Coastal Wetlands trends in the Narragansett Bay Estuary during the 20th century

              Coastal Wetland Trends in the Narragansett Bay Estuary
During the 20th Century
November 2004
A National Wetlands Inventory Cooperative Interagency Report
Coastal Wetland Trends in the Narragansett Bay Estuary
During the 20th Century
Ralph W. Tiner1, Irene J. Huber2, Todd Nuerminger2, and Aimée L. Mandeville3
1U.S. Fish & Wildlife Service
National Wetlands Inventory Program
Northeast Region
300 Westgate Center Drive
Hadley, MA 01035
2Natural Resources Assessment Group
Department of Plant and Soil Sciences
University of Massachusetts
Stockbridge Hall
Amherst, MA 01003
3Department of Natural Resources Science
Environmental Data Center
University of Rhode Island
1 Greenhouse Road, Room 105
Kingston, RI 02881
November 2004
National Wetlands Inventory Cooperative Interagency Report between
U.S. Fish & Wildlife Service, University of Massachusetts-Amherst, University of Rhode
Island, and Rhode Island Department of Environmental Management
This report should be cited as: Tiner, R.W., I.J. Huber, T. Nuerminger, and A.L.
Mandeville. 2004. Coastal Wetland Trends in the Narragansett Bay Estuary During the
20th Century. U.S. Fish and Wildlife Service, Northeast Region, Hadley, MA. In
cooperation with the University of Massachusetts-Amherst and the University of Rhode
Island. National Wetlands Inventory Cooperative Interagency Report. 37 pp. plus
appendices.
Table of Contents
Page
Introduction 1
Study Area 1
Methods 5
Data Compilation 5
Geospatial Database Construction and GIS Analysis 8
Results 9
Baywide 1996 Status 9
Coastal Wetlands and Waters 9
500-foot Buffer Zone 9
Baywide Trends 1951/2 to 1996 15
Coastal Wetland Trends 15
500-foot Buffer Zone Around Coastal Wetlands 15
Trends for Pilot Study Areas 25
Conclusions 35
Acknowledgments 36
References 37
Appendices
A. Baywide Summary Tables for the Narragansett Bay Estuary
B. Summary Tables for Individual Study Areas
List of Tables
No. Page
1. Aerial photography used for this study. 6
2. Causes of wetland losses, gains, and changes in type. 7
3. 1996 status of coastal wetlands and waters in the Narragansett bay Estuary. 10
4. Extent of altered coastal wetlands for the Narragansett Bay Estuary in 1996. 13
5. Land use/cover in the 500-foot buffer around coastal wetlands in the
Narragansett Bay Estuary in 1996. 14
6. Trends in coastal wetlands and waters in the Narragansett Bay Estuary
from the 1950s to the 1990s. 16
7. Nature and causes of coastal wetland changes in the Narragansett Bay
Estuary from the 1950s to the 1990s. 19
8. Land use/cover changes in the 500-foot buffer surrounding tidal wetlands
in the Narragansett Bay Estuary from the 1950s to the 1990s. 23
9. Status and trends in coastal wetlands for specific study areas. 27
10. Nature and causes of coastal wetland and deepwater habitat trends for
Allins Cove. 29
11. Nature and causes of coastal wetland and deepwater habitat trends for
Calf Pasture Point. 30
12. Nature and causes of coastal wetland and deepwater habitat trends for
Jacobs Point. 31
13. Nature and causes of coastal wetland and deepwater habitat trends for
Palmer River. 32
14. Nature and causes of coastal wetland and deepwater habitat trends for
Sachuset Point. 33
15. Nature and causes of coastal wetland and deepwater habitat trends for
Wesquage Pond. 34
Tables in Appendix A:.
1-A. Changes in estuarine emergent wetlands in the Narragansett Bay Estuary: 1950s to
1990s.
2-A. Changes in estuarine scrub-shrub wetlands in the Narragansett Bay Estuary: 1950s
to 1990s.
3-A. Changes in estuarine unconsolidated shores in the Narragansett Bay Estuary: 1950s
to 1990s.
4-A. Changes in vegetated coastal wetlands in the Narragansett Bay Estuary: 1950s to
1990s.
5-A. Changes in nonvegetated coastal wetlands in the Narragansett Bay Estuary: 1950s
to 1990s.
List of Tables (continued)
Tables in Appendix B:
1-B. Trends in estuarine wetlands for Allins Cove from the 1930s to the 1950s and from
the 1950s to the 1990s.
2-B. Trends in estuarine wetlands for Calf Pasture Point from the 1930s to the 1950s and
from the 1950s to the 1990s.
3-B. Trends in estuarine wetlands for Jacobs Point from the 1930s to the 1950s and from
the 1950s to the 1990s.
4-B. Trends in estuarine wetlands for Palmer River from the 1930s to the 1950s and
from the 1950s to the 1990s.
5-B. Trends in estuarine wetlands for Sachuest Point from the 1930s to the 1950s and
from the 1950s to the 1990s.
6-B. Trends in estuarine wetlands for Wesquage Pond from the 1930s to the 1950s and
from the 1950s to the 1990s.
List of Figures
No. Page
1. Location of the Narragansett Bay Estuary and its drainage area. 2
2. Limits of the Narragansett Bay Estuary as defined for this study. 3
3. Location of six pilot areas within the Narragansett Bay Estuary. 4
4. Percent loss of estuarine emergent wetland in the Narragansett Bay Estuary. 21
5. Percent gain in estuarine emergent wetland in the Narragansett Bay Estuary. 21
6. Percent change in estuarine scrub-shrub wetland in the Narragansett Bay
Estuary. 22
7. Percent change in estuarine unconsolidated shore in the Narragansett Bay
Estuary. 22
Introduction
The Rhode Island Department of Environmental Management's Narragansett Bay Estuary
Program's (NBEP) goal is to protect and preserve Narragansett Bay through conserving
and restoring natural resources and enhancing water quality. NBEP accomplishes this
through a variety of projects, including interagency partnerships and community
involvement. To manage these valuable resources, NBEP wanted baseline information
on coastal wetlands and their buffers. With the aid of the University of Massachusett
(UMass), University of Rhode Island (URI), and the U.S. Fish and Wildlife Service
(FWS), NBEP obtained an inventory of current coastal wetlands, the 500-foot buffer
zone, and potential wetland restoration sites for the estuary. While knowing the current
state of these resources is vital to managing the resource, an analysis of trends in these
resources would help identify threats and put the presentday resources in a historic
context.
In 1999, the NBEP and the FWS modified an existing cooperative agreement to produce
wetland trends information for the Narragansett Bay Estuary. The FWS works in
partnership with UMass (Department of Plant and Soil Sciences, Natural Resources
Assessment Group - NRAG) to conduct wetland mapping, trend analysis, and other
studies requiring interpretation of aerial photography. NBEP also has an agreement with
the URI to perform the geographic information system (GIS) services. URI also played a
major role in this project by providing these services. The NBEP will use the results of
this work to help develop a coastal wetland conservation and restoration strategy for the
Narragansett Bay Estuary.
