GMSWORKS-3 Peace River Side Channel Restoration - BC Hydro

dewatering, but habitat complexity has decreased over time due to river processes like fine
sediment infilling and deposition.
5.1.2 Ephemeral Open Side Channels
These areas regularly dewater or partially dewater under the existing regulated flow regime.
The characteristics of these side channels differ from the adjacent mainstem channel in several
ways: 1) the upstream inlet contains no surface water except during the highest flows, 2) the
bed material reflects the long term effects of infilling, 3) surface water that is present is
subjected to elevated water temperatures in summer, and 4) bed‐fast ice can develop during
winter. Ephemeral side channels either support very low numbers of fish or no fish. These side
channels are used opportunistically when surface waters are available. Fish either vacate
habitats within these side channels when water flow decreases, or become stranded and
perish. When suitable water flows do occur these side channels have the potential to provide
good quality habitat, particularly for small‐sized fish (e.g., rearing) due to the abundance of
shallow water habitat and more benign water velocities.
5.1.3 Closed Side Channels
These areas do not dewater under the typical regulated flow regime. The characteristics of
these side channels differ dramatically from the adjacent mainstem channel: 1) the upstream
inlet is closed except during extreme flood flows, 2) the bed material primarily consists of fine
sediments, 3) water clarity is high, and 4) water velocity is very low. These closed side channels
support viable populations of unique fish assemblages and are used by other fish populations
opportunistically (e.g., bull trout in spring); these side channels also support emergent and
submergent aquatic vegetation. Major factors limiting the quality of habitat and fish use in
these unique side channels are long‐term infilling (some side channels formerly used by fish
have infilled within the last 20 years) and fluctuating water levels that prevent establishment of
emergent vegetation.
5.2 Overview Assessment
The satellite imagery was initially reviewed and areas where side channel loss had occurred
were identified. Areas of potential interest were then examined in stereo using 1:5,000 scale
colour aerial photographs flown on October 26, 2008. Additional photogrammetric analyses
were used to estimate the type and area of side channels in the Peace River. Orthophotos were
imported to ARCGIS and MOE “blueline” shapefiles indicating stream thalweg were imported
and bank lines were digitized. Distances from PCN were scaled to the start of side channels or
side channel complexes, and the side channels were classified based on the dominant side
channel type. Standardized naming and classification was implemented for this study to provide
reference (Table 3).
Based on the overview assessment, there is a range of side channels in the study reach: 21
open, 8 ephemeral, and 6 closed, totalling 87.4 km. Based on a mainstem length of 102.5 km,
the braiding index is 1.85. Note these represent side channel complexes from an assessment
based on the predominant channel type. The total side channel area was estimated at 506.4 ha,
Peace River Side Channel Restoration 12