7 

Prepared in cooperation with the Rhode Island Water Resources Board

Hydrologic, Vegetation, and Soil Data Collected in Selected 

Wetlands of the Big River Management Area, Rhode Island, 

From 2008 Through 2010

Data Series 666

U.S. Department of the Interior

U.S. Geological Survey
Cover. Clockwise starting with top left - 

A. Herbaceous-survey plot at Cedar Swamp, West Greenwich, Rhode Island 

(photo taken by Jason Sorenson) 

B. Instrument shelter at Scarboro Swamp, West Greenwich, Rhode Island 

 (photo taken by Meredith Borenstein) 

C. Vegetation at Cedar Swamp, West Greenwich, Rhode Island 

 (photo taken by Robert Breault) 

D. Bear Brook near the piezometer cluster site, Coventry, Rhode Island 

 (photo taken by Jason Sorenson) 
Prepared in cooperation with the Rhode Island Water Resources Board

Hydrologic, Vegetation, and Soil Data Collected in Selected 

Wetlands of the Big River Management Area, Rhode Island, 

From 2008 Through 2010

By Meredith S. Borenstein, Francis C. Golet, David S. Armstrong, Robert F. Breault, Timothy D. McCobb, and 

Peter K. Weiskel

Data Series 666

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012 

For product and ordering information:

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its natural and living resources, natural hazards, and the environment:

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Suggested citation:

Borenstein, M.S., Golet, F.C., Armstrong, D.S., Breault, R.F., McCobb, T.D., and Weiskel, P.K., 2012, Hydrologic, 

vegetation, and soil data collected in selected wetlands of the Big River Management area, Rhode Island, from 2008

through 2010: U.S. Geological Survey Data Series 666, 11 p. plus 9 figures and 16 tables.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Acknowledgments

This research was a cooperative effort of the U.S. Geological Survey (USGS) and the Rhode Island 

Water Resources Board (RIWRB). Jason Sorenson, Mark Nimiroski, Gene Parker, Andrew Massey, and 

Greg Granato, all of the USGS, provided assistance during well installation and other field work. Matt 

Ricker, Suzanne Faubl, Raina Huebner, Mike Narcisi, and Jeff Mowrey of the University of Rhode Island 

also assisted in the field. Art Gold, Mark Stolt, and Liliana Gonzalez of the University of Rhode Island 

supplied technical guidance.
This page has been left blank intentionally.
iv

Contents

Acknowledgments ......................................................................................................................................................... iii

Abstract ......................................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 1

Previous Studies in the Big River Management Area................................................................................................. 2

Research Objectives.................................................................................................................................................. 2

Methods and Baseline Data........................................................................................................................................... 2

Selection of Wetland Study Sites ............................................................................................................................... 2

Identification of Wetland Edges.................................................................................................................................. 3

Establishment of Sampling Belt Transects................................................................................................................. 3

Monitoring Wetland Hydrology ................................................................................................................................... 3

Wetland Vegetation Sampling.................................................................................................................................... 4

Plant Life Forms Sampled ...................................................................................................................................... 4

Vegetation Plot Size and Layout ............................................................................................................................ 4

Vegetation Sampling Procedures........................................................................................................................... 5

Soil Sampling............................................................................................................................................................. 6

Summary ....................................................................................................................................................................... 6

References Cited........................................................................................................................................................... 7

Figures

1. Map showing the location of the Big River study area, surficial geologic deposits, wetland study sites, and the 

boundary of the Big River Management Area, Rhode Island............................................................................ 9

2. Map showing the location of the Bear Swamp, Reynolds Swamp, Cedar Swamp, and Scarboro Swamp 

wetland study sites in the Big River Management Area, Rhode Island............................................................10

3. Map showing the location of the Congdon Mill Swamp wetland study control site in the Big River Management 

Area, Rhode Island..........................................................................................................................................11

4. Schematic diagram showing the hydrologic, vegetation, and soil sampling design for a typical belt

transect............................................................................................................................................................12

5. Map of the Bear Swamp wetland study site in the Big River Management Area, Rhode Island, showing 

locations of transect lines, piezometers, and soil probes.................................................................................13

6. Map of the Scarboro Swamp wetland study site in the Big River Management Area, Rhode Island, showing 

locations of transect lines, piezometers, and soil probes.................................................................................14

