Restoration
Tools
Methods,
technology, materials and theories that can be used to restore functions to
wetlands
Tools:
Design
Ecological theory, including
landscape ecology
Control of hydrology
Engineering
Bio-engineering
Earth moving
Management of invasive species
Horticulture
Wildlife habitat structures
Other structures
Design
Matching each desired
ecological functions with a designed feature.
Example, sediment removal:
Slow water by directing it over
shallow floodplain.
Vegetate floodplain with dense
community of flexuous woody plants like willows.
Ecological
Theory
Disturbance (mowing, fire,
grazing)
Colonization
Succession (shading,
competition, dominance)
Productivity (organic material
production)
Competition and exclusion
Control? Ecological processes can be initiated, but
operate more-or-less independently.
Intervention in the form of
disturbance can be used to set back processes.
Example: planting quick-growing
deciduous trees to fill up ecological niche, shade out weedy grasses or shrubs,
and jump forward in the successional trajectory.
Hydrology
Water depth
Flood frequency
Flood duration
Flood season
Control?: direct
Examples: (raising water level)
To kill weedy emergents
Examples: (lowering water
level)
To encourage summer annuals
To revive over-flooded plants
To kill aquatic weeds
To kill trash fish
Example: Tule
Wetlands serve as storage
basins for excess runoff water.
Sites are on a rotation
schedule; some are drained every 5 to 15 years and used for agriculture.
Drawdown in flooded wetlands is
controlled to maximize the production of annuals whose seeds are eaten by
waterfowl.
Engineered
features
Levees or dams
Water control structures
(valves)
Floodways, spillways, rip-rap
Pumps
Conveyances (from detention
ponds)
Liners
Control? Some features (such as liners) are installed
prior to operation, and continue to exert passive control. Others, such as valves and gates, require
active control.
Example: Liners can be high-tech, such as large membrane
surfaces with heat-sealed seams. A more
economical liner might be constructed by spreading and compacting layer of
clayey soil.
Bio-engineered
features
Brush mats
Soft gabions
Fascines
Live cribbing
Brush layering
Live stakes, live poles
Geo-textiles
Control? As with most biological installations, they
are started on the desired trajectory, but little subsequent control is
available.
Example: Live material is often
used along river banks because of the availability of good live stake material
(usually willows), and because moisture conditions are often good for
establishment and survival of live stakes.
Earth
moving
To provide adequate drainage
Stream channels, temporary
cofferdams
Islands
Peninsulas, protection,
increased edge
Benches (sub-aqueous,
sub-aerial)
Precise grade for flooding
zones (PF, TF, PS, TS)
Features
Control? Initial control with earthwork is difficult
because precise grades are not possible in wet soils, soils may swell or erode
after flooding, and sedimentation may occur.
Example: Moving earth provides depressions for
storage, channels, dikes, islands, benches, and generally allows the design
contours of the site to be built.
Earth moving is required if a
wetland has been filled and is to be returned to appropriate elevations to
achieve wetland hydrology.
Management
of invasive species
Choosing a clean site
Keeping a site clean before
installation
Mechanical removal
Fire regimes
Herbicides
Excavation and burial
Control? An initially clean site is much easier to
control for invasive species if it is quickly planted and flooded. The dirtier the site, the more headaches in
controlling invasives.
Example: The UW Bothell site
was so infested with reed canarygrass that a foot and
a half of soil was excavated from 2/3 of the site, and the same depth of clean
fill was placed on the other 1/3 of the site.
Horticulture
Plant production
Plant material care and storage
Site analysis and preparation
Installation techniques
Vegetation maintenance
Monitoring
Replacement
Invasive
species plans
Watering
Control? Horticultural control is greatest when plants
are being produced and installed, and much diminished at a natural site without
water or protection against weather variability, herbivory,
flood damage, vandalism.
Example: At UW Bothell site, container plants were
bought off-site and stored until needed.
Live stakes from salvage material on site was rooted in the nursery.
Creation
of wildlife habitat structures
Birdhouses, duck boxes, bat
boxes
Brush and rock habitat
Watering stations
Isolated areas, islands, thick
brush
Stream features (pools,
riffles, logs, shading brush)
Large wood, medium wood for
invertebrates
Perches
Open water
Control? Initial control on installation. A number of manufactured wildlife structures
will require periodic replacement. Brushpiles may be renewed as a by-product of maintenance.
Example: Nests for bluebirds have been installed on
the
Construction
of other structures
Tree-throw depressions
Rootwads
Deflector logs in stream curves
Large woody debris
Control? Most of these features emulate
characteristics of more mature ecosystems, and so should not have to be replaced
as they will eventually occur naturally.
Example: At UW Bothell, two stream channels were
constructed; they were armored with logs and rootwads
at bends.
Large rootwads
were anchored into the ground away from channels and artificial windthrow depressions were excavated next to them.