This report presents the results of this multi-agency cooperative project. It summarizes
data for the entire estuary and for several pilot study areas where trends were analyzed
back to the 1930s.
Study Area
The Narragansett Bay Estuary is a 147-square mile coastal embayment (including Mount
Hope Bay) that dominates the Rhode Island landscape (Figures 1 and 2). It is the
receiving basin for seven major watersheds in Rhode Island and Massachusetts including
the Blackstone, Moshassuck, Pawtuxet, Taunton, Ten Mile, Warren, and
Woonaquatucket. The Estuary is defined by the limits of brackish tidal water and
hydrogeomorphology. The baywide coastal wetlands trends analysis (1950s-1990s) was
limited to the Rhode Island portion. Within the Narragansett Bay Estuary, six areas were
selected as pilot areas to examine wetland trends from the 1930s-1950s in addition to the
1950s-1990s analysis done baywide: 1) Allins Cove, 2) Calf Pasture Point, 3) Jacobs
Point, 4) Palmer River, 5) Sachuest Point, and 6) Wesquage Pond (Figure 3).
1
Figure 1. Location of the Narragansett Bay Estuary and its drainage area; the general
boundary of the estuary is the dark gray-shaded area.
2
Figure 2. Limits of the Narragansett Bay Estuary as defined for this study.
3
Figure 3. Location of six pilot areas within the Narragansett Bay Estuary.
4
Methods
Data Compiliation
Conventional photointerpretation techniques were used to identify trends in coastal
wetlands and the 500-buffer around these wetlands. For the Narragansett Bay study area,
trends from the 1950s to the 1990s were determined. For the six pilot study areas (Allins
Cove, Calf Pasture Point, Jacobs Point, Palmer River, Sachuset Point, and Wesquage
Pond), coastal wetland trends were identified for two time periods: the late1930s/early
1940s-1950s and the 1950s-1990s. Table 1 summarizes the aerial photography used for
the study.
Photointerpretation was performed using mirror stereoscopes. Wetlands and deepwater
habitats were classified according to "Classification of Wetlands and Deepwater Habitats
of the United States" (Cowardin et al. 1979), the national digital data standard for
wetland inventory and reporting on wetland trends. For this study, coastal wetlands
include Cowardin's marine and estuarine intertidal wetlands - tidal wetlands with
measurable traces of ocean-derived salts. Wetland changes to and from nonwetlands
were categorized according to the features presented in Table 2. These features represent
modifications of the Anderson et al. (1976) national land use/cover classification system.
Multiple codes may be assigned to a change in a given wetland. Wetland trends were
marked on acetate overlays attached to aerial photographs. Changes in wetlands and
deepwater habitats were interpreted using Bausch & Lomb stereo integration scopes.
Land use/cover changes in the 500-foot buffer around coastal wetlands were identified
using a Bausch & Lomb stereo zoom transfer scope (ZTS) which was also used to match
photointerpreted trends data to 1:24,000 frosted mylar maps (prepared by URI). The
mylar overlays showing trends were digitized for GIS analysis. The minimum mapping
unit for wetland change polygons was 0.25 acre, although smaller polygons of wetland
loss were mapped. For more detailed information on methods, see Huber and
Nuerminger (2003).
5
Table 1. Aerial photography used for this study. Note: The 1990s photographs for pilot
study areas were the same as used baywide for this period.
Study Area Study Aerial Photography Used
Period Scale Emulsion Date
Entire Bay 1990s 1:40,000 True Color 8/11/96
1:12,000 True Color 7/6/96
1950s 1:24,000 Black&White 10-11/51; 5/52
Allins Cove 1930s 1:28,000 Black&White 12/13/38
1950s 1:20,000 Black&White 5/15/52
Calf Pasture Point 1930s 1:28,000 Black&White 12/13/38
1950s 1:20,000 Black&White 10/26/51
Jacobs Point 1930s 1:28,000 Black&White 12/13/38
1950s 1:20,000 Black&White 10/21/51
Palmer River 1930/40s 1:28,000 Black&White 12/13/38; 10/24/41
1950s 1:20,000 Black&White 10/21/51
Sachuest Point 1930s 1:28,000 Black&White 12/13/38
1950s 1:20,000 Black&White 10/21/51
Wesquage Pond 1940s 1:28,000 Black&White 10/8/41
1950s 1:20,000 Black&White 10/26/51
6
Table 2. Causes of wetland losses, gains, and changes in type.
Cause Brief Definition
Agriculture Area subject to farming practices including cropland, orchards, nurseries,
vineyards, ornamental horticulture, pasture and hayfields
Barren Land Nonvegetated or sparsely vegetated lands including mixed, sandy
areas (not beaches), strip mines, quarries, and gravel pits
Coastal Processes Natural processes associated with tidal currents and wave action including
erosion, accretion, and dune migration (overwash)
Commercial & Services Commercial and institutional structures, marinas, paved surfaces, unpaved
surfaces, recreational structures, wharves, piers, and shipyards
Ditching Shallow linear excavation designed to improve drainage; ditches may be filled
into restore wetland hydrology
Erosion from Boat Traffic Shoreline erosion caused by wakes generated by boats (limited to marina areas)
Excavation Removal of earth or soil from wetlands or bay and channel bottoms
Forest Wooded area dominated by trees (deciduous, evergreen, or mixed)
Industrial & Commercial
Complexes Development involving a mixture of factories and business establishments
Jetties & Groins Artificial rocky structures to maintain navigable channels (jetty) or beaches
(groin); these structures may be built or removed
Oyster Colonization Establishment of an oyster reef
Rangeland Old fields and thickets (herbaceous, shrub and brush, or mixed cover)
Residential Development Houses and apartments including lawns
Soil Deposition Fill material from upland sources deposited in wetlands or waters
Spoil Deposition Dredged material deposited in wetlands or waters
Tidal Restriction Tidal flow limited by roadways, railroad embankments, undersized culverts, or
similar structures
Transportation,
Communications &
Utilities Roads, highways, railroads, powerlines, and similar structures
Unknown Cause not determined
Urban Development associated with towns and cities including golf
courses and landfills
Vegetation Change Succession; change in plant composition (specific species noted include Iva
frutescens, Phragmites australis, Typha angustifolia)
7
Geospatial Database Construction and GIS Analysis
Geospatial database construction was performed by URI's Environmental Data Center
(EDC). Each basemap was registered on the digitizing tablet with a RMS value <0.003.
All features delineated for this project were digitized in ArcEdit and coded using ArcGIS
8.2 software. Data for each quad were digitized separately and joined to form one
complete baywide coverage. Data for each USGS quadrangle were digitized, coded and
proofed before moving on to the next quadrangle. Proofing took place in two phases: 1)
on screen in ArcGIS 8.2 to check for coding errors as well as feature errors and 2) a proof
plot of the linework information was made and sent along with the mylar basemap for
NRAG to proof. Any feature omission or coding change was noted on the proof plot and
returned to EDC for final editing.
