watervulnerability

Chugach National Forest Watershed Vulnerability Assessment, Alaska Region (R10)
change are unlikely to decrease the success rate of salmonid egg incubation by the mechanism of increased
channel bed scour.
Thus, salmon spawning in the watershed may be less sensitive to scour even with the predicted increases
in flows, but this depends on maintaining floodplain connectivity. While it may seem appealing to elevate
the road bed of Power Creek Road so it is not subjected to flooding, this would constrict flows and
possibly make downstream spawning areas more susceptible to scour.
Aquatic Vegetation
While increased atmospheric carbon dioxide levels and a longer growing season are generally expected to
increase plant growth in Alaska (Haufler et al. 2010), site specific factors and individual species
responses make it difficult to predict the overall effect in wetland communities (Poff et al. 2002). Eyak
Lake already has large areas covered by aquatic plants, including various species of Potamogeton and the
non-native Elodea canadensis. If these species respond positively to climate changes, there may be
adverse effects to fish habitat.
One potential effect is that increased amounts of vegetation could lead to greater biological oxygen
demand under the winter ice when the plants die and decay. In areas where there are insufficient
streamflows entering the lake, localized anoxic zones could develop. This risk could be reduced if warmer
temperatures keep the lake surface ice-free for a greater part of the winter.
Eyak Lake Watershed Management Recommendations
The most important part of these climate change analyses should be determining what can and cannot be
done, or at least what should or should not be done.
Most of the current problems, stressors, and potential risks for the Eyak Lake watershed are outside of
National Forest land or are issues not managed by the Forest Service. There are, however, some actions
that can be taken either unilaterally by the Forest Service or in conjunction with cooperating agencies and
organizations. For the values identified for the Eyak Lake watershed, protecting the salmon stocks and
adopting measures to mitigate the predicted increase in flooding are the primary concerns.
Forest Service Management
The current Forest Plan manages most of the upper watershed as a “primitive” area, while other areas
have restrictive covenants that were established when the land was purchased from a local Native Alaskan
corporation. The area is not available for timber harvest, and while mineral development is conditional,
there are no active claims and no known mineral resources. There are no Forest Service roads. No offroad
vehicle use is permitted. Thus, management actions are limited, and with the relatively pristine state
of the National Forest land, there may not be much that can be done to improve conditions in preparation
for climate change.
There have been suggestions that large woody debris (LWD) could be added to streams to moderate flows
or provide refugia for juvenile fish, which could buffer the effects of predicted high flows or floods. This
can be useful where natural sources of LWD have been removed or in highly disturbed areas (Bair et al.
2002). However, Bakke (2008) points out that areas affected by climate change are likely to be unstable
and any structures or stream engineering will have to be carefully designed to accommodate change.
Redundant structures are recommended in anticipation that many structures may fail or may not have the
intended effect.
284 Assessing the Vulnerability of Watersheds to Climate Change