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Regional Mitigation: A Means for Restoring
Forested Ecosystems in Florida
B.F. Birkitt1
UPPER CHIPOLA RIVER
REFORESTATION SITE
Florida environmental regulations require compensatOly
mitigation for the loss of wetlands or wetland functions
associated with construction activities. After many years of
requiring on-site mitigation, the state environmental agencies are
beginning to recognize the ecological value of establishing
larger, off-site regional mitigation areas, particularly to address
impacts of linear projects such as roads, pipelines, and
transmission lines.
A large natural gas pipeline company is proposing a 600 mile
expansion of their existing line in Florida resulting in wetland
impacts at crossings throughout the state. To minimize impacts,
the pipeline has been sited along existing roads, railroads, and
transmission line corridors. There will be no loss of wetlands.
Mitigation is required to compensate for the permanent loss
of forested canopy in wetland areas and associated wildlife
benefits resulting from maintenance of the pipeline right-of-way
and temporary impacts to high quality forested systems.
Options for mitigation include:
• enhancement or restoration of wetlands
• preseIVation of high quality wetland systems
• creation of new wetlands
Enhancement or restoration of wetlands is the state's preferred
option. PreseIVation is only acceptable under certain
circumstances, and wetland creation is often discouraged except
where site conditions are particularly favorable. For the pipeline
project, wetlands on publicly-owned lands were identified which
were in need of reforestation or hydrologic enhancement. A
small creation site is also proposed at one location Three
regional mitigation sites located in the areas of predominant
impact have currently been identified.
Documentation of the existing condition of the mitigation
sites is being provided to detennine the extent of environmental
benefit and mitigation "credit" allotted for each site. Mitigation
ratios of 2:1 to 4:1 are expected based on the limited impacts
of the project and the benefits provided at the mitigation sites.
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The Upper Chipola River site is a floodplain forest which
has been clearcut in areas by foresUy operations. Erosion and
increased runoff are occurring and natural regrowth is sparse.
To establish a more diverse Gommunity resembling the natural
system and to ensure rapid reestablishment of a productive
wetland, replanting of mixed hardwood species is proposed.
Approximately 300 acres will be revegetated. The site is owned
by the North Florida Water Management District and was
selected because of their interest in revegetation of the site and
its proximity to the pipeline route.
Vegetative transects were sampled at seven locations within
the site including a natural area to determine appropriate native
species for replanting. Two year bare root trees approximately
18-24 inches in height will be planted. Species include Florida
maple, red maple, green ash, sweetgum, yellow poplar, black
gum, various oaks and bald cypress.
HYDROLOGIC ENHANCEMENT SITES
The other two regional mitigation sites located at the
ApalachicolaIFlorida River and Steinhatchee River involve
hydrologic enhancement of existing wetland systems by
breaching logging roads which block natural flow. The proposed
sites are owned by the North Florida Water Management District
and the Suwanneee River Water Management District,
respectively.
APALACHICOLA/FLORIDA RIVER
ENHANCEMENT SITE
The Apalachicola/Florida River site consists of floodplain
swamp with numerous backwater sloughs. The most common
dominant species are Ogeechee tupelo and water tupelo; other
dominant tree species include bald cypress, water hickory, river
birch, planer tree, black gum, green ash, and sweetgum.
The old logging roads currently obstruct nonnal drainage
patterns. A head differential of as much a 3.83 feet from one
side of the road to the other has been measured in some areas.
Dames & Moore, Tallahassee, Florida, USA.
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Six of the old logging roads on the site will be breached by
culverts or low water crossings at 14 locations to restore or
enhance historic drainage patterns. Willows will be removed and
such areas will be planted with native tree species.
Approximately 450 acres of forested wetlands will be enhanced
at this site.
Water does not overtop the roads except following stonns in
excess of 10 and 25 year events and seasonal high water
fluctuations of the river. Effects on the wetland system include:
changes to the heIbaceous strata, limited regeneration of tree
species, and interference with the transport of detrital material
and movement of aquatic otganisms.
Hydrologic improvements proposed consist of installation of
low water crossings or wooden bridges at 25 locations in the
roadway network to reduce extended inundation periods and to
more closely approximate natural sheetflow conditions.
Approximately 930 acres of floodplain forest will enhanced by
the activities proposed.
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FUTURE OF REGIONAL MITIGATION
AND BANKING
Regional mitigation is particularly suited for linear projects
such as pipelines, roads, and transmission lines. It provides
increased environmental benefits over small on-site mitigation
efforts. The establishment of regional mitigation "banks" for
future projects provides opportunities for continued development
as well as significant environmental benefits.
In Florida, regional mitigation and mitigation "banking" are
being encouraged as a means of restoring or protecting large
ecosystems or wildlife habitat. Regional mitigation is becoming
the noon for linear projects and the state is currently drafting a
rule to regulate how mitigation banks are established and used.
Several latge wetland "banks" and wildlife "parks" have been
established in the state. Many more are expected once
regulations clearly authorizing the use of mitigation" banks" are
in place.
STEINHATCHEE SPRINGS
ENHANCEMENT SITE
Hydrologic enhancement is also 1>roposed at the Steinhatchee
Springs mitigation site. This site is a hydric hammock which is
managed by the Florida Game & Fresh Water Fish Commission
as a Wildlife Management Area. Dominant tree species include
bald cypress, red maple, sweetgum, water oak and laurel oak.
At many of the sites, Carolina willow has encroached in the
areas impounded by the roads. Runoff does not overtop the roads
except for stonns greater than 10 and 25 year events.
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