HomeMy WebLinkAboutAgenda Packet - 2009-06-23 Special Revised 06/22/09
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LAKE OsCITY COUNCIL SPECIAL MEETING
iii
AGENDA
Tuesday, June 23, 2009
6:30 p.m.
OR EGOS
Council Chambers
2009 City Council City Hall
Jack Hoffman, Mayor 380 A Avenue
Donna Jordan, Council President
Roger Hennagin Also published on the internet at: ci.oswego.or.us
Kristin Johnson Contact: Robyn Christie, City Recorder
Mary Olson E-Mail: rhristie@ci.oswego.or.us
Sally Moncrieff Phone: 503-675-3984
Bill Tierney
The meeting location is accessible to persons with disabilities. To request accommodations,
please contact Public Affairs at 503-635-0236, 48 hours before the meeting.
1. CALL TO ORDER
2. ROLL CALL
3. PRESENTATION
3.1 Oregon National Guard Month Proclamation
4. COUNCIL BUSINESS
4.1 Resolution 09-42, declaring the City of Lake Oswego's intent to
vacate Patton Street between McVey Avenue and South Shore
Boulevard, setting a date for a public hearing (July 21, 2009), and
repealing Resolution 09-37
4.2 City Centennial Budget
5. STUDY SESSION
5.1 State of the Urban Forest Report
5.2 Sensitive Lands Program Update
6. ADJOURNMENT
Watch this meeting live on Channel 23 or rebroadcast on Channel 28:
Friday, 7:00 p.m. Sunday, 7:00 a.m.
Saturday, 3:00 p.m. Wednesday, 2:30 a.m.
3 1
THEODORE R. KULONGOSKI ■
*AI*
Governor
a . . t; 6-23-0
■
•
June 16, 2009
Mayors & City Councilors:
Governor Kulongoski has proclaimed July 2009 as the Oregon National Guard month.
There is a copy of the document enclosed. Governor Kulongoski hopes that your and your
community leadership will join him in honoring the sacrifice and service of all Oregon National
Guard troops and their families.
As you know, 2009 is an important year for the Oregon National Guard. This May over
2,500 men and women from the 41st Brigade Combat Team were mobilized for duties in Iraq.
This is the largest single mobilization of National Guard troops since World War II. And it—
along with previous mobilizations of Guard troops deployed for service abroad since the wars in
Afghanistan and Iraq began bring the total number to over 10,000 mobilizations.
It will also highlight the importance of community support for veterans. Although it is
often overlooked, Oregon has over 350,000 veterans (according to the U.S. Census) living in
neighborhoods spanning our state. We have veterans from conflicts spanning the past seven
decades—and veterans of every era require and deserve our assistance, help, and love.
This July, we can make time to come together and celebrate service to community and to
country. Find a way to reach out to the guard families living in your community—people that
may need help but not know how to ask.
Sometimes proclamations are merely words upon a page: I hope that this proclamation is
something far more—-a trumpet sounding the call to service—an opportunity to forge stronger
ties between those that wear the uniform on our behalf, the families that support them, and the
communities that care.
I want to publicly thank Mayor Hoffman from Lake Oswego for this proposal. His
leadership on this issue is the beginning of a statewide awareness effort that will bring people
together. Even though logistics prevented a single document with signatures from every
community, passing this proclamation will form an impressive patchwork quilt of support.
Please take time to consider this opportunity. Thank you for your consideration on this
matter. If you have any questions or would like additional information, call me at 503.949.6378
and/or email me at paul.evansga state.or.us.
Sincerely,
Paul L. Evans
Policy Advisor for Military and Veterans' Affairs
1
S TAT E. C.)f'' (.2.)REGON
PROCLAMATION
OFFICE OF -I 1-1 t: (:i:C,)VERNOR
WHEREAS: -The members of the Ort.,-.,-krigon.National Cium-d play an essential role in safeguarding the rights and
freedoms of Americans and unceasingly provide a Vital public service to Oregon citizens; and
WH„EREAS: The Oregon National Guard has consistently demonstrated its value to our state and our:nation-
,
and
WHEREAS: Our-mil.itary personnel face urgent and perilous duties associ.ated with their National Guard
responsibilities;and
WHEREAS: The families and loved ones of our mi.litary personnel face unique and challenging:obstach,-s
throughout each deployment cycle; and.
NVHEREAS: The :families and IoNscd. ones of our milita.ry personnel thee un.ique and challenging obstacik,--s
throughout each deployment cycle;and.
WHERE:A.:S: 2700 members of the 41 Infantry Brigade Combat Team of the Oregon National Guard will be
deployed Overseas for eleven months: and
WHEREAS: Oregon. Air and Army National Guard,troops have.fulfilled over I 0.000 individual mobilizations
in support of ongoing military operations in Afghanistan. Iraq,and throughout the.world. '
NOW,
THEREFORE: .I,Theodore R. .K...1.1.tongoski., Governor of the State of Qreo-on, hereby proclaim July 2009 to be
OREGON NATIONAL GUARD MONTH
In Oregon and encourage all Oregonians to join in this observance.
IN WITNESS NWHEREDIF„ 1 hereunto set my hand and:cause
the Great Seal of the State of Oregon:to he:affixed* Done„at-the
Capitol. in the C it of Salem::in the State of Oregon on this day„
June I 7. 2009.
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Katie Brown.'Secretary of.State
3
RESOLUTION 09-42
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF LAKE OSWEGO
DECLARING THE INTENT OF THE CITY COUNCIL TO VACATE PATTON STREET
BETWEEN MCVEY AVENUE AND SOUTH SHORE BOULEVARD, SETTING A DATE
FOR A PUBLIC HEARING, AND REPEALING RESOLUTION 09-37
WHEREAS, on the 16th day of June 2009, the City Council passed Resolution 09-37, declaring
its intent to vacate Patton Street between McVey Avenue and South Shore Boulevard, and
setting a date for a public hearing on the matter on July 7, 2009, and
WHEREAS, the City Council has subsequently decided not to meet on July 7, 2009, which
necessitates setting a new date for a public hearing on the matter of said vacation, now therefore
BE IT RESOLVED by the City Council of the City of Lake Oswego that:
Section 1. Resolution 09-37 is hereby repealed, and
Section 2. A public hearing shall for the proposal to vacate Patton Street between McVey
Avenue and South Shore Boulevard shall be held on the 21st day of July, 2009, at 6:30
p.m. in the City Council Chambers, located at 380 A Avenue in Lake Oswego.
Section 3. The City Recorder shall give notice of the proposed vacation and public hearing
required by ORS 271.110 by publishing a notice in the official city newspaper once each week
for two (2) consecutive weeks.
Section 4. The City Recorder, within five days after the first day of publication of the notice,
shall cause to be posted at or near each end of the street proposed to be vacated, a copy of the
notice which shall be headed"NOTICE OF STREET VACATION" and said notice shall be
posted in at least two (2) conspicuous places in the proposed vacation area. The posting and the
first day of publication of such notice shall not be less than 14 days before the hearing.
Considered and adopted at the regular Council meeting of the City of Lake Oswego held this
23rd day June, 2009.
Resolution 09-42
Page 1 of 2
AYES:
NOES:
ABSTAIN:
ABSENT:
Jack D. Hoffman
Mayor
ATTEST:
Robyn Christie
City Recorder
APPROVED AS TO FORM:
City Attorney's Office
Resolution 09-42
Page 2 of 2
4. 1
c° 6-23-0
r CITY OF LAKE OSWEGO
•
a
COUNCIL REPORT
OR EGOS
TO: Jack D. Hoffman, Mayor
Members of the City Council
Alex D. McIntyre, City Manager
FROM: Jonna Papaefthimiou, AICP, Natural Resources Planner
SUBJECT: State of the Forest Report
DATE: June 9, 2009
ACTION
No action is required. This memo introduces the City's first State of the Forest Report,
an informational report on the condition of the City's trees.
INTRODUCTION/BACKGROUND
In February, 2008, the Council adopted its first Urban and Community Forestry Plan.
The Plan was intended to bring together policies, practices, and plans related to tree
management in the City. Its overarching goal was to foster an integrated and
cooperative approach to tree stewardship on public and private lands in the City.
The Plan incorporated input from the general public, a technical advisory board of both
City staff and outside experts, and the City's Natural Resources Advisory Board. The
plan outlined goals related to:
• Public education and voluntary stewardship;
• Overall forest health and size;
• Public tree maintenance;
• Control of invasive species;
• Policy integration across departments; and
• Adequate funding.
