Coastal Zone Survey of Little Narragansett Bay

1
Deborah Surabian Soil Scientist Natural Resources
Conservation Service Connecticut
2
Coastal Zone Soil Survey of Little Narragansett
Bay

• Soil is a natural body that occurs on the land
  surface and is characterized by either
  horizons, or layers, that are distinguishable
  from the initial material as a result of
  additions, losses, transfers, and transformations
  of energy and matter, or
• The ability to support rooted plants in a natural
  environment.

3
Coastal Zone Soil Survey of Little Narragansett
Bay
The upper limit of soil is the boundary between
soil and air, shallow water, live plants, or
plant materials that have not begun to decompose.
The lower limit of soil has been arbitrarily
set at 200 cm. The horizontal boundaries of soil
are areas where the soil grades into deep water
(typically 2.5 meters deep), barren areas, rock,
or ice.
4
Coastal Zone Soil Survey of Little Narragansett
Bay
Subaqueous soils formed under a continuous water
column, although their sediments may have
originated from an upland area such as a dune.
Submerged soils formed in an upland environment
but are now underwater. Submerged soils became
submerged as a result of rising water tables,
flooding events, or sea level rise.
For USDA-NRCS purposes, both subaqueous and
submerged soils are considered subaqueous soils.
Terrestrial Soils
Subaqueous Soils
5
Coastal Zone Soil Survey of Little Narragansett
Bay
The geographic focus of this project is in the
ecologically significant estuary of Little
Narragansett Bay, located along the coast of
southeastern Connecticut and southwestern Rhode
Island. This area encompasses approximately
1100 hectares (2700 ac) and contains subaqueous
soils formed from a variety of parent materials
and aquatic environments.
6
Coastal Zone Soil Survey of Little Narragansett
Bay
NRCS, a member of the National Cooperative Soil
Survey, is the lead federal agency for the
mapping and interpretations of the nations soil
resources. The well established standards,
techniques, and protocols used to map and
interpret the nations soil resources have been
applied to this project.
7
Coastal Zone Soil Survey of Little Narragansett
Bay
National Oceanic and Atmospheric Administration
(NOAA) bathymetry, shown on this map, was
supplemented with bathymetry created by NRCS
technology to develop a 112,000 scale contour
map of the submerged topography.
The bathymetry, used in combination with aerial
photography, was used to delineate different
major soil landform units.
8
Coastal Zone Soil Survey of Little Narragansett
Bay
Major soil landform units are identified and
delineated to predict and explain soil
distributions. Due to overlying water, the
identification and delineation of submerged
landscape units is somewhat more complicated
than that of terrestrial landscapes.
9
Coastal Zone Soil Survey of Little Narragansett
Bay
Major soil landform units
Navigational Channel
Bay Bottom
Shore Complex
Dredged Navigational Channel
Washover-Fan Flat
Shore Face
Bay Bottom
Submerged Headland
10
Coastal Zone Soil Survey of Little Narragansett
Bay
Major soil landform units
Mainland Cove
Submerged Headlands
Bay Bottom
11
Coastal Zone Soil Survey of Little Narragansett
Bay
Major soil landform units
Submerged Stream Valley
12
Coastal Zone Soil Survey of Little Narragansett
Bay
Bucket augers and McCauley peat samplers were
used to investigate soil morphology.
13
Coastal Zone Soil Survey of Little Narragansett
Bay
Vibracore and push tube techniques are used to
obtain minimally disturbed samples for detailed
descriptions and sampling of typical pedons. The
URI Graduate School of Oceanography captured
these soil cores.
14
Coastal Zone Soil Survey of Little Narragansett
Bay
Soil cores are described and samples are sent to
our National Soil Survey Center, in Lincoln,
Nebraska, for laboratory analyses. Soil samples
are shipped and stored cold until lab tests are
completed. Upon exposure to air, the sulfides
oxidize and lower the pH by creating sulfuric
acid. This also effects the measurement of
salinity and percent clay.
Photographs of three vibracores taken from Little
Narragansett Bay. From left - the Napatree,
Anguilla, and Rhodesfolly proposed series.
15
Coastal Zone Soil Survey of Little Narragansett
Bay
The result of this endeavor is a detailed
seamless soil map extending from the land into
the estuary identifying subaqueous soil resources
at a scale of 112,000.
16
Coastal Zone Soil Survey of Little Narragansett
Bay
The result of this endeavor is a detailed
seamless soil map extending from the land into
the estuary identifying subaqueous soil resources
at a scale of 112,000.
17
Coastal Zone Soil Survey of Little Narragansett
Bay
The following is a list of specific soil based
interpretations that could be developed for
subaqueous soils and of potential uses of the
project information

• Potential for SAV Restoration
• Bottom Type
• Moorings
• Presence of Sulfidic Materials
• Crab Habitat
• Management for Sustainable Shellfish Production
• Nutrient Reduction
• Benthic Preservation Site Identification
• Wildlife Management
• Wading Shore Birds, Migratory Waterfowl,
  Nurseries and Spawning Areas
• Habitat Protection for Horseshoe Crab
• Dredging Island Creation
• Tidal Marsh Protection and Creation
• Bathymetric Map
• Navigational Channel Creation/Maintenance
• Effects of Dredging on Benthic Ecology
• Off -Site Disposal of Dredge Spoil
• Dune and Beach Maintenance/Replenishment
• Carbon Sequestration

