near, mid, and
far) and REs. Lower VZD scores are communities whose structure suggest more tidal flooding.
....................................................................................................................................................... 40
Figure 23. Principal component analysis for Christina River. Red labels are main analysis
variables; blue arrows are covariant environmental variables. Vertices of polygons are labeled A,
B, and C, for near, mid, and far, respectively, followed by the sample year ................................ 41
TABLES
Table 1. Land use cover in the Christina River watershed based on 2005 (PA), 2007 (DE), and
2010 (MD) Land-use/Land-cover datasets. .................................................................................... 8
Table 2. Wetland acreage and proportion for each hydrogeomorphic wetland type in the
Christina River Watershed. ............................................................................................................. 9
Table 3. Metrics measured with the Mid-Atlantic Tidal Rapid Method Version 3.0. .................. 13
Table 4. Metrics measured with the Delaware Rapid Assessment Procedure Version 6.0. ......... 15
Table 5. Condition categories and breakpoint values for tidal and non-tidal wetlands in the
Christina River watershed as determined by wetland condition scores. ....................................... 18
Table 6. Composition of wetland condition classes (left) and the occurrence of common wetland
stressors (right) of non-tidal flat wetlands in the Christina River watershed. .............................. 25
Table 7. Composition of wetland condition classes (left) and the occurrence of common wetland
stressors (right) of non-tidal riverine wetlands in the Christina River watershed. ....................... 27
viii Christina River Watershed Wetland Condition Report
Table 8. Surface Elevation Table heights for Christina River. Data are given as the difference in
mean pin height between sampling dates, error values are standard error. .................................. 36
Table 9. Marker Horizon Heights for Christina River. Data are given as the mean accretion
height at sampling dates. Error values are standard error. ............................................................ 37
Table 10. Mean blade heights (cm) of first and second dominant species within near, mid, and far
PVs. ............................................................................................................................................... 39
Table 11. Percent of light penetration is given by light intensity at the bottom of the canopy
divided by the light intensity above the canopy. ........................................................................... 40
Table 12. Percentages of the first two most dominant species found in each plot, followed by the
diversity index and mean VZD score. Percentages may not equal 100% as species coverage in
plot may be highly overlapped or sparse. ..................................................................................... 40
Table 13. Average total alkalinity, turbidity, chlorophyll α concentration, total suspended solids
respectively, measured from water samples taken from the main water body of Christina River in
2013. Error values are standard error, n = 5. ................................................................................ 42
Table 14. Average temperature, salinity (uS/cm and ppt), dissolved oxygen (percent and
concentration), and pH respectively, measured from YSI meter from the main water body of
Christina River. Error values are standard error. N = 5, except on 1/9/2011, only one
measurement was taken for values with no error due to an equipment malfunction, otherwise
n=2. ............................................................................................................................................... 42
Christina River Watershed Wetland Condition Report 1
EXECUTIVE SUMMARY
The Delaware Department of Natural Resources and Environmental Control (DNREC)
and the Partnership for the Delaware Estuary (PDE) documented wetland trends and ambient
condition of wetland resources in the Christina River Watershed in 2011. The goal of this
project was to identify historic and recent changes in wetland acreage, assess the condition of
tidal and non-tidal wetlands throughout the watershed, identify prevalent wetland stressors, and
make watershed specific management recommendations. We will utilize information on wetland
losses and sources of wetland degradation in the Christina Watershed to guide future protection
and restoration activities and educate the public on watershed stewardship.
The Christiana River watershed encompasses 78 square miles (20,000 ha) of northern
New Castle County, Delaware, northeastern Cecil County, Maryland, and southern Chester
County, Pennsylvania. The Christina River drains four additional watersheds from the Piedmont
Physiographic Province, which collectively forms the Christina River Basin. The Christina
River originates in Landenburg, PA and flows 35 miles (55 km) eastward through Newark,
Christiana, and Newport, DE before emptying into the Delaware River through the Port of
Wilmington. Approximately 10% of the watershed (5,000 acres) is covered by wetlands, namely
non-tidal headwater flats (40%), riverines (23%), depressions (16%), and tidal estuarine marshes
(19%).
We estimated historic and recent wetland losses in the watershed based on historic hydric
soil maps and past wetland mapping efforts. The Christina River and its tidal wetlands have
been altered significantly since European settlement, including channel modifications and
extensive diking for agriculture. As populations grew and heavy industries expanded, many
wetlands in the eastern half of the watershed were filled to allow for development.
Approximately 46% of the wetlands in the watershed have been filled or otherwise lost,
primarily in Wilmington, southern Newark, and along the Interstate 95 corridor. Despite stricter
wetland regulations in New Castle County, compared to Kent and Sussex counties, Delaware,
approximately 81 acres of wetlands were converted between 1992 and 2007. These wetland
losses were largely associated with residential development, road expansions, and disposal of
dredged material along the Delaware River.
To assess wetland condition and identify stressors affecting wetland health we conducted
rapid assessments at random wetland sites throughout the watershed. Wetland assessments were
performed in 30 tidal wetlands using the Mid-Atlantic Tidal Rapid Assessment Method Version
3.0 and in 40 non-tidal riverine wetlands, 32 non-tidal flat wetlands, and two non-tidal
depression wetlands using the Delaware Rapid Assessment Method Version 6.0. Assessed
wetland sites were located on public and private property and randomly selected utilizing a
probabilistic sampling design with the assistance of the Environmental Protection Agency’s
Ecological Monitoring and Assessment Program.
Estuarine wetlands in the Christina River watershed were primarily freshwater marshes
dominated by emergent vegetation, which cover almost 1,000 acres of land. The buffers
surrounding tidal marshes were generally in poor condition, with human disturbance found
surrounding nearly every wetland. Point source pollution inputs from these developed areas
2 Christina River Watershed Wetland Condition Report
were found in 40% of the wetlands. Invasive plant species were pervasive in the watershed and
found in a majority of the freshwater marshes.
Non-tidal flat wetlands were typically found in the western half of the watershed near the
headwaters, primarily in low-lying forested areas. Of the 2,000 acres of flat wetlands estimated
to be in the Christina River watershed, only 14% were found to be in a minimally stressed
condition, while 41% of flats were severely stressed. Altered plant communities were found in a
majority of flat wetlands, including invasive plant cover and recent forestry activities. Ditching,
filling, and disturbed wetland buffers were also common stressors found in non-tidal flat
wetlands.
Riverine wetlands were found along the upper reaches of the Christina River, as well as
its tributaries, and are vital for flood attenuation and improving surface water quality.
Approximately 1,200 acres of non-tidal riverine wetlands were found in the watershed, with only
8% in a nearly undisturbed condition and 40% highly disturbed. Invasive plant species were
found in nearly every riverine wetland, with almost half of the wetlands dominated by invasives.
Alterations to the stream channel, as either channelization or stream incision, occurred along
60% of riverine wetlands, with another 53% of riverine wetlands partially filled with yard waste
or spoil material.
Compared to five watersheds previously assessed in Delaware, non-tidal wetlands in the
Christina River watershed are in considerably worse condition. The Christina River watershed
contained the highest proportion of severely stressed wetlands, as well as the lowest proportion
of high-condition than any watershed in southern Delaware.
An intensive monitoring station was also established in freshwater tidal marshes along
the Christina River. Several permanent fixtures were installed at the Christina River SSIM
station including surface elevation tables (SETs) and permanent vegetation plots. These fixtures
were monitored from 2011 to 2013, along with a suite of other metrics including water quality
and plant biomass. Three years of data, however, is inadequate to make conclusions about long-
term trends. Yet, data reported here suggest that between 2011 and 2013, the marsh platform had
increased in elevation at SET benchmarks. These elevation changes are most likely the result of
subsurface swelling. Some disparate results were observed between SET benchmark and plant
community data; overall, however, these data suggested an increasing trend, but at least 5 years
of data is needed to determine the inherent natural variation.
Based on the findings of this study we propose seven wetland management
recommendations and needs for further data. One, preserve the unique and regionally rare
Delmarva Bays remaining in the watershed. Two, incorporate wetland restoration and
preservation into community development and urban revitalization plans. Three, explore options
for beneficially re-using dredged sediment for wetland creation and management. Four,
encourage living shorelines and other natural methods as an alternative to bulkheads and rip-rap
for shoreline stabilization. Five, educate landowners on the benefits of maintaining natural
buffers along surface waters and wetlands, and incentivize landowners who preserve extensive
buffers. Six, control the extent and spread of the invasive common reed (Phragmites australis)
through state- and federally-funded programs. Seven, update tidal wetland regulatory maps
using current aerial photography and georeferencing tools to aid landowners and regulators.
Christina River Watershed Wetland Condition Report 3
INTRODUCTION
The Christina River drains
land in Delaware, Maryland, and
Pennsylvania and the watershed is
covered by various land-use types.
Wetlands in the Christiana River
Watershed provide many benefits
to people, support natural
processes, and provide habitats that
are an integral part of the
landscape. Wetlands act as the
transition between terrestrial and
aquatic habitats and are one of the
most productive ecosystems in the
world. Wetlands provide multiple
ecosystem services including
minimizing flooding from storms
by storing excess water, controlling
erosion through vegetation
stabilization, and improving water quality by removing excess nutrient runoff and pollutants
from non-point sources. Sediment loads may increase with agricultural practices, land clearing,
construction, and bank erosion. Wetlands throughout the watershed serve as a buffer by
removing and retaining suspended sediment from waters before they enter tidal and nontidal
waterways. They also have substantial cultural and economic value as a source of recreation
(e.g. hunting, fishing, birding) and livelihood (e.g. fishing, crabbing, fur-bearer trapping). Tidal
wetlands are biologically rich habitats and are a critical resource for migrating shorebirds and
wintering waterfowl, and serve as
nurseries for commercial fish and
shellfish species. Freshwater
wetlands process and funnel
ground and surface waters into our
waterways, and provide wildlife
habitat for a wide array of species.
Available data suggest that these
wetlands continue to be lost and
threatened by continued
development and conversion,
degradation, sea level rise, sudden
marsh dieback and a host of other
factors. From 1996-2006, the
estimated loss of tidal wetlands
across the Delaware Estuary was
Non-tidal riverine wetland in the Christina River Watershed.
Non-tidal flat wetland in the Christina River Watershed.
4 Christina River Watershed Wetland Condition Report
Diagram of MACWA tiers
3% (Partnership for the Delaware Estuary 2012).
Wetlands have a rich history across the region and their aesthetics have become a symbol
of the Mid-Atlantic Coast. The State of Delaware remains committed to improving wetlands
through protection and restoration efforts, education, and effective planning to ensure that
wetlands will continue to provide these services to the citizens of Delaware (DNREC 2008). In
addition to assessing changes in wetland acreage over time, monitoring wetland condition and
functional capacity is necessary to guide management and protection efforts. The Delaware
Department of Natural Resources and Environmental Control (DNREC) has developed a wetland
assessment and monitoring program to evaluate the health of wetlands. DNREC is also part of
the Mid-Atlantic Coastal Wetlands Assessment (MACWA) program, a larger collaborative effort
with the Partnership for the Delaware Estuary and Drexel University, to study wetland health
throughout the Delaware Estuary. Evaluating wetland health, or condition, and documenting the
stressors that are degrading wetlands and preventing them from working at their full potential on
a watershed scale provides useful information that watershed organizations, state planning and
regulatory agencies, and other stakeholders can use to improve wetland restoration and
protection efforts. Protection efforts through acquisition or easements can be directed towards
wetland types in good condition, allowing restoration efforts to target altered and degraded
wetland types to increase functions and services.
Wetland assessment information identifies specific
stressors that are impacting wetlands, and can
direct restoration projects and set priorities.
The MACWA consists of a 4-tiered
strategy to provide rigorous, comparable data
across the Mid-Atlantic region: examining
wetlands from the landscape level to site-specific
studies. Two of these four tiers consist of active
wetland monitoring—the Rapid Assessment
Method (RAM, Tier 2) and the Site Specific
Intensive Monitoring (SSIM, Tier 4). Tier 1
consists of satellite imagery or landscape analyses,
and Tier 3 is cross over studies between various
tiers.
DNREC and its partners have developed, and continue to refine, scientifically valid
methods to assess the condition of wetlands on a watershed scale. These methods are used to
generate an overall evaluation of the ambient condition of wetlands in a watershed, as well as to
identify common stressors by wetland type. In this report, we review the changes in wetland
acreage, highlight potential changes in wetland function, summarize the condition of tidal and
freshwater wetlands, identify common stressors degrading wetlands, provide recommendations
for improving the wetlands of the Christina River watershed, and introduce preliminary results
from long-term monitoring sites in the Christina River watershed.
Christina River Watershed Wetland Condition Report 5
WATERSHED OVERVIEW
The Christina River watershed is primarily
located in New Castle County, Delaware with the
upper headwater reaches extending into
northeastern Cecil County, Maryland and southern
Chester County, Pennsylvania (Figure 1). The
Christina River watershed is approximately 78
square miles (20,000 ha) in size and is primarily
urban and suburban land-use with isolated areas of
forest and agriculture. The Christina River
originates in Landenburg, PA and flows 35 miles
(55 km) eastward through Newark, Christiana, and
Newport, DE before emptying into the Delaware
River through the Port of Wilmington. In addition
to the main branch of the Christina River, the
watershed also includes the Muddy Run and Little
Mill Creek subwatersheds.
The Christina River watershed is bordered
by the small Army Creek, Red Lion Creek, Dragon
Run Creek, and Chesapeake & Delaware Canal
watersheds of the Delaware River Basin to the
south. To the north of the watershed are the White
Clay Creek, Red Clay Creek, Brandywine Creek,
and Shellpot Creek watersheds which also drain
into the Christina River and are collectively form
the Christina Basin in the Piedmont region. The
watershed is bound to the west by the Elk River
watershed of the Chesapeake Bay Basin.
2.1 Geology and Hydrogeomorphology
The Christina River watershed lies primarily within the Atlantic Coastal Plain
physiographic province with portions of the upper Christina River and Little Mill Creek
extending north into the Appalachian Piedmont physiographic province. The boundary between
these two provinces, known as the Fall Line, is located just north of the Interstate 95 corridor.
The hills of the Piedmont are formed by remnant metamorphic rocks from the Appalachian
Mountains, which are overlain by coastal and marine sediments forming the Coastal Plain (Plank
and Schenck 1998). Groundwater for the Christina River watershed is supported by fractures in
the crystalline bedrock of the Piedmont and pore spaces within unconsolidated sedimentary
deposits of the Coastal Plain (Hodges 1984).
Figure 1. Location of the Christina River
Watershed and the major basins of Delaware.
Watersheds at the Hydrologic Unit Code 10
scale are outlined in gray.
6 Christina River Watershed Wetland Condition Report
Hydrogeomorphology differs considerably between the Piedmont and Coastal Plain
physiographic provinces due to topography, geology, and soil characteristics. Wetlands in the
rolling hills of the Piedmont are primarily confined to riparian floodplains and few, isolated
depressions within the landscape. The Atlantic Coastal Plain portion of the Christina River
watershed can be further divided into two distinct regions: the inner coastal plain, and
beaches/tidal marshes. When compared to the rest of Delmarva’s Coastal Plain, the inner coastal
plain region has significant topographic relief which is typified by fewer headwater flat wetlands
with more incised stream channels (Fretwell et al. 1996). Tidal wetlands can be found along the
Christina River, from DE Route 1 east to the Delaware River.
2.2 Watershed History and Land-use
The first permanent European settlement in Delaware was established by the Swedes in
1638 along the Christina River after the failed settlement in Lewes in 1631. Shortly after the
establishment of Fort Christina, European settlers began altering the landscape significantly with
dikes and impoundments to reclaim land for agriculture (Phillipp 1995; Figure 2). Wetlands
Figure 2. Land cover of the Christina River watershed based on 2005 (PA), 2007 (DE),
and 2010 (MD) Land-use/Land-cover datasets.
Christina River Watershed Wetland Condition Report 7
throughout the region were ditched and filled to allow for transportation corridors and growing
populations. During this period of reclamation, Phillipp (1995) estimated that nearly the entire
tidal reach of the Christina River was diked and over 2,000 acres of tidal marshes were converted
to upland. Marshes adjacent to navigational channels were filled and used as disposal sites for
dredged material throughout the 1800s which allowed for the establishment and expansion of
industries in Wilmington and northern Delaware. Dike maintenance declined during the Great
Depression and World War II resulting in many of these systems falling into disrepair and
ultimately returning to tidal marshes (Sebold 1992).
The main channel of the Christina River has also undergone significant modifications.
The Christina River’s confluence with the Delaware River has been channelized and dredged to
accommodate cargo traffic, and a majority of the shoreline in Wilmington is armored with
bulkheads and rip-rap revetments. One of the most notable impacts in recent history to the
River, and surrounding tidal marshes, occurred with the construction of Interstate 95 in the
1960s. To create a direct route from Baltimore to Philadelphia, the Delaware Turnpike portion
of the highway was built just south of the Fall Line along the Christina River floodplain. The
alignment of the highway required a segment of the Christina River near Newport to be
redirected 5 km northwest of its original location (Figure 3). Churchman’s Marsh was also
impounded during construction and converted to open-water. During construction over 400
hectares (1,000 acres) of tidal marsh were filled or otherwise impacted, primarily in
Churchman’s Marsh and Newport Marsh (Phillipp 1995).
Pre-construction (1961) Current alignment (2012)
Figure 3. Pre- and post-construction alignment of the Christina River following the completion of Interstate
95. The pre-construction channel boundary is outlined in orange, and the current alignment southeast of
Newport is outlined in red.
Coastal industries in Wilmington flourished during the Industrial Revolution and supplied
much of the nation with goods during the Civil War and World War I. In 1913, planning and
construction began for the Port of Wilmington, located at the mouth of the Christina River. The
first marine terminal was completed in 1923 which opened the port to international trade. The
port expanded considerably over the following decades to meet the needs of various companies,
Churchman’s
Marsh
8 Christina River Watershed Wetland Condition Report
including Volkswagon and Del Monte (Baumbach et al. 2013). Businesses in Wilmington’s
downtown and Riverfront areas are significant contributors to the state’s economy today,
including DuPont, Gore, and many major financial institutions. Based on the most recent 2010
census, 186,680 people reside in the Christina River watershed, which grew by 20,245 people
since 2000 (Baumbach et al. 2013).
Table 1. Land use cover in the Christina River watershed based on 2005 (PA), 2007
(DE), and 2010 (MD) Land-use/Land-cover datasets.
Land-use affects the health of wetlands directly through filling and conversion to other
land uses, or indirectly via runoff from intensive land cover. The Christina River watershed is
currently among the most urbanized in Delaware, with over half of the watershed in residential
or industrial development (Figure 2; Table 1). Extensive impervious surface cover and poorly-
managed stormwater causes stream destabilization and soil erosion, while reducing groundwater
recharge potential. Agricultural production is rare and found primarily along the western edge of
the watershed in Maryland and Pennsylvania. Few large tracts of forest remain in the watershed,
most notably being Iron Hill Park and Sunset Lake. Transitional land cover in the watershed
encompasses land that has been cleared for development or areas that are frequently filled,
including landfills.
