response to the installation of larger culverts within the
first year following construction (Roman et al., 2002).
Tide gate removal or modification
Tide gates are designed to constrain the natural hydrologic
regime in tidally influenced habitats. Culverts are fitted
with doors or flaps to allow freshwater to drain from
upland sources while minimizing and often eliminating
the inflow of salt water from adjacent tidal waters
(Giannico and Souder, 2004; Giannico and Souder,
2005). Tide gates can allow hydrologic connection and
permit limited fish access in projects where full connectivity is not possible.
Tidal channel development
Tidal restoration designs often include the plans for tidal
channel development. This development can occur by
means of passive formation, active creation, or
a combination of both. Channels are passively or voluntarily created following a particular action that restores
hydraulic and sediment processes to a tidal marsh.
Hydraulic geometry and other indices provide useful
guidelines for physical restoration and creation of estuarine tidal channels but do not clarify the ecological consequences of channel form (Hood, 2002; Diefenderfer et al.,
2008).
Ditch plugging and filling
In U.S. east coast tidal marshes, ditching was historically
implemented as a means for mosquito population
control. The channelization and drainage of surface water
within these ecosystems diminished natural water tables
within marshes and ultimately led to the loss of salt marsh
pond habitats (Adamowicz and Roman, 2005). Plugging
ditches can create salt marsh ponds, whereas filling
ditches can restore more natural tidal hydrology. Ecological effects of both of these methods should be given careful site-specific consideration (Corman and Roman,
2011).
Elevation manipulation
In a study by Cornu and Sadro (2002), the marsh surface
of a diked and subsided estuarine wetland in Coos Bay,
Oregon, was manipulated to examine structural and functional recovery at three intertidal elevations. Applying
dredge material as a means to restore marsh habitats offers
managers an opportunity to reclaim otherwise unusable
material. Conversely, removal of fill accompanied by
planting marsh species is an alternative method for elevation manipulation to restore tidal inundation and marsh
vegetation (USACE, 2007b).
Plant propagation and reintroduction
Goals for restoration often include increases in native
vegetation, habitat, aesthetics, and associated function.
To that end, a common area of experimental research
has focused on increasing the establishment, growth,
and functional benefits of native tidal marsh vegetation.
Soil amendments, including organic matter (e.g., composted
kelp and municipal sewage sludge) or inorganic fertilizers
(e.g., urea or ammonium nitrate), are experimental treatments that have been used in restoration sites with coarse
soils, such as dredge material or sandy upland areas,
where nitrogen is limiting (Callaway, 2001). The use of
seedlings continues to be an effective approach for
establishing diverse tidal marsh vegetation in smaller restoration projects.
Planting marsh vegetation offers managers an alternative to natural recolonization; however, this action may
be cost-prohibitive for some restoration projects. Recovery and overall project success is largely dependent on site
conditions such as marsh elevation, hydrodynamics, and
the presence of nearby source vegetation for natural
recolonization (Weinstein et al., 2001). Vegetative recovery can be influenced by these criteria, yet it is necessary
for planners and resource managers to understand that
the success of natural recolonization varies at multiple
spatial and temporal scales.
Invasive species control
Nonnative plants in tidal wetlands threaten the natural biodiversity of coastal ecosystems. Purple loosestrife
(Lythrum salicaria) and reed canary grass (Phalaris
arundinacea L.) have a broad geographic footprint, plaguing both east and west coast tidal marsh habitats (Lyons,
1998; Blossey, 2002).
Fundamental components of habitat restoration
projects
Fundamental components of successful habitat restoration
projects and programs can be divided into five phases
(Thom et al., 2011a): planning, implementation, monitoring, data management and dissemination of results, and
adaptive management and project evaluation.
Planning
Planning includes the establishment of goals, objectives,
and performance criteria for the project. Performance
criteria often include time scale, spatial scale, structural
conditions, functional conditions, self-maintenance, and
the potential resilience of the system to withstand and
recover from disturbance. The type of system to be
restored is determined, and the site is selected. This
involves examination of the historical or pre-disturbance
conditions, degree of present alteration, present ecological
conditions, and other factors. Conceptual ecosystem
models are often used to help this process. The actual
strategy used for restoration depends on the goals and
objectives, as well as the condition of the landscape and
the site. The level of physical effort, cost, schedule, contingency plan (i.e., in case something goes wrong), and
engineering design are all part of project planning.