18
Coastal Zone Soil Survey of Little Narragansett
Bay
Presence of Sulfidic Materials If soils
containing sulfidic materials are disturbed
without appropriate management and remediation,
they pose a significant threat to development and
the natural environment. The pH value, which
normally is near neutral before drainage or
exposure to air, will drop below pH 4.
The effects of actual acid sulfate soils are
evident in the foreground. This dredged spoil
material will remain either unvegetated or
suitable only to acid tolerant species.
19
Coastal Zone Soil Survey of Little Narragansett
Bay
Presence of Sulfidic Materials The impacts of
acid sulfate soils can be numerous and include

• Sulfuric acid mobilizes Fe, Al, Mn, and Cd, and
  lowers soil pH making some soils toxic to plant
  growth
• causing scalding (similar to salinity)
• Sulfuric acid corrodes concrete, iron and steel
  foundations and piping
• Acid waters can cause rust colored stains and
  slimes
• Plastic corrugated drainage becomes blocked by
  iron oxides
• Drainage waters can release sufficient sulfuric
  acid and Al to cause fish disease and mortality
• Acid waters can mobilize aluminum and heavy
  metals such as cadmium which can be adsorbed by
  fish and aquatic life
• Effects on aquaculture industries
• Poor quality stock water
• Road failure
• Irreversible soil shrinkage
• Low bearing capacity of soils
• Human health problems algae, heavy metals in
  drinking water, dermatitis, eye inflammations
• Arsenic toxicity
• Sulfidic odor caused by boat traffic or wave
  action

20
Coastal Zone Soil Survey of Little Narragansett
Bay
Presence of Sulfidic Materials Ideally, areas of
acid sulfate soils should not be disturbed by
development activities. The cost to the
surrounding environment and inevitably to the
development itself of releasing acid and metal
ions into the soil and groundwater outweighs any
short-term gain.
The corrosivity of acid sulfate drainage is
demonstrated by the concrete that has been eaten
away from around the aggregate down slope of the
road cut on which an AASS is present (Fanning,
2006). This photo demonstrates how remediation of
the actual acid sulfate soil surface for plant
growth does not stop the underlying acid sulfate
weathering and subsequent acid sulfate drainage.
21
Coastal Zone Soil Survey of Little Narragansett
Bay
Presence of Sulfidic Materials Where developments
have already occurred in upland or coastal acid
sulfate soils or where they may proceed within
the area at risk, remedial actions will be
necessary to reduce any adverse impacts and
rehabilitate the site and surrounding affected
areas.
Sulfidic materials encountered in a newly
constructed housing development on upland soils.
Neighborhood lawns in this subdivision have no
grass, in spite of being sodded with new turf two
times. The sidewalks are reddish-orange in color
due to being coated with iron (hydr)oxides
(Fanning, 2006).
22
Coastal Zone Soil Survey of Little Narragansett
Bay
Presence of Sulfidic Materials In recognition of
the disturbance caused by acid sulfate soils
to the environment, an upland and coastal
acid sulfate soils risk map is advised.
23
Coastal Zone Soil Survey of Little Narragansett
Bay
Submerged Aquatic Vegetation (SAV) SAV beds,
rooted vegetation that grows under water, are
among the most productive ecosystems in the
world. The ecological importance of eelgrass is
derived from this productivity and its
substantial habitat it creates.
Eelgrass beds on the shore face major soil
landform unit in Little Narragansett Bay. They
serve as a haven for crabs, scallops, numerous
species of fish, and other wildlife, providing
these creatures with shelter, nursery grounds,
and food.
24
Coastal Zone Soil Survey of Little Narragansett
Bay
Submerged Aquatic Vegetation (SAV)
To increase restoration success, such efforts may
focus on soil map units that have existing SAV
and locate areas of the same map unit without
SAV to determine the best sites for full scale
eelgrass or other SAV restoration.
25
Coastal Zone Soil Survey of Little Narragansett
Bay
Bottom Type The bottom type of soil material is
measured by the soil structure stability n-value
of the soil surface layers. An n-value of
slightly fluid through very fluid is classed as
a soft bottom. An n-value of nonfluid is hard
bottom.
26
Coastal Zone Soil Survey of Little Narragansett
Bay
Bottom Type
Knowledge of bottom types provides a framework
for mapping benthic habitats and managing marine
resources
27
Coastal Zone Soil Survey of Little Narragansett
Bay
Moorings In the last decade, the boating
population has exploded and moorings are
increasing in number. The n-value of the soil
surface layers (bottom type of material)
influences the type of anchor that boat mooring
facilities may use.
28
Moorings
Deadweight
Mushroom
29
Ultimately, new partners and stakeholders will
engage in the National Cooperative Soil Survey
efforts of mapping subaqueous soils in coastal
zone areas such as Little Narragansett Bay.
Connecticut NRCS soils websitewww.ct.nrcs.usda.g
ov/soils.html