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Wetlands

Freshwater Tidal Wetlands

Tidal spruce swamp, Blind Slough, Clatsop County

Tidal spruce swamp, Blind Slough, Clatsop County
(John A. Christy, Oregon Biodiversity Information Center)

Freshwater tidal wetlands occur in the intertidal zone along coastal rivers, upstream from the Estuarine system where salinity ranges from 0.5 ppt to 0 ppt. They extend along the edges of rivers and their tributaries to the head of tidal influence, which can be up to 20 miles inland along the shorter coastal river to 143 miles inland along the Columbia River. The tidal cycle is similar to that on the coast, but timing is delayed and the amplitude of tidal surge attenuates further upstream to about 3 feet at Portland and 1 foot near Bonneville Dam. Freshwater tidal wetlands can be herbaceous, shrubby, or forested, and like salt marshes are hydrated by meandering tidal creeks. Plant species diversity in these wetlands is extremely rich, and many of thousands of acres have been diked, drained, and farmed.

Freshwater Tidal Wetlands

Freshwater Tidal Wetlands

Habitat: Edges of tidal rivers and streams
Water regime: Tidal, regularly to irregularly flooded
Water chemistry: Fresh

Ecoregion*: BM = Blue Mountains, BR = Northern Basin and Range, CB = Columbia Basin, CR = Coast Range, EC = East Cascades, KM = Klamath Mountains, WC = West Cascades, WV = Willamette Valley  
Scientific & Common Name Global & State Rank Ecoregion*
wetland type image Carex lyngbyei Herbaceous Vegetation
Lyngby sedge freshwater marsh
G4S3 CR, WV
wetland type image Equisetum fluviatile Herbaceous Vegetation
Water horsetail
G4S3 CR, EC, WC
wetland type image Sagittaria latifolia Herbaceous Vegetation [Provisional]
Wapato
G3S2 WV
wetland type image Schoenoplectus (americanus, pungens) Tidal Herbaceous Vegetation [Provisional]
Bulrush (three-square bulrush, western bulrush) (freshwater tidal)
G4S3 CR, WV
wetland type image Sparganium angustifolium Herbaceous Vegetation
Narrowleaf bur-reed
G4S3 CR, WV
wetland type image Typha (latifolia, angustifolia) Western Herbaceous Vegetation
Cattail (broadleaf cattail, narrowleaf cattail)
G5S5 CR

Authored by John A. Christy, Wetlands Ecologist, (ORBIC) Oregon Biodiversity Information Center (2012)