Methods, technology, materials and theories that can be used to restore functions to wetlands
Ecological theory, including
Control of hydrology
Management of invasive species
Wildlife habitat structures
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.
Disturbance (mowing, fire, grazing)
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.
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
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.
Levees or dams
Water control structures (valves)
Floodways, spillways, rip-rap
Conveyances (from detention ponds)
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.
Live stakes, live poles
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.
To provide adequate drainage
Stream channels, temporary cofferdams
Peninsulas, protection, increased edge
Benches (sub-aqueous, sub-aerial)
Precise grade for flooding zones (PF, TF, PS, TS)
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
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.
Plant material care and storage
Site analysis and preparation
Invasive species plans
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
Isolated areas, islands, thick brush
Stream features (pools, riffles, logs, shading brush)
Large wood, medium wood for invertebrates
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
Construction of other structures
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.