Author
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Shields Jr, Fletcher |
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Submitted to: Temperate Wetland Restoration Workshop
Publication Type: Abstract Only Publication Acceptance Date: 12/1/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Pristine lowland river valleys are often dominated by temperate wetlands. The principal physical perturbations of these wetlands due to human activity may be classified as sedimentation, water level fluctuation, and dewatering. Loss of riverine wetlands due to sediment deposition is particularly severe along large, developed river corridors where construction of dams, river training works, and bank protection prevents formation of new off-channel and channel-margin wetlands by natural fluvial processes. Over a period of decades, existing wetlands are filled with sediments and converted to upland habitats or developed land uses. Deliberate filling of river shore wetlands and construction of bulkheads constitutes a special, extreme case of this type of perturbation. Riverine wetland structure is defined by the timing, frequency, and duration of flooding. Construction of impoundments that stabilize water levels is associated with conversion of temperate wetlands to open water or terrestrial habitats. Although the cumulative effect of numerous reservoir projects is significant, more extensive impacts may occur in the Great Lakes Basin if there is a significant long-term decline in lake levels due to climate change, consumptive use, or diversion. A worst-case scenario would involve lowered base level for lake tributaries with attendant channel incision and dewatering of wetlands and riparian zones. Channel incision can be especially deleterious to wetland and aquatic habitats. Riparian wetlands are sinks for suspended sediments and nutrients, but erosion triggered by channel incision can transform these areas into sources and destroy wetland habitats |