The plan directed the City to develop a State of the Forest Report, to enable to City to
identify tree maintenance needs and set realistic goals with respect to overall forest
health and size. The Report provides information about the health and extent of the
City's tree canopy, and the condition and stocking rate of street trees (trees / available
5
Council Report
06/09/2009
Page 2
planting spaces). It also provides a snapshot of the urban forest that can inform and
support public education efforts.
DISCUSSION
In preparing the State of the Forest Report, staff developed and utilized a street tree
inventory based on field studies of a sample of the City's street trees, and a City-wide
tree canopy cover analysis based on aerial photo interpretation.
1. Street Tree Inventory
The report calculates the value of benefits related to the City's street trees. These
benefits were calculated using Tree, a peer-reviewed software program developed by
the US Forest Service to assist cities in making accurate benefits estimations. This
software program accounts for regional and climatic variations and is adapted for use in
the Pacific Northwest. Some highlights include:
• The City has a street tree stocking rate (trees / available planting spaces) of 87%,
well above the 40-60% commonly found in this type of inventory;
• Nearly 80% of City street trees are in good condition;
• Less than 3% of street trees have conflict with pavement;
• Each street tree provides a net financial benefit (benefits — costs) of about $63 to the
City;
• Street trees make up 13% of the City's overall tree canopy cover; and
• English ivy is present on 35% of Lake Oswego street trees.
Based on the results of the canopy analysis, the 2009 State of the Forest Report
concludes that the City's management efforts should include efforts to reduce invasive
species, promote large-canopy and evergreen street trees, maintain the health of young
trees, and promote "right-tree-right-place" selection for new street trees.
2. Tree Canopy Analysis
The City's overall forest canopy was studied using infrared aerial photos. Metro
recently published a region-wide study of environmental indicators, including tree
canopy cover. This study enables the City to compare its overall tree canopy to other
cities in the region. Metro's study was necessarily less detailed, and resulted in
different (higher) estimated canopy cover for Lake Oswego. However, both Metro and
the City's studies indicate that Lake Oswego is a regional leader in overall urban forest
conservation. With a tree canopy cover of 44%, Lake Oswego is significantly higher
than the regional average (although still lower than the nearby jurisdictions of Durham
and Rivergrove).
6
Council Report
06/09/2009
Page 3
As a regional leader, the City can expect to reap the benefits of a healthy urban forest.
These benefits, discussed in detail in the report, include significant impacts to:
• increase property values;
• improve water quality;
• improve air quality; and
• reduce energy consumption in buildings.
As the earth grows warmer, other benefits of the urban forest, such as reducing the
urban heat island effect and sequestering carbon, will likely become increasingly
important. The City's investment in its tree canopy is one way in which the City has
also positioned itself as a resilient and forward-looking community.
The City has issued a press release summarizing the information in the State of the
Forest Report and staff is available for presentation to community groups.
ALTERNATIVES & FISCAL IMPACT
No action is required; no fiscal impacts are anticipated.
ATTACHMENTS
1. State of the Forest Report
Sustainability has been considered as part of this recommendation. As
w
Reviewed by:
Depart, ,crnt Dire tor
Alex D.\ c ntyre
City Manger
7
LAKE OswEGo's STATE OF THE
URBAN FOREST REPORT
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June 2009
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LAKE OSWEGO'S STATE OF THE URBAN FOREST REPORT
June 2009
Prepared by Lake Oswego Planning Division,
Urban and Community Forestry
PROJECT STAFF
Northwest Service Academy AmeriCorps
Lori Summers, Community Forestry Coordinator 2008-2009
Chelsea Smith, Community Forestry Coordinator 2007-2008
City of Lake Oswego
Alia Johnson, GIS Intern
TECHNICAL ADVISORS
City of Lake Oswego
Jonna Papaefthimiou,Natural Resource Planner
David Gilbey,Water Quality Program Coordinator
Natalie Strom,Natural Resources Coordinator,Parks and Recreation Department
David Odom,Associate Planner-Urban Forestry, Certified Arborist
Aulani Johnson,Natural Resources Technician,Parks and Recreation Department
Natural Resources Advisory Board
Morgan Holen,NRAB Chair, Certified Arborist and Tree Risk Assessor
REVIEWERS
City of Lake Oswego
Dennis Egner,Long-Range Planning Manager
Sidaro Sin, Senior Planner,Long Range Planning
Denise Frisbee,Planning and Building Services Department Director
Pam Peterson,Beautification Manager; Certified Arborist
Jim Sanders,Parks Maintenance Crew Leader; Certified Arborist
Bryn Knowles, Parks Maintenance
Natural Resources Advisory Board
Nancy Gronowski
Stephanie Wagner
Shawn Howard
Douglas Rich r°``""°SE City of Lake Oswego
Rishi Rajani Urban and Community Forestry
I 380 A Avenue
PO Box 369
Lake Oswego, OR 97034
10
TABLE OF CONTENTS
EXECUTIVE SUMMARY 1
Forest Condition 1
Resource Benefits 1
Management 2
INTRODUCTION 3
Background 3
Study Area 3
FUNCTIONS OF THE URBAN FOREST 5
Environmental 5
Habitat 6
Property Value 7
Social 8
METHODS 9
FOREST STRUCTURE FINDINGS 11
Overview 11
Tree Composition 11
Age Distribution 12
Importance Value 14
Health 15
Infrastructure Conflicts 17
Stocking Level 19
Tree Location 19
CANOPY COVER 21
ECONOMIC BENEFITS OF THE URBAN FOREST 27
MANAGEMENT IMPLICATIONS AND RECOMMENDATIONS 31
Ivy Removal 31
Maintain Existing Trees 32
Maintain Diversity 34
Right Tree in the Right Place 34
CONCLUSION 37
GLOSSARY 39
APPENDIX A A-1
Methods A-1
APPENDIX B B-1
Regional Canopy Coverages (Metro) B-1
Street Tree Population Summary B-2
11
TABLES AND FIGURES
TABLES
1. Impaired waterbodies under Clean Water Act 3o3(d) Section. 6
2. Breakdown of current tree size class into mature size potential expressed as percent 13
of total trees.
3. Condition of top 25 most abundant street tree species by percentage. 16
4. Sidewalk heave among street trees growing near sidewalks. 17
5. Distribution of street trees and planting spaces. 19
6. Land use of ROW trees and available planting spaces. 20
7. Total land area and canopy extent over various areas or zones. 23
8. Neighborhood canopy cover 25
9. Value of annual benefits provided by street trees. 27
io. Average annual benefits of top 25 most abundant street tree species in $/tree. 28
11. Total annual benefits, costs, and net benefits of street trees. 29
12. Replacement value of street trees by DBH class. 30
13. Replacement value for top 5 most valuable species in $. 30
B-1 Percent canopy cover for Metro regions in 2007. B-1
B-2 Complete population summary of street trees by functional type, species, and DBH B-2
class.
FIGURES
1. Species composition featuring top ten most abundant street tree species. 10
2. Percentage of street trees in each diameter class. 13
3. Importance values and percentage of total population for top 25 most abundant street 14
trees.
4. Percentage of major street tree health threats. 15
5. Conflict between street trees and overhead utility lines. 18
6. Number of sidewalk conflicts above 3/4 inch for the top io species causing upheaval. 18
7. Types of available planting spaces. 19
8. Location of planting spaces (empty or treed). 20
9. City-wide ground coverage. 21
io. Canopy cover over the (a) ROW and (b) paved surfaces. 22
11. Ground coverage on (a) public lands and (b) single family residential zoning. 23
12. Extracted ground cover in stream corridors using a (a) 5o ft. buffer and a (b) 1oo ft. 24
buffer.
12
More than half of the street trees are composed
EXECUTIVE SUMMARY of only ten species. The most abundant street tree
species in the City is bigleaf maple at 13% of the
Much of the character of the City of Lake street tree population, followed closely by
Oswego is defined by trees. Street trees beautify Douglas fir at 12%. These species are native to
the City and soften the built landscape. Trees in our region and well adapted to local
parks and natural areas provide shade and wildlife environmental conditions. However, both species
habitat. Trees in neighborhoods impart a sense of exceed the commonly held standard that no single
place and connection to the natural world. The species should represent more than 10% of the
total street tree population. An urban forest needs
urban forest as a whole adds to the livability and
more diversity than a naturally occurring forest to
desirability of the community. Trees are essential
to the urban ecosystem, cleaning our air, helping minimize disease or insect epidemics and expand
the availability of species well adapted to harsher
rainfall infiltrate, cooling buildings and streets,
and absorbing city noise. urban settings.
