Large Woody Debris
Functional wood in streams is called large woody debris (LWD) and usually includes
wood larger than four inches in diameter six feet in length. The preferred size
range falls between 18-36 inches in diameter and 12 - 32 feet in length. In
general, wood stocking in stream restoration is one functional log for every
channel width. In a typical watershed restoration project this would translate
to 100 - 400 pieces of large woody debris per mile of stream. Log jams and debris
complexes are vital for proper functioning of biological components within a
stream. The physical aspects of the river strongly influence the biological
components. Fallen trees alter the flow of stream current, which is important
not only for fish but also for all the other organisms that fish rely on for
forage.
LWD functions to:
- alter the stream flow to trap coarse sediment upstream of the LWD to create
bars or islands,
- modify stream flow to create pool habitat downstream of LWD,
- provide cover and shade for juvenile and adult salmonids,
- direct high-water flow to support hydraulic routing,
- trap and hold small organic materials (leaves, needles, carcasses, etc.),
- provide hydraulic roughness to the stream during high flow condition,
- provide habitat and perches for aquatic insects, amphibians, birds and
riparian mammals,
- provide structure and nutrients for microbiological organisms important
to the aquatic ecosystem
- provide habitat for aquatic and semi-aquatic plant communities by providing
crags and silt traps within the structure -provide a continuing flux of organic
carbon and decay products to a stream system.
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Life Watershed Society / All Rights Reserved / if you wish to use any info
for commercial or non commercial usage you must obtain permissions from The
Veins of Life Watershed Society