Environmental contamination is a significant issue in the Christina River watershed, with
four Superfund sites in the watershed and dozens of Brownfield sites in Wilmington.
Sedimentation and runoff from impervious surfaces (including oil, salt, and heavy metals) all
contribute to water quality concerns. The Christina River and its major tributaries exceed the
Total Maximum Daily Load of pollutants and are listed as impaired due to nutrients from
nonpoint source runoff and adjacent Superfund sites (USEPA 2006).
2.3 Wetland Resources
Wetlands, and the ecosystem services they provide, are crucial for the health of the
Christina River watershed. Economic benefits from consumptive wetland products (fish,
wildlife, timber, etc.) and the ecosystem services from water resources within the Christina River
watershed exceeds $7 billion annually (Baumbach et al. 2013). Within this urbanized watershed,
tidal and non-tidal wetlands are imperative for improving water quality, attenuating floodwaters,
and providing habitats for wildlife. Many species of amphibians, reptiles, waterfowl, mammals,
and insects rely on wetlands during various stages of their lives. Wetlands maintain and improve
water quality by trapping sediments, nutrients, heavy metals, and pathogens, which benefits
surface water and groundwater supplies. During storm events, tidal wetlands along the Christina
Land Use Category Percent Coverage
Developed 60
Scrub-Shrub and Forest 20
Agriculture 11
Wetlands 5
Open Water 2
Transitional 2
Christina River Watershed Wetland Condition Report 9
River act as a buffer by absorbing wave energy and storing excess floodwaters to protect coastal
businesses and residential properties. Non-tidal wetlands in urbanized areas of the watershed
also act as reservoirs during storm events protecting properties downstream. Wetlands are also
valuable recreational and educational resources, and downtown Wilmington is home to one of
the nation’s first urban wildlife refuges, the Russell Peterson Wildlife Refuge, located adjacent to
the Christina River. Civic groups in downtown Wilmington and conservation partners are also
experimenting with incorporating wetland restoration into a community revitalization plan to
remedy chronic flooding in the neighborhood of Southbridge.
Table 2. Wetland acreage and proportion for each hydrogeomorphic wetland type in the Christina River
Watershed.
Based on National Wetland Inventory (NWI) maps and Delaware’s State Wetland
Mapping Project (SWMP) maps, wetlands cover approximately 10% of the Christina River
watershed. Wetland inventory
maps are created by digitizing
orthophotos and supplemented with
historical aerial imagery and soil,
topography, and hydrology
datasets. The wetland acreage
identified using this mapping
criteria is 5% greater than the
wetland acreage identified by
coarser land-use/land-cover
datasets and reflects differences in
mapping standards and data
resolution. Non-tidal flats and
riverines are the most common
wetland type found in the Christina
River watershed (Table 2).
Tidal wetlands along the
Christina River extend from its
confluence with the Delaware
River west to Delaware Route 1 in
Christiana (Figure 4). A majority
of the non-tidal riverine wetlands
are found south of Interstate 95
Wetland Type Hectares (Acres) Proportion
Estuarine 395 (977) 19
Non-tidal Flat 815 (2,014) 40
Non-tidal Riverine 481 (1,191) 23
Non-tidal Depression 330 (817) 16
Non-tidal Lacustrine 35 (87) 2
Total 2,058 (5,085)
Figure 4. Distribution of wetlands in the Christina River
watershed, based on 2007 mapping.
10 Christina River Watershed Wetland Condition Report
along much of the Christina River and its tributaries. Non-tidal flat wetlands are also found
primarily south of Interstate 95 in southern Newark within forested headwaters areas. Natural
and man-made depressions make up a significant portion of the wetland acreage and can be
found throughout the watershed. Of particular note are Delmarva Bays, one of the region’s most
unique and irreplaceable wetland types. These isolated depressions are shallow, seasonally
flooded systems that support an abundance of rare plants and animals. Approximately 30 ha (73
ac) of Delmarva Bays remain in the Christina River watershed, most notably in the towns of
Brookside and Bear, Delaware. Lacustrine fringe wetlands (not pictured) are uncommon in the
Christina River watershed and are found exclusively along Beck’s Pond and Sunset Lake in
Bear, Delaware. These emergent systems differ from other non-tidal wetlands in the watershed
in that they are influenced by water levels in the lakes and can be subject to wind-driven wave
energy.
Christina River Watershed Wetland Condition Report 11
SECTION 1: CONDITION OF WETLANDS IN THE CHRISTINA RIVER
WATERSHED
METHODS
We documented the distribution of wetlands within the Christina River watershed and
estimated the number of wetlands that have been lost, both recently and historically. Wetland
condition assessments were completed in tidal and non-tidal wetlands in the Christina River
watershed during the summer of 2011. We used a probabilistic survey approach to assess
wetlands on both private and public property throughout the watershed. Tidal wetlands were
assessed using the Mid-Atlantic Tidal Rapid Assessment Version 3.0 (MidTRAM; Jacobs et al.
2010), and non-tidal wetlands were evaluated with the Delaware Rapid Assessment Protocol
Version 6.0 (DERAP; Jacobs 2010).
3.1 Changes to Wetland Acreage
We used Delaware wetland maps to determine the current distribution of wetlands across
the Christina River watershed, as well as where wetland loss has occurred in recent decades and
since colonization. Historic wetland acreage was estimated using a combination of current U.S.
Department of Agriculture soil maps and historic soil survey maps from 1915. These maps are
based on soil indicators such as drainage class, landform, and water flow. Hydric soils occurring
in areas that are currently not classified as wetlands due to significant human impacts, either
through urbanization, land clearing, or hydrologic alterations, are assumed to be historic
wetlands that have been lost. Recent losses are classified as wetlands converted during the 15-
year period of 1992 and 2007. Current acreage represents wetlands that were mapped in 2007
during Delaware’s most recent wetland mapping effort (State of Delaware 2007). Recent trends
in wetland acreage are classified as wetlands lost, created, or otherwise changed since 1992
(State of Delaware 1994).
3.2 Field Site Selection
Statistical survey methods developed by the U.S. Environmental Protection Agency’s
Ecological Monitoring and Assessment Program (EMAP) are used to extrapolate results from
random wetland sites to the condition of wetlands throughout the watershed. EMAP in
Corvallis, Oregon assisted with selecting 250 potential sample sites in estuarine intertidal
emergent wetlands and 500 potential sample sites in non-tidal wetlands using a generalized
random tessellation stratified design (Stevens and Olsen 1999, 2000). A target population was
created from all vegetated wetlands from the 2007 state wetland maps. Study sites were
randomly chosen points within mapped wetlands, with each point having an equal probability of
being selected. Sites were selected and sampled in numeric order as dictated by the EMAP
design - lowest to highest. Sites were only excluded from sampling if permission for access was
denied, the site was inaccessible, the site was of the wrong wetland classification, or if the site
12 Christina River Watershed Wetland Condition Report
was upland. Our goal was to sample 30 tidal sites and 30 non-tidal sites in each
hydrogeomorphic class (riverine, flats, and depression).
3.3 Data Collection
3.3.1 Landowner Contact and Site Access
We obtained landowner permission prior to assessing and sampling all sites. We
identified landowners using county tax records and mailed each landowner a post card providing
a brief description of our study goals, sampling techniques, and contact information. If a contact
number was available we followed the mailings with a phone call to discuss the site visit and
secure permission. If permission was denied the site was dropped and not visited. Sites were
deemed inaccessible if a landowner could not be identified or if the site was unsafe to visit.
3.3.2 Assessing Tidal Wetlands
We evaluated the condition of tidal wetlands using the MidTRAM protocol. MidTRAM
was designed and calibrated to assess polyhaline and mesohaline estuarine tidal wetlands and
developed with pilot data from Delaware, Maryland, and Virginia. MidTRAM was created by
adapting the New England Rapid Assessment Method (NERAM; Carullo et al. 2007) and the
California Rapid Assessment Method (CRAM; Collins et al. 2008) and consists of 14 scored
metrics that represent the condition of the wetland buffer, hydrology, and habitat characteristics
(Table 3). MidTRAM uses a
combination of qualitative evaluation
and quantitative sampling to record the
presence and severity of stressors in
the field or in the office using maps
and digital orthophotos.
MidTRAM was completed at
the first 30 random points that we
could access, and which met our
criteria of being of an estuarine
intertidal emergent wetland. Prior to
field assessments we produced site
maps and calculated buffer metrics
using ArcMap GIS software (ESRI,
Redlands, CA, USA). The attributes
measured included buffer width,
surrounding development, percent of
assessment area with a 5 m buffer, 250
m landscape condition, and barriers to
landward migration (Table 3). All
metrics measured in the office were
field verified to confirm accuracy.
Figure 5. Standard assessment area, subplot locations, and
buffer used to collect data for the Mid-Atlantic Tidal Rapid
Assessment Method Version 3.0.
Christina River Watershed Wetland Condition Report 13
We navigated to the EMAP points with a handheld GPS unit and established an
assessment area (AA) as a 50 m radius circle (0.78 ha) centered on each random point (Figure 5).
If a 50 m radius circle went beyond the wetland into upland or open water, we moved the circle
the least distance necessary (up to 50 m) or changed the AA to a rectangle of equal area to have
the entire AA within the wetland. We defined the AA buffer area as a 250 m radius area around
the AA.
Once the AA was established, eight 1 m2 subplots were placed along two perpendicular
100 m transects that bisected the AA. These subplots were used to measure horizontal vegetative
obstruction and soil bearing capacity (Table 3). We oriented one transect perpendicular to the
nearest source of open water (>30 m wide) and the other was perpendicular to the first. We
placed subplots 25 m and 50 m from the center of the AA along each transect. Subplots were
numbered clockwise starting with the plot 25 m from the AA center point, followed by the 50 m
one towards open water (Figure 5). If a subplot fell in a habitat type or patch that was not
characteristic of the site (e.g. in a ditch) we moved it along the transect to the nearest site
representative of the site location.
We completed all metrics within the AA via visual inspection during the field visit, with
the exception of horizontal vegetative obstruction and soil bearing capacity. Horizontal
vegetative obstruction was quantified at subplots 1, 3, 5, and 7 with a 1 m profile board, divided
into decimeters. With the profile board held at 0.25 m, 0.5 m, and 0.75 m above the wetland
surface the observer stood 4 m away from the profile board, and directly counted the number of
decimeter segments visible through the vegetation at eye level with the profile board. We
summed the 3 profile board readings for each subplot and recorded the average over the 4
subplots. We measured soil bearing capacity using a slide hammer technique on a random spot
in each subplot. To take the measurement, we raised the slide hammer and released it 5 times to
exert a consistent force on the soil surface. We subtracted the final depth below the marsh
surface of the bottom of the slide hammer from the initial depth to get the change in depth due to
the total force. Each metric was scored a 3, 6, 9, or 12, based on the narrative or numeric criteria
in the protocol.
Table 3. Metrics measured with the Mid-Atlantic Tidal Rapid Method Version 3.0.
Attribute
Group Metric Name Description
Measured
in AA or
Buffer
Qualitative or
Quantitative
Buffer/Landscape
Percent of AA
Perimeter with 5m-
Buffer
Percent of AA perimeter
that has at least 5m of
natural or semi-natural
condition land cover
Buffer Quantitative
(Office)
Buffer/Landscape Average Buffer
Width
The average buffer width
surrounding the AA that
is in natural or semi-
natural condition
Buffer Quantitative
(Office)
14 Christina River Watershed Wetland Condition Report
Table 3, continued:
Attribute
Group Metric Name Description
Measured
in AA or
Buffer
Qualitative or
Quantitative
Buffer/Landscape Surrounding
Development
Percent of developed
land within 250m from
the edge of the AA Buffer
Quantitative
(Office/Field)
Buffer/Landscape 250m Landscape
Condition
Condition of surrounding
landscape based on
vegetation, soil
compaction, and human
visitation within 250m
Buffer Quantitative
(Office/Field)
Buffer/Landscape Barriers to
Landward Migration
Percent of landward
perimeter of marsh
within 250m with
physical barriers
preventing marsh
migration inland
Buffer Quantitative
(Office/Field)
Hydrology Fill &
Fragmentation
The presence of fill or
marsh fragmentation
from anthropogenic
sources in the AA
AA Qualitative
(Field)
Hydrology Diking/Restriction
The presence of dikes or
other restrictions altering
the natural hydrology of
the wetland
AA and
Buffer
Qualitative
(Field)
Hydrology Point Sources
The presence of
localized sources of
pollution
AA and
Buffer
Qualitative
(Field)
Habitat Bearing Capacity Soil resistance using a
slide hammer AA subplots Quantitative
Field)
Habitat
Horizontal
Vegetative
Obstruction
The amount of visual
obstruction due to
vegetation AA subplots
Qualitative
(Field)
Habitat Number of Plant
Layers
Number of plant layers
in AA based on plant
height AA
Qualitative
(Field)
Habitat
Percent Co-
dominant Invasive
Species
Percent of co-dominant
species that are invasive
in the AA AA
Qualitative
(Field)
Habitat Percent Invasive Percent cover of invasive
species in the AA AA
Qualitative
(Field)
The average field time to sample each site was 2 h, with an average of 0.5 h needed to
complete computer-based metrics. Following field assessments, sites are assigned a Qualitative
Disturbance Rating from 1 (least disturbed) to 6 (most disturbed) using best professional
Christina River Watershed Wetland Condition Report 15
judgment (category descriptions can be found in Appendix A). Detailed instructions for using
MidTRAM are provided in the protocol (Jacobs et al. 2010).
3.3.3 Assessing Non-tidal Wetland Condition
DERAP is used to assess the condition of wetlands based on the presence and intensity of
stressors related to habitat, hydrology, and buffer elements. DERAP scores are calibrated,
separately for each HGM subclass, to comprehensive wetland condition data collected using the
Delaware Comprehensive Assessment Procedure (DECAP; Jacobs et al. 2009). DERAP was
completed at 32 non-tidal flats, 40 non-tidal riverines, and 2 depressions in the Christina River
watershed.
We navigated to EMAP points
with a handheld GPS unit and established
an assessment area (AA) as a 40 m radius
circle (0.5 ha) centered on each random
point (Figure 6). If the 40 m radius circle
extended beyond the wetland edge into
upland or open water, we moved the AA
the least distance necessary (up to 40 m)
or changed to a rectangle of equal area in
order to stay within the wetland. The
entire AA was explored and evidence of
wetland stressors were documented
(Table 4). Current and historic aerial
photos were used to determine forest
activity and buffer stressors and verified
in the field. Similar to MidTRAM, field
investigators assign the wetland a
Qualitative Disturbance Rating from 1
(least disturbed) to 6 (most disturbed;
Appendix A).
Table 4. Metrics measured with the Delaware Rapid Assessment Procedure Version 6.0.
Attribute Group Metric Name Description
Measured
in AA or
Buffer
Habitat Dominant Forest
Age
Estimated age of forest cover
class AA
Habitat Forest Harvesting
within 50 Years
Presence and intensity of
selective cutting or clear cutting
within 50 years
AA
Figure 6. Standard assessment area and buffer used to
collect data for the Delaware Rapid Assessment Procedure
Version 6.0.
16 Christina River Watershed Wetland Condition Report
Table 4, continued:
Attribute Group Metric Name Description
Measured
in AA or
Buffer
Habitat Forest Management
Conversion to pine plantation
or evidence of chemical
defoliation
AA
Habitat Vegetation
Alteration
Mowing, farming, livestock
grazing, or lands otherwise
cleared and not recovering AA
Habitat Presence of Invasive
Species
Presence and abundance of
invasive plant cover AA
Habitat Excessive Herbivory
Evidence of herbivory or
infestation by pine bark beetle,
gypsy moth, deer, nutria, etc. AA
Habitat Increased Nutrients
Presence of dense algal mats or
the abundance of plants
indicative of increased nutrients AA
Habitat Roads
Non-elevated paths, elevated
dirt or gravel roads, or paved
roads AA
Hydrology Ditches (flats and
depressions only)
Depth and abundance of ditches
within and adjacent to the AA AA and Buffer
Hydrology Stream Alteration
(riverines only)
Evidence of stream
channelization or natural
channel incision AA
Hydrology Weir/Dam/Roads
Man-made structures impeding
the flow of water into our out of
the wetland AA and Buffer
Hydrology Stormwater Inputs
and Point Sources
Evidence of run-off from
intensive land use, point source
inputs, or sedimentation AA and Buffer
Hydrology Filling and/or
Excavation
Man-made fill material or the
excavation of material AA
Hydrology Microtopography
Alterations
Alterations to the natural soil
surface by forestry operations,
tire ruts, and soil subsidence
AA
Buffer Development Commercial or residential
development and infrastructure Buffer
Buffer Roads Dirt, gravel, or paved roads Buffer
Buffer Landfill/Waste
Disposal
Re-occurring municipal or
private waste disposal Buffer
Buffer Channelized
Streams or Ditches
Channelized streams or ditches
>0.6 m deep Buffer
Christina River Watershed Wetland Condition Report 17
Table 4, continued:
Attribute Group Metric Name Description
Measured
in AA or
Buffer
Buffer Row Crops, Nursery
Plants, Orchards
Agricultural land cover,
excluding forestry plantations Buffer
Buffer Poultry or Livestock
Operation
Poultry or livestock rearing
operations Buffer
Buffer Forest Harvesting in
Past 15 Years
Evidence of selective or clear
cutting within past 15 years Buffer
Buffer Golf Course Presence of a golf course Buffer
Buffer Mowed Area Any re-occurring activity that
inhibits natural succession Buffer
Buffer Sand/Gravel
Operation
Presence of sand or gravel
extraction operations Buffer
DERAP produces one overall wetland condition score based on the presence and
intensity of various stressors. The final score obtained by DERAP is supported by the intensive
DECAP Index of Wetland Condition. The DERAP model was developed using a process to
screen variables specific to each hydrogeomophic wetland class to select the most important
variables that would represent wetland condition based on over 250 wetland sites (see Sifneos et
al. 2010; Appendix B). Wetland stressors included in the DERAP model were selected using
step-wise multiple regression and Akaike’s Information Criteria (AIC) approach to develop the
best model that correlated to DECAP data without over-fitting the model to this specific dataset.
Therefore, certain wetland stressors are more important than other stressors, while some stressors
are not included in final site scores. Coefficients, or stressor weights, associated with each
stressor were assigned using multiple linear regression (Appendix C). The DERAP IWC score is
calculated by summing the stressor coefficients for each of the selected stressors that were
present and subtracting the sum from the linear regression intercept:
DERAP IWCFLATS = 95 - (∑stressor weights)
DERAP IWCRIVERINE = 91 - (∑stressor weights)
DERAP IWCDEPRESSION = 82 - (∑stressor weights)
For all wetland subclasses, 23 terms were selected to be included in the DERAP IWC
calculation: 7 habitat stressors, 6 hydrology stressors, and 10 landscape or buffer stressors
(Appendix C).