Management of the urban forest begins with Lake Oswego has too many small street trees and
understanding the structure and functions of the only half of the large trees recommended for an
"ideal" age distribution to maintain canopy cover
resource. This report provides quantitative
information about the size and condition of our over time. Nearly 80% of Lake Oswego's street
urban forest and the functions it serves. It trees are in good condition and 14% in fair
contains detailed data about the City's street tree condition. The most pressing threat to street trees
resource based on field surveys and information is the ubiquitous presence of English ivy,which is
about City-wide tree canopy cover derived from found on more than 35% of street trees. English
satellite imagery. ivy is an aggressive non-native species that
competes with trees for water and nutrients,
The information provided in this report is deprives tree bark of normal contact with air and
intended to help planners and managers prioritize microorganisms, increases susceptibility to
projects and allocate funding related to the windthrow, and causes detrimental health effects.
community's urban forest resource.
A total of 9% of street trees have limbs that
Forest Condition currently conflict with power lines. Only 2% of
street trees cause significant sidewalk damage, or
Based on photogrammetric analysis of 2007 aerial more than three-quarters of an inch of sidewalk
heave.
photos, the City-wide canopy cover for Lake
Oswego is 44.4%. Canopy cover on public lands
is estimated at 62.8%. Street trees represent 13% Resource Benefits
of the entire canopy. Extrapolated from a 5%
sampling of street segments in Lake Oswego, an Using algorithms developed by the U.S. Forest
estimated 40,327 trees line the City's streets. This Service for urban areas in the Pacific Northwest
yields a stocking rate of 87%, above the national climate zone, the estimated value of benefits
average. Street tree canopy covers 430 acres, or provided by Lake Oswego's street tree population
36.5% of the right-of-way (ROW). The canopy alone is nearly $3 million per year, or $74 per
cover over Lake Oswego's paved surfaces within street tree per year. The net annual benefits (after
the ROW is 32.3%, above the minimum 25% costs) provided by street trees averages about $67
cover recommended by U.S. Forest Service per tree and $74 per capita. More than $1.9
researchers. million in property resale value per year is due to
the mere presence of street trees. Other benefits
State of the Forest Report 1
13
include stormwater interception, energy should be seen as opportunities to increase the
conservation, CO2 sequestration, and air quality diversity of the urban forest and plant the right
improvement. trees in the right places so that they may become
long-term amenities to community.
The replacement value of Lake Oswego's street
tree population is over $129 million. The highest-
valued tree species of all inventoried species are
Douglas-fir, bigleaf maple, Oregon white oak, and
Western redcedar. Of the 602 inventoried trees
with the largest diameters, 80% consist of these
four high-valued species.
Management
Due to the high stocking level and relatively high
canopy cover, management should focus on
maintenance of existing trees and ivy removal.
Though tree planting is not an urgent concern,
available planting spaces exist and can be utilized.
There is a large potential for increasing street trees
on private property. Nearly 70% of right-of-way
planting space is in residential neighborhoods.
Planting new trees and planting mitigation trees
s S
♦ I
a „t
•
401
_
View of Mt.Hood from Lake Oswego.
2 State of the Forest Report
14
threats to the forest and makes management
INTRODUCTION recommendations based on the findings.
Background Study Area
In 2008, the City adopted its first Urban & The City of Lake Oswego, with a population of
Community Forestry Plan' to guide planners and 36,345, is located between the Willamette and
policy-makers towards protection, restoration and Tualatin Rivers. The City is 11.2 square miles,
improvement of the urban forest as a whole. One including the 405-acre (0.63 square mile) Oswego
of the measures called for in the Plan was a State Lake. Five hundred seventy-three acres (0.9
of the Urban Forest Report. This document is the square miles) are dedicated to parks and open
first State of the Urban Forest Report, which spaces. Since the 1970s, Lake Oswego has taken
analyzes the structure, function and value of the an active role in tree preservation and natural
City's street tree population and provides basic resource management. The adoption of the Tree
information about City-wide tree canopy cover. Code in 1971 is largely responsible for the
preservation of many trees that continue to
This study documents the current condition of represent the aesthetic of Lake Oswego today.
Lake Oswego's urban forest and provides baseline The City's commitment to the urban forest is also
data from which further management and evidenced by its designation as a Tree City USA
monitoring can evolve. It is a starting point for for the past 20 years.
managers and planners who wish to make
informed decisions about their urban forest The benefits of urban trees are numerous, but
often unrecognized or undervalued. Trees provide
resource. Comprehensive and ongoing
management of the entire urban forest is many environmental, social, and economic
benefits that are difficult to quantify. Predicting
necessary to maximize benefits and gain the
the functionality of trees is complex because
optimal level of return on investment.2
rather than providing a single tangible product,
As Lake Oswego continues to grow and urban trees provide a number of public goods and
experience infill development, sustaining a healthy environmental services. Also, most built
community forest is important to maintain urban infrastructure depreciates with age, but trees
ecosystems and community livability. Increasing increase in value as they mature. Ecological
demands on natural resources and watersheds economists have developed methods to capture
combined with decreasing natural areas puts a these benefits. Analysis and economic valuations
great strain on the natural environment. While the of the environmental and aesthetic functions of
built environment may be altered and improved in urban trees help us understand how to maximize
3
relatively short time frames, the natural benefits while reducing costs.
environment may take decades to grow and
develop. This report explores the benefits of the This study focused primarily on calculating the
urban forest and makes a case for increased environmental and property value benefits of
support of this valuable resource. It also outlines street trees, or trees within the right-of-way
(ROW), using a statistically valid sample inventory
in the field. The ROW is land designated to
' City of Lake Oswego. (2007).Lake Oswego urban and accommodate roads and public utility
community forestry plan.Lake Oswego,OR:Lake Oswego
Planning Division.
2 Wolf,K.L. (2004).What could we Lose?Economic values 3 Maco S.E.,and E.G.McPherson. (2003).A practical
of urban forest benefits.In:A.Kenny(Ed.)Proceedings of approach to assessing structure,function,and value of street
the 6th Canadian Urban Forest Conference. Ottawa, tree populations in small communities.Journal of Arboriculture
Ontario:Tree Canada Foundation. 29(2):84-97.
State of the Forest Report 3
15
infrastructure. It usually extends beyond the road Canopy cover in stream corridors, public land,
to include sidewalks and sometimes a few feet private land, ROW corridors, neighborhoods, and
beyond sidewalks. Lake Oswego's street trees watershed sub-basins was assessed.
represent 13% of the entire canopy. A study of
Portland's street trees found that street trees
represent 17.2% of the urban forest canopy.4 A
nation-wide estimate puts street trees at less than
10% of the total urban forest.' Though these
percentages may seem low, street trees are
important due to their location along impervious
transportation corridors where environmental
services are much needed.
Though street trees provide many benefits, their ,, r"
growing conditions are severe. Often cutouts are
too small for adequate root growth, roots are '
restricted by sidewalks and buildings, soil is highly I: .
'
compacted, and trees are topped or harshly
pruned due to conflict with overhead utility lines. ;,
Despite these harsh circumstances, street trees are ,.1. ;
in an ideal location to create the most benefits 0., .
and are the trees seen most by people. Though .4 .
such an analysis has not yet been conducted in ` *ice �,
Lake Oswego, the City of Portland found that :g b .'
their street trees provide greater net benefits than , ``'•'" ,4 ``�"
their park trees ($52 more per tree).6 Though , ti " b �,
trees in the ROW are considered public .- 4,.
improvements, their maintenance is the - ' ti
responsibility of adjacent property owners. Street r r' 11. ,',.
trees are in a unique location to be more directly .. . • ?;.
managed by the City due to jurisdiction in the or.! a '•`.ro.
ROW. This is an opportunity to set an example - .ti d - G- .'
.
for tree practices throughout the City. .
In addition to the field study of street trees, a �r�` _ 't'
studyof City-wide canopycover was conducted ` „11, `' , •,,,,�
tY g k 64 g
using advanced analysis of aerial photos. This ,_
information was used to determine the tree At F'
canopy cover in different areas around the City. .;: .
4 Poracsky,J.,and D.Banis. (2005).Street trees in the urban b
forest canopy:Portland, Oregon.Portland,OR:Center for Spatial
Analysis and Research,Geography Department,Portland
State University.
5 Moll,G.,and C.Kollin. (1993).A new way to see our city
forests.American Forests. 99(9-10):29-31.
6 City of Portland. (2004).Portland urban forestry management Heritage Trees(Coast redwoods)on Glenmorrie Dr.
plan.Portland,OR:Portland Parks and Recreation
Department.