The land use/cover data were digitized into an existing coverage containing the upland
shoreline features from the coastal wetlands data layer and the 500-foot buffer line. Each
quad was digitized and proofed separately to be MAPJOINED after all land use/cover
data were completed. For those polygons coded as freshwater wetland, an item
ENHANCED was added and attributed with a Cowardin et al. (1979) classification.
Upon construction of the final digital database, summary tables were generated by EDC
using Arc/Info FREQUENCY command. These tables were used to prepare tables for
this report (in the Results section and Appendices A and B). The database was used to
prepare thematic maps showing wetland trends for the estuary and for each pilot area.
The maps are presented in a separate folder and hyperlinked to the report.
Palmer River salt marsh (F. Golet photo)
8
Results
Baywide 1996 Status
Coastal Wetlands and Waters
In 1996, the Narragansett Bay Estuary (NBE) had 130,028 acres of tidal and subtidal
saltwater-influenced habitats (Table 3). The Bay itself (estuarine and marine deepwater
habitat) predominates this tidal ecosystem, accounting for 95% of this acreage. Intertidal
habitats occupy only 5% of the estuary. Estuarine tidal marshes and swamps comprise
58% of this intertidal habitat, with the remainder made up mostly of nonvegetated tidal
unconsolidated shores. The latter includes sandy beaches, sand and mud flats, and
cobble-gravel shores. Nine acres of oyster reefs were inventoried.
Over 1,700 acres of vegetated coastal wetlands were altered by ditching and/or
impoundment (Table 4). This acreage represented 48% of the NBE's coastal marshes
(including estuarine scrub-shrub wetlands). Eighty-eight percent of this acreage was
ditched. Only 36 acres of nonvegetated wetlands were altered. Fifteen acres of
unconsolidated shore were created by spoil disposal, while nearly 5 acres of rocky shore
were created by rip-rap (e.g., groins).
500-Foot Buffer Zone
The 500-foot buffer zone surrounding Narragansett Bay's coastal wetlands accounted for
nearly 26,600 acres in 1996 (Table 5). Of this, 35% was represented by residential
development (80% single family residences and 18% lawns). Forests and rangeland
occupied 22% and 15% of the buffer, respectively. See Table 8 for more detailed
findings.
Sachuset Point shoreline (F. Golet photo)
9
Table 3. 1996 status of coastal wetlands and waters in the Narragansett Bay Estuary.
(Note: These data summarize totals for mapped polygons only; linear data are not
included.) EM=emergent; US=Unconsolidated Shore.
Wetland or Waterbody Type 1990s Acreage
Estuarine Water
Eelgrass Bed 93.1
Saline/Brackish 89,505.7
Oligohaline 143.2
------------------- -----------
Subtotal 89,742.0
Estuarine Marsh
Emergent Regularly Flooded 272.1
Phragmites Irregularly Flooded 217.0
EM/Phragmites Irregularly Flooded 14.7
EM/US Regularly Flooded 5.8
EM/US Irregularly Flooded 0.3
Emergent Irregularly Flooded 2,458.1
Phragmites/Shrub Irregularly Flooded 3.3
EM/Shrub Irregularly Flooded 6.9
------------------------------------------ -------------
Subtotal 2,978.2
Estuarine Oligohaline Marsh
Emergent Regularly Flooded 0.8
Phragmites Irregularly Flooded 142.0
EM/Phragmites Irregularly Flooded 115.5
Emergent Irregularly Flooded 172.9
------------------------------------ ------------
Subtotal 431.2
Estuarine Scrub-Shrub Wetland
Deciduous Irregularly Flooded 161.8
Shrub/EM Irregularly Flooded 0.7
------------------------------------------ -----------
Subtotal 162.5
Estuarine Reef
Mollusc (Oyster) 9.3
Estuarine Streambed
Sand and Mud Regularly Flooded 3.0
10
Table 3. (continued)
Estuarine Rocky Shore
Bedrock Regularly Flooded 29.1
Bedrock Irregularly Flooded 96.9
Rubble Regularly Flooded 76.6
Rubble Irregularly Flooded 16.1
----------------------------------- --------
Subtotal 218.7
Estuarine Unconsolidated Shore
Cobble-Gravel Regularly Flooded 68.2
Cobble-Gravel Irregularly Flooded 59.6
Sand Irregularly Exposed 254.4
Sand Regularly Flooded 443.5
Sand/Cobble-Gravel Regularly. Flooded 42.1
Sand/Emergent Regularly Flooded 5.9
Sand Irregularly Flooded 580.1
Mud Irregularly Exposed 200.4
Mud Irregularly. Exposed Oligohaline 0.9
Mud Regularly Flooded 105.5
Mud Regularly. Flooded Oligohaline 7.0
------------------------------------------- ---------
Subtotal 1,767.6
Estuarine Salt Panne
Irregularly Exposed 39.5
Irregularly Exposed Oligohaline 0.8
Regularly Flooded 1.7
------------------------------------------- ----------
Subtotal 42.0
------------------------------------------------------------------------------------------------------------
Total Estuarine Habitat 95,354.5
------------------------------------------------------------------------------------------------------------
Marine Water
Eelgrass Bed 2.6
Unconsolidated Bottom 34,130.3
------------------------------------------ -------------
Subtotal 34,132.9
Marine Rocky Shore
Regularly Flooded 142.5
Irregularly Flooded 202.2
------------------------------------------ ------------
Subtotal 344.7
11
Table 3. (continued)
Marine Unconsolidated Shore
Cobble-Gravel Regularly Flooded 5.9
Cobble-Gravel Irregularly Flooded 9.6
Sand Irregularly Exposed 2.3
Sand Regularly Flooded 100.7
Sand Irregularly Flooded 77.2
------------------------------------------- -------------
Subtotal 195.7
------------------------------------------------------------------------------------------------------------
Total Marine Habitats 34,673.3
------------------------------------------------------------------------------------------------------------
Narragansett Bay Grand Total 130,027.8
------------------------------------------------------------------------------------------------------------
12
Table 4. Extent of altered coastal wetlands for the Narragansett Bay Estuary in 1996.
Wetland Type Type of Alteration Acreage
Emergent
Regularly Flooded ditched 0.7
impounded 6.2
(subtotal) (6.9)
Irregularly Flooded ditched 1336.0
ditched/impounded 115.2
impounded 51.7
(subtotal) (1502.9)
Emergent Oligohaline
Regularly Flooded impounded 0.5
Irregularly Flooded ditched 19.0
ditched/impounded 5.6
impounded 143.7
(subtotal) (168.3)
Reef impounded 3.2
Rocky Shore artificial 4.7
Scrub-Shrub ditched 33.9
ditched/impounded 1.6
impounded 1.2
(subtotal) (36.7)
Unconsolidated Shore ditched 3.7
impounded 9.1
spoil 15.0
(subtotal) (27.8)
All Types 1,751.0
13
Table 5. Land use/cover in the 500-foot buffer around coastal wetlands in the
Narragansett Bay Estuary in 1996. (Note: % buffer totals 100.1% due to round-off
procedures.)