Example: Site D
Forested flat wetland with 25% of AA clear cut, 1-5% invasive plant cover, moderate
ditching, and commercial development in the buffer:
DERAP condition score = 95 – (19+0+10+3)
DERAP condition score = 63
18 Christina River Watershed Wetland Condition Report
3.4 Presenting Wetland Condition
We present our results at both the site- and population-level. We discuss site-level results
by summarizing the range of scores that we found in sampled sites (e.g. Habitat attribute scores
ranged from 68 to 98). Population level results are presented using weighted means and standard
deviations (e.g. Habitat for tidal wetlands averaged 87 ± 13) or weighted percentages (e.g. 20%
of riverine wetlands had channelization present). Population-level results have incorporated
weights based on the probabilistic design and correct for any bias due to sample sites that could
not be sampled and different rates of access on private and public lands to be able to extrapolate
to the total area of wetland in the watershed. The cumulative results represent the total area of
the respective wetland subclass for the entire watershed.
Table 5. Condition categories and breakpoint values for tidal and non-tidal wetlands in the Christina River
watershed as determined by wetland condition scores.
Sites in each HGM subclass were placed into 3 condition categories: Minimally stressed,
Moderately stressed, or Severely stressed (Table 5). Condition class breakpoints were
determined by applying a percentile calculation to the QDR’s and condition scores from sites in
several previously-assessed watersheds. Freshwater tidal wetland regional datasets included
combined MidTRAM data from Pennsylvania, New Jersey, and Delaware (n = 90), while non-
tidal regional datasets includes DERAP data from St. Jones, Murderkill, Inland Bays, and
Nanticoke watersheds (n = 160). Minimally stressed sites are those with a condition score in the
25th
percentile of sites assigned a QDR of 1 or 2. Severely stressed sites are those in the 75th
percentile of sites assigned a 5 or 6. Based on the three watersheds combined, the condition
breakpoints for non-tidal sites that we applied in the Christina River watershed are provided in
Table 5.
We used a cumulative distribution function (CDF) to display wetland condition on the
population level. A CDF is a visual tool to extrapolate assessment results to the entire
population and can be interpreted by drawing a horizontal line anywhere on the graph and
reading that as: ‘z’ proportion of the area of tidal wetlands in the watershed falls above (or
below) the score of ‘w’ for wetland condition. The advantage of these types of graphs is that
they can be interpreted based on individual user goals, and break points can be placed anywhere
on the graph to determine the percent of the population that is within the selected conditions. For
example, in Figure 7 roughly 40% of the wetland area scored above an 80 for wetland condition.
A CDF also highlights clumps or platueas where either a large or small portion of wetlands are in
Wetland Type Method Minimally or
Not Stressed
Moderately
Stressed
Severely
Stressed
Estuarine MIDTRAM ≥ 83 < 83 and ≥ 61 < 61
Non-tidal Riverine DERAP ≥ 85 < 85 and ≥ 47 < 47
Non-tidal Flats DERAP ≥ 88 < 88 and ≥ 65 < 65
Non-tidal Depression DERAP ≥ 73 < 73 and ≥ 53 < 53
Christina River Watershed Wetland Condition Report 19
similar condition. In the example, there is a condition plateau from 50 to approximately 75,
illustrating that only a small portion of the population had condition scores in this range.
Figure 7. An example CDF showing wetland condition. The red line is the population estimate. The orange
and green dashed lines show the breakpoints between condition categories.
20 Christina River Watershed Wetland Condition Report
RESULTS
4.1 Landscape Analysis of Changes in Wetland Acreage
Based on hydric soil mapping and evidence of historic wetland loss, wetlands formerly
covered an estimated 9,163 acres (3,708 hectares) of the Christina River watershed. Compared
to most recent wetland maps, this indicates a 46% loss of wetland acreage between the time of
settlement and 2007 (Figure 8). A majority of these losses have occurred in the headwaters in
southern Newark and along the Interstate 95 corridor.
Figure 8. Estimated historic and present wetland coverage in the Christina River watershed.
Christina River Watershed Wetland Condition Report 21
Despite strict zoning codes and open space requirements in New Castle County,
approximately 81 acres (33 hectares) of wetlands were lost in the Christina River watershed
between 1992 and 2007. Due to past land-use decisions and overdeveloped portions of New
Castle County, the County ratified the Unified Development Code (UDC) in 1997. The UDC
created stringent zoning specifications to guide development and protect the remaining natural
resources in the County, including preserving 100% of wetlands (Section 40.10.320). However,
wetland protection “may be reduced when a permit from the United States Army Corps of
Engineers is issued for filling or disturbance” (Section 40.10.320). A majority of the wetlands
lost during the 15-year period were non-tidal forested systems related to the construction of new
housing developments, widening roadways, and the realignment of Route 273 through Ogletown,
DE. The single largest wetland loss (33 acres) occurred along the Delaware Bay at a disposal
site for dredged material which was covered with hydrophytic vegetation, most likely common
reed (Phragmites australis). Comparisons between 1992 and 2007 wetland maps also revealed
156 acres (63 hectares) of mapped wetlands were created in the Christina River watershed.
However, this small increase in wetland acreage was due to construction stormwater retention
ponds or excavated basins which do not function as natural wetlands.
As a result of recent changes in wetland acreage, the wetland functions potentially
provided in the Christina River watershed have further been altered. A recent landscape-level
analysis of wetland function predicted that, as a result of wetland losses between 1992 and 2007,
the potential for existing wetlands to perform nutrient transformation, sediment retention, surface
water detention, and serve as wildlife habitat were reduced (Tiner 2011). The direct replacement
of natural wetlands with stormwater retention ponds can also negatively affect wildlife that
utilize these habitats for breeding, nesting, or foraging. In developed landscapes, unnatural
hydroperiods and the accumulation of contaminants in stormwater ponds can create ecological
traps for birds, reptiles, and amphibians (Brand et al. 2010).
4.2 Landowner Contact and Site Access
Figure 9. Ownership of sampled wetland sites in the Christina River watershed (left) and success rates for
sampling private wetland sites (right).
22 Christina River Watershed Wetland Condition Report
The majority of our sampled
sites were located on private property
(Figure 9). Almost every assessed
wetland was located in Delaware, with
only one wetland assessment
performed in Maryland and zero in
Pennsylvania (Figure 10). We were
granted permission to 32 of the 34
non-tidal flat wetlands we attempted to
access, of which 66% of the wetlands
were on private property and 34%
were on public property. We were
denied permission to one non-tidal
riverine site, while two other riverine
sites proved to be inaccessible. Of the
40 riverine wetlands that were
sampled, 58% were privately owned
and 42% were on public property. We
only visited two depression wetlands
in the Christina River watershed, with
both sites found on private property.
Tidal wetland assessments were
conducted in 30 estuarine wetlands,
though access was attempted at 40 sites. Six sites were dropped because landowners could not
be contacted. Records are not available to determine why the other four sites were dropped, so it
is unknown if these sites were upland, non-tidal, or if permission was denied. Of the 30
estuarine sites that were assessed, 30% were on public property and 70% were privately owned.
4.3 Condition of Tidal Wetlands
Tidal estuarine wetlands comprise 19% of the total wetland acreage in the Christina River
watershed and provide more ecosystems services than any other wetland type. These systems
are crucial for buffering storm surges and storing floodwaters, controlling erosion, and
improving water quality by sequestering sediments and other pollutants. Within Delaware, a
majority of tidal wetlands are fringing salt marshes with salinities between 5 and 30 ppt. Salt
marshes are extremely productive systems that contain few species capable of surviving in these
environments. Uncommon in Delaware are freshwater tidal wetlands which occur along the
uppermost reaches of tidal rivers and streams that are still influenced by lunar tides. In these
areas, salt water from the Atlantic Ocean is diluted by substantial upstream freshwater inputs and
maintains salt concentrations below 0.5 ppt. These wetlands can be dominated by trees, shrubs,
or herbs and are generally more diverse than typical salt marsh communities. Within the
Christina River watershed, all of the 30 MidTRAM assessment sites were freshwater tidal
marshes.
The average score for the Buffer attribute group was 49 ± 24, with attribute scores
ranging from 93 to 20 (Figure 11). Intensive land uses were found around a majority of the tidal
Figure 10. Location of wetland assessments performed in the
Christina River watershed in 2011.
Christina River Watershed Wetland Condition Report 23
Buffer
Hydrology
Habitat
0 20 40 60 80 100
Value
wetlands in the Christina River
watershed, with 97% of wetlands having
some degree of disturbance in the
surrounding buffer. Development covers
approximately 19% of the 250 m buffers
surrounding tidal wetlands in the
watershed, due largely to the density of
roadways and commercial properties
surrounding marshes. Furthermore,
barriers to landward migration occurred
along 64% of the wetland/upland
boundaries in the watershed. In
undisturbed landscapes, tidal wetlands
respond to rising sea levels by migrating
inland and converting uplands to wetland
ecosystems. In the Christina River
watershed, the ability for marsh
migration is obstructed by these
hardened structures.
Hydrology scores were marginally better than buffer scores, ranging from 100 to 17 and
averaging 73 ± 29 (Figure 11). Thirty percent of the tidal wetlands in the watershed received a
perfect 100 for the Hydrology attribute group. Evidence of historic diking, as well as recent road
construction, was found throughout the watershed and affected the hydrology of 60% of the tidal
wetlands. Pollution entering tidal wetlands was also pervasive in the Christina River watershed
due to the close proximity of residential and commercial development. Point-source discharges
into wetlands were typically pipes, culverts, or ditches originating from anthropogenic land uses
and were found in 40% of marshes. Ditching freshwater marshes is a less common practice than
ditching salt marshes, with only 7% of the tidal wetlands in the watershed containing low
ditching.
Marshes in the Christina watershed generally had a deep peat layer with an average depth
of the organic later at 28.0 ±12.6 cm. Although the marshes had a thick organic layer, the
composition was not firm as evidenced by low bearing capacity. Bearing capacity is inversely
associated with the distance traveled by the slide hammer and this distance was relatively high in
Christina marshes (mean = 4.9±2.0 cm).
Invasive plant species were abundant in the watershed and found in 63% of freshwater
marshes. An estimated 34% of the tidal wetland acreage in the watershed was covered by
invasive species. Common reed was the most common invasive in tidal wetlands, though purple
loosestrife (Lythrum salicaria), narrowleaf cattail (Typha angustifolia) and mile-a-minute weed
(Persicaria perfoliata) also contributed to the invasive plant cover. Soil bearing capacity depth,
which measures marsh stability and reflects bulk density and below-ground biomass, averaged
4.88 ± 2.03 cm, which is deeper than values found in salt marshes.
Figure 11. Box and whisker plot of buffer, hydrology, and
habitat attribute group scores from tidal wetlands in the
Christina River watershed.
24 Christina River Watershed Wetland Condition Report
The integrated final score of Christina marshes averaged 58.9 ± 16.6. The cumulative
distribution function graph for tidal wetlands in the Christina watershed (Fig. 12) represents the
condition of the entire population of tidal wetlands. Top percentiles to determining comparative
break points among all freshwater tidal marsh condition scores were: <60 severely stressed; 61-
82 moderately stressed; >83 minimally stressed. Based on this, 57% of the tidal wetlands in the
Christina watershed were highly stressed, approximately 30% were moderately stressed, and
17% were minimally or not stressed. This implies that more than 80% of the freshwater tidal
wetlands in Christina were in comparatively poor condition.
Figure 12. The cumulative distribution function for tidal wetlands in the Christina watershed. The orange
and green dashed lines signify the condition category breakpoints dividing severely stressed from moderately
and minimally stressed portions of the tidal wetland population.
MidTRAM data from the 30 tidal wetland assessment sites can be found in Appendix D.
4.4 Condition of Non-tidal Wetlands
4.4.1 Non-tidal Flat Wetland Condition
Flat wetlands total approximately 40% of the of the wetland acreage in the Christina
River Watershed, primarily in low-lying forested areas. A majority of the non-tidal flat wetlands
are found in the western half of the watershed within the Coastal Plain province. Sizable non-
tidal flat wetlands can be found in Newport, south of the Interstates 95 and 295 interchange in an
area that was historically covered with tidal wetlands.
0
10
20
30
40
50
60
70
80
90
100
20 30 40 50 60 70 80 90 100
% o
f Ti
dal
We
tlan
d P
op
ula
tio
n
Wetland Condition Score
Minimum Maximum
Moderate
Christina River Watershed Wetland Condition Report 25
Table 6. Composition of wetland condition classes (left) and the occurrence of common wetland stressors
(right) of non-tidal flat wetlands in the Christina River watershed.
The highest possible score for non-tidal flats using DERAP is 95, and condition scores in
the Christina River watershed ranged from 91 to 43, with an average of 70±16. Nearly all (85%)
of flat wetlands in the watershed at least moderately disturbed, while only 16% of the flats are in
minimally stressed condition (Table 6). Invasive plant species were found in 85% of the flat
wetlands, with 13% of flats dominated by invasives. Recent forest harvesting was documented
in half of the non-tidal flat wetlands in the watershed, with clear cutting occurring in 31% of
wetlands and selective thinning found in 19% of wetlands. Wetland draining was also pervasive
in the watershed, with ditches found in 44% of flat wetlands. As expected within a heavily
urbanized landscape, intensive land-uses were found in most of the buffers surrounding flat
wetlands. Impervious surface cover, such as paved roads and development, occurred in 91% of
the wetland buffers in the watershed. Regularly mowed and cleared areas were found in the
buffers of 56% of flat wetlands in the watershed, which were typically maintained right-of-ways
associated with high-voltage powerlines that traverse Bear and Newark.
Though intensive land-use was found in the most wetland buffers, non-stormwater point
source inputs were not observed in any flats in the watershed. Notable stormwater inputs were
found in 9% of flat wetlands, evident by wrack lines or stormwater drainage structures directly
emptying into the wetland. Unlike Delaware’s Kent and Sussex counties, forest conversion to
pine plantations is rare in New Castle County and was not found in any flat wetlands in the
watershed. Excessive herbivory was documented in one flat wetland (3% of the population) due
to heavy browsing by white-tailed deer (Odocoileus virginianus).
Proportion of Sites with Stressor Present:
Wetland Stressor
Minimally
Stressed
(n = 5)
Moderately
Stressed
(n = 14)
Severely
Stressed
(n = 13)
Forest clear cutting 0% 0% 77%
Invasive plants present 40% 86% 100%
Ditching in wetland 0% 43% 62%
Fill material in wetland 20% 43% 85%
Development in buffer 80% 79% 69%
26 Christina River Watershed Wetland Condition Report
The cumulative distribution function for flat wetlands in the Christina River watershed
shows a wetland population skewed towards lower condition classes (Figure 13). Approximately
900 acres of flat wetlands in the watershed are functioning in a severely stressed condition.
Generally, these wetlands have been extensively cleared or thinned and plant communities with
moderate to extensive coverage of invasive plant species. A majority of these sites have also
been ditched and partially filled, and have multiple stressors in the surrounding landscape. Only
200 acres of flat wetlands in the watershed are estimated to be in a minimally stressed state.
These wetlands have a low occurrence of invasive plants and selective forest thinning, no
ditches, little to no fill material, and relatively intact buffers. The DERAP stressor checklist
from the 32 flat wetland assessment sites in the Christina River watershed are provided in
Appendix E.
Figure 13. Cumulative distribution function for non-tidal flat wetlands in the Christina River watershed.
Condition scores for the wetland population are represented as the red line with 95% confidence intervals
(gray dashed lines). The orange and green dashed lines designate condition category breakpoints dividing
severely stressed, moderately stressed, and minimally stressed wetlands.
Christina River Watershed Wetland Condition Report 27
4.4.2 Non-tidal Riverine Wetland Condition
Riverine wetlands in the Christina River watershed are associated with floodplains of the
Christina River and its tributaries. These wetlands cover approximately 481 hectares (1,191
acres) which is 23% of the total wetlands acreage in the watershed. Riverine wetlands act as
buffers between streams and adjacent land use and are valued for water quality maintenance
through sediment retention and nutrient uptake. They are also vital for flood abatement by
allowing for overbank flood water storage during storm events.
The maximum score possible for riverine wetlands using DERAP is 91, and riverine
wetland scores in the Christina River watershed ranged from 88 to 6, with an average of 53±22.
Only 8% of the riverine wetlands in the watershed were functioning in a minimally stressed
condition, while 40% of the wetlands were severely stressed (Table 7). A majority of the buffers
surrounding riverine wetlands in the watershed were significantly impacted, with 95% of
wetlands containing impervious surfaces in the buffer. Similar to flat wetlands in the watershed,
regularly mowed areas were also found in a majority (83%) of riverine wetland buffers. Ten
percent of the riverine wetlands also had reoccurring mowing within the wetland itself. As
development and land clearing occurs adjacent to wetlands, edge effects, such as increased
sunlight and wind penetration, have profound impacts on the remaining wetland habitat and
increase the likelihood of colonization by invasive species. As expected, 95% of the riverine
wetlands in this watershed contained invasive plant species, with 48% of riverine wetlands
dominated by invasive plant cover. Stream channelization or natural channel incision was the
most common impact to wetland hydrology, occurring in 60% of riverine systems. Fill material,
such as spoil piles and yard waste, was also found in 53% of riverine wetlands. Forestry activity
was less common in riverine wetlands than flats in the Christina River watershed, though 25% of
riverine sites were selectively thinned or clear-cut.
Table 7. Composition of wetland condition classes (left) and the occurrence of common wetland stressors
(right) of non-tidal riverine wetlands in the Christina River watershed.
Proportion of Sites with Stressor Present:
Wetland Stressor
Minimally
Stressed
(n = 3)
Moderately
Stressed
(n = 21)
Severely
Stressed
(n = 16)
Forestry activity 0% 10% 50%
Dominated by invasive spp. 0% 38% 69%
Stream channelized/incised 0% 38% 100%
Fill material in wetland 0% 38% 81%
Development in buffer 67% 57% 88%
Evidence of stormwater inputs were more common in riverine wetlands than flats in the
watershed. Excessive sedimentation was found in 8% of riverine wetlands, and stormwater
inputs in another 10% of wetlands. Generally, elevated roads and all-terrain vehicle trails are less
common in riverine wetlands due to the saturated soil conditions, though these features were
28 Christina River Watershed Wetland Condition Report
nearly as common in riverine wetlands (28%) as they were in flats (31%) within the Christina
River watershed. Excessive herbivory was slightly more common in riverine wetlands (5%) due
to forest clearing and significant impounding by North American beavers (Castor canadensis).
Fewer than 50 acres of minimally stressed riverine wetlands remain in the Christina River
watershed based on cumulative distribution function estimates (Figure 14). These wetlands were
absent of forest cutting, stream alterations, and fill material. However, these wetlands vary in the
amount of invasive plant species present and the intensity of impacts to the surrounding buffer.
