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A GIS Analysis to Identify Future Study Site Locations in the Cedar River Municipal Watershed, WA. Jenna E. Forsyth Commissioned by Seattle Public Utilities, Seattle, WA. RESULTS I (1) New Site 1 Potential Area: 5,368,861 sq. feet New site 1 (Figure 5)
A GIS Analysis to Identify Future Study Site Locations in the Cedar River Municipal Watershed, WA
Jenna E. Forsyth
Commissioned by Seattle Public Utilities, Seattle, WA
A current study in the Cedar River Watershed near North Bend, WA investigates the effects of forest density and structure on snow accumulation. Cedar River Watershed is located approximately 34 miles east of Seattle off Interstate-90 (Figure 1). The watershed is approximately 3,946,330,736.44 sq. feet in area and provides drinking water for the 1.45 million residents of Seattle.
Table 2. Forest and topographic characteristics of current study sites.
Figure 1. Location of the Cedar River Municipal Watershed with current study sites, and meteorologic and hydrologic station information.
What is the effect of forest density and structure on snow accumulation in the watershed?
Forests can impact snow accumulation based on canopy density and forest type. Greater canopy density means that more of the snow will be caught or “intercepted” in the trees rather than falling to the ground. Much of this intercepted snow is sublimated and the water vapor returns to the air. In terms of forest type, coniferous forests tend to intercept more snow than deciduous forests due to branch geometry. Forest stand age may also affect snow accumulation because younger forests tend to be packed more tightly but may have smaller branches, whereas older forests are less dense but have bigger branches to intercept snow.
Figure 5. Potential areas and new site locations fitting all criteria for sites 1 and 2.
Table 1. Canopy density, forest age, and forest type positively or negatively affect snow accumulation.
Figure 3. a) Elevation ranges, b) slope ranges, c) aspect, and d) forest ages representative of the current study sites.
Figure 6. Potential areas and new site locations fitting all criteria for sites 1,2 (no change), and 3.
Figure 4. Potential site area greater than 100 feet but less than 1,000 feet from the road.
Figure 2. Cedar River Watershed current study locations.