Land Use/Cover Acreage %of Buffer
Residential 9,324.7 35.1
Commercial 2,235.5 8.4
Industrial 106.1 0.4
Transportation, Communications, Utilities 744.9 2.8
Other Urban or Built-up Land 845.7 3.2
Agriculture 1,507.5 5.7
Rangeland 3,965.2 14.9
Forest 5,734.9 21.6
Water and Freshwater Wetland 1,669.6 6.3
Barren Land 26,589.7 1.7
---------------------------------------------- ----------- -------
Total 26,589.7 100.1
14
Baywide Trends 1951/2 to 1996
Coastal Wetlands
From the 1950s to the 1990s, the NBE experienced a net loss of 548 acres of tidal habitat.
The losses concentrated on intertidal habitats with 306 acres of net loss of estuarine
marshes (excluding oligohaline marshes) and a net loss of 205 acres of intertidal
nonvegetated wetlands (estuarine unconsolidated shores). During this period, 7.2% of the
NBE's estuarine intertidal wetland acreage was lost. Nearly 10% of the estuarine marsh
acreage (excluding oligohaline marshes) was lost. Almost 110 acres of coastal waters
were lost. Details are provided in Table 6.
The nature and causes of coastal wetland changes are summarized in Table 7. Please
note that a loss of a given wetland may be attributed to more than one cause, so the
acreage totals from this table may be greater than the net acreage figures reported in
Table 6. Causes of wetland changes are illustrated in Figures 4 through 7. Over 50% of
the loss of estuarine marsh was due to filling that created upland (dryland) (Figure 4).
Nearly 40% of the loss was attributed to conversion to open water (15%), palustrine
wetland (12%), and tidal flats (11%). Nine percent of the loss was represented by
acreage that changed to estuarine scrub-shrub wetland. While estuarine marshes
experienced net losses, there were some gains in estuarine wetland acreage in places.
Gains largely came from tidal flats and estuarine water which accounted for over 70% of
the estuarine marsh acreage gained (Figure 5). Of the changes to estuarine scrub-shrub
wetlands, nearly 60% was due to a gain from estuarine emergent wetland (Figure 6).
Forty percent of the changes in these shrub swamps were losses to estuarine marshes
(33%) and to upland (7%). Most of the change in estuarine nonvegetated flats and shores
were losses (Figure 7). More acreage was converted to open water than came from open
water (Table 7). This may be a sign of the impact of rising sea level associated with
global warming. About 106 acres of nonvegetated coastal wetlands were converted to
upland. (Note: See Appendix A for more detailed findings.)
The locations of these changes are shown on a series of maps. To access information for
individual towns, click on the town name: Barrington, Bristol, Cranston, East Greenwich,
East Providence, Jamestown, Little Compton, Middletown, Narragansett, Newport, North
Kingstown, Pawtucket, Portsmouth, Providence, South Kingstown, Tiverton, Warren,
and Warwick.
500-foot Buffer Zone Around Coastal Wetlands
Significant changes in the buffer occurred during the 40-year study interval. A 37%
increase in residential land occurred largely at the expense of rangeland and agricultural
land which decreased by 30% and 52%, respectively (Table 8). This increase was mostly
(94%) attributed to a rise in single-family homes along the coastal wetlands, whereas
92% of the loss of agricultural land was from pasture and haylands.
15
Table 6. Trends in coastal wetlands and waters in the Narragansett Bay Estuary from the
1950s to the 1990s. (Note: These data summarize totals for mapped polygons only; linear
data are not included.) EM=emergent; US=Unconsolidated Shore; Phrag=Phragmites
australis.
1950s 1990s Net
Wetland or Waterbody Type Acreage Acreage Change
Estuarine Water
Saline/Brackish 89,680.9 89,598.8 -82.1
Oligohaline 170.6 143.2 -27.4
------------------- ------------- ----------- ---------
Subtotal 89,851.5 89,742.0 -109.5
Estuarine Marsh
Emergent Regularly Flooded 309.7 272.1 -37.6
Phragmites Irregularly Flooded 129.5 217.0 +87.5
EM/Phrag Irregularly Flooded 18.7 14.7 -4.0
EM/US Regularly Flooded 7.9 5.8 -2.1
EM/US Irregularly Flooded 0.3 0.3 0
Emergent Irregularly Flooded 2,808.8 2,458.1 -350.7
Phrag/Shrub Irregularly Flooded 3.3 3.3 0
EM/Shrub Irregularly Flooded 5.9 6.9 +1.0
------------------------------------- ------------- ----------- ---------
Subtotal 3,284.1 2,978.2 -305.9
Estuarine Oligohaline Marsh
Emergent Regularly Flooded 3.3 0.8 -2.5
Phragmites Irregularly Flooded 68.7 142.0 +73.3
EM/Phrag Irregularly Flooded 41.6 115.5 +73.9
Emergent Irregularly Flooded 244.9 172.9 -72.0
------------------------------------ ------ ------------- ---------- ---------
Subtotal 358.5 431.2 +72.7
Estuarine Reef
Mollusc (Oyster) 10.7 9.3 -1.4
Estuarine Rocky Shore
Bedrock Regularly Flooded 29.2 29.1 -0.1
Bedrock Irregularly Flooded 97.1 96.9 -0.2
Rubble Regularly Flooded 76.7 76.6 -0.1
Rubble Irregularly Flooded 15.9 16.1 +0.2
----------------------------------- ------------- -------- ---------
Subtotal 218.9 218.7 -0.2
16
Table 6. (continued)
Estuarine Streambed
Sand and Mud Regularly Flooded 2.0 3.0 +1.0
Estuarine Scrub-Shrub Wetland
Deciduous Irregularly Flooded 143.6 161.8 +18.2
Shrub/EM Irregularly Flooded 0.7 0.7 0
------------------------------------ ----- ----------- ----------- ---------
Subtotal 144.3 162.5 +18.2
Estuarine Unconsolidated Shore
Cobble-Gravel Regularly Flooded 54.8 68.2 +13.4
Cobble-Gravel Irregularly Flooded 55.2 59.6 +4.4
Sand Irregularly Exposed 333.6 254.4 -79.2
Sand Regularly Flooded 445.7 443.5 -2.2
Sand/Cobble-Gravel Reg. Flooded 39.3 42.1 +2.8
Sand/Emergent Regularly Flooded 5.9 5.9 0
Sand/EM Irregularly Flooded 0.5 0 -0.5
Sand Irregularly Flooded 654.2 580.1 -74.1
Sand Reg. Flooded Oligohaline 82.1 0 -82.1
Sand Irreg. Flooded Oligohaline 3.5 0 -3.5
Mud Irregularly Exposed 226.2 200.4 -25.8
Mud Irreg. Exposed Oligohaline 0.9 0.9 0
Mud Regularly Flooded 68.0 105.5 +37.5
Mud Reg. Flooded Oligohaline 2.3 7.0 +4.7
------------------------------------- -------------- ------------- ---------
Subtotal 1,972.2 1,767.6 -204.6
Estuarine Salt Panne
Irregularly Exposed 56.6 39.5 -17.1
Irregularly Exposed Oligohaline 0.8 0.8 0
Regularly Flooded 2.9 1.7 -1.2
--------------------------------------- --------- ---------- --------
Subtotal 60.3 42.0 -18.3
------------------------------------------------------------------------------------------------------------
Total Estuarine Habitat 95,902.5 95,354.5 -548.0
------------------------------------------------------------------------------------------------------------
(Marine totals on following page)
17
Table 6. (continued)
Marine Water
Unconsolidated Bottom 34,133.7 34,132.9 -0.8
------------------------------------- ---------------- ------------- --------
Subtotal 34,133.7 34,132.9 -0.8
Marine Rocky Shore
Regularly Flooded 142.8 142.5 -0.3
Irregularly Flooded 201.9 202.2 +0.3
-------------------------------------- ----------------- ------------ --------
Subtotal 344.7 344.7 0
Marine Unconsolidated Shore
Cobble-Gravel Regularly Flooded 5.9 5.9 0
Cobble-Gravel Irregularly Flooded 9.6 9.6 0
Sand Irregularly Exposed 2.3 2.3 0
Sand Regularly Flooded 94.9 100.7 +5.8
Sand Irregularly Flooded 83.0 77.2 -5.8
-------------------------------------- --------------- ------------- --------
Subtotal 195.7 195.7 0
------------------------------------------------------------------------------------------------------------
Total Marine Habitats 34,674.1 34,673.3 -0.8
------------------------------------------------------------------------------------------------------------
Narragansett Bay Grand Total 130,564.9 130,027.6 -537.8
------------------------------------------------------------------------------------------------------------
18
Table 7. Nature and causes of coastal wetland changes in the Narragansett Bay Estuary
from the 1950s to the 1990s. Note: The acreage of areas of change affected by multiple
causes has been listed under each of the relevant causes, so acreage totals in this table
exceed actual acreage of loss or gain for each coastal wetland type as reported in Table 6.