Conversely, approximately 500 acres of riverine wetlands in the Christina River watershed are
severely stressed. Invasive plant species were found in each of the severely stressed riverines,
with invasives as the dominant plant cover in 69% of these wetlands. Stream morphology and
wetland hydrology is also significantly altered, including channelization or incision (100% of
riverine wetlands), fill material (81%), and constricted or impounded streamflow (63%).
Impervious landcover was also found in the buffers around each of the severely stressed riverine
wetlands. The DERAP stressor checklist from the 40 riverine wetland assessment sites in the
Christina River watershed are provided in Appendix F.
Figure 14. Cumulative distribution function for non-tidal riverine wetlands in the Christina River watershed.
Condition scores for the wetland population are represented as the red line with 95% confidence intervals
(gray dashed lines). The orange and green dashed lines designate condition category breakpoints dividing
severely stressed, moderately stressed, and minimally stressed wetlands.
Christina River Watershed Wetland Condition Report 29
4.4.3 Non-tidal Depression Wetland Condition
Approximately 330 hectares (817 acres) of depression wetlands are found in the Christina
River watershed. These wetlands naturally form in low-lying areas and topographical
depressions within the landscape. Most of the natural depressions in the Christina River
watershed occur in forested areas south of Newark, though they can be found throughout the
watershed. The acreage of depression wetlands in the watershed is inflated by a number of large
man-made impoundments within cloverleaf interchanges on Interstate 95 and a dredge disposal
area south of the Cherry Island landfill in Wilmington. Natural depressions in the watershed are
otherwise rare and only two depression wetlands were assessed, so conclusions on the condition
of depressions at the watershed-scale cannot accurately be drawn. The DERAP stressor checklist
from the two depression assessments can be found in Appendix G.
4.5 Overall Condition and Watershed Comparison
For an overall view of non-tidal wetland condition in the Christina River watershed, and
to compare to five recently assessed watersheds in southern Delaware, we created an overall
condition score weighted by the acreage of flat and riverine wetlands in each watershed.
Non-tidal wetlands in the Christina River watershed were in considerably worse
condition than wetlands in southern Delaware (Figure 15). The Christina River watershed
contained more severely stressed wetlands than any other watershed, as well as the fewest
proportion of minimally stressed wetlands.
Figure 15. Combined condition of non-tidal flat and riverine wetlands in the Christina River watershed,
compared to wetland condition in the St. Jones, Murderkill, Mispillion, Broadkill, and Inland Bays
watersheds.
30 Christina River Watershed Wetland Condition Report
MANAGEMENT RECOMMENDATIONS
Based on our study, we offer the following seven recommendations to improve ecosystems
provided by wetlands, guide wetland restoration and management efforts, identify additional
management needs, and encourage informed decisions concerning the future of wetland
resources in the Christina River watershed.
1. Preserve remaining Delmarva Bays. Coastal Plain Seasonal Ponds, also known as
Delmarva Bays, have been identified as a regionally-unique wetland type and are
considered irreplaceable and a significant component of Delaware’s natural heritage
(McAvoy and Clancy 1994). These wetlands contain unique hydrological and biological
characteristics that are imperative for the survival of many plants and animals in
Delaware. Many Delmarva Bays throughout the state have traditionally been ditched,
filled, or excavated and are exceedingly rare in Delaware, with only an estimated 73 acres
of Delmarva Bays remaining in the Christina River watershed. New Castle County’s
Unified Development Code preserves 100% of wetlands (Section 40.10.32) unless a
permit from the United States Army Corps of Engineers is issued for filling or
disturbance (Section 40.10.320), leaving Delmarva Bays vulnerable to impacts.
Protecting Delmarva Bays, and biologically-significant buffers, through easements and
planning will preserve these irreplaceable wetlands.
2. Incorporate wetland creation and restoration into urban planning. Many
neighborhoods in Wilmington are marred by chronic flooding and inadequate drainage
which stifles local economies. An example of utilizing the natural ecosystem services
provided by wetlands are found in the management plan developed for South Wilmington
and the neighborhood of Southbridge. This large-scale community revitalization plan is
held as a national model for incorporating wetland restoration to alleviate flooding,
improve water quality, and provide habitat for wildlife. The 27-acre restored wetland
will also serve as greenspace for the community and an educational resource for urban
school students. Many opportunities for wetland restoration and outreach can be found
along the Christina River and should be considered in land-use decisions.
3. Utilize clean dredged material for wetland creation. The mouth of the Christina River
and the navigational channel in the Delaware Bay is frequently dredged to accommodate
cargo ships reaching the Port of Wilmington. Traditionally, dredged materials are
disposed of in confined disposal facilities found along the Delaware Bay. Re-using
uncontaminated dredged material for wetland restoration and creation has been used
elsewhere in the United States and can be explored in the Christina River watershed.
Considerations must be made on the source of sediments used for restoration because a
number of areas in the Delaware River and Bay have elevated concentrations of
contaminants that would limit the feasibility of habitat restoration. In 2011 DNREC and
its conservation partners began a project applying a thin layer of dredged material to a
fragmenting salt marsh in Dagsboro to increase surface elevation and promote Spartina
altiniflora growth. Dredged sediment has also been beneficially re-used throughout the
country to create wetlands in areas that were previously open water. Opportunities for
Christina River Watershed Wetland Condition Report 31
wetland creation should be investigated in open water areas of Churchman’s Marsh and
around the confluence of the Brandywine River. The Delaware Estuary Regional
Sediment Management Plan Workgroup has developed documents outlining potential
uses of dredged sediments and special considerations.
4. Encourage alternative shoreline protection designs. Shorelines are dynamic systems
that respond to sediment supply and wave energy through erosion and accretion.
Shorelines along the Christina River are significantly altered by bulkheads, gabions,
revetments, and rip-rap which lack the capacity to respond to these natural processes. In
these areas lacking estuarine wetlands, shorelines have reduced capacity to buffer storm
surges, trap sediments, and provide habitat for wildlife due to the hardened shorelines.
Along shorelines with lower wave energy, alternative shoreline stabilization approaches
should be considered if erosion threatens public infrastructure. Living shorelines are a
natural alternative which utilizes coconut fiber logs and natural vegetation to anchor the
shoreline and prevent erosion. Shellfish or low-profile rock sills can also be used with
living shorelines to dissipate wave energy. In situations with greater energy or steeper
banks, timber cribbing and log revetments may be employed. The Delaware Estuary
Living Shoreline Initiative was developed to showcase natural alternative to protect
shorelines (for more information, see http://delawareestuary.org/Living_Shorelines).
5. Develop incentives and encourage maintaining natural buffers along riverine and
tidal wetlands. As sea levels rise and extreme storm events bring more flooding, the
importance of wetland buffers between water and upland is taking center stage. The need
exists to inform Delawareans on the importance of allowing tidal wetlands to migrate
inland unobstructed by roads, rip-rap and bulkheads. Sufficient buffers along streams
and rivers stabilize shorelines and improve water quality by trapping sediments and
pollutants before they reach surface waters. Landowners along riverine and estuarine
wetlands, as well as those directly abutting surface waters, should be educated about the
ecological and societal benefits that can be attained by preserving natural buffers. In
addition to awareness, an incentive program could attract an interest in maintaining larger
natural buffers between wetlands and development.
6. Control the extent and spread of the non-native, invasive common reed (Phragmites
australis). Invasive plants such as Phragmites are capable of spreading rapidly,
outcompeting native species, reducing plant diversity in undisturbed areas, and reducing
the success of other organisms by changing habitat structure and food availability. The
DNREC Phragmites Control Program in the Division of Fish and Wildlife has treated
more than 20,000 acres on private and public property since 1986. Without continued
support from state funds and federal State Wildlife Grant funds Phragmites will degrade
more wetlands. Phragmites was the most abundant invasive species in estuarine
wetlands in the Christina River watershed and a significant stressor in non-tidal flat and
riverine wetlands.
7. Update tidal wetland regulatory maps. In addition to improving the protection of
nontidal wetlands, it is prudent to maximize the authority that already exists within
DNREC. Tidal wetland impacts are regulated by the State of Delaware and permit
32 Christina River Watershed Wetland Condition Report
reviewers need accurate and recent wetland maps to guide wetland permitting. Currently
1988 wetland maps are used, which must be verified in person and are difficult to read.
Evidence of recent coastal development and inundation of coastal wetlands due to sea
level rise creates a greater need to adopt updated wetland maps as regulatory maps.
Christina River Watershed Wetland Condition Report 33
SECTION 2: ESTABLISHMENT OF A PERMANENT INTENSIVE
MONITORING STATION IN THE CHRISTINA RIVER WATERSHED
SUMMARY
In September of 2010, a permanent Site Specific Intensive Monitoring (SSIM) station
was established at Christina River, in South Wilmington, Delaware. This SSIM location is a part
of a larger monitoring scheme entitled the Mid-Atlantic Coastal Wetlands Assessment
(MACWA). The major goal of MACWA SSIM is to provide long term monitoring data to aid
land managers in the conservation and protection of wetlands, especially from the threats of sea
level rise due to climate change. Several permanent fixtures were installed at the Christina River
SSIM station including surface elevation tables (SETs) and permanent vegetation plots. These
fixtures were monitored from 2011 to 2013, along with a suite of other metrics including water
quality and plant biomass. Three years of data, however, is inadequate to make conclusions
about long-term trends. Yet, data reported here suggest that between 2011 and 2013, the marsh
platform had increased in elevation at SET benchmarks. These elevation changes are most likely
the result of subsurface swelling. Some disparate results were observed between SET benchmark
and plant community data; overall, however, these data suggested an increasing trend, but at
least 5 years of data is needed to determine the inherent natural variation. The next two sampling
years will be very important to confirming these trend, as well as making conclusions about other
cause and effect relationships that will be monitored at Christina River.
INTRODUCTION
To provide insight into cause and effect relationships in accordance to overall wetland
health, Site Specific Intensive Monitoring (SSIM) seeks to track changes in wetland composition
at fixed locations over time. As part of this effort, field methodologies consist of the installation
of permanent fixtures that aid in our ability to return to exact locations, and to monitor
characteristics of the marsh that are
usually difficult to study. These fixtures
include surface elevation tables (SET),
designed to track elevation changes due to
shrink and swell of the marsh platform;
nine permanent vegetation plots, designed
to observe changes in plant communities at
precise locations; and vegetation real time
kinetic (RTK) GPS transects (accurate ±2
cm), designed to track vegetation
distribution changes at specific elevations
(Figure 16). Along with monitoring these
fixed features, other metrics are monitored
which consist of additional physical,
chemical and biological variable, such as
Figure 16. Example of Site Specific Intensive Monitoring
sampling lay-out along the main waterway.
34 Christina River Watershed Wetland Condition Report
water quality and biomass measurements. These variables in association with permanent fixtures
are collectively referred to as a SSIM “station.” Understanding changing relationships among
key ecoregion features aids in our ability to decipher stressor-response relationships in wetlands
across SSIM stations in the estuary, and offer insights into how landscape and climatic changes
are affecting wetland health and condition.
METHODS
5.1 Components of Site Specific Intensive Monitoring Stations
5.1.1 Surface Elevation Tables (SETs) and Marker Horizons (MH)
On September
17, 2010, three deep
rod surface elevation
table benchmarks were
installed at the
Christina River study
site, which also marks
the establishment of
this SSIM station.
Surface elevation tables
(SETs) and feldspar
marker horizons (MHs;
3 per SET) were
installed in accordance
with protocol
established by Cahoon
(2002; Figure 17).
Marker horizons allow
us to discern surface
accretion, and are used
in conjunction with
SET heights to
ascertain causes of
marsh elevation
change. SET heights are the cumulative height change of 9 pins on a portable SET arm, which is
positioned on the benchmark. Accretion is measured as the distance from the top of the layer of
feldspar to the surface of marsh as seen from a core taken from a marker horizon plot. More
detailed methodologies can be found online at USGS Patuxent Wildlife Research Center. SET
readings were taken March 15, 2011 (baseline); September 1, 2011; June 13, 2012; September
12, 2012; and June 5, 2013. Accretion rates at the Christina River SSIM station were obtained
Figure 17. Site Specific Intensive Monitoring (SSIM) point locations at Christina
River, Wilmington, DE: permanent vegetation plots (PVs; groups of three) and
random edge plots (REs) distributed along shoreline of main water bodies.
Christina River Watershed Wetland Condition Report 35
on March 15, 2011 (baseline); June 13, 2012; September 12, 2012; June 5, 2013 and August 14,
2013. Our partners, the Academy of Natural Science of Drexel University, collected these data.
5.1.2 Soil Quality and Biomass
Three plots were established for biomass sample collection in both low marsh or nearest
distance to the main water body and high marsh or farthest distance from the main water body
~10 m landward of two of the three SETs at each monitoring station. Three plots were
established no less than 10 m from any SET-MH. For appropriate consistency and replication,
the three plots were placed in the same or similar plant communities to the SET-MH.
Aboveground biomass was harvested in 0.5 m2 quadrats for salt marshes or 1.0 m
2
quadrats for tidal fresh marshes by clipping all standing vegetation at the marsh surface.
Aboveground biomass was placed into labeled plastic bags and brought to the lab for processing.
Belowground biomass was collected in the center of this plot as a 15-cm diameter x 30-cm depth
soil core by pounding a PVC core barrel. The belowground biomass was washed over a 5 mm
mesh sieve then separated into live and dead material. All material was washed, dried, ground,
and measured for loss on ignition. Samples were stored for biochemical analysis if needed.
5.1.3 Vegetation Transects
Three transects were established that represent the gradient from the marsh edge to its
interior in the proximity of each of the SET and MH fixtures (Figure 2). A total of nine transects
were assessed by storing point data using Real Time Kinetic GPS, which collects precise
latitude, longitude, and elevation data. Dominant vegetation was recorded in association to these
data so that elevation changes can be correlated with changes in plant communities. Data were
collected July 13, 2011 and September 27, 2013. The Academy of Natural Science of Drexel
University also collected these data.
5.1.4 Vegetation Data in Fixed Plots
Nine 1 m2 permanent vegetation plots (PVs) and six ¼ m
2 random edge (REs) plots
(Figures 16 and 17) were assessed on August 8, 2011, September 20, 2012, and July 22, 2013.
The nine PVs are grouped transversely across the three transects, so that PVs are triplicates
within their proximity (“near”: PV numbers 1,2, 3, closest to mouth or water edge; “mid”: 4,5,6
and “far”: 7,8,9 furthest upstream or from water). Therefore, calculations represent the average
PV value for its group (near, mid or far). All plots were relocated using handheld GPS units, but
only PVs were marked with permanent PVC markers. Percent plant species cover, species
dominance, light obstruction, and average blade heights were recorded for all plots (MACWA
SSIM QAPP 2010). From these measurements, canopy closure (light in kfc/blade height in cm),
alpha diversity (Shannon-Weiner), and vegetation zone dominance scores (VZD; a novel method
for estimating flood frequency using plant community structure, see Appendix B) were
calculated.
A principal component analysis (PCA) was run on these metrics, as well as SET and
accretion data, which were introduced into the PCA as environmental covariants. PCA is a
multivariate comparison that allows us to discern differences between years among the suite of
36 Christina River Watershed Wetland Condition Report
SSIM variables since temporal data are currently too limited to perform robust linear regressions.
Each year, therefore, is compared to the others as an independent sample. From the PCA, an
ordination plot is generated. An ordination plot allows us to visualize correlations between
variables, and the strength of these relationships.
5.1.5 Water Quality
Five points were established along the nearest main channel or tidal creek for spot
measurements using an YSI and water collection. Tidal creek surface water samples were
collected, filtered, and analyzed for dissolved and particulate nutrients. Sampling and data
collection occurred approximately two hours after high tide (i.e., during ebb tide). One gallon
cubitainers were rinsed with site water and then filled at each of the five locations along the main
water body or tidal creek. Cubitainers were stored on ice in the dark while in the field. Water
samples were analyzed for total suspended solids, suspended Chlorophyll (fluorometric;
acidification method), dissolved ammonium + ammonia, dissolved nitrate + nitrite, soluble
reactive phosphorus, dissolved organic carbon, total nitrogen (TKN+dissolved nitrate+nitrite)
and total phosphorus. Our partners at the Academy of Natural Sciences of Drexel University
also collected these water quality data.
RESULTS
5.2.1 Surface Elevation Tables (SETs) and Marker Horizons (MH)
Average SET heights were converted into height change per SET (Table 8). Values per
SET were then averaged to give cumulative height change (Figure 5). A linear regressions of
these data per SET produces trend lines with equations of y(SET1 height) =0.0432x-1741.5,
y(SET2 height) = 0.0245x-988.25, y(SET3 height) =0.0227x-909.62 (Figure18). These produce
a yearly (slope * 365) increase of 15.6, 12.5, 8.2 mm/yr or an average of 12.1 mm/yr. Linear
models predict no significant differences from slopes of zero. Accretion rates (MHs) are
measured as sediment heights above feldspar marker, and then are converted to cumulative
changes in height (Table 9). Daily accretion rate is given by a linear regression (slope NS from
zero) of height change, where y(accretion height) =0.0035x-136.38, or an accretion rate of 1.27
mm/year (Figure 19). Shallow subsidence (MH minus SET) is -10.83, which is a cumulative
increase in elevation at SET benchmarks.
Table 8. Surface Elevation Table heights for Christina River. Data
are given as the difference in mean pin height between sampling
dates, error values are standard error.
Date SET 1 SET 2 SET 3
3/15/2011 0 (baseline) 0 (baseline) 0 (baseline)
9/1/2011 18.96 ± 5.15 36.26 ± 6.43 25.4 ± 6.42
6/13/2012 -9.00 ± 4.38 -9.08 ± 4.23 -1.97 ± 6.14
9/12/2012 15.33 ± 6.07 7.61 ± 2.72 16.1 ± 4.24
6/5/2013 -1.58 ± 15.52 10.67 ± 14.51 -21.0 ± 6.60
Christina River Watershed Wetland Condition Report 37
Table 9. Marker Horizon Heights for Christina River. Data are given as the mean
accretion height at sampling dates. Error values are standard error.
Date SET 1 SET 2 SET 3
3/15/2011 0 (baseline) 0 (baseline) 0 (baseline)
6/13/2012 24.5 ± 5.37 46.3 ± 0.440 23.6 ± 1.63
9/12/2012 20.6 ± 0.816 25.5 ± 1.5 27.3 ± 0.421
6/5/2013 27.7 ± 6.64 NA 29.1 ± 2.19
8/14/2013 41.1 ± 3.94 33.8 ± 3.92 39.11 ± 2.87
Figure 18. Cumulative accretion height change for Christina River. Heights are given as the difference in
mean accretion height of all SETs between sampling dates, error bars are standard error. Arrow marks the
approximate date of the landfall of Hurricane Sandy in New Jersey (October 29, 2012). Yearly SET height
changes (mm) are 15.6, 12.5, 8.2 for SET 1, 2, and 3, respectively, averaging 12.1 mm/yr. Linear models
predict NS from slope =0.