7. Map of the Reynolds Swamp wetland study site in the Big River Management Area, Rhode Island, showing 

locations of transect lines, piezometers, and soil probes.................................................................................15

8. Map of the Cedar Swamp wetland study site in the Big River Management Area, Rhode Island, showing 

locations of transect lines, piezometers, monitoring wells, and soil probes .....................................................16

9. Map of the Congdon Mill Swamp wetland study site in the Big River Management Area, Rhode Island, 

showing locations of transect lines, piezometers, and soil probes...................................................................17

Tables (Click here for link to tables 1–16)

1. General characteristics and codes for the wetland study sites in the Big River Management Area, 

Rhode Island, from July 2008 through February 2010

2. Physical properties of locations of continuous water-level monitoring and periods of record in the 

Big River Management Area, Rhode Island, from July 2008 through January 2010
v 

3. Physical properties of locations of intermittent water-level monitoring and periods of record in the 

Big River Management Area, Rhode Island, from June 2008 through December 2009

4. Daily mean water-level depths and altitudes computed from continuous water-level records in the 

Big River Management Area, Rhode Island, from July 2008 through January 2010

5. Intermittent groundwater depths and altitudes in the Big River Management Area, Rhode Island, 

from October 2008 through December 2009

6. Surface moisture conditions at the wetland study sites during the 2009 growing season in the 

Big River Management Area, Rhode Island

7. Vegetation sampling design for each belt transect at the wetland study sites in the 

Big River Management Area, Rhode Island

8. Tree- and sapling-layer structural characteristics in the five wetland study sites for the 2008 growing 

season, Big River Management Area, Rhode Island

9. Shrub-layer characteristics in the five wetland study sites in the Big River Management Area, 

Rhode Island, by belt transect for the 2008 growing season

10. Cover classes used to estimate herb and moss cover

11A. Herb-layer composition and relative wetness (weighted average) by sample plot in the Bear Swamp 

wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing 

seasons

11B. Herb-layer composition and relative wetness (weighted average) by sample plot in the Scarboro Swamp 

wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing 

seasons

11C. Herb-layer composition and relative wetness (weighted average) by sample plot in the Reynolds Swamp 

wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing 

seasons

11D. Herb-layer composition and relative wetness (weighted average) by sample plot in the Cedar Swamp 

wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing 

seasons

11E. Herb-layer composition and relative wetness (weighted average) by sample plot in the Congdon Mill 

Swamp wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 

growing seasons

12. Total herb and Sphagnum moss cover in 2008 and 2009 at the wetland study sites in the Big River 

Management Area, Rhode Island

13. Locations and thickness of organic-rich soil material determined using a soil probe along each belt 

transect in the five wetland study sites in the Big River Management Area, Rhode Island

14. Locations and thickness of organic-rich soil material determined using a soil probe outside of the belt 

transects in the five wetland study sites in the Big River Management Area, Rhode Island

15. Soil descriptions from test profiles in the five wetland study sites in the Big River Management Area, 

Rhode Island, in July 2009

16. Saturated and unsaturated properties determined by laboratory testing of soil cores from each 

of the five wetland study sites in the Big River Management Area, Rhode Island
This page has been left blank intentionally.
vi

Conversion Factors and Datum

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

square foot (ft2) 0.09290 square meter (m2)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F–32)/1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Acronyms and Abbreviations

BRMA Big River Management Area

dbh diameter at breast height

GIS geographic information system

GPS Global Positioning System

MM management model

PVC polyvinyl chloride

RIWRB Rhode Island Water Resources Board

URI University of Rhode Island

USGS U.S. Geological Survey
1 

Hydrologic, Vegetation, and Soil Data Collected in 

Selected Wetlands of the Big River Management Area, 

Rhode Island, From 2008 Through 2010

By Meredith S. Borenstein,1 Francis C. Golet,2 David S. Armstrong,1 Robert F. Breault,1 Timothy D. McCobb,

1 and 

Peter K. Weiskel1

Abstract

The Rhode Island Water Resources Board planned to develop public water-supply wells in the 

Big River Management Area in Kent County, Rhode Island. Research in the United States and abroad 

indicates that groundwater withdrawal has the potential to affect wetland hydrology and related 

processes. In May 2008, the Rhode Island Water Resources Board, the U.S. Geological Survey, and the 

University of Rhode Island formed a partnership to establish baseline conditions at selected Big River 

wetland study sites and to develop an approach for monitoring potential impacts once pumping begins. 

