Salem Tree Canopy Analysis

January 2002

Prepared by City of Salem's Natural Resources Section

• Introduction
• Methodology
• Results

Introduction

Functional urban ecosystems include a mix of tree species, sizes and ages, and possess enough soil to support tree growth and productivity. When urban trees are healthy, they provide communities with valuable ecosystem services that can be quantitatively measured. Studies show that trees provide environmental and social benefits directly related to restoring and maintaining natural cycles. Trees help reduce air pollution, slow stormwater runoff, conserve energy, and provide wildlife habitat.

American Forests, a nonprofit conservation organization, received a federal grant from the United States Forest Service to conduct a regional ecosystem analysis for the Portland metropolitan region in 2001. Using a combination of satellite data, field surveys, and Geographical Information Systems (GIS) technology, the region between Longview, Washington, and Eugene, Oregon, was evaluated to assess changes in the forest canopy from 1972 to the year 2000.

American Forests also provided Salem with the opportunity to obtain an analysis of the current tree canopy cover within the city's Urban Growth Boundary. During the summer of 2001, Salem purchased the following from American Forests:

High resolution satellite imagery (4 meter scale compared to 30 and 80 meter); An analysis of tree canopy cover within each of Salem’s twelve sub-basins; and, An analysis of the extent of canopy cover within 50' and 200' on each side of streams within the urban growth boundary.

Using sophisticated satellite imagery, American Forests mapped the tree canopy and then analyzed the environmental and economic benefits that the trees provide. Benefits such as stormwater runoff reduction, decreased air pollution, and an increase in carbon storage (which reduces greenhouse gasses), are all important parts of a healthy urban ecosystem. The canopy analysis will provide important inventory data for a tree preservation work program, as well as Endangered Species Act (ESA) information on watershed health and riparian corridors.

The report below summarizes the analysis of Salem’s forest canopy. Three areas of interest—the Urban Growth Boundary, Salem’s 12 sub-basins, and riparian corridors—are grouped together.

Results

The results below are divided into 3 sections:

1. Salem's Urban Growth Boundary
2. Salem's 12 sub-basins (watersheds)
3. Salem's riparian corridors (area that borders city streams)

1. Salem's Urban Growth Boundary

Salem's Urban Growth Boundary (UGB) is a line that surrounds the greater Salem area and marks the area where future growth is most likely to occur. The information below summarizes the economic and environmental benefits that trees provide within the entire UGB.

Click on the icons to see a map or UGB summary.

Figure 1 - Map of Salem watersheds

UGB benefits

2. Salem’s 12 sub-basins (watersheds)

Once land cover types were identified, American Forests estimated the ecological and economic benefits of each sub-basin. The results of Salem’s watershed analysis are summarized in the following figures and tables.

Watershed areas	Click on the colored figures below to see a digitally produced map of each watershed.	Click on the icons below to see the economic and environmental benefits trees provide in each separate watershed.
Figure 2 - Lower Claggett Watershed		Lower Claggett benefits
Figure 3 - Little Pudding Watershed		Little Pudding benefits
Figure 4 - Upper Claggett Watershed		Upper Claggett benefits
Figure 5 - Glenn/Gibson Watershed		Glenn/Gibson benefits
Figure 6 - East Bank Watershed		East Bank benefits
Figure 7 - West Bank Watershed		West Bank benefits
Figure 8 - Mill Creek Watershed		Mill Creek benefits
Figure 9 - Pringle Creek Watershed		Pringle Creek benefits
Figure 10 - Croisan Creek Watershed		Croisan Creek benefits
Figure 11 - Pettijohn Creek Watershed		Pettijohn Creek benefits
Figure 12 - Battle Creek Watershed		Battle Creek benefits
Figure 13 - Willamette Slough		Willamette Slough benefits

3. Salem Riparian Corridors

The Ikonos satellite imagery was analyzed to estimate the total percentage of tree cover along fifty perennial (year round flow) streams. Table 15 estimates the total canopy cover for fifty perennial streams based on a 50' and 200' riparian corridor.

Click here to view map .

Table 15 - Riparian Buffer (% Tree Cover) Tree Cover (m2) Other (m2) Total Cover (m2) % Tree Cover 50 ' Buffer 2,171,188 3,780,768 5,952,256 36.5% 200' Buffer 5,736,720 14,414,480 20,154,200 28.5%

Land cover compositions were also modeled to estimate the ecological and economic benefits of Salem’s Riparian Corridors. The results, calculated for 50' and 200' buffers are summarized in the following two tables.

For questions or comments about this report contact City of Salem Community Development at 503-588-6173.