Figure 19. Cumulative accretion height change for Christina River. Heights are given as the difference in
mean accretion height of all SETs between sampling dates, error bars are standard error. Arrow marks the
approximate date of the landfall of Hurricane Sandy in New Jersey (October 29, 2012). Yearly accretion rate
is 1.27 mm/yr. Slope NS from zero
y = 0.0245x - 988.25
y = 0.0432x - 1741.5 y = 0.0227x - 909.62
0
10
20
30
40
50
60
70
Cu
mu
lati
ve H
eig
ht
Ch
ange
(m
m)
Date
SET 1 SET 2 SET 3 Linear (SET 1) Linear (SET 2) Linear (SET 3)
y = 0.0035x - 136.38 R² = 0.007
-20
-10
0
10
20
30
40
Cu
mu
lati
ve H
eig
ht
Ch
ange
(m
m)
Date
Δ Accretion (mm) Linear (Δ Accretion (mm))
38 Christina River Watershed Wetland Condition Report
9%
4%
11%
2%
2%
2% 70%
Impatiens capensis
Nuphar lutea
Peltandra virginica
Pontederia cordata
Sagittaria latifolia
Scirpus fluviatilis
Typha angustifolia
2%
8% 2% 2%
6% 2%
2% 2%
2% 6%
2% 2%
2% 2%
53%
2%
4%
Amaranthus cannabinusImpatiens capensismix Acorus calamus/Scirpus fluviatilismix Amaranthus cannabinus/Typha angustifolia/mix Impatiens capensis/Typha angustifoliamix Peltandra virginica/Polygonum punctatummix Polygonum arifolium/Polygonum punctatummix Polygonum punctatum /Zizania aquaticamix Sagittaria latifolia/Peltandra virginicamix Typha angustifolia/Impatiens capensisPeltandra virginicaPolygonum arifoliumPolygonum punctatumSagittaria latifoliaTypha angustifoliaUnidentified vine/ Gleditsia tricanthosZizania aquatica
5.2.2 Soil Quality and Biomass
Aboveground biomass collected > 10m landward of SETs 1 and 3 averaged 761.2 gm-2
in
2011; the corresponding belowground biomass averaged 900.73 gm-2
. Soil cores were collected
>10m landward of SETs 1and 3 on November 8, 2010, March 15 and September 1, 2011.
Averaged across time periods, surface (5cm depth) organic matter (OM) content averaged 23%.
Averaged between the two time periods, Chl concentrations at Christina were 14.7 µg g-1
.
5.2.3 Vegetation Transects
The average
orthoheight derived from
RTK GPS of all transects
at Christina River was
0.6530.015 m in 2011
and 0.5190.028 m in
2012 (t-test p<0.0001).
Vegetation transects
were designed to create
GIS contour elevation
maps which can be used
to perform spatial
analyses in GIS for plant
community distribution.
These maps and analyses
are not yet available as
models are currently
being constructed.
Narrow leaf cattail Typha angustifolia) was the most abundant species observed along these
transects. Percentages of species dominance along the transects are in Figure 20 and 21.
Figure 21. Percentages of dominant vegetation type over all three RTK GPS
transects in 2011.
Figure 20. Percentages of dominant vegetation type over all three RTK GPS transects in 2012.
Christina River Watershed Wetland Condition Report 39
5.2.4 Vegetation in Fixed Plots
The following tables (Tables 10-12) contain mean values for raw or calculated values
(i.e. percentages) for measurements taken at fixed vegetation plots, including faunal data.
Although three years of data are currently available for vegetation in fixed plots, more years of
collection are necessary to make robust conclusions about vegetation community trends at the
Christina River. Future analyses will include linear models of year to year changes in community
structures.
Table 10. Mean blade heights (cm) of first and second dominant species within near, mid, and far PVs.
Plot Area
Year All Species First Dominant Species Second Dominant Species
Mean (n=3) SE Species Mean SE Species Mean SE
near PVs
2011 212.60 7.41 Typha angustifolia 246.59 4.54 Peltandra virginica 121.73 4.88
2012 177.93 7.08 Typha angustifolia 181.09 7.09 Impatiens capensis 115.00 6.43
2013 169.43 7.72 Typha angustifolia 236.38 4.97 Impatiens capensis 108.00 7.56
mid PVs
2011 175.32 8.53 Typha angustifolia 245.41 6.92 Peltandra virginica 129.03 5.16
2012 103.09 7.99 Peltandra virginica 77.11 4.66 Impatiens capensis 80.12 4.38
2013 199.80 8.40 Typha angustifolia 261.55 4.71 Nuphar lutea 59.64 5.24
far PVs
2011 203.43 9.57 Typha angustifolia 257.47 10.12 Peltandra virginica 129.11 6.34
2012 103.88 7.67 Typha angustifolia 211.28 9.68 Impatiens capensis 80.93 3.87
2013 196.63 6.77 Typha angustifolia 240.26 4.93 Peltandra virginica 118.52 2.57
all REs
2011 127.77 3.45 Nupar lutea 106.19 3.78 Pontedaria cordata 140.68 3.57
2012 77.81 2.62 Nuphar lutea 72.27 2.78 Polygonum sp. 77.46 3.44
2013 119.72 2.17 Nuphar lutea 119.75 2.27 Pontedaria cordata 131.47 5.84
40 Christina River Watershed Wetland Condition Report
0.00
0.50
1.00
1.50
2.00
2.50
2011 2012 2013
Near
Mid
Far
RE
Table 11. Percent of light penetration is given by light
intensity at the bottom of the canopy divided by the
light intensity above the canopy.
Table 12. Percentages of the first two most dominant species found in each plot, followed by the diversity
index and mean VZD score. Percentages may not equal 100% as species coverage in plot may be highly
overlapped or sparse.
Plot Area
Year
Dominant Species, Diversity and VZD
Dominant Species % Subdominant Species % Diversity VZD
near PVs
2011 Typha angustifolia 58.3% Lonicera sp. 40.0% 0.633 2.02
2012 Typha angustifolia 76.7% none 0.66 2.1
2013 Typha angustifolia 52.7% Impatiens capensis 31.5% 0.56 1.88
mid PVs
2011 Peltandra virginica 37.5% Typha angustifolia 35.0% 0.32 1.96
2012 Impatiens capensis 80.0% Nuphar lutea 20.0% 0.523 1.81
2013 Typha angustifolia 65.0% Nuphar lutea 40.0% 0.483 2.19
far PVs
2011 Typha angustifolia 63.3% Peltandra virginica 57.5% 0.69 2.08
2012 Typha angustifolia 47.5% Impatiens capensis 30.0% 0.44 1.98
2013 Typha angustifolia 52.5% Peltandra virginica 50.0% 0.55 2.14
all REs
2011 Nuphar lutea 61.3% Pontedaria cordata 40.0% 0.93 1.42
2012 Nuphar lutea 24.2% Pontedaria cordata 15.0% 0.87 0.71
2013 Nuphar lutea 55.2% none 0.89 0.99
A principal component analysis (PCA) was then run on the vegetation data, which
included group wise VZD score, canopy closure, blade height, canopy density and alpha
diversity constrained (i.e. treated as independent co-variables) by the environmental variables:
cumulative SET height and accretion rates. The red variable labels indicate the approximate
direction of each metric's increasing values. The blue arrows indicate the strength and direction
of the covariant environmental variables' with the main variables (red labels). Each polygon is
one sampling year, with near (A), mid (B), and far (C) PVs. Differences between years are
highlighted by the shape of each polygon, and the distance between them. The vectors indicate
Plot Area
Year Percent Light Penetration
All Species
Mean (n=3) SE
near PVs
2011 3.57 0.96
2012 8.85 1.91
2013 5.03 0.82
mid PVs
2011 7.29 2.78
2012 17.52 12.25
2013 8.69 2.25
far PVs
2011 4.20 0.60
2012 7.17 0.52
2013 8.46 1.36
all REs
2011 15.00 7.20
2012 35.78 7.59
2013 11.37 3.44
Figure 22. Three year trend of Vegetation Zone
Dominance (VZD) scores at PVs (near, mid, and far) and
REs. Lower VZD scores are communities whose
structure suggest more tidal flooding.
Christina River Watershed Wetland Condition Report 41
which sampling years (polygons) exhibit larger metrics with greater lengths. Notable
relationships may be observed when arrows point in the same direction (positive correlation) or
when they are opposing (negative correlation). It should also be noted that arrows that are
orthogonal to one another have no correlation.
Figure 23. Principal component analysis for Christina River. Red labels are main analysis variables; blue
arrows are covariant environmental variables. Vertices of polygons are labeled A, B, and C, for near, mid,
and far, respectively, followed by the sample year
For the Christina River SSIM station, the ordination plot shows a large degree of polygon
overlap, which suggests that year to year variation among all SSIM metrics analyzed in the PCA
shows no specific trend. Individually, however, VZD scores and accretion appear to be
negatively correlated, which implies that higher accretion rates have lower VZD scores. SET
heights and diversity show a similar negative correlation. SET heights appear to have a stronger
influence over the differences between sampling locations (near, mid, far) than accretion rates.
This coincides with our findings that SET height change is much larger, on average, than surface
accretion rates (~12 mm/yr versus ~1 mm/yr), which is also reflected in the ordination plot as the
blue accretion arrow is shorter than the SET height arrow. The remaining metrics appear to be
relatively orthogonal to one another, and of similar lengths.
42 Christina River Watershed Wetland Condition Report
5.2.5 Water Quality
Average water quality values are described in the following tables:
Table 13. Average total alkalinity, turbidity, chlorophyll α concentration, total suspended
solids respectively, measured from water samples taken from the main water body of Christina
River in 2013. Error values are standard error, n = 5.
Date Total Alk
(mg/L) Turbidity
(NTU) Chloro a
(ug/L) TSSn(mg/L)
6/2/13 58.9 ± 1.57 12.9 ± 1.22 46.1 ± 3.41 20.3 ± 1.13
22/7/13 58.1 ± 0.451 12.1 ± 0.552 65.9 ± 5.49 23.9 ± 2.62
14/8/13 24.5 ± 0.889 45.3 ± 1.19 6.1 ± 0.554 51.3 ± 5.29
Table 14. Average temperature, salinity (uS/cm and ppt), dissolved oxygen (percent and concentration), and pH
respectively, measured from YSI meter from the main water body of Christina River. Error values are standard error. N =
5, except on 1/9/2011, only one measurement was taken for values with no error due to an equipment malfunction, otherwise
n=2.
Date TEMP SAL (uS/cm) SAL DO (%) DO (mg/L) pH
3/9/10 26.8 ± 0.0195 2883 ± 120 1.48 ± 0.0643 83.6 ± 0.378 NA NA
1/11/10 11.06 ± 0.743 145.6 ± 53.4 0.0680 ± 0.0281 79.1 ± 1.34 8.78 ± 0.147 NA
16/2/11 3.06 ± 0.0437 786.8 ± 27.3 0.384 ± 0.0146 38.1 ± 1.19 5.09 ± 0.140 NA
1/9/11 21.4 ± 0.0250 234 NA 48.6 4.31 6.94 ± 0.0400
11/6/12 23.7 ± 0.0198 313.4 ± 1.43 0.150 ± 0 95.1 ± 0.630 8.01 ± 0.0535 7.35 ± 0.0497
12/9/12 24.1 ± 0.117 1331 ± 212 0.726 ± 0.112 82.1 ± 1.61 6.84 ± 0.146 7.29 ± 0.0363
5/6/13 24.3 ± 0.0663 413.7 ± 13.1 0.198 ± 0.00583 98.9 ± 1.41 8.30 ± 0.102 7.41 ± 0.0459
INTENSIVE MONITORING CONCLUSIONS
Site specific intensive monitoring requires several years of data to elucidate and make
conclusions about trends in the data collected. Five years of data is the least recommended for
these purposes, but only three years of data have been collected at Christina River. It is
extremely important to continue to collect data for the next two years to fulfill the minimum
requirement to discern relevant trends. It is equally important that monitoring be continued even
further, as more data substantiates these trends, and more cause and effect relationships can be
teased from larger datasets. This is especially important for tracing the effects of increasing
storm frequencies due to climate change, as more frequent storms with greater intensities have
observable effects on sediment loads, and therefore accretion on the marsh platform.
Between 2011 and 2013, there are some observable patterns, but given that there are only
three years of data, these patterns could change within another sampling year. This report will
discuss these important patterns in brief, especially in light of the goals of SSIM for the
MACWA, but it should be noted that more data are needed to make definitive conclusions.
Because data produced no significant linear trends, a principal component analysis (PCA)
was performed. PCA is useful because it does not require many years of data to highlight key
Christina River Watershed Wetland Condition Report 43
differences between sample periods. This is why a PCA was chosen to aid in the analysis of the
data collected from the Christina River SSIM station. Permanent plot data and SET-MH data
were utilized for the PCA, as water quality, soil quality, biomass, and line transect data are too
sparse as of yet. Key PCA findings suggest that differences between years at Christina River are
minimal, but SET heights, i.e. subsurface processes, drive elevation changes. Furthermore, a
negative correlation between accretion rates and VZD scoring it apparent, which alludes to
differential sediment deposition across the marsh platform as higher accretion rates are found
where plant communities are closer to tidal influence.
From the SET height data the marsh platform at Christina River appears to be increasing.
Because SET heights are not equal to accretion, the primary source of elevation change is likely
subsurface processes—specifically swelling. The more direct cause of platform swelling,
however, requires more in depth studies of belowground biomass and water flux. Although SET
data suggest that the platform is increasing in elevation, vegetation transects suggested that
between 2011 and 2012, the platform had subsided. These disparate results could be due to a lack
of data, or could be contributed to natural variation in the sink-swell patterns of the marsh
platform, such as those that arise from varying distances to the main water channel. Plant
community structures through VZD scores appear to have increased marginally in mid and far
plots, but decreased in near plots and random edges. More data is needed to test correlations
between marsh elevation and plant communities, especially as there appears to be differential
elevation changes.
Many marshes along the Mid-Atlantic suffer from subsidence, or landmass sinking; this
characteristic, coupled with decreasing sediment loads from anthropogenic or natural causes,
reduces the marsh’s ability to maintain its platform with increasing sea levels. At the time of this
report, NOAA predicts that at Reedy Point, at the C&D Canal, DE sea level is rising
approximately 3.46±0.66 mm/yr. Given this estimate of sea level rise, from 2011-2013 the
Christina River benchmarks have actually increased in elevation at an excess of 7.4 mm/yr. On
the other hand, vegetation transects suggest that elevation between 2011-2012 in the proximity of
the SET-MH has decreased by 0.133m. Coupling these findings with community structure will
be extremely important to elucidating what processes drive elevation change at Christina River
and how these processes are affected by the overall condition of the watershed. This may be
especially important in terms of sediment loads, which control accretion rates, as well as nutrient
patterns that fuel plant community robustness, which affects belowground structure through root
biomass and/or decomposition.
44 Christina River Watershed Wetland Condition Report
LITERATURE CITED
Baumbach, E., C. Cruz-Ortiz, and K. Miller. 2013. Economic Value of the Christina River
Watershed prepared for The Christina Basin Clean Water Partnership. University of
Delaware Institute for Public Administration-Water Resources Agency.
Brand, A.B, J. W. Snodgrass, M.T. Gallagher, R. E. Casey, R. Van Meter. 2010. Lethal and
sublethal effects of embryonic and larval exposure of Hyla versicolor to stormwater pond
sediments. Archives of Environmental Contamination and Toxicology 58:325-331.
Cahoon, D. R. and R. E. Turner. 1989. Accretion and canal impacts in a rapidly subsiding
wetland II. Feldspar marker horizon technique. Estuaries 12: 260-268.
Cahoon, D. R., J. C. Lynch, P. Hensel , R. Boumans, B. C. Perez, B. Segura, and J. W. Day, Jr.
2002. A device for high precision measurement of wetland sediment elevation: I. Recent
improvements to the sedimentation-erosion table. Journal of Sedimentary Research 72:
730-733.
Cahoon, DR, JC Lynch, BC Perez, B Segura, R Holland, C Stelly, G Stephenson, and PF Hensel.
2002. High precision measurement of wetland sediment elevation: II. The rod surface
elevation table. Journal of Sedimentary Research 72(5):734-739.
Carullo, M., B.K. Carlisle, and J.P. Smith. 2007. A New England Rapid Assessment Method for
Assessing Condition of Estuarine Marshes; A Boston Harbor, Cape Cod and Islands Pilot
Study. Massachusetts Office of Coastal Zone Management, Boston, USA.
Collins, N. N., E. D. Stein, M. Sutula, R. Clark, A. E. Fetscher, L. Grenier, C. Grosso, and A.
Wiskind. 2008. California Rapid Assessment Method (CRAM) for Wetlands, Version
5.0.2.
DNREC. 2008. Delaware Wetlands Conservation Strategy. Delaware Department of
Natural Resources and Environmental Control, Dover, USA.
Fretwell, J. D., J. S. Williams, and P. J. Redman. 1996. National water summary on wetland
resources. United State Geological Survey Water Supply Paper: 2425. U.S. Government
Printing Office, Washington, D.C.
Hodges, A. L. Jr. 1984. Delaware in National Water Summary 1984: Hydrologic events--
Selected water-quality trends, and Groundwater resources, p. 243-248.
Jacobs, A.D. 2010. Delaware Rapid Assessment Procedure Version 6.0. Delaware Department
of Natural Resources and Environmental Control, Dover, DE, USA.
Jacobs, A.D., A.M. Howard, and A.B. Rogerson. 2010. Mid-Atlantic Tidal Wetland Rapid
Assessment Method Version 3.0. Delaware Department of Natural Resources and
Environmental Control, Dover, DE, USA. 47pp.
Christina River Watershed Wetland Condition Report 45
Jacobs, A.D., D. Whigham, D. Fillis, E. Rehm, and A. Howard. 2009. Delaware Comprehensive
Assessment Procedure Version 5.2. Delaware Department of Natural Resources and
Environmental Control. Dover, Delaware, USA. 72pp.
Jacobs, A.D., M.E. Kentula, and A.T. Herlihy. 2009. Developing an index of wetland condition
from ecological data: an example using HGM functional variables from the Nanticoke
watershed, USA. Ecological Indicators 10: 703-712.
MACWA SSIM QAPP. 2010. Intensive Monitoring and Assessment Program for Tidal Wetlands
of Delaware, New Jersey & Pennsylvania, Version 1.0. Partnership for the Delaware
Estuary: Danielle Kreeger, Angela Padeletti; Barnegat Bay Partnership: Martha Maxwell-
Doyle.
McAvoy, W. and K. Clancy. 1994. Community Classification and Mapping Criteria for
Interdunal Swales and Coastal Plain Pond Wetlands in Delaware. Final Report
Submitted to Watershed Assessment Branch, DNREC Division of Water Resources,
Dover, DE.