In 2008 and 2009, baseline data were collected on the hydrology, vegetation, and soil characteristics at 

five forested wetland study sites in the Big River Management Area. Four of the sites were located in 

areas of potential drawdown associated with the projected withdrawals. The fifth site was located 

outside the area of projected drawdown and served as a control site. The data collected during this study 

are presented in this report. 

Introduction

Water demand in Rhode Island is increasing (Deb and others, 1991; Wild and Nimiroski, 2004; 

Granato and Barlow, 2005). Concerned that increases in demand may exhaust the capacity of existing 

water supplies, the Rhode Island Water Resources Board (RIWRB) proposed the establishment of 

public supply wells in the Big River Management Area (BRMA). The BRMA encompasses 8,600 acres 

[3,480 hectares (ha)] within the Pawtuxet River watershed and includes parts of the towns of Coventry, 

Exeter, and West Greenwich (fig. 1).

The BRMA is composed mainly of upland and wetland forest [4,374 acres (1,770 ha) of needleleaved evergreens and 1,781 acres (721 ha) of deciduous trees] and nonforested wetlands [1,288 acres 

(521 ha)]. In addition, the area contains 233 acres (94 ha) of agricultural lands and 407 acres (165 ha) of 

gravel mining, residential development, and other land uses (Rhode Island Geographic Information 

System, 2005). The dominant wetland types in the management area are riverine marshes, scrub-shrub 

and forested wetlands, riverine open water, and ponds (Rhode Island Geographic Information System, 

1993). The Big River flows north into the Flat River Reservoir.

 

1

U.S. Geological Survey

2

University of Rhode Island
2 

Previous Studies in the Big River Management Area

Several U.S. Geological Survey (USGS) reports have been published on water resources within 

the Big River watershed. Craft (2001) documented a hydrogeologic data collection effort. Stone and 

Dickerman (2002) described the geologic setting and properties of the glacial sediments, including the 

results of aquifer tests. Granato and others (2003) described the development and simulations of a 

numerical model designed to analyze the effects of selected groundwater development options on 

streamflow. Granato and Barlow (2005) described the optimization techniques used to evaluate the 

potential effects of instream-flow criteria and water-supply demands on groundwater development 

options and resultant streamflow depletions in the Big River area. 

Research Objectives

The overall goal of the study described here was to increase understanding of the wetlands of the 

BRMA and lay the groundwork for assessing potential impacts of groundwater withdrawals on these

wetlands and their ecological processes. The specific objectives were to (1) establish baseline conditions 

at selected Big River wetland study sites prior to installation of proposed public supply wells, and (2) 

develop a protocol for monitoring potential impacts of groundwater withdrawal on those wetlands once 

pumping begins. In addition, this study was designed to improve understanding of surface water and 

groundwater interaction in the wetlands of the BRMA. 

Methods and Baseline Data

Baseline ecological conditions for Big River wetlands were established through selection and 

delineation of representative study sites; monitoring of site hydrology using nested piezometers, watertable wells, and surface moisture measurements; sampling of vegetation structure, floristic composition, 

and relative wetness; and description of soil profiles, thickness of organic-rich layers, and hydraulic 

properties. 

Selection of Wetland Study Sites

Wetlands were selected for evaluation based on their location within areas of water-table 

drawdown projected by management model 9 (MM09; Granato and Barlow, 2005). This groundwater 

flow model estimates the amount of groundwater that may potentially be withdrawn from three basins in 

the study area (Big River Basin, Carr River Basin, and Mishnock River Basin) when constrained by 

streamflow requirements and by the maximum rates of withdrawal at 13 existing and hypothetical well 

sites. Wetlands within the projected drawdown areas were identified through inspection of the Rhode 

Island Geographic Information System (Rhode Island Geographic Information System, 1993) wetlands 

database, the Rhode Island Soil Survey (Rector, 1981), USGS topographic maps, stereoscopic 

interpretation of panchromatic aerial photographs from 1980, and examination of true-color digital 

orthophotographs taken in 2004. A list of threatened and endangered species, obtained from the Rhode 

Island Natural Heritage Program, also was used to identify potential wetland study sites of interest in the 

BRMA (Enser, 2007). 

