Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

characterized by emergent aquatic plants and species that thrive on close proximity to
water, such as willows. This vegetation maintains a healthy river system by reducing
erosion, stabilizing main channels, and providing shade. Leaf litter that enters the river
becomes an important source of nutrients for invertebrates (Bisson and Bilby 2001).
Riparian zones are also the major source of large woody debris (LWD). When trees fall
and enter the water, they become an important part of the ecosystem. The LWD alters
the flow, creating the pools of slower moving water preferred by salmon (Bilby, Fransen
et al. 2001). While not necessary for pool formation, LWD is associated with around
80% of pools in northern California, Washington, and the Idaho pan-handle (Bilby and
Bisson 2001).
Bilby and Bisson (2001) discuss several studies that associate increased LWD with
increased pools, and both pools and LWD with salmonid productivity. Their review also
includes documented decreases in salmonid productivity following the removal of LWD.
Other benefits of LWD include deeper pools, increased sediment retention, and channel
stabilization.
Floodplains are relatively flat areas adjacent to larger streams and rivers. They allow for
the lateral movement of the main channel and provide storage for floodwaters during
periods of high flow. Water stored in the floodplain is later released during periods of
low flow. This process ensures adequate flows for salmonids during the summer months,
and reduces the possibility of high-energy flood events destroying salmonid redds (Smith
2005).
Periodic flooding of these areas creates habitat used by salmonids. Storms also wash
sediment and LWD into the main stem river, often resulting in blockages. These
blockages may force the water to take an alternate path and result in the formation of side
channels and sloughs (Benda, Miller et al. 2001). Side channels and sloughs are
important spawning and rearing habitat for salmonids. The degree to which these offchannel
habitats are linked to the main channel via surface water connections is referred
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