NOAA Tides and Currents. 2014. Mean Sea Level Trend, 8551910 Reedy Point, Delaware.
Accessed 19 June 2014
http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8551910
Partnership for the Delaware Estuary. 2012. Technical Report For the Delaware Estuary and
Basin. PDE Report No. 12-01 255 pages.
www.delawareestuary,=.org/science_programs_state_ of_the_estuary.asp.
Partnership for the Delaware Estuary. May 2012. Development and Implementation of an
Integrated Monitoring and Assessment Program for Tidal Wetlands. PDE Report No. 12-
03. 77 pp.
Phillipp, K. R. 1995. Tidal wetlands characterization – then and now. Delaware Estuary
Program Final Report to Delaware River Basin Commission. 165pp.
Plank, M. O. and W. S. Schenck. 1998. Delaware Piedmont Geology: Including a guide to the
rocks of Red Clay Valley. Delaware Geological Survey, University of Delaware.
Special Publication No. 20.
USEPA. 2006. Nutrient and Dissolved Oxygen Total Maximum Daily Loads Under High-Flow
Conditions in the Christina River Basin, Pennsylvania-Delaware-Maryland. U.S.
Environmental Protection Agency, Region III, Philadelphia, PA.
USGS Patuxent Wildlife Research Center. 2014. Surface Elevation Table (SET). Accessed 7
June 2014. http://www.pwrc.usgs.gov/set/
Sebold, K. R. 1992. From marsh to farm: The landscape transformation of coastal New Jersey.
National Park Service, U.S. Department of the Interior, Washington, D.C.
46 Christina River Watershed Wetland Condition Report
Sifneos, J. C., A. T. Herlihy, A. D. Jacobs and M. E. Kentula. 2010. Calibration of the
Delaware rapid assessment protocol to a comprehensive measure of wetland condition.
Wetlands 30:1011-1022.
State of Delaware. 1994. Statewide Wetland Mapping Project (SWMP). Prepared for the State
of Delaware’s Department of Natural Resources and Environmental Control (DNREC)
and for the Department of Transportation (DELDOT), Dover, DE. USA.
State of Delaware. 2007. Statewide Wetland Mapping Project (SWMP). Prepared for the State
of Delaware’s Department of Natural Resources and Environmental Control (DNREC).
Dover, DE, USA.
Stevens, D.L. Jr., and A.R. Olsen. 1999. Spatially restricted surveys over time for aquatic
resources. Journal of Agricultural, Biological, and Environmental Statistics 4:415-428.
Stevens, D.L. Jr., and A.R. Olsen. 2000. Spatially-restricted random sampling designs for
design-based and model-based estimation. Pages 609-616 in Accuracy 2000: Proceedings
of the 4th International symposium on spatial accuracy assessment in natural resources
and environmental sciences. Delft University Press, Delft, The Netherlands.
Christina River Watershed Wetland Condition Report 47
APPENDIX A: Qualitative Disturbance Rating (QDR) Category Descriptions
Qualitative Disturbance Rating: Assessors determine the level of disturbance in a
wetland through observation of stressors and alterations to the vegetation, soils,
hydrology in the wetland site, and the land use surrounding the site. Assessors should
use best professional judgment (BPJ) to assign the site a numerical Qualitative
Disturbance Rating (QDR) from least disturbed (1) to highly disturbed (6) based on the
narrative criteria below. General description of the minimal disturbance, moderate
disturbance and high disturbance categories are provided below.
Minimal Disturbance Category (QDR 1 or 2): Natural structure and biotic
community maintained with only minimal alterations. Minimal disturbance sites
have a characteristic native vegetative community unmodified water flow into and
out of the site, undisturbed microtopographic relief, and are located in a landscape of
natural vegetation (100 or 250 m buffer). Examples of minimal alterations include a
small ditch that is not conveying water, low occurrence of invasive species, individual
tree harvesting, and small areas of altered habitat in the surrounding landscape,
which does not include hardened surfaces along the wetland/upland interface. Use
BPJ to assign a QDR of 1 or 2.
Moderate Disturbance Category (QDR 3 or 4): Moderate changes in structure
and/or the biotic community. Moderate disturbance sites maintain some components
of minimal disturbance sites such as unaltered hydrology, undisturbed soils and
microtopography, intact landscape, or characteristic native biotic community despite
some structural or biotic alterations. Alterations in moderate disturbance sites may
include one or two of the following: a large ditch or a dam either increasing or
decreasing flooding, mowing, grazing, moderate stream channelization, moderate
presence of invasive plants, forest harvesting, high impact land uses in the buffer,
and hardened surfaces along the wetland/upland interface for less than half of the
site. Use BPJ to assign a QDR of 3 or 4.
High Disturbance Category (QDR 5 or 6): Severe changes in structure and/or
the biotic community. High disturbance sites have severely disturbed vegetative
community, hydrology and/or soils as a result of ≥1 severe alterations or >2 moderate
alterations. These disturbances lead to a decline in the wetland’s ability to effectively
function in the landscape. Examples of severe alterations include extensive ditching
or stream channelization, recent clear cutting or conversion to an invasive vegetative
community, hardened surfaces along the wetland/upland interfaces for most of the
site, and roads, excessive fill, excavation or farming in the wetland. Use PBJ to
assign a QDR of 5 or 6.
48 Christina River Watershed Wetland Condition Report
APPENDIX B: DERAP Stressor Codes and Definitions
Habitat Category (within 40m radius of sample point)
Hfor50 Forest age 31-50 years
Hfor30 Forest age 16-30 years
Hfor15 Forest age 3-15 years
Hfor2 Forest age ≤2 years
Hcc10 <10% of AA clear cut within 50 years
Hcc50 11-50% of AA clear cut within 50 years
Hcc100 >50% of AA clear cut within 50 years
Hforsc Selective cutting forestry
Hpine Forest managed or converted to pine
Hchem Forest chemical defoliation
Hmow Mowing in AA
Hfarm Farming activity in AA
Hgraz Grazing in AA
Hnorecov Cleared land not recovering
Hinv1
Invasive plants cover <1% of AA
Hinv5 Invasive plants cover 1-5% of AA
Hinv50 Invasive plants cover 6-50% of AA
Hinv100 Invasive plants cover >50% of AA
Hherb Excessive Herbivory/Pinebark Beetle/Gypsy Moth
Halgae Nutrients dense algal mats
Hnis50 Nutrient indicator plant species cover <50% of AA
Hnis100 Nutrient indicator plant species cover >50% of AA
Htrail Non-elevated road
Hroad Dirt or gravel elevated road in AA
Hpave Paved road in AA
Hydrology Category (within 40m radius of sample point)
Wditchs Slight Ditching; 1-3 shallow ditches (<.3m deep) in AA
Wditchm Moderate Ditching; 3 shallow ditches in AA or 1 ditch >.3m
within 25m of edge Wditchx Severe Ditching; >1 ditch .3-.6 m deep or 1 ditch > .6m deep
within AA Wchannm Channelized stream not maintained
Wchan1 Spoil bank only one side of stream
Wchan2 Spoil bank both sides of stream
Wincision Natural stream channel incision
Wdamdec Weir/Dam/Road decreasing site flooding
Wimp10 Weir/Dam/Road impounding water on <10% of AA
Wimp75 Weir/Dam/Road impounding water on 10-75% of AA
Wimp100 Weir/Dam/Road impounding water on >75% of AA
Wstorm Stormwater inputs
Wpoint Point source (non-stormwater)
Wsed Excessive sedimentation on wetland surface
Christina River Watershed Wetland Condition Report 49
Hydrology Category (continued)
Wfill10 Filling or excavation on <10% of AA
Wfill75 Filling or excavation on 10-75% of AA
Wfill100 Filling or excavation on >75% of AA
Wmic10 Microtopographic alterations on <10% of AA
Wmic75 Microtopographic alterations on 10-75% of AA
Wmic100 Microtopographic alterations on >75% of AA
Wsubsid Soil subsidence or root exposure
Landscape/Buffer Category (within 100m radius outside site/AA)
Ldevcom Commercial or industrial development
Ldevres3 Residential development of >2 houses/acre
Ldevres2 Residential development of ≤2 houses/acre
Ldevres1 Residential development of <1 house/acre
Lrdgrav Dirt or gravel road
Lrd2pav 2-lane paved road
Lrd4pav ≥4-lane paved road
Llndfil Landfill or waste disposal
Lchan Channelized streams or ditches >0.6m deep
Lag Row crops, nursery plants, or orchards
Lagpoul Poultry or livestock operation
Lfor Forest harvesting within past 15 Years
Lgolf Golf course
Lmow Mowed area
Lmine Sand or gravel mining operation
50 Christina River Watershed Wetland Condition Report
APPENDIX C: DERAP IWC Stressors and Weights
** Stressors with weights in boxes were combined during calibration analysis and are counted only once, even if more than one
stressor is present.
Category/Stressor Name* Code Stressor Weights**
*DERAP stressors excluded from this table are not in
the rapid IWC calculation. Flats Riverine Depression
Habitat Category (within 40m radius site)
Mowing in AA Hmow
15 3 24 Farming activity in AA Hfarm
Grazing in AA Hgraz
Cleared land not recovering in AA Hnorecov
Forest age 16-30 years Hfor16 5 4 2
≤10% of AA clear cut within 50 years Hcc10
Forest age 3-15 years Hfor3
19 7 12 Forest age ≤2 years Hfor2
11-50% of AA clear cut within 50 years Hcc50
>50% of AA clear cut within 50 years Hcc100
Excessive Herbivory Hherb 4 2 2
Invasive plants dominating Hinvdom 2 20 7
Invasive plants not dominating Hinvless 0 5 7
Chemical Defoliation Hchem 5 9 1
Managed or Converted to Pine Hpine
Non-elevated road in AA Htrail
2 2 2 Dirt or gravel elevated road in AA Hroad
Paved road in AA Hpave
Nutrient indicator species dominating AA Hnutapp 10 12 10
Nutrients dense algal mats Halgae
Hydrology Category (within 40m radius site)
Slight Ditching Wditchs 10
0
5 Moderate Ditching Wditchm 0
Severe Ditching Wditchx 17 0
Channelized stream not maintained Wchannm 0 13 0
Spoil bank only one side of stream Wchan1 0 31
0
Spoil bank both sides of stream Wchan2 0 0
Stream channel incision Wincision 0 21 0
WeirDamRoad decreasing site flooding Wdamdec
2 2 2 WeirDamRoad/Impounding <10% Wimp10
WeirDamRoad/Impounding 10-75% Wimp75
WeirDamRoad/Impounding >75% Wimp100
Stormwater Inputs Wstorm
2 2 2 Point Source (non-stormwater) Wpoint
Excessive Sedimentation Wsed
Christina River Watershed Wetland Condition Report 51
APPENDIX C continued
** Stressors with weights in boxes were combined during calibration analysis and are counted
only once, even if more than one stressor is present.
Hydrology Category (continued)
Filling, excavation on <10% of AA Wfill10 2 0 8
Filling, excavation on 10-75% of AA Wfill75 16 11 2
Filling, excavation on >75% of AA Wfill100
Soil Subsidence/Root Exposure Wsubsid 7 0 0
Microtopo alterations on <10% of AA Wmic10
Microtopo alteations on 10-75% of AA Wmic75 16 11 2
Microtopo alterations on >75% of AA Wmic100
Buffer Category (100m radius around site)
Development- commercial or industrial Ldevcom
1 buffer
stressor = 3
2 buffer
stressors = 6
≥ 3 buffer
stressors = 9
1 buffer
stressor = 1
2 buffer
stressors = 2
≥ 3 buffer
stressors = 3
1 buffer
stressor = 4
2 buffer
stressors = 8
≥ 3 buffer
stressors = 12
Residential >2 houses/acre Ldevres3
Residential ≤2 houses/acre Ldevres2
Residential <1 house/acre Ldevres1
Roads (buffer) mostly dirt or gravel Lrdgrav
Roads (buffer) mostly 2- lane paved Lrd2pav
Roads (buffer) mostly 4-lane paved Lrd4pav
Landfill/Waste Disposal Llndfil
Channelized Streams/ditches >0.6m deep Lchan
Row crops, nursery plants, orchards Lag
Poultry or Livestock operation Lagpoul
Forest Harvesting Within Last 15 Years Lfor
Golf Course Lgolf
Mowed Area Lmow
Sand/Gravel Operation Lmine
Intercept/Base Value 95 91 82
Flats IWCrapid= 95 -(∑weights(Habitat+Hydro+Buffer))
Riverine IWCrapid= 91 -(∑weights(Habitat+Hydro+Buffer))
Depression IWCrapid= 82 -(∑weights(Habitat+Hydro+Buffer))
52 Christina River Watershed Wetland Condition Report
APPENDIX D: MidTRAM Raw Data and Metric Scores from Estuarine Sites in
the Christina River Watershed
Blue columns indicate raw variable values; orange columns indicate corresponding metric scores
Buffer Metrics:
Site Number* QDR
Mid-
TRAM
Score
B1:
% of AA
with 5m-
buffer
B2:
Average
Buffer
Width
B3:
Percent
Develop-
ment
B5:
% of
Landward
Edge
Obstructed
B1
Score
B2
Score
B3
Score
B4
Score
B5
Score
RMDTCH11X005 3 86.7 100 242 0 0 12 12 12 6 12
RMDTCH11X011 2 84.4 100 154 1 0 12 9 9 9 12
RMDTCH11X018 2 83.3 100 189 0 0 12 9 12 12 12
RMDTCH11X022 2 80.0 100 250 10 100 12 12 6 9 3
RMDTCH11X008 2 77.8 100 250 0 0 12 12 12 9 12
RMDTCH11X000 3 77.8 100 235 10 10 12 12 6 6 6
RMDTCH11X027 2 75.6 100 119 5 100 12 6 9 9 3
RMDTCH11X004 4 75.6 100 177 25 10 12 9 3 6 6
RMDTCH11X001 2 73.3 100 216 18 100 12 12 3 6 3
RMDTCH11X010 6 72.8 100 142 40 100 12 9 3 3 3
RMDTCH11X024 1 71.1 100 250 0 0 12 12 12 9 12
RMDTCH11X020 3 62.2 100 248 15 0 12 12 6 3 12
RMDTCH11X016 5 61.1 100 75 20 100 12 6 3 3 3
RMDTCH11X025 6 60.0 100 117 25 100 12 6 3 3 3
RMDTCH11X007 5 58.3 100 187 22 100 12 9 3 3 3
RMDTCH11X033 4 55.6 100 233 1 0 12 12 9 6 12
RMDTCH11X037 5 53.9 100 93 20 100 12 6 3 3 3
RMDTCH11X012 5 53.3 100 123 20 60 12 6 3 3 3
RMDTCH11X030 5 47.8 100 151 40 30 12 9 3 3 3
RMDTCH11X002 6 45.6 100 205 5 100 12 12 9 3 3
RMDTCH11X032 5 45.6 85 159 12 100 9 9 6 3 3
RMDTCH11X019 6 45.0 80 166 30 50 9 9 3 3 3
RMDTCH11X009 6 43.3 100 168 15 100 12 9 6 3 3
RMDTCH11X029 6 43.3 100 141 25 100 12 9 3 3 3
RMDTCH11X036 6 42.8 100 195 17 50 12 12 3 3 3
RMDTCH11X023 5 42.2 100 172 35 100 12 9 3 3 3
RMDTCH11X003 6 41.7 100 147 40 100 12 9 3 3 3
RMDTCH11X038 6 40.6 100 218 12 100 12 12 6 3 3
RMDTCH11X015 6 37.2 80 132 45 100 9 9 3 3 3
RMDTCH11X039 6 30.0 75 83 50 100 9 6 3 3 3
* Site numbers are coded by condition categories (green are minimally stressed, yellow are moderately stressed,
red are severely stressed)
Christina River Watershed Wetland Condition Report 53
APPENDIX D continued
Orange columns indicate corresponding metric scores
Hydrology Metrics:
Site Number* QDR
Mid-
TRAM
Score
H1
Score
H2
Score
H3
Score
H4
Score
RMDTCH11X005 3 86.7 12 12 12 12
RMDTCH11X011 2 84.4 12 12 12 12
RMDTCH11X018 2 83.3 12 12 6 12
RMDTCH11X022 2 80.0 12 12 12 12
RMDTCH11X008 2 77.8 12 12 3 12
RMDTCH11X000 3 77.8 12 12 12 12
RMDTCH11X027 2 75.6 12 12 12 12
RMDTCH11X004 4 75.6 12 12 12 12
RMDTCH11X001 2 73.3 12 12 12 12
RMDTCH11X010 6 72.8 12 9 12 12
RMDTCH11X024 1 71.1 12 12 3 12
RMDTCH11X020 3 62.2 12 12 3 12
RMDTCH11X016 5 61.1 12 6 12 12
RMDTCH11X025 6 60.0 12 12 12 12
RMDTCH11X007 5 58.3 12 12 3 12
RMDTCH11X033 4 55.6 12 12 3 12
RMDTCH11X037 5 53.9 12 12 9 6
RMDTCH11X012 5 53.3 12 12 12 12
RMDTCH11X030 5 47.8 12 12 3 3
RMDTCH11X002 6 45.6 12 12 3 3
RMDTCH11X032 5 45.6 12 3 3 12
RMDTCH11X019 6 45.0 12 6 6 3
RMDTCH11X009 6 43.3 12 12 3 3
RMDTCH11X029 6 43.3 12 3 12 3
RMDTCH11X036 6 42.8 12 3 3 9
RMDTCH11X023 5 42.2 12 3 3 6
RMDTCH11X003 6 41.7 12 3 3 3
RMDTCH11X038 6 40.6 9 12 3 3
RMDTCH11X015 6 37.2 12 3 3 3
RMDTCH11X039 6 30.0 9 3 3 3
* Site numbers are coded by condition categories (green are minimally stressed, yellow are moderately
stressed, red are severely stressed)
54 Christina River Watershed Wetland Condition Report
APPENDIX D continued
Blue columns indicate raw variable values; orange columns indicate corresponding metric scores
Habitat Metrics:
Site Number* QDR
Mid-
TRAM
Score
HAB1:
Bearing
Capacity
HAB2:
Veg
Obstruc-
tion
HAB3:
# of
Plant
Layers
HAB4:
Percent
Co-dom
Invasive
spp.