An initial pool of 15 potential wetland study sites included a variety of wetland types, 

hydrogeomorphic settings, water regimes, soil types, and degrees of drawdown. During field visits, 

these wetland study sites were evaluated in terms of minimum acceptable size [less than 40 meters (m) 

wide] for vegetation sampling, lack of disturbance by humans or beavers, and accessibility. Wetlands 

along the main stem of the Big River were not considered because of the biannual water-level 

manipulation downstream at the Flat River Reservoir. Five sites were selected for study (fig. 1). Four 
3 

wetland study sites (fig. 2) from north to south (Bear Swamp, Reynolds Swamp, Cedar Swamp, and 

Scarboro Swamp) were located within areas projected for water-table drawdown under MM09. A fifth 

wetland study site, Congdon Mill Swamp, was selected as a control or reference site; it was located 

approximately 2 miles [3.22 kilometers (km)] south of Scarboro Swamp (fig. 3) and outside the area of 

projected drawdown. Bear, Cedar, and Scarboro Swamps were forested wetlands located along 

perennial streams. Reynolds Swamp was a forested wetland located northwest of Reynolds Pond and 

was the only site not directly associated with a flowing water body. Congdon Mill Swamp was a 

forested wetland that had riparian and nonriparian sections and contained the full range of soil types and 

water regimes found at the other four sites (table 1). 

Identification of Wetland Edges

The location of the edge, or perimeter, of each wetland study site was approximated through 

stereoscopic interpretation of large-scale (1:12,000) aerial photographs. Toward the upland end of the 

baseline transect established at each site (see Establishment of Sampling Belt Transects below), the 

wetland edge was located and staked at the boundary between hydric (wetland) and nonhydric (upland) 

soils. Hydric soils were identified using criteria described by the New England Hydric Soils Technical 

Committee (2004). Perimeter coordinates were collected with a handheld Global Positioning System 

(GPS) unit. The GPS data points were then plotted using a geographic information system (GIS), and 

the location of the wetland perimeter was defined by interpolation (Haag and others, 2005). Study sites 

were mapped using GIS and classified according to the National Wetlands Inventory methodology 

(Cowardin and others, 1979; table 1).

Establishment of Sampling Belt Transects 

At each wetland study site, a baseline transect was established that extended from the upland 

into, and in some cases through, the wettest part of the wetland. Three to six belt transects for sampling 

wetland surface moisture, groundwater levels, soils, and vegetation were laid out perpendicular to the 

baseline transect at a spacing of 32.8 to 144 feet (ft) [10 to 44 meters (m)], depending on the length of 

the baseline transect, which varied from site to site. Each belt transect was 52.4 ft (16 m) long and 19.7 

ft (6 m) wide and centered on the baseline transect (fig. 4). Belt transects were located so as to 

maximize the diversity of ground altitude, soil types, water levels, and vegetation sampled within each 

wetland study site. Belt transect coordinates were collected using a GPS unit. 

Monitoring Wetland Hydrology

The hydrology of each wetland study site was characterized through both groundwater 

measurements and surface-moisture assessments. The depth to the water table was measured biweekly 

during the 2009 growing season (April 15–November 30). Allen and others (1989) established these 

dates based on that period of the year when soil temperatures were continuously above biological zero 

(5 degrees Celsius) at their study site in southern Rhode Island. Shallow water-table wells were 

constructed of 1.25-inch (in.) [3.2-centimeter (cm)] perforated polyvinyl chloride (PVC) pipe and were 

capped. One well was installed near the center of each belt transect (fig. 4) and within the plant root 

zone to a depth ranging from 0.5 to 3 ft (0.2 to 0.9 m) below land surface, depending on the depth to a 

dense soil layer, if present. One belt transect at each wetland study site was instrumented with a nest of 

three piezometers (figs. 5–9), including one shallow piezometer, which was installed in the peat to a 

depth of 0.5 to 3 ft (0.15 to 0.9 m); one intermediate piezometer, which was installed to a depth of 3 to 6 

ft (0.9 to 1.8 m) in either sand or peat, depending on the characteristics of the site; and one deep 
4 

piezometer, which was installed in the underlying stratified sediments to a depth of 8 to 23 ft (2.4 to 7.0 

m). These three piezometers were outfitted with data-loggers, which recorded water levels at 15-minute 

intervals.