Wetland Acreage Gain From or Major Causes
Type* Affected Lost To (% of affected acreage)
E2EM 52.6 From open water coastal processes (67), succession
(15)
87.1 FromE2US tidal restriction (48), coastal
processes(37)
33.4 From E2SS Phragmites invasion (55), ditching
(36)
8.8 FromP-wetland tidal restriction (36), ditching (31),
excavation/impoundment (23)
16.4 From upland coastal processes (48), unknown
(28)
50.9 To open water coastal processes (49), tidal
restriction(31)
38.3 To E2US coastal processes (85)
0.5 To E2SB coastal processes (100)
78.8 To E2SS Iva succession (61), succession
following ditching (33)
111.1 To P-wetland ditching (41), tidal restriction (37),
succession (11)
189.8 To upland rangeland (36), residential (19),
commercial/services(14),
transportation/utilities (13)
280.6 Change in EM type Phragmites (59), other succession
(20), tidal restriction (9, excluding
Phragmites)
E2SS 0.8 FromE2US coastal processes (100)
78.8 FromE2EM Iva succession (61), succession/
ditching (33)
33.1 To E2EM Phragmites (56), succession/
ditching (36)
6.0 To upland commercial/services (33), forest
(27), industrial/commercial (14),
agriculture (9), residential (9)
19
Table 7. (continued)
Wetland Acreage Gain From or Major Causes
Type* Affected Lost To (% of affected acreage)
E2US 140.5 From open water coastal processes (89)
36.6 FromE2EM coastal processes (89)
1.5 FromE2RS coastal processes (83)
34.0 Fromupland coastal processes (80)
250.1 To open water coastal processes (99)
112.3 To E2EM succession (40), tidal restriction
(37), coastal processes (17)
0.8 To E2SS coastal processes (100)
21.5 To P-wetland tidal restriction (52), succession
(44)
105.3 To upland golf course (33), rangeland (30),
barren land (14),
commercial/services(5)
48.5 Change in Type coastal processes (73)
------------------------------------------------------------------------------------------------------------
*E2EM - estuarine emergent wetland; E2SS - estuarine scrub-shrub wetland; E2US -
estuarine unconsolidated shore; E2SB - estuarine streambed; E2RS - estuarine rocky
shore; P - palustrine.
20
Figure 4. Percent loss of estuarine emergent wetland in the Narragansett Bay Estuary.
Loss to Estuarine Streambed
0%
Loss to Palustrine Wetland
12%
Loss to Estuarine Scrub-
Shrub Wetland
9%
Loss to Estuarine
Unconsolidated Shore
11%
Loss to Estuarine Water
15%
Loss to Upland
53%
Figure 5. Percent gain in estuarine emergent wetland in the Narragansett Bay Estuary.
Gain from Estuarine
Unconsolidated Shore
44%
Gain from Estuarine Water
29%
Gain from Upland
8%
Gain from Estuarine Scrub-
Shrub Wetland
16%
Gain from Palustrine Wetland
3%
21
Figure 6. Percent change in estuarine scrub-shrub wetland in the Narragansett Bay Estuary.
Gain from Estuarine Emergent
Wetland
59%
Gain from Estuarine
Unconsolidated Shore
1%
Loss to Upland
7%
Loss to Estuarine Emergent
Wetland
33%
Figure 7. Percent change in estuarine unconsolidated shore in the Narragansett Bay Estuary.
Loss to Estuarine Scrub-
Shrub Wetland
0%
Loss to Palustrine Wetland
2%
Loss to Estuarine Emergent
Wetland
11%
Loss to Estuarine Water
37%
Gain from Estuarine Emergent
Wetland
6%
Gain from Upland
5%
Loss to Upland
16%
Gain from Estuarine Water
23%
22
Table 8. Land use/cover changes (acres and % of 1950s area) in the 500-foot buffer
surrounding tidal wetlands in the Narragansett Bay Estuary from the 1950s to the 1990s.
