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Chugach National Forest Watershed Vulnerability Assessment, Alaska Region (R10) Historically, wildfires have been infrequent and of low intensity in the Resurrection Creek watershed, but predicted increased temperatures and higher evapotranspiration rates may dry fuels and increase the number of hazardous fire days on the peninsula as a whole (Haufler et al. 2010). Earlier snowmelt dates could also extend the period during which grasses and other dead vegetation can dry and provide flammable material, before the spring green-up, thus extending the fire season (Ecology and Environment Inc. 2006). Hydrologic/Geomorphic Risks The predicted annual increase in precipitation is relatively small at 2 to 3 inches, so unlike rainier areas of the Chugach National Forest, flooding may not be seen as a great concern. High initial infiltration rates also reduce the risk (Kalli and Blanchet 2001). An increased risk of floods from rain-on-snow events may not be likely. Hamlet and Lettenmaier (2007) state that cold systems where snow processes dominate the hydrologic cycle may be less prone to flooding. Even though winter temperatures are expected to increase by 4 °C, mean temperatures at sea level are still predicted to be below freezing. The usual rain-on-snow events in the fall and spring may occur, but not throughout the winter, as they would in a warmer area. The town of Hope and the infrastructure in the Resurrection Creek valley are unlikely to be affected by floods. Most of the town straddles a low ridge between two watersheds. The town’s buildings are set on higher areas away from where the creek enters the ocean. The buildings, roads, and the airstrip in the valley are also on relatively high ground. There are only 20 developed parcels within the 100-yr floodplain (Kenai Peninsula Borough 2011). Despite frequent extreme weather in recent years, which has caused flooding in other areas of the Kenai Peninsula, no flood damage was reported for the Hope area (Kenai Peninsula Borough 2011). A later freeze date and earlier spring melt would change flow timing, however. The current peak discharge is in mid-June and would be expected to occur earlier. Reduced flows from July to September could be partially offset by increases in precipitation ranging roughly from one-half to one inch of rain per month. Also, given the high mean elevation of the watershed and the predicted increase in winter precipitation, there could be an increased snowpack at the higher elevations that would last longer into the summer. In warmer, rainier areas, erosion and sediment transport are expected to increase because of higher precipitation, rain on snow events, increased freeze/thaw cycles, avalanches, and exposed glacial moraines. The Resurrection Creek watershed, however, should be less exposed to these factors because of the low predicted increases in precipitation, low winter temperatures even with warming, and limited area of glaciers and icefields. Thus, the risk of increased filling and shifting of channels is not expected to be much higher than existing levels. Biological Risks Although the Kenai Peninsula is a relatively dry area for Alaska, low flows are not expected to be a major concern for fish. As discussed earlier, the changes in the hydrograph may be offset by increases in summer precipitation and an increased snowpack at high elevations. The lowest flows are in the winter, and given the warmer temperatures, precipitation falling as rain in early winter could increase flows then. The risk is also lessened by the fact that most fish habitat is in the low gradient channels near the valley floor, rather than small headwater streams. These lower elevation streams drain larger areas and are less likely to dry up. Higher precipitation is not likely to increase the risk of salmon redds and juveniles being scoured by high flows, given the moderate increases. This risk is probably more dependent on other factors, such as the 292 Assessing the Vulnerability of Watersheds to Climate Change
Chugach National Forest Watershed Vulnerability Assessment, Alaska Region (R10) channelization of the stream from mining activity. The recent restoration work that lowered the stream gradient and restored floodplain connectivity should provide some help to reduce the risk of redd scour, however, there has been no monitoring of this yet. The use of lower-velocity side channels as spawning areas by coho, chum, and pink salmon also reduces the risk of redd scour. The issues related to warmer water temperatures that were discussed in the Eyak Lake watershed section also apply here. Resurrection Creek and its tributaries are currently cold enough that increased water temperatures will not be beyond optimal temperatures. However, unknown problems may be caused by faster egg development, increased metabolic rates, and the desynchronization of life-stage timing with other biological and physical conditions. The biggest risk for salmon is that their populations are small, except for pink salmon. A disastrous event or adverse conditions for several years could extirpate the less abundant species, particularly the sockeye salmon, which generally do not use systems without large lakes. A large fire could be such an event if it removes vegetation and leads to significant erosion, sedimentation, or channel changes. As discussed, the fish habitat in the system has been highly disrupted already. More restoration work is planned, but until the salmon species become more established, they will remain susceptible. Resurrection Creek Management Recommendations There has already been extensive planning for the Kenai Peninsula area, including the Resurrection Creek watershed. The Kenai Peninsula Borough, in cooperation with other partners, has developed the All- Hazard Mitigation Plan that includes strategies for addressing eight hazards, including wildfire, floods, weather, and avalanches. There are detailed action plans, mitigation measures, hazardous site evaluations, and ideas for future actions and cooperative efforts. Thus, there is little need for land managers to reinvent the wheel; there might simply be a need to continue the ongoing work while keeping the implications of climate change in mind. A primary concern for land managers is public safety, and there is an immediate risk of wildfire near the town of Hope. The wildfire section of the Mitigation Plan includes specific goals for fuel reduction, controlled burns, fire breaks, and public education. The Chugach National Forest has completed its first five-year action program under this plan and is now working on strategies for the next five years. Actions in the Resurrection Creek watershed have included controlled burns, seeding areas with birch (in place of spruce, which is susceptible to beetle kill), and working with private landowners to make structures less vulnerable to fires. The Mitigation Plan also addresses the danger of snow avalanches, which increases with variable temperatures creating layers of wet and dry snow. Although mean winter temperatures are expected to remain below freezing in the Resurrection Creek watershed, the high degree of winter recreational use makes it an issue to be dealt with. The Forest Service currently operates the Chugach National Forest Avalanche Information Center, which provides recreationists with current snow conditions. The Forest is also hiring a meteorological technician to help with this program. This is another example of how existing programs can address future risks. The other main action that can be taken in the watershed is to continue with the stream restoration program. Although there are some conflicts between existing claims and the areas to be restored, returning the channels to a more natural condition will provide the best long-term protection from floods and for fish habitat. The costs are significant. The previous restoration project cost about $700,000 per mile, and simply removing the tailings piles to establish floodplain connectivity might cost $300,000 per mile. However, 293 Assessing the Vulnerability of Watersheds to Climate Change
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ASSESSSING THE VULNERABILITY OF WAT
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staff; the task group included repr
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Figure 2. Conceptual model for asse
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Figure 3. Density of springs and sm
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Using Historic Data One finding con
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NF (Region 8) relied on information
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level of uncertainty. Though there
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climate (Casola et al. 2005). Only
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sensitivity. Most were derived from
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The sensitivity evaluation typicall
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in exposure. The result of combinin
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highest priority for management act
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to information affected the assessm
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with and rely on in many resource d
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Pilot National Forest Reports Conte
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