Physical properties of piezometer sites measured continuously between July 2008 and January 

2010 are available in table 2, and physical properties of piezometer sites measured intermittently 

between June 2008 and January 2010 are listed in table 3. Water-level data collected continuously 

between July 2008 and January 2010 are reported in table 4. Water-level data collected intermittently 

between October 2008 and December 2009 are reported in table 5. 

Surface moisture was monitored monthly during the growing season at 20 sampling points along 

each belt transect (fig. 4). If surface water was present, the depth of the surface water was measured. If 

surface water was absent, the soil at the ground surface was characterized as saturated or nonsaturated, 

depending on whether water appeared under the pressure of a human foot. A summary of surface 

moisture conditions is available in table 6.

Wetland Vegetation Sampling

Trees, saplings, shrubs, herbs, and mosses growing within belt transects at each wetland study 

site were identified and quantified using the methods outlined below. 

Plant Life Forms Sampled

Wetland vegetation was sampled in five life-form layers—trees, saplings, shrubs, herbs, and 

mosses (table 7). Trees were defined as woody plants with a stem diameter at breast height (dbh) of at 

least 5.0 in. (12.7 cm). Saplings were woody plants with a dbh ranging from 2.0 to 4.9 in. (5.1 to 12.6 

cm). Shrubs were woody plants at least 3.3 ft (1.0 m) tall with stem diameter of less than 2.0 in. (5.1 

cm). The herb layer included all nonwoody vascular plants except mosses, as well as woody plants less 

than 3.3 ft (1.0 m) tall. The only moss sampled was peat moss (Sphagnum spp.), which grows only in 

wetlands.

Vegetation Plot Size and Layout

Plants from each life-form layer were sampled in permanent plots laid out in a systematic 

fashion within each 19.7-ft × 52.4-ft (6-m × 16-m) belt transect (fig. 4). Fixed plots provide an ideal 

method for monitoring changes in vegetation over time (Haag and others, 2005). Accurate estimates of 

plant abundance and structural characteristics require that plot size increase with life-form height 

(Mueller-Dombois and Ellenberg, 2002). In this study, trees and saplings were sampled in four 

contiguous 258-square foot (ft2) [24-square meter (m

2

)] plots within each belt transect, shrubs were 

sampled in four 53.8-ft2 (5-m2) plots, and herbs and Sphagnum moss were sampled in twelve 10.8-ft2 (1-

m

2

) plots (fig. 4; table 7).

To minimize human disturbance of shrubs, herbs, and mosses, no plots were located within 3.3 ft 

(1 m) of a belt transect center line or within 9.8 ft (3 m) of a baseline transect. One-in. (2.5-cm)-square 

oak stakes were used to mark the ends of each belt transect center line and two adjacent corners of each 

herb plot. Stakes that marked each herb plot assured that a 3.3-ft × 3.3-ft (1-m × 1-m) PVC sampling 

frame could be situated in exactly the same position during subsequent sampling sessions. Herb plots 

were later marked with landscaping nails or steel reinforcing rod so that they can be located in the future 

using a metal detector.
5 

Vegetation Sampling Procedures

Trees, saplings, and shrubs were sampled between July and August 2008. Herbs and mosses 

were sampled between July 8 and August 8, 2008, and between June 22 and July 31, 2009. All plants 

except Sphagnum were identified to species level; taxonomy was based on Gleason and Cronquist 

(1991). The same investigator sampled all 252 herb plots in 2008 and 2009. 

Trees, saplings, and shrubs were sampled primarily for broad characterization of the wetland 

study sites; hence they were only sampled during the first year of this study. Because of the persistent 

nature, relatively deep roots, and tolerance for variable soil and moisture conditions of these plants, the 

composition of the species in the plots that include trees, saplings, and shrubs is unlikely to change 

dramatically or quickly, even if site hydrology becomes significantly drier as a result of groundwater 

withdrawal. Because herbs and Sphagnum are very shallowly rooted, they are likely to be highly 

sensitive to changes in soil moisture over time; thus these life forms were sampled for site 

characterization purposes and to provide baseline data for assessing the potential impacts from 

groundwater withdrawal.

