Water Stewardship Information Sources

Citation Hogan, DL and Millard, TH. 1998. Gully assessment methods. In: Hogan, D.L., P.J. Tschaplinski, and S. Chatwin (Editors). B.C. Min. For., Res. Br., Victoria, B.C. Land Manage. Handb. No. 41.
Organization FLNRO
URL https://www.for.gov.bc.ca/hfd/pubs/docs/Lmh/Lmh41.htm
Abstract/Description or Keywords Large woody debris (LWD) is a fundamental
structural element in small coastal streams found
throughout the Pacific Northwest (see, for example,
Keller and Swanson 1979; Marston 1982; Hogan
1987; Robinson and Beschta 1990). The influence of
log jams on channel morphology, riparian areas, and
fish habitat, both in Carnation Creek and in streams
on the Queen Charlotte Islands, is reviewed by
Hogan et al. (this volume). In the early phases of
channel adjustment following jam formation, fish
habitat is degraded as spawning areas (riffles)riffles
are buried (upstream of the jam) or eroded (downstream
of the jam), rearing pools are infilled, and
egg incubation environments are smothered with
fine-textured sediments. Over the long term (on the
order of half a century), log jams deteriorate and
create complex, diverse stream channels and riparian
areas that become highly productive fish habitats.
Log jams are spatially prevalent in small coastal
streams. Considering longitudinal surveys that
included almost 44 km of channel in streams
throughout the Queen Charlotte Islands, Hogan
et al. (in prep.) found the median spacing of log
jams to be 2.85 and 2.30 bankfull widths (Wb) in
forested and logged streams, respectively. In
Carnation Creek, individual log jams determine
local channel morphology and control the pattern of
channel evolution, both upstream and downstream
of a jam (see Figure 5, Hogan et al., this volume).
Because of the importance of log jams, it is therefore
important that channel assessments in small coastal
streams, documenting changes in channel morphology
and associated impacts on fish habitat, use a
consistent and repeatable classification of log jams
and their related morphological features.
This paper presents just such a classification, one
that is field-based and can be used to assess the
spatial and temporal response of a stream channel to
disturbance. The objective of the classification is to
assess current channel conditions and to consider
the probable long-term temporal response of a
channel following the development of a log jam. The
classification is based on a description of log jams
and their individual characteristics, an inventory of
relevant field indicators of channel disturbance
associated with each jam, and the identification of the
stage of channel recovery following jam formation.
Information Type Article
Regional Watershed Coast Region
Sub-watershed if known
Aquifer #
Project status complete
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