+ = gain and - = loss
Acreage
Land Use/cover Type 50s Acreage 90s Acreage Change
(% Change)
Residential
Single-family 5,106.5 7,461.1 +2,354.6 (46)
Lawns 1,550.4 1,637.5 +87.1 (6)
Multi-family 36.4 177.8 +141.4 (389)
Mobile home 13.6 13.8 +0.2 (2)
Other 112.8 34.6 -78.2 (69)
Subtotal 6,819.7 9,324.7 +2,505.0 (37)
Commercial
Comm.&Institutional Structures 871.3 1,104.5 +233.2 (27)
Wharves, Piers, Shipyards 567.2 561.7 +5.5 (1)
Paved Surfaces 131.7 261.2 +129.5 (98)
Marinas 134.1 206.2 +72.2 (54)
Unpaved Surfaces 91.0 49.2 -41.8 (46)
Recreational Structures 36.9 51.5 +4.6 (13)
Junkyard 0.1 0.1 0 (0)
Other 1.2 1.2 0 (0)
Subtotal 1,843.5 2,235.5 +392.0 (21)
Industrial 243.7 90.2 -153.5 (63)
Industrial & Commercial Complexes 23.8 15.9 -7.9 (33)
Transportation, Communications,
& Utilities 409.5 744.9 +335.4 (82)
Other Urban or Built-up Land
Golf Courses 273.6 420.7 +147.1 (54)
Landfills 18.3 38.8 +20.5 (112)
Cemetaries 52.5 56.3 +3.8 (7)
Other 148.6 329.9 +181.3 (122)
Subtotal 493.0 845.7 +353.7 (72)
Agriculture
Pasture/hayfields 2,037.9 532.5 -1,505.4 (74)
Cropland 1,037.7 917.9 -119.8 (12)
Orchards, Nursuries, Vineyards 55.3 53.7 -1.6 (3)
Confined Feeding Lots 6.9 3.4 -3.5 (51)
Subtotal 3,137.8 1,507.5 -1,630.3 (52)
23
Table 8. (continued)
Acreage
Land Use/cover Type 50s Acreage 90s Acreage Change
(% Change)
Rangeland
Herbaceous 1,102.9 451.2 -651.7 (59)
0
. Shrub and Brush 3,211.2 2,640.4 -570.9 (18)
Mixed 1,379.5 873.7 -505.9 (37)
Subtotal 5,693.7 3,965.2 -1,728.5 (30)
Forest
Deciduous 2,212.1 2,309.8 +97.7 (44)
Evergreen 235.5 14.6 -220.9 (94)
Mixed 2,836.1 3,410.4 +574.3 (20)
Subtotal 5,283.8 5,734.9 +451.1 (9)
Water & Wetlands
Vegetated Freshwater Wetland 1,390.7 1,486.2 +95.5 (7)
Nonvegetated Freshwater Wetland 8.0 11.5 +3.5 (44)
Fresh Water 171.9 172.0 +0.1 (1)
Subtotal 1,570.6 1,669.6 +99.0 (6.3)
Barren Land
Beaches 19.1 0.9 -18.2 (95)
Other Sand Areas 188.9 129.5 -59.4 (31)
Mixed Barren Land 300.7 247.1 -53.6 (18)
Strip Mines 10.0 33.4 +23.4 (234)
Bare Exposed Rock 8.6 3.4 -5.2 (61)
Transitional Area 44.7 41.4 -3.3 (7)
Subtotal 572.1 455.6 -116.5 (20)
24
Trends for Pilot Study Areas
Wetland trends from the 1930s to the 1950s and the 1950s to the 1990s were examined
for six study areas in the Narragansett Bay Estuary: 1) Allins Cove (including West Shore
of Barrington), 2) Calf Pasture Point (North Kingstown), 3) Jacobs Point (Warren), 4)
Palmer River (Warren), 5) Sachuest Point (Middletown), and 6) Wesquage Pond
(Narragansett). All sites experienced net losses of coastal wetlands (Table 9). With a net
loss of 104.0 acres, Calf Pasture Point lost the most coastal wetland acreage between the
1930s and the 1990s. Wesquage Pond was next ranked with a net loss of 52.6 acres,
followed by Sachuest Point (net loss of 27.9 acres). The other areas experienced only
minor net losses (Allins Cove - 7.4 acres; Jacobs Point - 4.4 acres; Palmer River - 0.7
acre). The nature and causes of changes in wetlands and deepwater habitats are presented
for each study area in Tables 10 through 15. More detailed findings are given in
Appendix B.
The location of these changes are documented on a series of maps showing trends from
the 1930s to the 1950s and from the 1950s to the 1990s. To view the maps, click here.
Calf Pasture Point lost more acreage of coastal marsh prior to the 1950s, while it lost
more unconsolidated shore (e.g., flats) since then (Table 11). In the earlier period,
roughly 70 acres of marsh were lost, with 83% converted to upland; 17 acres of tidal flats
were lost with about 14 acres filled (10 acres - commercial/services). Most of this new
land was undeveloped in the 1950s (e.g., barren land and rangeland). The rest of the lost
marsh was classified as irregularly flooded nonvegetated wetland (spoil deposits in the
high marsh) which likely were converted to upland thereafter. From the 50s to the 90s,
Calf Pasture Point lost 86 acres of tidal flat and 17 acres of coastal marsh. About 60% of
the former losses resulted in an increase in estuarine open water possibly due to a
combination of coastal processes (erosion) before the shoreline was stabilized. Filling at
Calf Pasture Point created nonvegetated wetlands from open water during the earlier
period (this operation was ongoing in the 1950s) and as more fill was deposited these
areas were converted to upland. Most of the marsh loss in this area took place during the
early stages of this filling operation. By the 1990s, much of the lost coastal marsh
between the 1950s and 1990s had become palustrine Phragmites marsh.
Wesquage Pond lost most of its tidal flats prior to the 1950s, accounting for 87% of the
losses between the 1930s and 1990s (Table 15). Nearly all of these losses were attributed
to tidal restriction which converted intertidal flats mostly to estuarine open water
(oligohaline). This action also affected tidal marshes contributing to about a one-acre
gain and a five-acre change in tidal marsh type (i.e., some irregularly flooded wetland to
regularly flooded marsh and creating oligohaline conditions). About five acres of tidal
marshes were filled in Wesquage Pond between the 1950s and the 1990s, with most
being undeveloped (rangeland) in the 1990s. About four acres of marsh became open
water due to tidal restriction.
Sachuest Point lost most of its coastal wetlands from the 1950s to the 1990s (Table 14).
Thirty-eight acres of emergent wetlands were filled during this time. Filling most likely
25
took place prior to passage of the tidal wetland protection act. Spoil deposition was a
major factor impacting wetlands from the 1930s into the 1950s. In the 1990s, much of
this acreage remained undeveloped in shrub or herbaceous cover. Some filling also took
place at Sachuest Point between the 1930s and 1950s with about 6 acres of tidal flat
(estuarine unconsolidated shore) impacted.
High-tide bush marsh at Patience Island (F. Golet photo)
26
Table 9. Status and trends in coastal wetlands for specific study areas.
Study Area Wetland 1930s 1950s Net Change 1990s Net Change Total Change
Type* Acreage Acreage in Acreage Acreage in Acreage 1930s-1990s
(%Change) (%Change) (%Change)
Allins Cove EEM 65.8 62.7 -3.2 (-5) 45.7 -17.0 (-27) -20.1 (-31)
EEMO 13.7 7.2 -6.5 (-47) 8.7 +1.5 (+21) -5.0 (-37)
ESS 1.1 0.4 -0.7 (-64) 5.9 +5.5 (+1375) +4.8 (+436)
EUS 22.3 20.2 -2.1 (-9) 35.2 +15.0 (+74) +12.9 (+58)
Calf Pasture Point EEM 128.1 66.8 -61.3 (-48) 50.1 -16.7 (-25) -78.0 (-61)
EEMO 18.5 18.8 +0.3 (+2) 14.9 -3.9 (-21) -3.6 (-20)
ESS 5.3 0 -5.3 (-100) 4.4 +4.4 (NA) -0.9 (-17)
EUS 42.5 100.0 +57.5 (+135) 20.8 -79.2 (-79) -21.7(-51)
ERS 0.3 0.3 0 0.5 +0.2 (+67) +0.2 (+67)
Jacobs Point EEM 22.3 22.3 0 23.9 +1.6 (+7) +1.6 (+7)
EEMO 9.7 7.1 -2.6 (-27) 12.6 +5.5 (+78) +2.9 (+30)
ESS 12.7 12.7 0 1.8 -10.9 (-86) -10.9 (-86)
EUS 7.3 7.3 0 9.3 +2.0 (+27) +2.0 (+27)
ERS 0.7 0.7 0 0.7 0 0
Palmer River EEM 214.9 212.7 -2.2 (-1) 219.3 +6.6 (+3) +4.4 (+2)
EEMO 1.2 0 -1.2 (-100) 0 0 -1.2 (100)
ESS 15.2 15.2 0 9.0 -6.2 (-41) -6.2 (-41)
EUS 8.1 8.7 +0.6 (+8) 10.4 +1.7 (+20) +2.3 (+28)
* EEM - estuarine emergent; EEMO - estuarine emergent oligohaline; ESS - estuarine scrub-shrub; EUS - estuarine unconsolidated
shore; ERS - estuarine rocky shore; ESB - estuarine streambed; MUS - marine unconsolidated shore; MRS - marine rocky shore.