The dbh of each tree and sapling was measured in centimeters using a diameter tape, and stem 

density values in stems per hectare were computed. Stem basal area [measured in square meters per 

hectare (m2

/ha)] was computed for deciduous and evergreen species separately. Total sample size for 

trees and saplings ranged from 3,100 ft2 (288 m2) at Scarboro Swamp (three belt transects) to 6,200 ft2

(576 m2) at Congdon Mill Swamp (six belt transects). Values from individual belt transects were 

combined to produce a single value for the site. Tree canopy cover (reported as a percentage) was 

calculated from 18 presence-absence determinations made at 6.6-ft (2-m) intervals along the two 52.4-ft 

(16-m) edges of each belt transect using a densitometer (fig. 4). Canopy cover for evergreen and 

deciduous trees at each wetland study site was calculated as a percentage of all points sampled in a 

given wetland study site. Tree and sapling data are available in table 8.

All shrubs within the five 5-m2 plots associated with each belt transect were counted by species. 

Shrub density was expressed as stems per square meter and as stems per hectare for each belt transect

and each wetland study site. Shrub data are available in table 9.

Herbs and mosses were sampled during the 2008 and 2009 growing seasons to permit analysis of 

natural annual variation prior to pumping. Using cover classes (table 10), the abundance of each herb 

species in 2008 and 2009 was estimated visually within the 1-m × 1-m sampling frame (fig. 4). For each 

plot, the abundance of each species was recorded as the midpoint value of its cover class. Percent cover 

of herb-layer vegetation is reported in tables 11A–E. Total herb cover and Sphagnum cover also were 

estimated in each herb plot, using the same cover classes and midpoint values. Midpoint values for the 

12 plots on each belt transect were averaged to obtain an estimate of cover by belt transect. Total herb 

and Sphagnum moss cover for each wetland study site were calculated as the average of all the herb 

plots in all belt transects in a given wetland study site (table 12). 

During the late 1980s, the U.S. Fish and Wildlife Service published the National List of Plant 

Species that Occur in Wetlands (Reed, 1988), which assigned each species known to occur in U.S. 

wetlands to one of five indicator categories describing a plant’s probability (or frequency) of occurrence 

in wetlands. Using a preliminary draft of the list, Wentworth and others (1988) devised a method using 

weighted averaging, for quantifying the relative wetness of a site based on the relative abundance of 

plants in each of the indicator categories. A numerical value, termed an ecological index, was assigned 

to each category and then used with the abundances of all plant species found in a plot to generate a

weighted average, ranging from 1 to 5, that represented the relative wetness of that plot, based on plants. 

The formula for calculating this weighted average may be written as follows:
6 

1 ( ) [2 ( )] [3 ( )] [4 ( )] [5 ( )]

 

AOBL AFACW AFAC AFACU AUPL

WA

AOBL AFACW AFAC AFACU AUPL

  × +× +× +× +×   = + ++ +

(1)

where

WA = weighted average

A = abundance, in percent cover 

OBL = obligate wetland (ecological index 1)

FACW = facultative wetland (ecological index 2)

FAC = facultative (ecological index 3)

FACU = facultative upland (ecological index 4) 

UPL = obligate upland (ecological index 5) 

Tables 11A–E provide the wetland indicator status and ecological index for each herb species, as well as 

the weighted average for each sampling plot at the Big River wetland study sites.

Soil Sampling

Groundwater withdrawal has been associated with soil subsidence in wetlands (Rochow and 

Rhinesmith, 1991; Mortellaro and others, 1995). The thickness of organic-rich soil material in the 

BRMA was measured to provide a baseline for assessing soil subsidence in future years. Organic-rich 

soil material is defined to include both organic material and organic-rich mineral material as defined by 

the Soil Conservation Service (1993). In July 2008, the combined thickness of organic-rich soil material 

was estimated, using a tile probe, at six points along the center line of each belt transect; measurements

were located at 6.6-ft (2-m) intervals beginning at 9.8 ft (3 m) from the baseline transect in each 

direction (fig. 4). The six measurements were then averaged to calculate the mean thickness of organicrich soil material for each belt transect (table 13). Up to 36 additional measurements of organic-rich soil 

material were collected outside of the belt transects at each wetland study site (table 14).

