watervulnerability

Sawtooth National Forest Watershed Vulnerability Assessment, Intermountain Region (R4)
controlled by shallow groundwater flow convergence. Also included are landforms with slow soil mass
movements with deep earth-flows and rotational slumps, snow avalanche and rock fall areas (Figure 3).
Figure 2. Subwatershed vulnerability within the Upper
Salmon subbasin on the Sawtooth NRA. Red areas have
high risk, yellow have moderate risk and green have
low risk of surface erosion.
WATERSHED CONDITION
Watershed condition was determined using the "Matrix of Pathways and Indicators" and Bayesian belief
networks. The "Matrix of Pathways and Indicators" has been a consultation requirement for species listed
under the Endangered Species Act since the late 1990’s. Baseline information was already organized and
summarized by the matrix according to important environmental parameters for each subwatershed within
the Upper Salmon subbasin within Sawtooth NRA. This matrix was divided into six overall pathways:
-- Water Quality -- Channel Condition and Dynamics
-- Habitat Access -- Flow/Hydrology
-- Habitat Elements -- Watershed Conditions
Each of the above pathways is further broken down into watershed condition indicators (WCIs). WCIs are
described in terms of functionality (Appropriate {FA}, At Risk {FR}, and At Unacceptable Risk {FUR}).
The Functioning Appropriately column represents the desired condition to strive toward for each
particular WCI. The current condition of each WCI is represented as falling within its respective
functionality class (Figure 5). The units of measure for WCIs are generally reported in one of two ways:
(1) quantitative metrics that have associated numeric values (e.g., “large woody debris: > 20 pieces per
mile”); or (2) qualitative descriptions based on field reviews, professional judgment, etc. (e.g., “physical
barriers: man-made barriers present”). The suite of relevant WCIs, considered together, encompasses the
environmental baseline or current condition for the subwatershed and associated aquatic resources.
Bayesian belief networks (Lee and Rieman, 1997) were used to evaluate relative differences in predicted
physical baseline outcomes. They are appealing because their basic structure (a box-and-arrow diagram
161 Assessing the Vulnerability of Watersheds to Climate Change
Figure 3. Landslide-prone terrain within the Upper
Salmon sub-basin on the Sawtooth NRA. Red areas have
high risk, yellow have moderate risk, and green have low
risk of landslides