4 State of the Forest Report
16
Heat is also a significant pollutant that trees help
FUNCTIONS OF THE to reduce. The Willamette River and many of its
tributaries, including Tryon Creek, exceed the
URBAN FOREST maximum water temperature standard for the
State of Oregon. Temperature standards were
designed to protect targeted fish species during
Environmental critical periods when they use rivers for spawning,
rearing, migration, or other life stages. The
The urban forest reduces stormwater runoff by Federal Clean Water Act requires that impaired
intercepting rainwater that would otherwise flow water quality be addressed. Remediation of the
across impermeable city surfaces directly into Willamette River is monitored using the Act's
streams or pipes that lead to streams. This is Total Maximum Daily Load (TMDL) provisions.'
perhaps the most valuable environmental service
provided by trees, since stormwater in Lake TMDLs are the amount of a particular pollutant,
Oswego does not go to a wastewater treatment including temperature, that a particular waterbody
facility and stormwater pollution is conveyed to can have without violating state water quality
streams with minimal filtration. Lake Oswego's standards. TMDLs for temperature and the
current street tree canopy has the potential to take resultant Water Quality Management Plans
up about 10% of the stormwater that falls in the typically set a goal of 85% canopy cover over
ROW, a significant benefit. streams. Maintaining high canopy cover in stream
corridors is essential for water quality. Several
Rain interception by trees improves groundwater water bodies in Lake Oswego are impaired
recharge, mitigates flooding, and slows the flow according the Clean Water Act's 303(d) Section
of water in streams. Reducing the amount and (Table 1).
speed of water flowing through streams during
precipitation events helps maintain healthy Trees reduce heat pollution in two ways. First,
streams and reduces erosion and the resultant tree canopy over impervious surfaces reduces
sediment loads in the surface water. Trees also pavement temperature. During a rainfall event,
provide direct erosion control by stabilizing soil thermal energy is transferred from impervious
with root systems and decreasing the impact of surfaces to stormwater runoff, causing the runoff
rain on bare soil with canopy cover. to become warmer. This high temperature runoff
can be harmful to coldwater habitat in receiving
-
waters. Second, canopy cover over streams
i4 reduces direct heat gain by streams from solar
radiation. The average canopy cover in Lake
Oswego's stream corridors using a 100 foot
buffer is 70.2% and 77.2% using a 50 foot buffer.
�,. According to Metro studies, Lake Oswego's
streamside canopy cover within 50 feet of streams
r'y a is about 15% above the regional average. 8
7 Rounds,S.A. (2007)..Temperature effects of point sources,
riparian shading,and dam operations on the Willamette
River,Oregon:U.S. Geological Survey Scientific
Investigations Report 2007-5185.
s Metro recently published a region-wide study of
1 i n t environmental indicators,including stream canopy cover.
The study was necessarily less detailed,and resulted in
Stormwater running into catch basin. different(higher) estimated canopy cover for Lake Oswego.
State of the Forest Report 5
17
Table 1. Impaired waterbodies under Clean Water Act 303(d)Section
Waterbody 303(d) List Impairment
Tualatin River phosphorus, bacteria, temperature, settleable volatile solids
Oswego Lake phosphorus
Willamette River bacteria, mercury, temperature,pH
Springbrook Creek bacteria,pH, total phosphorus
Tryon Creek temperature
Trees work to reduce atmospheric carbon dioxide monoxide, sulfur dioxide, and some particulate
through direct sequestration into tree biomass and matter from the air.12
through avoided carbon emissions. Carbon
accounts for about half the dry weight of most In an urban area, impervious asphalt surfaces
trees.' About 51,000 tons of carbon, valued at (roads,parking lots, sidewalks, and driveways) and
$342,550, are stored in Lake Oswego's street pervious residential lawns comprise a significant
trees. When planted strategically around buildings, portion of the land. Tree canopy mitigates the
trees provide shade in the summer and act as a urban heat island effect caused largely by
wind block in the winter, reducing the need for increased paved or built surfaces. Urban
air-conditioning and heating. As a direct result of impervious surfaces absorb and store thermal
tree shading, residents of the Willamette/Lower energy, particularly during warm summer months,
Columbia Region save about 138,000 tons of causing surface temperatures to rise. Along with
carbon emissions annually.10 Every street tree in direct shading, trees cool the air through
Lake Oswego yields $2.63 in energy savings (gas transpiration, where solar energy is diverted from
and electric combined) per year. Reducing energy heating urban surfaces and used to convert
use decreases emissions created during electric moisture from plants into water vapor. Cooler air
power production and natural gas use. To achieve temperatures also prevent ozone formation in two
long term atmospheric carbon dioxide reductions, ways. Shading asphalt and parked cars reduces
the urban forest must be sustained through hydrocarbon emissions from evaporated gasoline.
continual replacement of removed trees.11 Urban These emissions are a principal component in
trees also improve air quality by removing ozone formation.13 Secondly, higher air
pollutants such as nitrogen dioxide, ozone, carbon temperatures contribute to ozone formation,
which is lessened by the cooling effects of trees.
However,both local and regional research seem to support Habitat
the assertion that Lake Oswego's canopy cover is above the
regional average,though not the highest in the region. See Urban forests play an important role in providing
Hennings,Lori. (2009).State of the Watersheds 2008
Environmental Indicators.Portland,OR:Metro Regional wildlife habitat and serving as a link or corridor
Government.
9 Regional ecosystem analysis of the Willamette/Lower Columbia
region of Northwestern Oregon and Southwestern Washington State. 12 McPherson,E.G.,S.E.Maco,J.R.Simpson,P.J.Peper,Q.
(2001).Washington D.C.:American Forests. Xiao,A.M.VanDerZanden,and N.Bell. (2002). Western
to Regional ecosystem analysis of the Willamette/Lower Washington and Oregon Community Tree Guide:Benefits, Costs, and
Columbia region of Northwestern Oregon and Strategic Planning.Silverton,OR:International Society of
Southwestern Washington State. (2001).Washington D.C.: Arboriculture,Pacific Northwest Chapter.
American Forests. 13 Maco S.E.,and E.G.McPherson. (2002).Assessing
11 McPherson,E.G. (2007).Urban tree planting and canopy cover over streets and sidewalks in street tree
greenhouse gas reductions.Arborist News. 16:32-34. populations.Journal ofArboriculture 28(6):270-276.
6 State of the Forest Report
18
between larger patches of habitat.14 Expanding connectivity and overall ecosystem health.15
development drastically alters wildlife habitat by Habitat corridors in the City of Lake Oswego
fragmenting the landscape around urban areas serve to connect the Willamette river shoreline,
into smaller and more isolated tracts of forestland. Tryon Creek State Park, and undeveloped lands in
Fragmented habitat causes edge effects such as the Stafford triangle. Streams also serve as travel
change in microhabitat (usually causing dryer corridors and provide habitat for wildlife. Stream
conditions, more extreme temperature swings, corridors are often found in conjunction with
and more invasive vegetation) and an increase in riparian habitat and wetlands that provide habitat
predation. Urban forest corridors aid in wildlife for fish and amphibians.
movement and contribute to greater landscape
Dead or dying trees are another important and
4:3\ often overlooked component of an urban forest
ecosystem. Coarse woody debris is broken down
by fungi to provide soil nutrients and habitat for
birds, mammals, and insects. Dead trees and
downed wood act as breeding, nesting, and
hunting areas for a wide range of animals.
Retaining wildlife trees that are dead or dying in
urban areas is unpopular because they are often
considered unsightly and hazardous. However,
with proper precaution and placing, these trees
can be modified to become an asset for wildlife
habitat. Large dead trees deemed too tall and
unstable can be cut to a safe height and then left
to decay while providing valuable habitat,
primarily for birds. Trees that must be removed
can be cut into manageable pieces and left to
it-cyA,"*4.
decay on the ground or stuck back into the
ground like giant posts. Wildlife trees are not
,ems z' generally appropriate in the ROW, but very
a p° valuable in parks, stream corridors, natural areas
and other open spaces. The City's Tree Code
_. recognizes the importance of wildlife trees by
allowing the retention of dead trees in appropriate
r - r3 places.16 The Code also allows the City to approve
snag creation in open spaces and undeveloped
areas by topping a tree that would otherwise be
completely removed.
.. Property Value
The effect of urban trees on the appraised value
of residential and business properties is
Canopy provides habitat near Tryon Creek State Park.
15 Orlando,C. (2008). Wildlife habitat in urban areas.Salem,
14 Dunster,J.A. (1998).The role of arborists in providing OR: ODF Urban and Community Forestry Assistance
wildlife habitat and landscape linkages throughout the urban Program.
forest.Journal of Arboriculture 24(3):160-167. 16 LOC 55.02.042
State of the Forest Report 7
19
significant. Residential properties that have trees Many scientific studies show the correlation
are valued 3 to 10 percent higher than those between nature and physical health. The presence
without." A recent study of street tree value in of trees and other vegetation in urban areas
Portland found that surrounding trees add an encourages physical activity and exercise that
average of $7,020 to the price of a house. defers potential medical costs associated with
Neighborhood trees positively influence house increasingly sedentary lives.22 Simply having views
prices beyond the house they front, adding an of trees and vegetation improves the mood of
average total of $9,241 to the value of office workers and has beneficial effects on
surrounding houses.18 These values are capitalized hospitalized patients. A well-managed urban
by the municipality in annual property tax forest contributes to walkable neighborhoods and
revenues. Another study found that office pride in the shared community asset. The
buildings with verdant landscaping had rental presence of trees has even been shown to reduce
rates that were approximately 7% higher than the crime through two mechanisms.23 First, by
average rate.19 The total property value increase creating a walkable neighborhood with desirable
attributable to Lake Oswego's street trees is about socializing grounds, trees increase residents'
$1.9 million per year. activity outdoors, thus increasing informal
surveillance of the area. Crimes are less likely to
The economic returns of street trees in business be committed in well-used residential areas with
districts are many. Several studies showed that more people out and about. Second, well-
treed districts are judged to have a more favorable maintained naturescapes lessen the psychological
character, which increases both patronage and precursors to violence, such as mental fatigue and
willingness to pay. Consumers report that they are irritability. This relationship between crime and
willing to spend about 9 to 12 percent more for the environment extends to both property and
products in downtown shopping districts with violent crimes. One study found that the
trees than in those without.20 They are also willing incidence of vandalism was 90% on sites without
to pay more for parking, spend more time in the vegetation, compared to 10% on sites with
business district, travel farther to visit it, and plantings.24
return more frequently.
Social
Noise can be problematic in cities, and even
unhealthy. Plants aid in noise attenuation by
absorbing sound waves, especially the higher
frequencies that are most distressing to people.'
17 Wolf,K.L. (2004).What could we Lose?Economic values
of urban forest benefits.In:A.Kenny(Ed.)Proceedings of
the 6th Canadian Urban Forest Conference. Ottawa,
Ontario:Tree Canada Foundation. Washington and Oregon Community Tree Guide:Benefits, Costs, and
18 Donovan,G. (2008). The Value of Street Trees in Portland, Strategic Planning.Silverton,OR:International Society of
Oregon.Portland,OR:USDA Forest Service,PNW Research Arboriculture,Pacific Northwest Chapter.
Station. 22 Wolf,K.L. (2004).What could we Lose?Economic values
19 Laverne,R.J.,and K.Winson-Geideman. (2003).The of urban forest benefits.In:A.Kenny(Ed.)Proceedings of
influence of trees and landscaping on rental rates at office the 6th Canadian Urban Forest Conference. Ottawa,
buildings.Journal of Arboriculture 29(5):281-290. Ontario:Tree Canada Foundation.
20 Wolf,K.L. (2005).Business district streetscapes,trees, 23 Kuo,F.E.,and W.C.Sullivan. (2001).Environment and
and consumer response.Journal of Forestg 103(8):396-400. crime in the inner city:Does vegetation reduce crime?
21 McPherson,E.G.,S.E.Maco,J.R.Simpson,P.J.Peper,Q. Environment and Behavior 33:343-367.
Xiao,A.M.VanDerZanden,and N.Bell. (2002). Western 24 Ibid.
8 State of the Forest Report
20
METHODS
This study consisted of two parts: a street tree
inventory and a City-wide canopy analysis.
The street tree inventory was conducted over a
randomly generated sample of 5% (a statistically
valid sample) of the street segments in Lake
Oswego. The width and location of the ROW on
selected streets was determined for each street
using a combination of plat maps, "as-built"
diagrams, GIS-generated maps and field surveying
techniques.
Tree data was collected from July to November
2008, detailing attributes of all the street trees and
available planting spaces within the ROW along
selected street segments. Data was analyzed using
iTree's STRATUM software, a program created
specifically for street tree inventories. The U.S.
Forest Service, in collaboration with private and
non-profit organizations, developed the iTree
software suite, which includes several
scientifically-based computer programs that can
be used to quantify structure, function, value and
management needs of the urban forest resource.
The City-wide canopy analysis was conducted
using 2007 one-foot resolution aerial infrared
photos. The photos were classified into 5 land
cover classes including Forest, Herbaceous, Bare
Ground, Impervious, and Water. All further
analysis was performed using ArcGIS 9.3. Canopy
coverages over specific geographical areas or
zones in Lake Oswego were derived by extracting
the vegetation data with existing City data.
For more detail methods see Appendix.
State of the Forest Report 9
21
, }, ry l ,11E t . -, ',i • }M }L
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7 7
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-'404'.'%;e)r titiv,,,f42 , 1.,..,', ''' . ::-74,.j.. ii.' .:10-=•.;4%......24 1-.1
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ii
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.
J s _ G A "D S - R
Cottonwoods at Foothills Park provide habitat and riverbank stabiliation.
10 State of the Forest Report
22
(Pseudotsuga menr<iesia), both native trees to the
FOREST STRUCTURE region. These native trees produce many benefits
and are well adapted to our region. However,
FINDINGS while the dominance of native trees is valuable for
wildlife habitat and native ecology, the top two
species exceed the common management
Overview standard that no single species should represent
more than 10% of the total street tree
The information in this section was derived from population.25 Dominance by a few species makes
the street tree inventory data. Street trees in Lake the City's street tree resource more vulnerable to
Oswego are numerous and healthy. A total of species-specific diseases.
40,327 trees are estimated to line the City streets,
at an 87% stocking rate. More than 100 different Due to their large sizes at maturity Douglas-fir
tree species were identified during the inventory and bigleaf maple are now planted less often in
process. Though the street tree population is the ROW. As older trees die, these species will
structurally healthy, more than half of the trees decline in the population and are not likely to be
are composed of only ten species, leaving the replanted as heavily as they currently exist. A shift
majority of trees poorly represented (Figure 1). away from planting these trees would cause a
More than 75% of all street trees are 12 inches or large gap in their presence in the future as older
less in diameter. The most pressing threat to trees die off and are not replaced. Therefore,
street trees is the ubiquitous presence of English these trees should still be considered for use as
Ivy (Helix hedera). street trees where the location can accommodate
them.
• Bigleaf maple 13%
13% • Douglas-fir 12%
L Arborvitae 8%
0 12% ❑ Cherry species 6%
45/o
❑ Norway maple 3%
K` � ■ Red alder 3%
•Western redcedar 3%
PIAIP8% • Filbert 3%
6% ■ Red maple 2%
2% 3 2% 3% ° 3% 3%
/o ❑ English hawthorn 2%
■ Other species 45%
Figure 1. Species composition featuring top ten most abundant street tree species.
Tree Composition Another urban tree recommendation is that no
single genus makes up more than 12% of the
The streets of Lake Oswego are lined with a wide
variety of trees. The most abundant street tree 25 Maco S.E.,and E.G.McPherson. (2003).A practical
approach to assessing structure,function,and value of street
species in the City is bigleaf maple (Acer
tree populations in small communities.Journal of Arboriculture
macrophyllum), followed closely by Douglas-fir 29(2):84-97
State of the Forest Report 11
23
population.26 Maples exceed this standard, "1,',_!, ,;,.‘,..
constituting more than 18% of the population, f. "" „, . s .
,....
indicating that maples are too heavily relied on in ; t,
street tree planting. Though there is not a lack of - w 'a 4 "".
diversity in the number of trees found throughout r jik w 1 i 1 ;:;,,. ".
the City, the majority of them are under- �'`;:, :�, 4 ,r;i t {
represented. A diverse urban forest with balanced ,
species representation minimizes disease or insect . ,
epidemics and expands the availability of well- a ,
�adapted species. ti °,
z
The street tree population consists of three main .A _� f:..x ''
tree types; broadleaf deciduous, broadleaf - .
evergreen and coniferous evergreen. Broadleaf = '-={
deciduous trees compose nearly 62% of the $ z ,Q,� „ _; ` ` ,'
population, while coniferous evergreens make up - 4 „ , _L '` ;r ]7 ' '
about 31% and broadleaf evergreens 7%. rf 4 '$ 'Ins; t0 �,- �
Evergreens intercept rainfall and particulates year- -• _
of �., �" -
round. They also tend to have more Leaf Surface r .
Area (LSA) than similarly sized deciduous trees.27 Mature laceleaf maple(in foreground)will never reach DBH of mature
LSA is the measurement of area on one side of a Dog-fir(in background).
tree's leaves. The LSA is a good indicator of
species importance since greater surface area to approximate the age of street tree populations,
allows for more benefit production. In Lake using DBH may be misleading since smaller
Oswego, the mean annual precipitation is about stature trees are often deliberately planted in the
45 to 50 inches, falling mostly during the winter. ROW to avoid sidewalk and infrastructure
Thus, the presence of more evergreen trees could conflicts. Thus age distribution may be similar,
substantially increase stormwater interception. but not identical to the DBH class distribution.
Lake Oswego's street tree population has a high
Age Distribution percentage of trees measuring 12 inches or
smaller in DBH and a relatively small percentage
The easiest way to determine the age distribution of large trees (Figure 2). An uneven aged tree
of a tree population is by using the diameter at population containing trees at various stages of
breast height (DBH) measurement since trees maturity is desirable for managing maintenance
typically increase in size as they age. However, costs over time.28 While large mature trees
provide the most benefits,
DBH distribution is only an approximation of age age complexity ensures
distribution because different tree species reach that as senescent trees die they will be replaced by
maturity at various sizes and girths. When trying younger trees and canopy cover willo be
maintained. In an ideal DBH distribution, 40% of
trees should be less than 8 inches in diameter and
26 McPherson,E.G.,S.E.Maco,J.R.Simpson,P.J.Peper,Q. about 10% of trees more than 24 inches in
Xiao,A.M.VanDerZanden,and N.Bell. (2002). Western 29
Washington and Oregon Community Tree Guide:Benefits, Costs, and
diameter. According to this recommendation,
Strategic Planning.Silverton,OR:International Society of
Arboriculture,Pacific Northwest Chapter. 28 City of Portland. (2004).Portland urban forestry management
27 McPherson,E.G.,S.E.Maco,J.R.Simpson,P.J.Peper,Q. plan.Portland,OR:Portland Parks and Recreation
Xiao,A.M.VanDerZanden,and N.Bell. (2002). Western Department.
Washington and Oregon Community Tree Guide:Benefits, Costs, and 29 Maco S.E.,and E.G.McPherson. (2002).Assessing
Strategic Planning.Silverton,OR:International Society of canopy cover over streets and sidewalks in street tree
Arboriculture,Pacific Northwest Chapter. populations.Journal of Arboriculture 28(6):270-276.
12 State of the Forest Report
24
45 -
40 -
0 35
0 30
0
0
a)
02 25 -
m
22 20 -
V)
15 -
a)
U
L
a>
a 10
II
5
II
0 I I -
0-5 6-12 13-18 19-24 25-30 31-36 37-42 >42
DBH class (in.)
Figure 2. Percentage of street trees in each diameter class.
Lake Oswego has a disproportionate number of decrease the percentage of trees in all size classes,
small diameter street trees and half of the and future tree plantings that will contribute to
recommended large diameter trees. the small tree size class. Continuing to plant large-
at-maturity trees in the ROW, when possible, will
The high proportion of small trees is due to the eventually help reduce the predominance of trees
presence of many young trees, but also partially in small DBH classes.
because there are many small-at-maturity trees
planted in the ROW. Trees that are small now and
will remain small in the future make up 29% of all
the street trees (Table 2). About 23% of street
trees are small now but have the potential to gain
large sizes at maturity. However, the estimates of
future street tree sizes do not take into account
mortality of old trees and tree removal, which will
Table 2. Breakdown of current tree site class into mature site potential expressed as a percent of total trees.
Small now Medium now Large now Future potential totals
Small future potential 29% 0% 0% 29%
Medium future potential 24% 7% 0% 32%
Large future potential 23% 11% 5% 39%
Current totals 76% 19% 5%
State of the Forest Report 13
25
Importance Value i. .4 < ' 4<1 {. i ; � '
��, e .. ¢
4
A tree's importance value reveals how reliant the .,; d
community is upon that species. It is determined y, + -,. � t $ a-f
using percent of total trees, percent of total LSA, =k - , ,
and percent of canopy cover. Importance values 7''' . - Jx + `" TMs
range from 0 to 100, higher numbers suggesting '` 'IAsn
more reliance on the functional benefits of that
:40 A
, Pl.'." ,, '"fix- 1• }'J C 1 ,; ..
particular species. This valuation method is usefulii
f,, i d ` _'
in comparing relative dominance among tree i J g a
types in a population. The importance value also rt i k k
represents the functionality of a tree species, or ¢ ,
the ability to produce more benefits. Trees that - r .0
have higher importance values than percentages , ' ' '
of total population produce more benefits than ,,,, ,j ' ' `�
, r
trees with low importance values that compose a j;. :Y r '� ' s' ` .T-.<•.
high percent of the tree population. Bigleaf maple, ,,L ,... f
Doulas-fir, and Oregon white oak (Quercus '� `
garryana) stand out as very beneficial trees, while A .:
arborvitae (Thuja orientalis), English laurel (Prunus - -- , % f
laurocerasus), and Filbert trees (Corylus cornuta) do
Oregon white oak is a very long-lived and important species.
not provide many benefits (Figure 3).
20
•Importance Value
18 -
■%of Total Trees
16 -
14 -
12
s=
a) 10
o_
m
8 -
6 -
4 -
2 — 1-11-1 itil1 1.1 irMirldillild11 .1 [11
0 1 1 I 1 I 1 I I I I 1 I 1 ,
�t 0 0 <0 l t 0 € ¢�i `E- 0 0 0 0 �� 0 0 a
Q �� '' 10 Q ao pm ¢, o J 0 oc �o �¢, \F ,; Q �0 0' am o Q o
tc`° oc` 00 Fm tr 0 �� Fm .• ‹0 \0 a 0 0U a.Q 0 �� 0V 0 6' �• Fm - 0so
-:y -o Co - Oa a a y c m Co Co m 0 ¢, Co 0 0 0 wo 0
\� Oo 0� ohm Y00 �0 \� •co' o� \F ,0 0 o) ,� co, �0 a, •or c moo 8
0CIJ �o0 Ica, O`.. Quo �`� �� CZ Q �4 c y�o, ,ft9 �\r
Tree species
Figure 3. Importance values and percentage of total population for top 25 most abundant street trees.
14 State of the Forest Report
26
Health mindful planning to choose tree species suitable
for specific site conditions.
The health of the street tree population is
resoundingly good. This study based health on the The most prevalent threat to the City's street tree
apparent condition of foliage and bark and the population is the overwhelming presence of
presence of obvious defects. Though street trees English ivy (Figure 4). English ivy is an aggressive
face harsher growing conditions than most yard, invasive species, with vines that commonly grow
park, or open space trees, the mild climate of the up tree trunks causing detrimental effects.
Pacific Northwest allows many tree species to English ivy competes with trees for water and
thrive. 80% of Lake Oswego's street trees are in nutrients, deprives tree bark of normal contact
good condition and 14% in fair condition (Table with air and microorganisms, and increases
3) susceptibility to windthrow. More than 35% of
Lake Oswego's street trees have ivy on them in
This study found that most causes of poor tree varying degrees of severity. Though a tree with
health are preventable through proper planting minimal ivy may not initially show signs of
and maintenance practices. Some trees in poor or decreased health, without removal, the ivy can
dying conditions may be unable to adapt to the eventually cause major structural damage and
challenges of growing in an urban environment, even death.
are not well-suited to growing in this climate, or
were planted in a space without adequate room to
grow. When trees become larger than a space can
accommodate, they are often excessively pruned
or topped. Though these maintenance practices
are detrimental to trees, they are often necessary
to avoid overhead conflicts and line-of-sight
obstructions. Such problems can be avoided with
2% 1%3%
■iwuo no evident problems
35% ri ivy present
IIgrowth obstructions
MME111111114
59% ❑ tree topped
• combination of 2 or more
Figure 4. Percentage of major street tree health threats.
State of the Forest Report 15
27
Table 3. Condition of top 25 most abundant street tree species by percentage.
Species Dead or dying Poor Fair Good
Bigleaf maple 0 6 17 76
Douglas-fir 2 11 14 72
Oriental arborvitae 0 21 0 79
Cherry species 2 3 18 77
Norway maple 0 0 13 87
Red alder 2 3 26 69
Western redcedar 0 0 3 97
Filbert 0 2 5 93
English hawthorn 0 2 12 86
Red maple 0 0 2 98
English laurel 0 0 0 100
Oregon white oak 0 10 15 75
Pacific madrone 0 2 9 89
Maple species 2 0 16 82
Willow species 0 2 13 84
Purple leaf plum 2 0 21 77
Sweetgum 0 0 0 100
Vine maple 6 0 3 92
Kwanzan cherry 0 14 25 61
Pear species 0 0 14 86
Incense-cedar 4 4 63 30
Washington hawthorn 11 15 4 70
Japanese maple 0 0 0 100
Black cottonwood 0 4 12 84
Scotch pine 0 8 44 48
Citywide total 1 5 14 80
16 State of the Forest Report
28
Infrastructure Conflicts
This study looked at the two infrastructure
conflicts that occur most often with trees located
in the ROW: overhead wire conflicts and sidewalk
damage. Along with being harmful to tree health,
the placement of over-sized trees under
powerlines or in spaces lacking room for root
growth can result in costly damages. I"
Throughout the City, 27% of street trees are
planted under power lines (Figure 5). Of these
trees,two-thirds do not interfere with power lines.
A total of only 9% of street trees have limbs that
grow in the same space as power lines.
Sidewalk upheaval is even less prevalent than wire
conflicts. Only 21% of street trees in Lake
Oswego grow near enough to potentially affect
sidewalks. Of these trees, 90% of them cause little
Mak
to no sidewalk damage (Table 4). Only 2% of
street trees cause more than three-quarters of an _ �
inch of sidewalk heave.
Most trees cause less than 11/2 inches of sidewalk
lift. Of the trees that cause more than 3/4 of an Excessive power line pruning can be avoided by planting the right tree
in the right place.
inch of sidewalk lift, sweetgums (Liquidambar
styraciflua) cause far more conflicts than any other
tree species (Figure 6). About one-quarter of all
sweetgums in the ROW cause sidewalk lift. Since
their strong, aggressive roots can easily lift curbs
and sidewalks, sweetgums should be planted at
least 8 to 10 feet from sidewalks.30 Due to this
restriction sweetgums are not preferable street
trees.
Table 4.Sidewalk heave among street trees growing near sidewalks.
Sidewalk 0 - 3/4 3/4 - 11/2 11/2 - 3 3+
heave inches inches inches inches
Percent 90 8 1 1
30 Gillman,E.F.,and D.G.Watson. (1993).Liquidambar
styraciflua,sweetgum fact sheet.USDA Forest Service.
State of the Forest Report 17
29
80
70 -
60
50 -
c
a)
2 40 -
a)
a_
30 -
20 -
10
0
No lines present Present and not conflicting Present and conflicting
Figure 5. Conflict between street trees and overhead utility lines.
250
•3 inches +
w 200 -
■ 1'/2 - 3 inches
0 150 -
o ■3/4 - 11/2 inches
a) 100
E
Z 50 -0 1 • _1 1 • 1 •
co o m
v.(?) @ 0 0 .Q 0 PCs �0
�' o .moo,
Czo
Q OI
Tree species
Figure 6. Number of sidewalk conflicts above 3/4 inch for the top 10 species causing upheaval.
18 State of the Forest Report
30
21% 1%
❑ available planting space without
1y� preperatory work
available planting space needing
preperatory work
❑ empty cut-out
78%
Figure 7. Types of available planting spaces.
Stocking Level Tree Location
Tree stocking level indicates the amount of Though the potential for street tree planting is
available planting space within the ROW that is limited due to the high stocking rate, there are still
planted. Available planting spaces, including more than 6,000 available planting spaces. This
stretches of 25 feet of unoccupied land, 25 feet of space is a valuable commodity that should be
land needing preparatory work (clearing of other planted to maximize benefits. The location of
vegetation or built surfaces), and empty cut-outs ROW planting spaces (empty or treed)
in sidewalks, were inventoried to give an accurate throughout the City shows a large potential for
stocking level. A space in the ROW is only increasing street trees exists on private property
considered available for planting if it is large (Figure 8). The ROW often extends several feet
enough to accommodate a tree (including into front and back yards. These yard spaces
overhead space), not being used for other compose 39% of the planting spaces in the ROW.
purposes (sidewalks, driveways, other beneficial Planting strips, or land between the road and
vegetation, etc.), and would not impede lines of sidewalk, hold another large portion of ROW
sight for signs and signals. planting spaces on private property.
With a total population of 40,327 street trees out
of 46,530 available planting spaces, Lake Oswego Table 5. Distribution of street trees and planting spaces.
has a stocking level of 87%, well above average
levels. Most city stocking rates in the United Total trees 40,327
States average between 40% and 60%.3' Of the Total planting spaces 46,530
unplanted spaces in Lake Oswego, the majority of
them are ready to be planted without much Square miles (excluding Oswego 10.6
preparatory work (Figure 7). Lake)
The total land area of the City, excluding Oswego Planting spaces/square mile 4,390
Lake, is 10.6 square miles, yielding an average of Trees/square mile 3,804
3,804 street trees per square mile (Table 5). The
City has 178 street miles with 34 available planting Street miles 178
spaces per street mile. Planting spaces/street mile 261
31 Maco S.E.,and E.G.McPherson. (2003).A practical Trees/street mile 227
approach to assessing structure,function,and value of street
tree populations in small communities.Journal of Arboriculture Stocking rate 87%
29(2):84-97.
State of the Forest Report 19
31
30% in Front yard
34% • Backyard
E Planting strip
❑ Cutout
❑ Median
•Other maintained locations
12% 5%
•Other un-maintained locations
1%J/_/ 17%
1%
Figure 8. Location of planfing.oaces(empty or treed).
Cutouts and median planting spaces are usually Table 6. Land use of ROW trees and available planting spaces.
owned by businesses or the City. The large
portion of "other" spaces includes parks, Land use Percent
undeveloped land, and other communal spaces, Single family residential 68
both private and public.
Multi-family residential 1
By another measure, it is obvious that the Park/vacant/other 20
majority of ROW trees and available planting
spaces exist on private land,particularly residential Light industrial/commercial 11
land. Nearly 70% of ROW planting space is in
residential neighborhoods (Table 6).
to maximize environmental and property value
To take advantage of the available planting space, benefits. The mature size of a tree should be the
the right trees must be planted in the right spaces basis for picking appropriately sized planting
. spaces. Small trees are
'- y k., 1 predominant in the City's
`': street tree population.
.- _ $.""'^ 4,_ "` For health and
I
�-.� +. M , infrastructure purposes,
*` &` fir �1" large growing species
•{ ,:i '- tir ' should not be planted in
• a
�. ' ,� : small, confined spaces.
On the other hand, a tree
.� that is small at maturity
' planted in a large space
{,^ represents missed
.
opportunities to increase:cy e„1 � L;
benefits. Most small trees
* have low importance
v�
111-
. - — - - - -_ - --- values because they lack
- the LSA and longevity of
larger trees.
The majority of Lake Oswego's urban forest exists in neighborhoods.
20 State of the Forest Report
32
CANOPY COVER
x' a '•• � '�' • ij1%-,•. 'j-
•
Jly_..fir :
iry • k. - * .'k �yc
' N •
Oyst > i:rf titi'' zz_�i,.ro- �: .;.. v.-.
it_
" '1:'. 'L4 ,&' �,ry " yam" Y a."* rr'Ir y+,.e. l'� "•
.
•
;1 "..'1 �- � � �'' .#� ;t +. ,�f1 %.i , . �'Y �4..F1. .R}
fir ' '•xxky':ii. rr. -�piyie'�'I. `+:hr:4' 7 C.,'y` - ," '.": Y .
PI — .'' ,':'•'' 44-94."F.-'-',4.4_;%”,:::fil;!12).0": 11,00.*le: .4...L.-,-1..thigi.:.k4Notr.
'''.=••' L `37 1,..i..4 v.rt•N'V.-i. ;r••••/regt.r.
.. .• lit.; 'pi• . • .r!'..t.77::!+r .. 1. . . 1;i4:'7.:g'X'6W{ .. V ' ::.. 1
_ yA*i;4 !I4
-'t /,',;.:-.....:r•19.'5,. Irlatt_ti”r 4...'art3:}4...7i: .•'94 ::1:-...;.,..• ...-. gt ' : ' '• ..IV• , •-le
•
":ir "
pry •
• i r.�;''1 " r ,r ',r ...Sr .!:% ,. +•2'
.l' �+p 1 y'tr''�{7.,y :.." *:fy• ' :. F131`E5t =�'�'.�':o ,
•
fi I. M1 ¢:
• L:areGround='..),
I111pe1'Yio115 =3 2%
•
*t
.0.4 , -kti':ater = 5.3%
Figure 9. City-wide ground coverage.