280
ESTUARINE HABITAT RESTORATION
first year following construction (Roman et al., 2002).
Tide gate removal or modification
Tide gates are designed to constrain the natural hydrologic
regime in tidally influenced habitats. Culverts are fitted
with doors or flaps to allow freshwater to drain from
upland sources while minimizing and often eliminating
the inflow of salt water from adjacent tidal waters
(Giannico and Souder, 2004; Giannico and Souder,
2005). Tide gates can allow hydrologic connection and
permit limited fish access in projects where full connectivity is not possible.
Tidal channel development
Tidal restoration designs often include the plans for tidal
channel development. This development can occur by
means of passive formation, active creation, or
a combination of both. Channels are passively or voluntarily created following a particular action that restores
hydraulic and sediment processes to a tidal marsh.
Hydraulic geometry and other indices provide useful
guidelines for physical restoration and creation of estuarine tidal channels but do not clarify the ecological consequences of channel form (Hood, 2002; Diefenderfer et al.,
2008).
Ditch plugging and filling
In U.S. east coast tidal marshes, ditching was historically
implemented as a means for mosquito population
control. The channelization and drainage of surface water
within these ecosystems diminished natural water tables
within marshes and ultimately led to the loss of salt marsh
pond habitats (Adamowicz and Roman, 2005). Plugging
ditches can create salt marsh ponds, whereas filling
ditches can restore more natural tidal hydrology. Ecological effects of both of these methods should be given careful site-specific consideration (Corman and Roman,
2011).
Elevation manipulation
In a study by Cornu and Sadro (2002), the marsh surface
of a diked and subsided estuarine wetland in Coos Bay,
Oregon, was manipulated to examine structural and functional recovery at three intertidal elevations. Applying
dredge material as a means to restore marsh habitats offers
managers an opportunity to reclaim otherwise unusable
material. Conversely, removal of fill accompanied by
planting marsh species is an alternative method for elevation manipulation to restore tidal inundation and marsh
vegetation (USACE, 2007b).
Plant propagation and reintroduction
Goals for restoration often include increases in native
vegetation, habitat, aesthetics, and associated function.
To that end, a common area of experimental research
has focused on increasing the establishment, growth,
and functional benefits of native tidal marsh vegetation.
Soil amendments, including organic matter (e.g., composted
kelp and municipal sewage sludge) or inorganic fertilizers
(e.g., urea or ammonium nitrate), are experimental treatments that have been used in restoration sites with coarse
soils, such as dredge material or sandy upland areas,
where nitrogen is limiting (Callaway, 2001). The use of
seedlings continues to be an effective approach for
establishing diverse tidal marsh vegetation in smaller restoration projects.
Planting marsh vegetation offers managers an alternative to natural recolonization; however, this action may
be cost-prohibitive for some restoration projects. Recovery and overall project success is largely dependent on site
conditions such as marsh elevation, hydrodynamics, and
the presence of nearby source vegetation for natural
recolonization (Weinstein et al., 2001). Vegetative recovery can be influenced by these criteria, yet it is necessary
for planners and resource managers to understand that
the success of natural recolonization varies at multiple
spatial and temporal scales.
Invasive species control
Nonnative plants in tidal wetlands threaten the natural biodiversity of coastal ecosystems. Purple loosestrife
(Lythrum salicaria) and reed canary grass (Phalaris
arundinacea L.) have a broad geographic footprint, plaguing both east and west coast tidal marsh habitats (Lyons,
1998; Blossey, 2002).
Fundamental components of habitat restoration
projects
Fundamental components of successful habitat restoration
projects and programs can be divided into five phases
(Thom et al., 2011a): planning, implementation, monitoring, data management and dissemination of results, and
adaptive management and project evaluation.
Planning
Planning includes the establishment of goals, objectives,
and performance criteria for the project. Performance
criteria often include time scale, spatial scale, structural
conditions, functional conditions, self-maintenance, and
the potential resilience of the system to withstand and
recover from disturbance. The type of system to be
restored is determined, and the site is selected. This
involves examination of the historical or pre-disturbance
conditions, degree of present alteration, present ecological
conditions, and other factors. Conceptual ecosystem
models are often used to help this process. The actual
strategy used for restoration depends on the goals and
objectives, as well as the condition of the landscape and
the site. The level of physical effort, cost, schedule, contingency plan (i.e., in case something goes wrong), and
engineering design are all part of project planning.
280
ESTUARINE HABITAT RESTORATION