In July 2009, a soil profile was described within 3.3 ft (1 m) from the center of each belt transect

(fig. 4), except for Reynolds T4, where there was 2.0 ft (0.6 m) of standing water. A bucket auger was 

used to pull soils from the ground so horizons could be described to a depth of approximately 4.9 ft (1.5 

m). Descriptions include horizon name, depth, boundary, texture, color, redoximorphic features if 

present, structure, and consistence (Soil Conservation Service, 1993; table 15). The abundance of roots 

also was noted for each soil horizon. 

Soil cores were collected from five locations (one from each wetland study site) for analysis of 

unsaturated and saturated hydraulic properties. Cores were collected using a piston corer and slide 

hammer to a depth of up to 4.0 ft (1.2 m). Soil hydraulic properties are reported in table 16. 

Summary 

Between June 2008 and January 2010, the U.S. Geological Survey collected hydrologic, 

vegetation, and soil data to establish baseline conditions at selected wetland study sites and to develop 

an approach for monitoring potential impacts from groundwater withdrawals in the Big River 

Management Area, Rhode Islands. This report presents the field data collected and laboratory soil 

analyses performed. 
7 

References Cited

Allen, S.D., Golet, F.C., Davis, A.F., and Sokoloski, T.E., 1989, Soil-vegetation correlations in 

transition zones of Rhode Island red maple swamps: U.S. Fish and Wildlife Service Biological Report 

89(8), 47 p. 

Cowardin, L.M., Carter, Virginia, Golet, F.C., and LaRoe, E.T., 1979, Classification of wetlands and 

deepwater habitats of the United States: U.S. Fish and Wildlife Service FWS/OBS-79/31, 103 p. 

Craft, P.A., 2001, Hydrogeologic data for the Big River-Mishnock River stream-aquifer system, central 

Rhode Island: U.S. Geological Survey Open-File Report 2001–250, 104 p. 

Deb, A.K., Archer, W.J., and Berger, H.T., 1991, Safe yield methodology for the Scituate Reservoir 

complex: Journal of the New England Water Works Association, v. 105, p. 27–33. 

Enser, R.W., 2007, Rare native plants of Rhode Island: Rhode Island Department of Environmental 

Management, accessed May 20, 2010, at http://www.rinhs.org/wpcontent/uploads/ri_rare_plants_2007.pdf. 

Gleason, H.A., and Cronquist, Arthur, 1991, Manual of vascular plants of northeastern United States 

and adjacent Canada: Bronx, N.Y., New York Botanical Garden, 910 p. 

Granato, G.E., and Barlow, P.M., 2005, Effects of alternative instream-flow criteria and water-supply 

demands on ground-water development options in the Big River area, Rhode Island: U.S. Geological 

Survey Scientific Investigations Report 2004–5301, 110 p. 

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York, N.Y., John Wiley & Sons, Inc., 547 p. 

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New England, version 3: Lowell, Mass., New England Interstate Water Pollution Control 

Commission, 86 p. 

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Fish and Wildlife Service Biological Report 88(24), 244 p. 

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8 

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12 p. 

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delineation manual—Northcentral and Northeast Region: Vicksburg, Miss., U.S. Army Corps of 

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9 

Figures

Figure 1. Map showing the location of the Big River study area, surficial geologic deposits, wetland study sites, 

and the boundary of the Big River Management Area, Rhode Island.
10

Figure 2. Map showing the location of the Bear Swamp, Reynolds Swamp, Cedar Swamp, and Scarboro Swamp 

wetland study sites in the Big River Management Area, Rhode Island.
11

Figure 3. Map showing the location of the Congdon Mill Swamp wetland study control site in the Big River 

Management Area, Rhode Island. 
12

Figure 4. Schematic diagram showing the hydrologic, vegetation, and soil sampling design for a typical belt 

transect. Each belt transect was 19.7 feet (6 meters) wide and 52.4 feet (16 meters) long.
13