HAB5:
Percent
Invasive
Cover
HAB1
Score
HAB2
Score
HAB3
Score
HAB4
Score
HAB5
Score
RMDTCH11X005 3 86.7 5.19 0.75 3 14 35 6 12 9 12 6
RMDTCH11X011 2 84.4 9.28 0.5 3 0 0 3 12 9 12 12
RMDTCH11X018 2 83.3 7.47 0 3 0 0 3 12 9 12 12
RMDTCH11X022 2 80.0 6.19 0.25 3 0 0 6 12 9 12 12
RMDTCH11X008 2 77.8 5.78 2.25 4 0 0 6 12 12 12 12
RMDTCH11X000 3 77.8 9.41 3.25 2 0 0 3 12 9 12 12
RMDTCH11X027 2 75.6 7.06 1 3 0 0 3 12 9 12 12
RMDTCH11X004 4 75.6 5.5 6.75 3 0 0 6 12 9 12 12
RMDTCH11X001 2 73.3 5.94 8.75 3 0 0 6 9 9 12 12
RMDTCH11X010 6 72.8 1.5 4 3 0 0 12 12 9 12 12
RMDTCH11X024 1 71.1 4.31 13.5 2 0 0 6 6 9 12 12
RMDTCH11X020 3 62.2 5.75 15 3 0 0 6 6 9 12 12
RMDTCH11X016 5 61.1 6.19 4.25 3 12.5 12.5 6 12 9 12 9
RMDTCH11X025 6 60.0 4.66 5.5 3 17 55 6 12 9 9 3
RMDTCH11X007 5 58.3 2.91 10.75 3 28.6 15 9 9 9 9 9
RMDTCH11X033 4 55.6 6.94 9.75 3 33 60 3 9 9 6 3
RMDTCH11X037 5 53.9 5.16 3.5 3 25 45 6 12 9 9 6
RMDTCH11X012 5 53.3 5.09 6.75 1 100 96 6 12 6 3 3
RMDTCH11X030 5 47.8 3.13 2.5 4 40 60 9 12 12 6 3
RMDTCH11X002 6 45.6 3.28 11.75 1 100 94 9 9 6 3 3
RMDTCH11X032 5 45.6 4.22 7.25 3 0.33 24 6 9 9 12 9
RMDTCH11X019 6 45.0 3.88 8.5 4 20 45 9 9 12 9 6
RMDTCH11X009 6 43.3 2.13 6 1 100 95 9 12 6 3 3
RMDTCH11X029 6 43.3 3.03 3.75 4 50 80 9 12 12 3 3
RMDTCH11X036 6 42.8 3.41 8.25 3 50 30 9 9 9 3 6
RMDTCH11X023 5 42.2 6.47 7 3 14 20 3 9 9 12 9
RMDTCH11X003 6 41.7 1.84 0 3 29 45 9 12 9 9 6
RMDTCH11X038 6 40.6 2.69 7.25 1 100 95 9 9 6 3 3
RMDTCH11X015 6 37.2 2.78 11 3 33 20 9 9 9 6 9
RMDTCH11X039 6 30.0 5.06 5.5 1 100 85 6 12 6 3 3
* Site numbers are coded by condition categories (green are minimally stressed, yellow are moderately stressed,
red are severely stressed)
Christina River Watershed Wetland Condition Report 55
APPENDIX E: DERAP Wetland Assessment Stressor Checklist for Non-tidal Flat
Wetlands in the Christina River Watershed
Stressor descriptions are listed in Appendix B. ‘1’ indicates stressor presence; ‘0’ indicates
stressor absence.
Habitat and Plant Community Stressors
Site
Number* QDR
DERAP
Score
Hfo
r31
Hfo
r16
Hfo
r3
Hfo
r2
Hcc1
0
Hcc5
0
Hcc1
00
Hfo
rsc
Hp
ine
Hch
em
Hm
ow
Hfarm
Hg
raz
Hn
oreco
v
Hin
v1
Hin
v5
Hin
v5
0
Hin
v1
00
Hh
erb
Halg
ae
Hn
is50
Hn
is10
0
Htrail
Hro
ad
Hp
ave
CH0124 2 91 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
CH0013 2 89 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0030 2 89 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0060 3 89 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0068 2 88 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
CH0021 3 86 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0015 3 85 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0019 3 84 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0029 3 84 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0063 3 82 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0071 3 82 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0046 4 80 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0009 4 79 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0027 3 79 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0107 2 78 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0001 4 76 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0
CH0079 5 75 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0075 4 71 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0004 5 65 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0003 4 61 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0091 4 61 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0081 4 58 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1 0 0
CH0131 5 58 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0022 5 56 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0038 4 55 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0100 5 55 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0065 5 52 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0007 6 51 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0076 3 51 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0121 6 46 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0055 6 45 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1
CH0017 5 43 0 1 0 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0
* Site numbers are coded by condition categories (green are minimally stressed, yellow are moderately
stressed, red are severely stressed)
56 Christina River Watershed Wetland Condition Report
APPENDIX E continued
Stressor descriptions are listed in Appendix B. ‘1’ indicates stressor presence; ‘0’ indicates
stressor absence.
Hydrology Stressors
Site
Number* QDR
DERAP
Score
Wd
itchs
Wd
itchm
Wd
itchx
Wch
ann
m
Wch
an1
Wch
an2
Win
cision
Wd
amd
ec
Wim
p1
0
Wim
p7
5
Wim
p1
00
Wsto
rm
Wp
oin
t
Wsed
Wfill1
0
Wfill7
5
Wfill1
00
Wm
ic10
Wm
ic75
Wm
ic10
0
Wsu
bsid
CH0124 2 91 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0013 2 89 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0030 2 89 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0060 3 89 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0068 2 88 0 0 0 - - - - 0 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0021 3 86 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0015 3 85 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 1
CH0019 3 84 0 0 0 - - - - 0 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0029 3 84 0 0 0 - - - - 0 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0063 3 82 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 1 0 0 0
CH0071 3 82 1 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0046 4 80 0 0 0 - - - - 0 0 0 0 1 0 0 0 0 0 1 0 0 0
CH0009 4 79 0 1 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0027 3 79 0 1 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0107 2 78 1 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0001 4 76 0 0 0 - - - - 0 0 0 0 0 0 0 0 1 0 1 0 0 0
CH0079 5 75 0 1 0 - - - - 0 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0075 4 71 0 0 0 - - - - 0 0 0 0 1 0 0 1 0 0 1 0 0 0
CH0004 5 65 0 0 1 - - - - 0 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0003 4 61 1 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0091 4 61 0 0 0 - - - - 0 0 0 0 0 0 0 1 0 0 1 0 0 0
CH0081 4 58 0 0 0 - - - - 0 0 0 0 1 0 0 1 0 0 0 0 0 0
CH0131 5 58 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 1 1 0 0 0
CH0022 5 56 1 0 0 - - - - 0 0 0 0 0 0 0 1 0 0 0 1 0 0
CH0038 4 55 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 0 0 1 0 0
CH0100 5 55 1 0 0 - - - - 0 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0065 5 52 0 0 1 - - - - 0 0 0 0 0 0 0 0 1 0 0 1 0 0
CH0007 6 51 0 0 0 - - - - 0 0 0 0 0 0 0 0 0 1 0 0 0 0
CH0076 3 51 0 1 0 - - - - 0 0 0 0 0 0 0 1 0 0 1 0 0 0
CH0121 6 46 0 0 1 - - - - 0 0 0 0 0 0 0 0 0 1 0 0 0 0
CH0055 6 45 0 1 0 - - - - 1 0 0 0 0 0 0 0 1 0 0 1 0 0
CH0017 5 43 1 0 0 - - - - 0 0 0 0 0 0 0 1 0 0 1 0 0 0
* Site numbers are coded by condition categories (green are minimally stressed, yellow are moderately
stressed, red are severely stressed)
Christina River Watershed Wetland Condition Report 57
APPENDIX E continued
Stressor descriptions are listed in Appendix B. ‘1’ indicates stressor presence; ‘0’ indicates
stressor absence.
Buffer Stressors
Site
Number* QDR
DERAP
Score
Ld
evco
m
Ld
evres3
Ld
evres2
Ld
evred
1
Lrd
grav
Lrd
2p
av
Lrd
4p
av
Lln
dfil
Lch
an
Lag
Lag
po
ul
Lfo
r
Lg
olf
Lm
ow
Lm
ine
CH0124 2 91 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0013 2 89 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0
CH0030 2 89 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0060 3 89 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0
CH0068 2 88 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0021 3 86 0 0 0 1 1 0 0 0 1 0 0 0 0 1 0
CH0015 3 85 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0019 3 84 0 0 0 0 0 0 1 0 1 1 0 0 0 0 0
CH0029 3 84 1 0 0 0 1 0 0 0 0 0 0 1 0 1 0
CH0063 3 82 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0
CH0071 3 82 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0046 4 80 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0009 4 79 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0027 3 79 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0107 2 78 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0001 4 76 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0
CH0079 5 75 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0
CH0075 4 71 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0
CH0004 5 65 1 0 0 0 1 0 0 0 1 0 0 0 0 1 0
CH0003 4 61 1 0 0 0 0 0 1 0 1 0 0 0 0 1 0
CH0091 4 61 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0081 4 58 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0
CH0131 5 58 1 0 0 0 0 0 1 0 0 0 0 1 0 1 0
CH0022 5 56 1 0 0 0 1 0 0 0 1 0 0 0 0 1 0
CH0038 4 55 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0100 5 55 0 0 0 0 0 0 1 0 1 0 0 1 0 1 0
CH0065 5 52 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0
CH0007 6 51 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0076 3 51 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0
CH0121 6 46 1 0 0 0 0 0 1 0 1 0 0 1 0 1 0
CH0055 6 45 0 1 0 0 0 1 0 0 1 0 0 0 0 1 0
CH0017 5 43 0 1 0 0 0 0 0 0 1 0 0 0 0 1 0
* Site numbers are coded by condition categories (green are minimally stressed, yellow
are moderately stressed, red are severely stressed)
58 Christina River Watershed Wetland Condition Report
APPENDIX F: DERAP Wetland Assessment Stressor Checklist for Non-tidal
Riverine Wetlands in the Christina River Watershed
Stressor descriptions are listed in Appendix B. ‘1’ indicates stressor presence; ‘0’ indicates
stressor absence.
Habitat and Plant Community Stressors
Site
Number* QDR
DERAP
Score
Hfo
r31
Hfo
r16
Hfo
r3
Hfo
r2
Hcc1
0
Hcc5
0
Hcc1
00
Hfo
rsc
Hp
ine
Hch
em
Hm
ow
Hfarm
Hg
raz
Hn
oreco
v
Hin
v1
Hin
v5
Hin
v50
Hin
v10
0
Hh
erb
Alg
ae
Hn
is50
Hn
is100
Htrail
Hro
ad
Hp
ave
CH0028 3 88 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0092 3 87 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
CH0002 2 85 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0047 3 84 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0016 4 83 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0125 3 83 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0104 3 80 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0
CH0066 5 71 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0050 3 70 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0072 3 69 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0032 4 68 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0036 5 68 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0054 4 68 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0037 3 63 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0044 4 62 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0051 3 62 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0114 4 62 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0062 3 59 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0010 4 57 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0058 6 55 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0136 4 51 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0064 4 49 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0098 5 49 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0101 5 48 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0005 4 46 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0113 5 45 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0134 4 45 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0
CH0096 6 39 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1
CH0126 4 38 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1 0 0
CH0014 4 37 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0025 5 37 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0052 5 36 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0082 5 36 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
CH0049 4 31 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0006 5 24 0 0 0 1 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1 0
CH0031 5 21 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0
CH0020 5 20 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0
CH0069 5 16 1 1 1 1 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1
CH0033 5 13 1 1 1 1 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1
CH0067 6 6 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
* Site numbers are coded by condition categories (green are minimally stressed, yellow are moderately
stressed, red are severely stressed)
Christina River Watershed Wetland Condition Report 59
APPENDIX F continued
Stressor descriptions are listed in Appendix B. ‘1’ indicates stressor presence; ‘0’ indicates
stressor absence.
Hydrology Stressors
Site
Number* QDR
DERAP
Score
Wd
itchs
Wd
itchm
Wd
itchx
Wch
ann
m
Wch
an1
Wch
an2
Win
cision
Wd
amd
ec
Wim
p1
0
Wim
p7
5
Wim
p1
00
Wsto
rm
Wp
oin
t
Wsed
Wfill1
0
Wfill7
5
Wfill1
00
Wm
ic10
Wm
ic75
Wm
ic10
0
Wsu
bsid
CH0028 3 88 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0092 3 87 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
CH0002 2 85 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0047 3 84 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
CH0016 4 83 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0125 3 83 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0104 3 80 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0066 5 71 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0050 3 70 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0072 3 69 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0032 4 68 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0036 5 68 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0054 4 68 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0037 3 63 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1
CH0044 4 62 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0051 3 62 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0114 4 62 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0062 3 59 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0
CH0010 4 57 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0058 6 55 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
CH0136 4 51 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0064 4 49 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0098 5 49 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 1 0 0 0
CH0101 5 48 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 1 0 0 0
CH0005 4 46 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0113 5 45 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0134 4 45 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0096 6 39 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 1 0 0 0
CH0126 4 38 0 0 0 0 0 0 1 0 0 1 0 0 0 0 1 0 0 1 0 0 0
CH0014 4 37 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
CH0025 5 37 0 0 0 0 0 0 1 1 0 0 0 0 0 1 1 0 0 0 0 0 0
CH0052 5 36 0 0 0 1 0 0 0 0 1 0 0 1 0 0 1 0 0 0 0 0 0
CH0082 5 36 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0049 4 31 0 0 0 0 0 0 1 1 0 0 0 0 0 0 1 0 0 1 0 0 0
CH0006 5 24 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 1 0 0 0 0
CH0031 5 21 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0020 5 20 0 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 1 0 0 0
CH0069 5 16 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 0 0
CH0033 5 13 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0
CH0067 6 6 0 0 0 0 1 0 0 1 0 0 0 0 0 1 0 1 0 0 0 0 0
* Site numbers are coded by condition categories (green are minimally stressed, yellow are
moderately stressed, red are severely stressed)
60 Christina River Watershed Wetland Condition Report
APPENDIX F continued
Stressor descriptions are listed in Appendix B. ‘1’ indicates stressor presence; ‘0’ indicates
stressor absence.
Buffer Stressors
Site
Number QDR
DERAP
Score
Ld
evco
m
Ld
evres3
Ld
evres2
Ld
evred
1
Lrd
grav
Lrd
2p
av
Lrd
4p
av
Lln
dfil
Lch
an
Lag
Lag
po
ul
Lfo
r
Lg
olf
Lm
ow
Lm
ine
CH0028 3 88 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0092 3 87 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0002 2 85 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0047 3 84 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0016 4 83 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0
CH0125 3 83 1 0 0 0 0 1 0 0 1 0 0 0 0 1 0
CH0104 3 80 0 1 0 0 1 0 0 0 0 0 0 0 0 1 0
CH0066 5 71 0 0 0 1 0 0 1 0 1 0 0 0 0 0 0
CH0050 3 70 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
CH0072 3 69 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0032 4 68 0 0 0 1 1 0 0 0 0 0 0 0 0 1 0
CH0036 5 68 1 0 0 0 0 0 0 0 1 0 0 1 0 1 0
CH0054 4 68 0 0 0 0 0 0 1 0 0 0 0 1 0 1 0
CH0037 3 63 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0
CH0044 4 62 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0051 3 62 0 0 0 0 1 0 0 0 0 0 0 1 0 1 0
CH0114 4 62 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0062 3 59 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0
CH0010 4 57 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0
CH0058 6 55 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0136 4 51 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0
CH0064 4 49 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0098 5 49 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0101 5 48 0 0 0 0 1 0 0 0 1 0 0 0 0 1 0
CH0005 4 46 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
CH0113 5 45 0 1 0 0 0 1 0 0 1 0 0 0 0 1 0
CH0134 4 45 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0096 6 39 0 0 0 1 0 0 1 0 1 1 0 0 0 1 0
CH0126 4 38 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
CH0014 4 37 0 0 0 1 0 1 0 0 1 0 0 0 0 1 0
CH0025 5 37 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0
CH0052 5 36 0 1 0 0 1 0 0 0 0 0 0 0 0 1 0
CH0082 5 36 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0
CH0049 4 31 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0
CH0006 5 24 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0
CH0031 5 21 1 0 0 0 0 0 0 0 1 0 0 0 0 1 0
CH0020 5 20 0 0 0 1 1 0 0 0 0 0 0 0 0 1 0
CH0069 5 16 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0033 5 13 1 0 0 0 1 0 0 0 0 1 0 0 0 1 0
CH0067 6 6 1 0 0 0 0 0 1 0 1 0 0 0 0 1 0
* Site numbers are coded by condition categories (green are minimally stressed,
yellow are moderately stressed, red are severely stressed)
Christina River Watershed Wetland Condition Report 61
APPENDIX G: DERAP Wetland Assessment Stressor Checklist for Non-tidal
Depression Wetlands in the Christina River Watershed
Stressor descriptions are listed in Appendix B. ‘1’ indicates stressor presence; ‘0’ indicates
stressor absence.