27
Table 9. (continued)
Study Area Wetland 1930s 1950s Net Change 1990s Net Change Total Change
Type Acreage Acreage in Acreage Acreage in Acreage 1930s-1990s
(%Change) (%Change) (%Change)
Sachuest Point EEM 62.6 69.9 +7.3 (+12) 32.2 -37.7 (-54) -30.4 (-49)
EEMO 3.1 1.9 -1.2 (-39) 14.3 +12.4 (+653) +11.2 (+361)
ESS 5.3 0 -5.3 (-100) 0 0 -5.3 (-100)
EUS 20.6 14.4 -6.2 (-30) 17.2 +2.8 (+19) -3.4 (-17)
ERS 2.0 2.0 0 2.0 0 0
MUS 46.7 46.7 0 46.7 0 0
MRS 34.4 34.4 0 34.4 0 0
Wesquage Pond EEM 7.7 8.4 +0.7 (+9) 0 -8.4 (-100) -7.7 (-100)
EEMO 19.3 19.6 +0.3 (+2) 24.1 +4.5 (+23) +4.8 (+25)
ESS 0.4 0.3 -0.1 (-25) 0 -0.3 (-100) -0.4 (-100)
EUS 51.4 2.3 -49.1 (-96) 1.7 -0.6 (-26) -49.7 (-97)
EUS/EM 0.2 0.5 +0.3 (+150) 0 -0.5 (-100) -0.2 (-100)
ESB 0.2 0.2 0 0.6 +0.4 (+200) +0.4 (+200)
ERS 11.5 11.5 0 11.7 +0.2 (+2) +0.2 (+2)
MUS 11.8 11.8 0 11.8 0 0
MRS 3.5 3.5 0 3.5 0 0
28
Table 10. Nature and causes of coastal wetland and deepwater habitat trends for Allins Cove.
Time Wetland Change Acreage Causes
Period Type* Type
1930s-50s NVW loss 2.9 coastal processes, filling (residential development)
gain 0.7 coastal processes
type change 1.0 coastal processes
no change 18.5 n/a
VW loss 11.0 coastal processes, filling (golf course)
gain 0.6 coastal processes, unknown
type change 0.7 Phragmites, unknown
no change 69.0 n/a
CW loss 1.0 coastal processes, unknown
gain 5.4 coastal processes
no change 20.7 n/a
1950s-90s NVW loss 1.0 coastal processes
gain 15.9 coastal processes, unknown
type change 2.2 coastal processes
no change 17.0 n/a
VW loss 14.0 tidal restriction, filling (golf course, residential development), coastal
processes
gain 4.1 coastal processes, Phragmites invasion
type change 6.9 ditching/Iva succession, tidal restriction, Phragmites, unknown
no change 46.2 n/a
CW loss 16.2 coastal processes, spoil deposition, Phragmites invasion
no change 9.9 n/a
* NVW - nonvegetated wetland; VW - vegetated wetland; CW - coastal water (deepwater habitat); n/a - not applicable.
29
Table 11. Nature and causes of coastal wetland and deepwater habitat trends for Calf Pasture Point.
Time Wetland Change Acreage Causes
Period Type* Type
1930s-50s NVW loss 17.1 filling (commercial/services, barren land), coastal processes
gain 74.5 spoil deposition, coastal processes
type change 0.6 spoil deposition
no change 25.0 n/a
VW loss 70.3 filling (barren land, rangeland, commercial/services, spoil deposition),
coastal processes, ditching/succession,
gain 4.0 coastal processes, Phragmites, unknown
type change 8.4 spoil deposition, unknown
no change 73.2 n/a
CW loss 123.0 filling (spoil deposition, barren land, commercial/services),
coastalprocesses,Phragmites invasion
gain 6.1 coastal processes, tidal restriction
no change 6.0 n/a
1950s-90s NVW loss 85.7 coastal processes, filling (rangeland)
gain 6.2 coastal processes, spoil deposition
type change 3.7 spoil deposition, coastal processes, jetty/groin removal
no change 10.9 n/a
VW loss 17.2 Phragmites invasion, filling (forest, rangeland, landfill, golf course, spoil
deposition), coastal processes, tidal restriction
gain 8.5 coastal processes, succession/ditching
type change 28.3 succession/ditching, Phragmites, Iva, spoil deposition, unknown
no change 40.1 n/a
CW loss 5.1 coastal processes, excavation
gain 54.8 coastal processes
no change 5.3 n/a
*NVW - nonvegetated wetland; VW - vegetated wetland; CW - coastal water (deepwater habitat); n/a - not applicable.
30
Table 12. Nature and causes of coastal wetland and deepwater habitat trends for Jacobs Point.
Time Wetland Change Acreage Causes
Period Type* Type
1930s-50s NVW no change 8.0 n/a
VW loss 2.6 agriculture, tidal restriction/agriculture
no change 29.4 n/a
CW no change 0.6 n/a
1950s-90s NVW loss 1.4 coastal processes
gain 0.6 coastal processes
no change 8.0 n/a
VW loss 3.8 filling (rangeland, residential development), coastal processes,
type change 14.5 succession/ditching, Phragmites, Iva
no change 23.8 n/a
CW loss 0.6 coastal processes
*NVW - nonvegetated wetland; VW - vegetated wetland; CW - coastal water (deepwater habitat); n/a - not applicable.
31
Table 13. Nature and causes of coastal wetland and deepwater habitat trends for Palmer River.
Time Wetland Change Acreage Causes
Period Type* Type
1930s-50s NVW gain 0.6 unknown
no change 8.1 n/a
VW loss 3.4 tidal restriction, filling (commercial/services, barren land, residential),
coastalprocesses
no change 227.9 n/a
CW loss 39.7 impoundment
gain 0.5 coastal processes
no change 10.0 n/a
1950s-90s NVW gain 2.2 coastal processes, unknown
loss 0.6 unknown
no change 8.1 n/a
VW gain 3.8 coastal processes, spoil deposition, succession/ditching, unknown
loss 3.3 filling (residential development, commercial/services, rangeland)
type change 21.0 Phragmites, succession/ditching, Iva, unknown
no change 203.6 n/a
CW loss 8.0 filling (rangeland, commercial/services, residential development), coastal
processes, succession/ditching, unknown
* NVW - nonvegetated wetland; VW - vegetated wetland; CW - coastal water (deepwater habitat); n/a - not applicable.
