Disturbed stream banks in many portions of Big River are infested with reed canary grass (Phalaris arundinacea) that has altered channel and floodplain interactions. Japanese knotweed (Polygonum cuspidatum) and Giant knotweed (Polygonum sachalinense) are rapidly colonizing portions of the lower mainstem. These non-native invasive plants are competing with native riparian plant colonization of stream banks and floodplains, which can alter floodplain and channel migration dynamics (e.g., floodplain roughness and sediment filtering efficiency; bank stability and erosion rates; and future LWD recruitment).
Below is a list of noxious weed inventories within the Lake Ozette Watershed.
Colonization of native and non-native vegetation along the lake shoreline may influence
sediment particle size distribution along the spawning beaches. Ritchie (2005) and
Herrera (2005, 2006) both found increases in shoreline vegetation during the last 50
years. Herrera (2005) determined that vegetation has substantially encroached along the
lake shoreline as a result of the lowering of both winter and summer lake levels following
large scale wood removal operations in the Ozette River. Vegetation colonization of the
spawning gravels can decrease wave energy in and around the spawning gravels, which
can result in increased fine sediment deposition. A positive feedback loop can develop
between vegetation colonization and sediment deposition: increased sediment improves
vegetation colonization, and increased vegetation further increases sediment deposition.
The dense root networks of vegetation submerged in the winter act as excellent filters for
trapping fine sediment and building up a soil layer over previous gravel bed surfaces.
Furthermore, vegetation colonization that blocks or limits wave energy and wave-driven
currents can negatively affect sockeye spawning in lake shore areas where sockeye are
dependent on wave-driven currents for egg oxygenation.
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