Figure 5. Map of the Bear Swamp wetland study site in the Big River Management Area, Rhode Island, showing 

locations of transect lines, piezometers, and soil probes.
14

Figure 6. Map of the Scarboro Swamp wetland study site in the Big River Management Area, Rhode Island, 

showing locations of transect lines, piezometers, and soil probes.
15

Figure 7. Map of the Reynolds Swamp wetland study site in the Big River Management Area, Rhode Island, 

showing locations of transect lines, piezometers, and soil probes.
16

Figure 8. Map of the Cedar Swamp wetland study site in the Big River Management Area, Rhode Island, showing 

locations of transect lines, piezometers, monitoring wells, and soil probes.
17

Figure 9. Map of the Congdon Mill Swamp wetland study site in the Big River Management Area, Rhode Island, 

showing locations of transect lines, piezometers, and soil probes.
18

Tables (Click here for link to tables 1–16)

Table 1. General characteristics and codes for the wetland study sites in the Big River Management Area, Rhode 

Island, from July 2008 through February 2010.

Table 2. Physical properties of locations of continuous water-level monitoring and periods of record in the Big 

River Management Area, Rhode Island, from July 2008 through January 2010.

Table 3. Physical properties of locations of intermittent water-level monitoring and periods of record in the Big 

River Management Area, Rhode Island, from June 2008 through December 2009.

Table 4. Daily mean water-level depths and altitudes computed from continuous water-level records in the Big 

River Management Area, Rhode Island, from July 2008 through January 2010.

Table 5. Intermittent groundwater depths and altitudes in the Big River Management Area, Rhode Island, from 

October 2008 through December 2009.

Table 6. Surface moisture conditions at the wetland study sites during the 2009 growing season in the Big River 

Management Area, Rhode Island.

Table 7. Vegetation sampling design for each belt transect at the wetland study sites in the Big River 

Management Area, Rhode Island.

Table 8. Tree- and sapling-layer structural characteristics in the five wetland study sites for the 2008 growing 

season, Big River Management Area, Rhode Island.

Table 9. Shrub-layer characteristics in the five wetland study sites in the Big River Management Area, Rhode 

Island, by belt transect for the 2008 growing season.

Table 10. Cover classes used to estimate herb and moss cover.

Table 11A. Herb-layer composition and relative wetness (weighted average) by sample plot in the Bear Swamp 

wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing seasons.

Table 11B. Herb-layer composition and relative wetness (weighted average) by sample plot in the Scarboro 

Swamp wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing 

seasons. 

Table 11C. Herb-layer composition and relative wetness (weighted average) by sample plot in the Reynolds 

Swamp wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing 

seasons. 

Table 11D. Herb-layer composition and relative wetness (weighted average) by sample plot in the Cedar Swamp 

wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing seasons.
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Table 11E. Herb-layer composition and relative wetness (weighted average) by sample plot in the Congdon Mill 

Swamp wetland study site in the Big River Management Area, Rhode Island, for the 2008 and 2009 growing 

seasons. 

Table 12. Total herb and Sphagnum moss cover in 2008 and 2009 at the wetland study sites in the Big River 

Management Area, Rhode Island.

Table 13. Locations and thickness of organic-rich soil material determined using a soil probe along each belt 

transect in the five wetland study sites in the Big River Management Area, Rhode Island.

Table 14. Locations and thickness of organic-rich soil material determined using a soil probe outside of the belt 

transects in the five wetland study sites in the Big River Management Area, Rhode Island.

Table 15. Soil descriptions from test profiles in the five wetland study sites in the Big River Management Area, 

Rhode Island, in July 2009.

Table 16. Saturated and unsaturated properties determined by laboratory testing of soil cores from each of the 

five wetland study sites in the Big River Management Area, Rhode Island.
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For more information concerning this report, contact

Director

U.S. Geological Survey

Massachusetts-Rhode Island Water Science Center

10 Bearfoot Road

Northborough, MA 01532

dc_ma@usgs.gov

or visit our Web site at:

http://ma.water.usgs.gov
Borenstein and others— Hydrologic, Vegetation, and Soil Data Collected in Selected Wetlands of the Big River Management Area, R.I., from 2008 through 2010—Data Series 666