32
Table 14. Nature and causes of coastal wetland and deepwater habitat trends for Sachuest Point.
Time Wetland Change Acreage Causes
Period Type* Type
1930s-50s NVW loss 6.2 filling (spoil deposition, commercial/services), coastal processes,
Phragmites invasion
no change 97.5 n/a
VW loss 4.8 filling (residential, transportation/comm./utilities, commercial/services)
gain 5.7 spoil deposition, Phragmites invasion, coastal processes
type change 29.0 spoil deposition
no change 37.2 n/a
CW no change 2.2 n/a
1950s-90s NVW gain 2.8 coastal processes
type change 1.9 coastal processes
no change 95.5 n/a
VW loss 26.3 filling (spoil deposition, rangeland, commercial/services, barren land)
gain 1.0 revegetation (sediment accretion after excavation)
type change 20.6 tidal restriction, Phragmites invasion, succession/ditching
no change 24.9 n/a
CW loss 1.6 revegetation (excavation), coastal processes
no change 0.6 n/a
*NVW - nonvegetated wetland; VW - vegetated wetland; CW - coastal water (deepwater habitat); n/a - not applicable.
33
Table 15. Nature and causes of coastal wetland and deepwater habitat trends for Wesquage Pond.
Time Wetland Change Acreage Causes
Period Type* Type
1930s-50s NVW loss 49.1 tidal restriction, coastal processes
gain 0.3 coastal processes
no change 29.5 n/a
VW loss 0.4 filled (commercial)
gain 1.5 tidal restriction, coastal processes
type change 5.0 tidal restriction, Phragmites
no change 21.9 n/a
CW loss 0.5 coastal processes, tidal restriction
gain 47.6 tidal restriction
no change 20.5 n/a
1950s-90s NVW loss 1.1 filling (residential development)
gain 0.7 coastal processes, jetty/groin construction
no change 28.7 n/a
VW loss 9.2 tidal restriction, filling (commercial/services, rangeland, residential)
gain 5.0 tidal restriction, Phragmites, unknown
type change 4.0 tidal restriction, Phragmites, unknown
no change 15.0 n/a
CW loss 5.7 tidal restriction, Phragmites, filling (residential), jetty/groin construction,
unknown
gain 4.4 tidal restriction
type change 0.3 impounded/tidal restriction
no change 62.1 n/a
* NVW - nonvegetated wetland; VW - vegetated wetland; CW - coastal water (deepwater habitat); na - not applicable.
34
Conclusions
The Narragansett Bay Estuary (NBE) contains about 130,000 acres of tidal and subtidal
habitats. Open water is the predominant feature of the Bay occupying about 95% of the
tidal ecosystem. Intertidal habitats (marshes, beaches, flats, and other shores) represent
only 5% of the ecosystem. Of this, vegetated wetlands (mostly salt marshes) comprise
58% of the acreage, with the rest made up mostly of tidal flats. Nine acres of oyster reefs
were inventoried. Over 1,700 acres (or 48%) of the coastal marshes have been ditched
and/or impounded. Slightly more than one-third of the 500-foot buffer around the coastal
wetlands is occupied by residential development. Forests and rangeland (i.e., fields and
shrub thickets) represent 22% and 15% of the buffer, respectively.
Between the 1950s and 1990s, the NBE lost a net total of about 110 acres of estuarine
open water, nearly 306 acres of salt and brackish marshes, and 205 acres of intertidal
shores. A net gain of 73 acres of slightly brackish marshes took place, mostly at the
expense of more saline wetlands. About 190 acres of salt/brackish marshes were filled.
Common reed (Phragmites australis), a widespread invasive grass, increased its
distribution during the study period by roughly 240 acres. Major causes of coastal marsh
loss and degradation were filling and tidal restriction. Gains and losses of coastal marsh
attributed to coastal processes (erosion/accretion) were nearly even, where these
processes caused about 1.5 times more loss of unconsolidated shores than gains between
the 1950s and 1990s.
For six areas in the NBE, wetlands trends were examined back to the 1930s (Allins Cove,
Calf Pasture Point, Jacobs Point, Palmer River, Sachuest Point, and Wesquage Pond).
All sites experienced net losses of coastal wetlands, but only Calf Pasture Point (104
acres), Wesquage Pond (53 acres), and Sachuest Point (28 acres) lost more than 10 acres.
The other areas lost less than eight acres each.
35
Acknowledgments
Funding for this project was provided by the Narragansett Bay Estuary Program (NBEP).
Helen Cottrell served as project officer for NBEP. She reviewed the draft manuscript and
products and provided photographs for use in this report. Ralph Tiner was project officer
for the U.S Fish and Wildlife Service (FWS). He was responsible for study design,
project oversight, data analysis and synthesis, and report preparation.
Wetland trends data were collected by the Natural Resources Assessment Group (NRAG)
in the Department of Plant and Soil Sciences, University of Massachusetts-Amherst,
under the direction of Dr. Peter Veneman, principal investigator. Most of the
photointerpretation and cartographic work was performed by Irene Huber and Todd
Nuerminger. Mary Johnson (NRAG) assisted in photointerpretation of land use/cover
trends in the 500-foot buffer around coastal wetlands. Craig Polzen also did some work
on this photo-analysis and provided GIS support to NRAG.
Digital database construction and GIS analyses were accomplished by Aimée Mandeville
of the University of Rhode Island's Environmental Data Center. She digitized map
overlay products to create the geospatial database, performed analytical inquiries, and
produced color-coded maps and statistical summaries presented in this report including
the Appendices. Figure 1 was prepared by Paul Jordan, Rhode Island Department of
Environmental Management, Geographic Information System Program, while Aimée
created Figures 2 and 3. Herbert Bergquist (FWS) assisted in preparing the cover of this
report, while Lorraine Fox (FWS) scanned the photos for conversion to digital images.
Dr. Frank Golet, University of Rhode Island, gratiously provided color photographs of
coastal wetlands for use in this report.
.
36
References
Anderson, J.R., E.E. Hardy, J.T. Roach, and R.E. Witmer. 1976. A Land Use and Land
Cover Classification System for Use with Remote Sensor Data. U.S. Geological Survey
Professional Paper 96A, U.S. Government Printing Office, Washington, DC.
Cowardin, L.W., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
Wetlands and Deepwater Habitats of the United States. U.S. Fish and Wildlife Service,
Washington, DC.
Huber, I. and T. Nuerminger. 2003. Rhode Island Narragansett Bay Project Area:
Trends Analysis Methodology. Department of Plant and Soil Sciences, Natural
Resources Assessment Group, University of Massachusetts, Amherst, MA.
37
Appendices
Click here for Appendices
38