Habitat and Plant Community Stressors
Site
Number* QDR
DERAP
Score
Hfo
r31
Hfo
r16
Hfo
r3
Hfo
r2
Hcc1
0
Hcc5
0
Hcc1
00
Hfo
rsc
Hp
ine
Hch
em
Hm
ow
Hfarm
Hg
raz
Hn
oreco
v
Hin
v1
Hin
v5
Hin
v5
0
Hin
v1
00
Hh
erb
Alg
ae
Hn
is50
Hn
is10
0
Htrail
Hro
ad
Hp
ave
CH0011 4 15 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0
CH0080 5 48 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0
Hydrology Stressors
Site
Number* QDR
DERAP
Score
Wd
itchs
Wd
itchm
Wd
itchx
Wch
ann
m
Wch
an1
Wch
an2
Win
cision
Wd
amd
ec
Wim
p1
0
Wim
p7
5
Wim
p1
00
Wsto
rm
Wp
oin
t
Wsed
Wfill1
0
Wfill7
5
Wfill1
00
Wm
ic10
Wm
ic75
Wm
ic10
0
Wsu
bsid
CH0011 4 15 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0
CH0080 5 48 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0
Buffer Stressors
Site
Number* QDR
DERAP
Score
Ld
evco
m
Ld
evres3
Ld
evres2
Ld
evred
1
Lrd
grav
Lrd
2p
av
Lrd
4p
av
Lln
dfil
Lch
an
Lag
Lag
po
ul
Lfo
r
Lg
olf
Lm
ow
Lm
ine
CH0011 4 15 1 0 0 0 0 1 0 0 1 0 0 0 0 1 0
CH0080 5 48 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0
* Site numbers are coded by condition categories (green are minimally stressed,
yellow are moderately stressed, red are severely stressed)
62 Christina River Watershed Wetland Condition Report
APPENDIX H: SITE SPECIFIC INTENSIVE MONITORING PLOT
LOCATIONS AND SAMPLING DATES
Permanent vegetation (PV) plot locations and sampling dates at the Christina River SSIM:
Plot Area
PV Number Latitude Longitude
Dates Sampled Photo Examples
2011 2012 2013 PV No. Date
Near
1 39.72015 -75.56193 8/8/2011 9/20/2012 7/22/2013
PV1
7/22/2013
2 39.72006 -75.56208 8/8/2011 9/20/2012 7/22/2013
3 39.71995 -75.56228 8/8/2011 9/20/2012 7/22/2013
Mid
4 39.72156 -75.56485 8/8/2011 9/20/2012 7/22/2013
PV5
7/22/2013
5
39.72139 -75.56496 8/8/2011 9/20/2012 7/22/2013
6 39.72128 -75.56510 8/8/2011 9/20/2012 7/22/2013
Far
7 39.72234 -75.56648 8/8/2011 9/20/2012 7/22/2013
PV9
7/22/2013
8 39.72220 -75.56659 8/8/2011 9/20/2012 7/22/2013
9
39.72204 -75.56675 8/8/2011 9/20/2012 7/22/2013
Random edge (RE) plot locations and sampling dates at the Christina River SSIM:
RE Number Latitude Longitude
Dates Sampled Photo Examples
2011 2012 2013 PV No. Date
1 39.71978 -75.56271 8/8/2011 9/20/2012 7/22/2013
RE1
7/22/2013
2 39.71939 -75.56369 8/8/2011 9/20/2012 7/22/2013
3 39.71911 -75.56491 8/8/2011 9/20/2012 7/22/2013
4 39.71864 -75.56716 8/8/2011 9/20/2012 7/22/2013
RE6
7/22/2013
5 39.71896 -75.56760 8/8/2011 9/20/2012 7/22/2013
6 39.72004 -75.56779 8/8/2011 9/20/2012 7/22/2013
Christina River Watershed Wetland Condition Report 63
GPS coordinates of line transect RTK points. Included data are orthoheights (plus standard deviation),
dominant and subdominant species observed, as well as sampling data and time:
Date/Time Latitude Longitude Ortho Ht Sd Height Dom Spp Subdom Spp
13/7/11 9:33 39.72213 -75.56681 0.6958 0.009 Typha angustifolia Peltandra virginica
13/7/11 9:35 39.72200 -75.56651 0.7511 0.011 Typha angustifolia Peltandra virginica
13/7/11 9:39 39.72182 -75.56630 0.6035 0.0085 Peltandra virginica Typha angustifolia
13/7/11 9:43 39.72158 -75.56613 0.6481 0.0082 Typha angustifolia Peltandra virginica
13/7/11 9:46 39.72152 -75.56601 0.7037 0.0101 Typha angustifolia Impatiens capensis
13/7/11 9:58 39.72204 -75.56624 0.6854 0.0138 Typha angustifolia Peltandra virginica
13/7/11 10:03 39.72220 -75.56662 0.7081 0.0103 Typha angustifolia Peltandra virginica
13/7/11 10:05 39.72226 -75.56662 0.7292 0.0102 Typha angustifolia Peltandra virginica
13/7/11 10:18 39.72207 -75.56656 0.7211 0.0121
13/7/11 10:30 39.72197 -75.56590 0.5582 0.0098 Typha angustifolia Peltandra virginica
13/7/11 10:41 39.72183 -75.56568 0.6186 0.0099 Sagittaria latifolia Peltandra virginica
13/7/11 11:41 39.72120 -75.56568 0.4958 0.0092 Typha angustifolia Peltandra virginica
13/7/11 11:45 39.72133 -75.56530 0.7442 0.0085 Peltandra virginica Typha angustifolia
13/7/11 11:49 39.72122 -75.56494 0.6353 0.0112 Typha angustifolia Impatiens capensis
13/7/11 11:55 39.72141 -75.56487 0.681 0.0071 Typha angustifolia Sagittaria latifolia
13/7/11 11:58 39.72150 -75.56506 0.6261 0.0092 Typha angustifolia Peltandra virginica
13/7/11 12:03 39.72166 -75.56532 0.6163 0.0085 Typha angustifolia Peltandra virginica
13/7/11 12:08 39.72189 -75.56537 0.7085 0.0092
13/7/11 12:11 39.72200 -75.56558 0.7102 0.0077 Typha angustifolia Peltandra virginica
13/7/11 12:13 39.72202 -75.56573 0.589 0.0086 Typha angustifolia mix P. virginica/A. cannabinus
13/7/11 12:22 39.72180 -75.56503 0.6414 0.0083 Peltandra virginica Typha angustifolia
13/7/11 12:26 39.72179 -75.56501 0.5609 0.0077 Nuphar lutea Peltandra virginica
13/7/11 12:28 39.72177 -75.56498 0.5559 0.008 Typha angustifolia Pontederia cordata
13/7/11 12:31 39.72157 -75.56487 0.7226 0.0103 Typha angustifolia Peltandra virginica
13/7/11 12:45 39.72144 -75.56462 0.5615 0.0091 Peltandra virginica Typha angustifolia
13/7/11 12:46 39.72150 -75.56456 0.8289 0.0117 Nuphar lutea Sagittaria latifolia
13/7/11 12:49 39.72142 -75.56419 0.5271 0.0096 Typha angustifolia Peltandra virginica
13/7/11 12:53 39.72122 -75.56396 0.7477 0.0112 Typha angustifolia Impatiens capensis
13/7/11 12:58 39.72099 -75.56401 0.6792 0.0109 Impatiens capensis Peltandra virginica
13/7/11 13:01 39.72109 -75.56427 0.695 0.0124 Typha angustifolia Peltandra virginica
13/7/11 13:08 39.72119 -75.56458 0.5056 0.0118 Typha angustifolia
13/7/11 13:10 39.72120 -75.56463 0.4802 0.0122 Pontederia cordata Sagittaria latifolia
13/7/11 13:11 39.72121 -75.56467 0.5277 0.018 Typha angustifolia Sagittaria latifolia
13/7/11 13:12 39.72123 -75.56473 0.6671 0.0121 Typha angustifolia Peltandra virginica
13/7/11 13:17 39.72109 -75.56483 0.5746 0.01 Typha angustifolia Peltandra virginica
13/7/11 13:20 39.72098 -75.56459 0.6528 0.0093 Peltandra virginica Typha angustifolia
13/7/11 13:22 39.72088 -75.56431 0.8082 0.0114 Typha angustifolia Impatiens capensis
13/7/11 13:25 39.72085 -75.56428 0.5631 0.0118 Typha angustifolia Impatiens capensis
13/7/11 13:44 39.71991 -75.56239 0.8303 0.0121 Typha angustifolia Peltandra virginica
64 Christina River Watershed Wetland Condition Report
GPS coordinates of line transect RTK points continued: 13/7/11 13:50 39.71998 -75.56261 0.6359 0.0133 Impatiens capensis Sagittaria latifolia
13/7/11 13:53 39.72009 -75.56287 0.7504 0.0115 Impatiens capensis Sagittaria latifolia
13/7/11 14:05 39.72019 -75.56192 1.0291 0.0197 Scirpus fluviatilis Typha angustifolia
13/7/11 14:10 39.72024 -75.56219 0.6818 0.0168 Typha angustifolia Peltandra virginica
13/7/11 14:13 39.72034 -75.56235 0.5482 0.0145 Typha angustifolia Peltandra virginica
13/7/11 14:13 39.72037 -75.56236 0.4876 0.0134 Typha angustifolia Peltandra virginica
27/9/12 10:13 39.72212 -75.56682 0.5115 0.0099 Typha angustifolia Impatiens capensis
27/9/12 10:18 39.72199 -75.56651 0.667 0.0121 Typha angustifolia Impatiens capensis
27/9/12 10:24 39.72181 -75.56631 0.4078 0.0124 Typha angustifolia Peltandra virginica
27/9/12 10:31 39.72157 -75.56614 0.5097 0.011 Typha angustifolia Peltandra virginica
27/9/12 10:36 39.72152 -75.56602 0.6346 0.0116 Typha angustifolia mix Impatiens
capensis/Sagittaria latifolia
27/9/12 9:15 39.72232 -75.56682 0.2595 0.0134 Zizania aquatica Amaranthus cannabinus
27/9/12 14:01 39.72009 -75.56209 0.9185 0.0115 mix Typha angustifolia/Impatiens
capensis Aster sp./Acer negundo
27/9/12 11:14 39.72122 -75.56397 0.482 0.3099 Typha angustifolia Impatiens capensis
27/9/12 13:44 39.72023 -75.56219 0.6313 0.0098 Typha angustifolia Impatiens capensis
27/9/12 13:47 39.72034 -75.56236 0.5398 0.0085 Impatiens capensis Typha angustifolia
27/9/12 13:48 39.72036 -75.56237 0.5453 0.0124 Typha angustifolia Impatiens capensis
27/9/12 13:35 39.72018 -75.56193 1.0091 0.0108 mix Acorus calamus/Scirpus fluviatilis
27/9/12 9:11 39.72212 -75.56684 0.1667 0.0158 Typha angustifolia mix Zizania
aquatica/Peltandra virginica
27/9/12 11:23 39.72122 -75.56393 0.2657 0.0117 Typha angustifolia Impatiens capensis
27/9/12 11:22 39.72122 -75.56397 0.6967 0.0108 Typha angustifolia Impatiens capensis
27/9/12 13:49 39.72037 -75.56236 0.2932 0.0109 Typha angustifolia Polygonum punctatum
Christina River Watershed Wetland Condition Report 65
APPENDIX I: VEGETATION ZONE DOMINANCE
Synopsis of Vegetation Zone Dominance “VZD”
Each plant species was assigned a score, based on its suggested proclivity for soil
saturation. For this, multiple sources were utilized including the USDA Plant Database's Wetland
Indicator Statuses and Pennsylvania Natural Heritage habitat description reports (both available
online). Scores vary from 1 to 4; 1 representing a location that is within regular tidal influence,
and flooded at least twice daily, and 4 representing the back levee of the wetland or its upland
border. These scores were then proportioned to the first three most dominant plant's estimated
percent cover in each permanent plot, according to a dominance scheme, where the most
dominant plants take priority and less dominant plants act to add better resolution to the scoring
process. A sum of these scores is the total score, or the VZD score for the plot.
Introduction
One of the objectives of MACWA is to identify ways we can quantify the subtle changes
within wetlands over time in a reproducible and comparable way. A major source of change is
sea level rise due to climate change, which has direct effects on tidal marshes. Vegetation Zone
Dominance (VZD) was designed to allow us to track the frequency of inundation, a direct effect
of rising sea level, at each PV based on the composition of the plant community. It is well
understood that certain plants occupy different areas along a hydrologic gradient, where
assemblages are considered uplands or wetlands. On a finer scale, however, specifically within
tidal wetlands, this gradation is also discernible—some plants occupy extremely saturated or
frequently to semi-permanently inundated habitats, whereas through competition or adaptation,
others are found at higher elevations, further from the water’s edge, in locations that may be
temporarily or seasonally flooded.
In this methodology, we seek to take advantage of flood gradients to elucidate a plant
community’s relationship to the water’s edge with expected zone affiliations in the tidal frame.
Permanent vegetation plots of one by one meter were established and reassessed over
consecutive years. By assigning numbers, or scores, to these plots that represent the plant
community, we hope to observe quantitatively any changes in the communities' proximity to the
water’s edge over time. This metric is designed to track how plant communities keep pace with
changes in sea level and land elevations, thus detecting cases where plant communities might
shift to wetter assemblages if a marsh is not keeping pace. More data collection is needed to
fully evaluate the utility of this new approach, and results included in this appendix should be
interpreted as preliminary.
Floristic quality index (FQI) was first considered, because it was designed to allow
researchers and managers to compare various plant communities quantitatively. The focus of this
index is quality, which for this sense is ultimately related to the presence of invasive species
(lower qualities) or rare natives (higher qualities). This index can also be described as a measure
of disturbance. Although this index is similar to what we sought to achieve, it does not share a
similar focus. It will, however, be used as a framework for our scoring system. In the FQI plants
66 Christina River Watershed Wetland Condition Report
are assigned a number (the conservation coefficient) that relates to the probability of its
occurrence in habitats unaltered since European settlement—larger numbers correspond to plants
with more restricted distributions. Mirroring this, in our scoring system, wetland plants were
assigned numbers that correspond with its distribution along a tidal flood gradient—larger
numbers are those further from the water’s edge. Lastly, the FQI does not include species cover.
We incorporated percent covers in our study because our plots are of a small scale, we are
investigating within larger wetland habitats, and the changes in dominant plant cover may be the
most important indicator of water level alterations.
Scoring Methodology
Plant species were assigned a score (see Figure 1A). These were based on the wetland
delineation statuses provided by the USDA and the U.S. Army Corps’ National Wetland Plant
List, along with habitat descriptions by Pennsylvania’s Natural Heritage for freshwater marshes
(“Freshwater Tidal Mixed High Marsh” and “Riverbank Freshwater Tidal Marsh”; see
http://www.naturalheritage.state.pa.us/Wetlands.aspx) and community descriptions by the
Barnegat Bay Partnership for saltwater marshes (http://bbp.ocean.edu/pages/305.asp).
A.
B.
Figure 1A. Diagram of plant zone scores for fresh water (A) and salt water (B) marshes.
Generic diagram of plant zones for freshwater (A) and salt water (B) marshes.
Christina River Watershed Wetland Condition Report 67
Dominance Score
To calculate the dominance score, the first two most dominant plants, as recorded
proportions of observed cover (cover/total observed cover of plot) are multiplied by their
respective zone score (Score1). The two most dominant plant species must fall within 20% of
each other to be considered first dominant and second dominant. Otherwise, the second or the
third greatest plant coverage is considered the third dominant.
Also, the dominant plants must constitute at least or approximately half of the total
observed cover (see special treatments below). Frequently, co-dominance occurs at each level.
Co-dominance is defined for this study as two or more plant species with equal percent covers. If
this is the case for second or third level dominance, the proportions are added together and the
zone scores are averaged between the two plant species. Furthermore, if the third species falls
within 20% of the first two co-dominant species, the third fulfills the second level dominance
and if a fourth is present, it fulfills the third level. If this is true for first level dominance,
however, each species then fulfills the role of either first or second dominant. These levels are
weighted equally, so no other special considerations need to be implemented.
Third Level Dominance Score
In order to summarize the potential effects of a third dominant plant, a third level
dominance score is calculated (Score2). To obtain this, the first two dominant species’ zones are
averaged, and then subtracted from the third dominant plant’s zone, summarizing the zone
change. The third dominant plant cover is then multiplied by the zone change.
Score2 = zone3 - ( zone1 + zone2
) * ( observed cover3
) 2 total cover
This aims to capture how the presence of a third dominant species may be useful in
capturing where along the marsh gradient the community may lay. Third level dominance
numbers may be positive, zero, or negative. As such, a negative third level score would indicate
the presence of a species that is found typically closer to the bank, thereby giving the community
a score that is lower than just the dominance score.
Score1 = ( observed cover1
) * zone1 + ( observed cover2
) * zone2 total cover total cover
68 Christina River Watershed Wetland Condition Report
Total VZD Score
The addition of the Dominance Score (Score1) and the Third Level Dominance Score
(Score2) gives total vegetation zone dominance score, hereby referred to as simply the VZD
Score.
Total VZD = Score1 + Score2
Special treatments
Occasionally, the highest percentages listed do not account for a large enough portion of
the total observed cover. Such an error can cause spurious scores that are much lower than
expected based on the plants present. This error may be better corrected by establishing a “line”
for dominance. That is, no species can obtain first dominance unless it makes up at least or
approximately half of observed total cover. A community of dominance must be established if
this is not met. Dominant species covers should be added until this level is reached. For example,
consider a plot with a total cover of 90%; where Typha angustifolia is 25%, Acorus calamus
15%, and Impatiens capensis 8%. The total first dominance cover is then 48% (more than half of
90) and the three zones should be averaged. This plot's first dominant label would therefore be
"Typha-Acorus-Impatiens." The next dominant would constitute the 3rd
level not the second.
If the total observed cover recorded is much less than the gross or additive species covers,
scoring over estimates the proportion of each species’ cover. When this occurs, the first and
second dominant covers are added and used instead of what was recorded in the field. Third level
dominance cover is not added because although the discrepancy for first and second cover must
be altered to make mathematical sense, there was likely significant plant cover overlap within the
plot. By not including the third level at least a notion of this situation can be preserved while also
avoiding a majority of the mathematical error that these records produce. It is also important to
note that the scores of monoculture plots are simply the percent cover multiplied by the zone
score. As there are no other dominance effects in play, this is inherent in the way things are
scored, so this does not represent a special treatment.
Score Interpretation
Freshwater marshes VZD scores fall between 0 and 3.5; where 1 is the maximum extent
of the riverbank habitat. Half a meter from mean high tide theoretically delineates this limit. A
score of 3.5 represents beyond the back levee of the flood plain; plants at this point and beyond
are some degree facultative or considered upland species. Mixed marsh scores (<1.5) represent
communities that mostly exist within regular tidal influence, and higher scores (~1.5 to 3) are
those that occupy the higher marsh. It should be noted that the mixed high marsh is generally
considered to be an area of poor zonation. Poor zonation may be in part related to the multitude
of competitive interactions within freshwater marshes. The most important interpretations of
these data should focus on scores that fall from 0 to ~1.5 due to this phenomenon. Scores from 0-
1.5 may represent communities consisting largely of Nuphar lutea, which opportunistically
occupies muddy river or creek banks; Nuphar lutea can withstand large tidal fluxes and uses
Christina River Watershed Wetland Condition Report 69
asexual or rhizomatous reproduction to colonize and recolonize these areas. These unique
characteristics may make N. lutea the ideal plant to gauge changing freshwater tidal marsh
topography. Other Nuphar communities do exist outside of river or creek banks—the species is
very opportunistic. Other plants of interest that exist at the bank include: Sagittaria sp. and
Scirpus fluvialitis. Scirpus sp. are also thought to be opportunistic and can withstand tidal energy
well (which other high mixed marsh species may deal with poorly).
For saline marshes, VZD scores fall between 0 and 2.5; where scores of 1 indicate plants
that are regularly inundated by the tide. This area is largely dominated by high vigor Spartina
alterniflora, whose rhizomatous growth habits tend to create a natural levee that reduces flooding
of plant communities behind it. Scores from 1.25 to 1.75 indicate that the plant community exists
directly behind this front levee; these plants are adapted to saturated and extremely haline soils.
Scores of 2 and above represent the plant communities of slightly higher elevations, where soils
are less haline and flooding occurs less frequently. Although some zonation is apparent in
freshwater marshes, saline marshes are considered to have much more distinct zonation, despite
the dense monoculture stands of Spartina alterniflora. Zonation can be deciphered regardless of
this due to the growth form of Spartina alterniflora. The plant's phenotypic plasticity is a good
indicator for zonation, as well as its presence or absence.
Over time, scores may be seen as increasing or decreasing. Increasing scores indicate
increasing average group scores over time. This means that the communities are shifting to
consist of more facultative or higher marsh species, and likely shifting away from wetter
habitats. Likewise, decreasing scores depict communities that are shifting to more flood tolerant
species representing toward wetter habitats.
70 Christina River Watershed Wetland Condition Report
This report and other watershed condition reports, assessment methods, and scoring
protocols can be found on the Delaware Wetlands website: