FOREDUNE
Michael J. Kennish
Department of Marine and Coastal Sciences,
School of Environmental and Biological Sciences,
Rutgers University, New Brunswick, NJ, USA
Synonyms
Beach ridge; Frontal dune; Primary dune; Transverse dune
Definition
A foredune is a shore-parallel dune ridge that forms on
the back beach of an ocean, estuary, or bay by aeolian
depositional processes (Hesp, 1988; Nordstrom, 1992;
Nordstrom and Jackson, 1994).
Description
As part of a dune system, the foredune is located closest to
the water body. Vegetation in the backshore plays an
important role in the accumulation and retention of sand
to form the dune ridge. Plant succession occurs as the dune
develops. Foredunes often exhibit different morphologies
(from convex ridges to flat terraces) and variable ecological characteristics (Hesp, 1988). As the foredune enlarges,
it traps more windblown sand and hence can expand rather
rapidly.
There are two main types of foredunes: incipient and
established types (Hesp, 2002). Incipient foredunes are
new or embryo dunes formed by sand deposition within
discrete vegetation (e.g., Ammophila, Ipomoea, and Spinifex) from the immediate backshore to back-barrier flats
(Carter et al., 1992). They develop into established
foredunes (up to 30–35 m in height) with the growth of
larger and more mature vegetation, notably woody
plants. A number of factors control the developmental
process, including the plant species present, degree of
vegetation cover, sand supply, accretion rate, wave and
wind forces, storm erosion, extent of human impact and
use, as well as other elements (Hesp, 2002).
Bibliography
Carter, R. W. G., Bauer, B. O., Sherman, D. J., Davidson-Arnott,
R. G. D., Gares, P. A., Nordstrom, K. F., and Orford, J. D.,
1992. Dune development in the aftermath of stream outlet closure: examples from Ireland and California. In Carter,
R. W. G., Curtis, T. G. F., and Sheehy-Skeffington, M. J.
(eds.), Coastal Dunes: Geomorphology, Ecology and Management for Conservation. Rotterdam: Balkema, pp. 57–69.
Hesp, P., 2002. Foredunes and blowouts: initiation, geomorphology,
and dynamics. Geomorphology, 48, 245–268.
Hesp, P. A., 1988. Foredune morphology, dynamics, and structures.
Journal of Sedimentary Geology, Special Issue on Aeolian
Sediments, 55, 17–41.
Nordstrom, K. F., 1992. Estuarine Beaches. London: Elsevier.
Nordstrom, K. F., and Jackson, N. L., 1994. Aeolian processes and
dune fields in estuaries. Physical Geography, 15, 358–371.
Cross-references
Back Dune
Beach Processes
Coastal Barriers
Coastal Landforms
Estuarine Beaches
FORESTED WETLAND HABITAT
Jamie A. Duberstein
1 and Ken W. Krauss
2
1
Baruch Institute of Coastal Ecology and Forest Science,
Clemson University, Georgetown, SC, USA
2
U.S. Geological Survey, National Wetlands Research
Center, Lafayette, LA, USA
Synonyms
Mangrove forest; Swamp; Tidal freshwater forested
wetland; Tidal saltwater forested wetland; Tidal várzea
Definition
A forested wetland (swamp) is a forest where soils are saturated or flooded for at least a portion of the growing season, and vegetation, dominated by trees, is adapted to
tolerate flooded conditions.
A tidal freshwater forested wetland is a forested wetland that experiences frequent but short-term surface
flooding via tidal action, with average salinity of soil
porewater less than 0.5 g/l. It is known locally as tidal
várzea in the Amazon delta, Brazil.
A tidal saltwater forested wetland (mangrove forest) is
a forested wetland that experiences frequent but shortterm surface flooding via tidal action, with average salinity often exceeding 3 g/l and reaching levels that can
exceed seawater. Mangrove ecosystems are composed of
facultative halophytes that generally experience better
growth at moderate salinity concentrations.
Introduction
Forested wetlands represent a globally diverse array of
types but are restricted to only a few true estuarine types.
The primary component differentiating various types of
forested wetland habitat is the vegetation, which is dominated by trees and shrubs. The specific composition of tree
and shrub species (i.e., the community) is mostly
influenced by the local hydrology (Mitsch and Gosselink,
2000). Because estuarine systems are dominated by the
oceanic processes of sea level and tidal action on one side
and the continental processes of river discharge and sediment load on the other, hydrologic characteristics within
the estuary vary considerably. Depth, duration, and frequency of flooding; salinity of the soil porewater; and
regional climate all determine the type of forested wetland
habitat. Estuarine forested wetlands are divided into tidal
freshwater forested wetlands and mangroves, also known
as tidal saltwater forested wetlands.
