watervulnerability

Chugach National Forest Watershed Vulnerability Assessment, Alaska Region (R10)
reducing the risk of redd scour and creating additional high-quality fish habitat would help maintain and
improve the small salmon populations that are becoming re-established, and would help maintain the
recreational fisheries that draw people to Hope. Smaller scale work, such as adding more LWD to offchannel
rearing areas and secondary channels could provide some benefit since the past mining operations
removed the natural LWD and the riparian trees (Martin et al. 2010).
Resurrection Creek Watershed Summary
The Resurrection Creek watershed was chosen because it is more typical of the drier, colder Kenai
Peninsula climate. Given these conditions, and the relative lack of infrastructure in the watershed, the
predicted increases in temperature and the relatively small increase in precipitation are not expected to
have as great an effect as in other areas.
Management direction is also made simpler because of the existing plans for addressing wildfire, snow
avalanches, and watershed restoration. The actions that are already outlined in these plans appear to be the
same steps that should be taken to mitigate for climate change. Managers should review the plans in light
of the predicted changes – accounting for higher flows when reconstructing stream channels, for example
– but the basic direction and schedule of work appears to be what is needed.
DISCUSSION AND GENERAL GUIDELINES FOR MANAGERS
Given that most of the watersheds on the Chugach National Forest are essentially unaltered and are
functioning naturally, this assessment was limited to two specific watersheds where there has been some
development and where at least some hydrologic and climate data were available. The intent, then,
became not to identify which watersheds in the Forest were the most vulnerable, but rather to look at
these two watersheds and identify specific vulnerabilities and possible mitigation.
This assessment was limited in some ways, not because of the lack of predicted climate change data, but
because of the problems associated with drawing specific conclusions from the data. As mentioned
earlier, without data on lake and river levels in the Eyak Lake watershed, it was not possible to determine
the specific risk of floods, although existing conditions and climate predictions point to greater risks. The
predictions of the increased frequency of extreme events also make it difficult to determine risk.
Looking at the effects of climate change from a general viewpoint can be valuable, despite the
uncertainties. By examining specific watersheds and issues, land managers can determine actual on-theground
actions that can be taken to help mitigate the effects of climate change even if the specific degree
of risk is not known. The following sections discuss this approach, which was used for this assessment,
along with some shortcomings and lingering questions.
Climate Change Data Acquisition and Analysis
For Alaska, there is a considerable amount of predictive climate change data available online; the main
question is how to analyze and apply it to specific areas. It is relatively easy for a competent GIS user to
manipulate mean temperature and precipitation values, but determining how these changes might affect
flows and salmon habitat requires many additional levels of information. It may be easy to get caught up
in the GIS data, while losing sight of what it actually means on the ground. Thus, before delving too
deeply into data analysis, managers need to determine what they need and how they can use these results
in a practical manner.
One other type of analysis that was attempted was NetWeaver, a knowledge-based decision support
system using fuzzy logic. It can be used when data are not complete, and expert opinion or other means
294 Assessing the Vulnerability of Watersheds to Climate Change