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Shasta Trinity National Forest Watershed Vulnerability Assessment, Pacific Southwest Region (R5)<br />

to “high” as a 5. The process is repeated, merging this new combined data set with the sensitivity ranking.<br />

This is done to produce an overall score of vulnerability that includes values, stressors, and sensitivity.<br />

Subbasins<br />

Drying<br />

Lake<br />

Density<br />

Rank<br />

Spring<br />

Density<br />

Rank<br />

Aquatic Features Susceptible to Loss from Drying<br />

Values at Risk Exposure<br />

Sum of<br />

Values<br />

Weighted<br />

Value<br />

(Sum-<br />

Min/Max-<br />

Min) 1<br />

Value<br />

Score<br />

Matrix<br />

Value<br />

Score =<br />

Value<br />

x 10<br />

NetMap<br />

Thermal<br />

Exposure<br />

Rank<br />

2030 A2<br />

Global<br />

Climate<br />

Model<br />

Rank<br />

201 Assessing the Vulnerability of Watersheds to Climate Change<br />

Sum of<br />

Exposure<br />

Weighted<br />

Exposure<br />

(Sum-Min<br />

/Max-Min)<br />

Exposure<br />

Score<br />

Combined<br />

Value &<br />

Exposure<br />

Cottonwood 1 2 3 0.1 1 10 1 1 2 0.3 2 1<br />

Cow 4 5 9 0.9 5 50 1 1 0.0 1 3<br />

Lower Pit<br />

River 3 2 5 0.4<br />

2 20<br />

5 5 10 1.0 5 4<br />

McCloud 1 4 5 0.4 2 20 4 5 9 0.9 5 4<br />

Sacramento<br />

Headwaters 2 5 7 0.6<br />

4 40<br />

2 4 6 0.5 3 4<br />

Sacramento/<br />

Clear 4 1 5 0.4<br />

2 20<br />

1 5 6 0.5 3 2<br />

Shasta 5 5 10 1.0 5 50 4 4 0.8 4 5<br />

South Fork<br />

Trinity River 2 3 5 0.4<br />

2 20<br />

3 3 6 0.5 3 2<br />

Trinity 3 3 6 0.5 3 30 2 4 6 0.5 3 3<br />

Table 3. Combining multiple attributes into final scores (sample table)<br />

High Exposure Low<br />

Rank 5 4 3 2 1 Rank<br />

High 50 H H H MH M 50 High<br />

40 H H MH M ML 40<br />

30 MH MH M ML ML 30<br />

20 MH M ML L L 20<br />

Low 10 M ML L L L 10 Low<br />

Rank 5 4 3 2 1 Rank<br />

High Exposure Low<br />

Values<br />

Figure 17. Example of matrix used to combine resource and sensitivity (stressor) ratings. Results shown in pink<br />

received overall rating of “5”; those in light blue received a rating of “1”.<br />

Value<br />

Exposure<br />

Score 2<br />

It is important to note that this very simplistic model has many limitations. Other factors and more refined<br />

datasets could be employed to improve this model. The results presented are a first cut at identifying and<br />

analyzing factors that can be considered in evaluating watershed vulnerability to climate change.<br />

1 This calculation is based on the weighted average approach used in the Watershed Vulnerability Assessment.<br />

Technical Guide USDA 2011. ( 5= >0.8, 4=0.6 to 0.8, 3= 0.4 to 0.6, 2=0.2 to 0.4 and 1 =

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