334
FOREDUNE
Michael J. Kennish
Department of Marine and Coastal Sciences,
School of Environmental and Biological Sciences,
Rutgers University, New Brunswick, NJ, USA
Synonyms
Beach ridge; Frontal dune; Primary dune; Transverse dune
Definition
A foredune is a shore-parallel dune ridge that forms on
the back beach of an ocean, estuary, or bay by aeolian
depositional processes (Hesp, 1988; Nordstrom, 1992;
Nordstrom and Jackson, 1994).
Description
As part of a dune system, the foredune is located closest to
the water body. Vegetation in the backshore plays an
important role in the accumulation and retention of sand
to form the dune ridge. Plant succession occurs as the dune
develops. Foredunes often exhibit different morphologies
(from convex ridges to flat terraces) and variable ecological characteristics (Hesp, 1988). As the foredune enlarges,
it traps more windblown sand and hence can expand rather
rapidly.
There are two main types of foredunes: incipient and
established types (Hesp, 2002). Incipient foredunes are
new or embryo dunes formed by sand deposition within
discrete vegetation (e.g., Ammophila, Ipomoea, and Spinifex) from the immediate backshore to back-barrier flats
(Carter et al., 1992). They develop into established
foredunes (up to 30–35 m in height) with the growth of
larger and more mature vegetation, notably woody
plants. A number of factors control the developmental
process, including the plant species present, degree of
vegetation cover, sand supply, accretion rate, wave and
wind forces, storm erosion, extent of human impact and
use, as well as other elements (Hesp, 2002).
Bibliography
Carter, R. W. G., Bauer, B. O., Sherman, D. J., Davidson-Arnott,
R. G. D., Gares, P. A., Nordstrom, K. F., and Orford, J. D.,
1992. Dune development in the aftermath of stream outlet closure: examples from Ireland and California. In Carter,
R. W. G., Curtis, T. G. F., and Sheehy-Skeffington, M. J.
(eds.), Coastal Dunes: Geomorphology, Ecology and Management for Conservation. Rotterdam: Balkema, pp. 57–69.
Hesp, P., 2002. Foredunes and blowouts: initiation, geomorphology,
and dynamics. Geomorphology, 48, 245–268.
Hesp, P. A., 1988. Foredune morphology, dynamics, and structures.
Journal of Sedimentary Geology, Special Issue on Aeolian
Sediments, 55, 17–41.
Nordstrom, K. F., 1992. Estuarine Beaches. London: Elsevier.
Nordstrom, K. F., and Jackson, N. L., 1994. Aeolian processes and
dune fields in estuaries. Physical Geography, 15, 358–371.
Cross-references
Back Dune
Beach Processes
Coastal Barriers
Coastal Landforms
Estuarine Beaches
FORESTED WETLAND HABITAT
Jamie A. Duberstein
1 and Ken W. Krauss
2
1
Baruch Institute of Coastal Ecology and Forest Science,
Clemson University, Georgetown, SC, USA
2
U.S. Geological Survey, National Wetlands Research
Center, Lafayette, LA, USA
Synonyms
Mangrove forest; Swamp; Tidal freshwater forested
wetland; Tidal saltwater forested wetland; Tidal várzea
Definition
A forested wetland (swamp) is a forest where soils are saturated or flooded for at least a portion of the growing season, and vegetation, dominated by trees, is adapted to
tolerate flooded conditions.
A tidal freshwater forested wetland is a forested wetland that experiences frequent but short-term surface
flooding via tidal action, with average salinity of soil
porewater less than 0.5 g/l. It is known locally as tidal
várzea in the Amazon delta, Brazil.
A tidal saltwater forested wetland (mangrove forest) is
a forested wetland that experiences frequent but shortterm surface flooding via tidal action, with average salinity often exceeding 3 g/l and reaching levels that can
exceed seawater. Mangrove ecosystems are composed of
facultative halophytes that generally experience better
growth at moderate salinity concentrations.
Introduction
Forested wetlands represent a globally diverse array of
types but are restricted to only a few true estuarine types.
The primary component differentiating various types of
forested wetland habitat is the vegetation, which is dominated by trees and shrubs. The specific composition of tree
and shrub species (i.e., the community) is mostly
influenced by the local hydrology (Mitsch and Gosselink,
2000). Because estuarine systems are dominated by the
oceanic processes of sea level and tidal action on one side
and the continental processes of river discharge and sediment load on the other, hydrologic characteristics within
the estuary vary considerably. Depth, duration, and frequency of flooding; salinity of the soil porewater; and
regional climate all determine the type of forested wetland
habitat. Estuarine forested wetlands are divided into tidal
freshwater forested wetlands and mangroves, also known
as tidal saltwater forested wetlands.
334
FOREDUNE