The information in this section was determined a 19.7% canopy cover with a goal of 28%.33
by analysis of aerial photos. The total City-wide However, many of the benefits of trees described
canopy cover, or the amount of ground covered in this report depend on their location and site
by tree canopy, in Lake Oswego is 44.4% (Figure specific placement. For example, heavy canopy
9). This is a relatively high percentage of canopy cover over pavement and in stream corridors is
cover when compared to many surrounding cities. imperative for stormwater runoff mitigation and
Portland has a 26% City-wide canopy cover with stream health.
a goal of 33%,32 The City of Vancouver, WA has
33 Kaler,Dan,and R.Charles. (2005).City of Vancouver
32 City of Portland. (2007).Portland's urban forest canopy: Canopy Report:GIS Analysis Using 2002 LIDAR Data.
Assessment and public tree evaluation.Portland OR:Portland Vancouver WA: City of Vancouver Urban Forestry and
Parks and Recreation Department. Clark County GIS Department.
State of the Forest Report 21
33
Street tree canopy covers 430 acres, or 36.5% of the built environment also mitigates the urban
the ROW. This represents about 13% of the total heat island effect caused largely by buildings and
City-wide canopy cover (Table 7). The land area pavement. Furthermore, shading streets and
in the ROW is 1,180 acres, but not all of it is parking lots decreases hydrocarbon emissions
covered by impervious surfaces. The land area from evaporated gasoline, which are principal
covered by roads and sidewalks is about 580 components in ozone formation. The
acres, or about 8% of the total land area. Canopy recommended minimum canopy cover over
that shades pavement is beneficial for several streets and sidewalks is 25%.35 The canopy cover
reasons. Shading asphalt increases the over Lake Oswego's paved surfaces exceeds this
performance of roads by decreasing the recommendation at 32.3% (Figure 10).
volatilization of the asphalt binder that leads to
hardening and cracking.34 Shading the surfaces of •
rah .., ,, ',"r..
.)• t fit. '� , ' ,- i , '' ael � ,4 y 3
t
i. i-_, fir' -m, .. ,•r•f - 4. r' ,.e
I.
rid 011' _I- _ Tyr- _y ;' "'� 1: -.
tlri ,1�- 7 - Cam•- , l� kJ 5_�E i J ,L) 1i. :' . i
I._7L�11 ' Y_S 4
..„,,,,-
r T— W F . .
.•. -Canopy i - '�� 0 i,
b)
j&r01 F-:'' .A.' @ :l 44T
Jam' °'t. V -55 �:r-L-LirA ....L0.1,-,azzli.,- i. ‘.--e7„.r., , i: . _` •a t -
, .,--i, ,„. ,,, ,,,, , ,, .., ,J _,.-... 4 i 4., , .-.. , `,,,. ' 157: . i
,.., •••• , ,, -.,:-.1. iii. , . ,, „.,
+! v.`_s
`�15.eir4
"r,` _Canopy-3d.3% .-
4-000.
Figure 10. Canopy cover over the (a) ROW and (b) pavea
surfacer. Grove of Douglas-fir Heritage Trees in Lake Grove.
34 McPherson,E.G.,and J.Muchnick. (2005).Effects of 35 Maco S.E.,and E.G.McPherson. (2002).Assessing
street tree shade on asphalt concrete paving performance. canopy cover over streets and sidewalks in street tree
Journal of Arboriculture 31(6):303-310. populations.Journal ofArboriculture 28(6):270-276.
22 State of the Forest Report
34
Table 7. Total land area and canopy extent over various areas or zones.
Area/Zone Total % of total Acres of canopy % canopy % of total
acres land area cover w/in area cover w/in area canopy cover
Lake Oswego 7,278 100% 3,231 44.4% 100%
ROW 1,180 16% 430 36.5% 13%
Paved surfaces (roads
579 8% 187 32.3% 6%
and sidewalks)
Public lands 1,030 14% 647 62.8% 20%
Single family
5,150 71% 2,245 43.6% 70%
residential zoning
Stream corridors
322 4`°o 249 77.2% 8%
(50 ft.)
Stream corridors
663 9% 465 70.2% 14%
(100 ft.)
Single family residential zoning composes much due to pollutants from stormwater runoff and
of the City and has a canopy cover of 43.6% erosion from high flows and vegetation removal.
(Figure 11). The canopy cover over public lands Riparian vegetation, both overstory and
includes fire department property, open space, understory, minimizes erosion and maintains
parks, property general, water property, school healthy streams. The canopy cover over stream
district property, and sanitary district property. corridors in Lake Oswego is high. Using a 50 foot
Public property canopy cover is 62.8%. buffer (25 feet on each side of the stream
centerline), the canopy cover is 77.2%. Doubling
The degradation of stream corridors is primarily the buffer to 100 feet, thus including more land
rTIT li
a) IT1 '1 b)
I -I
f ' * GIs
• ,4,;•_7,,,- -,,,.., _..,,i.,,,,,,
t,L_
1 r;'' F ; lig -3 , - ,,./.4L__ . -t, ,
,,,e--
, 1,.., , I -- 0
. �9..` F • !r
iti,:i 1..1 i
rpm
,.:..
�(� ['.annpy-62.8% v ..1 _Cauo ro py-43.6
Figure 11. Ground coverage on(a)public lands and(b)single family residential zoning.
State of the Forest Report 23
35
area farther from the stream, the canopy cover retention, causing pollution and fast-moving
decreases to 70.2% (Figure 12). In the larger water in streams.
Metro region, only 55.4% of the land within 50
feet of streams is forested.36 There are few other
jurisdictions that have higher canopy cover near • � „�
streams. • , •s . 'r,',..++
y -`
Despite the high canopy cover, Lake Oswego's +: . . - ".5
stream corridors are naturally unstable and , ,
erosion prone due to steep topography and therl
inherent characteristics of our native soils. This ''�' ' y�" '�
analysis does not indicate the amount or y ' • , �a1
composition of understory vegetation. Even with i � 't • f "- •-/'t9
high canopy cover in stream corridors, the ,wY
removal of native understory riparian vegetation
si ficantl increases erosion. Forests and other .Z
riparian vegetation in stream corridors and _. L y '
wetlands provide some of the highest value
habitat and are used by terrestrial wildlife species - `';: .
more than any other habitat type.37 This
vegetation also provides numerous water quality ` ? ,V,,
functions. .H�
..
Having canopy cover over paved surfaces is also - '
very important for watershed health. Stormwater
that flows off impervious streets and sidewalks Canopy cover over streets and sidewalks has the potential to take up
10%of stormwater that falls in the ROW.
enters streams with minimal infiltration and
a) / 1 b)
± — (f./.. -7:3/ , ,- ..„-", .
-Ili/ ("1: .5%..... j IC ,11111791.1s'1/4...,
, 4 i Z:,..... 1
'7 at,---1 -7- ', --(7,_ _
{t i ex z
. .....,,,il
,, , ,. i____,,
,, .,...1
, ,
,1 r
x 4
411
•= -Cvuiopy-17.2% ,� c',,.at”,- 'lO.L%
Figure 12. Extracted ground cover in stream corridors using a(a)50 ft buffer and a(b) 100 ft. buffer.
36 Hennings,Lori. (2009).State of the Watersheds 2008
Environmental Indicators.Portland,OR:Metro Regional
Government.
37 Ibid.
24 State of the Forest Report
36
Neighborhood canopy cover varies throughout
the City of Lake Oswego. Some neighborhoods
have a higher canopy cover than the average City-
wide percentage. Excluding Birdshill, since only
26 acres out of 240 are in Lake Oswego City
limits, Childs, Glenmorrie, Lake Grove,
Lakeview-Summit, and Uplands have the highest
canopy cover (Table 8). However, the
neighborhoods that contain the highest
percentages of the City-wide canopy are Palisades,
Mountain Park, First Addition, Bryant, and Lake
Grove.
State of the Forest Report 25
37
Table 8. Neighborhood Association canopy coverages.
Neighborhood % canopy cover % of total Total acres Acres of N.A. in Acres of canopy
Association in City limits canopy cover of N.A. City limits in City limits
Birdshill 64.02% 0.51% 17 26 240
Blue Heron 50.22% 2.95% 95 190 190
Bryant 53.87% 5.62% 182 337 343
Childs 57.80% 2.09% 67 117 119
Country Club-
41.85% 3.68% 119 284 284
North Shore
Evergreen 25.80% 0.80% 26 101 101
First Addition 51.45% 6.05% 195 380 380
Foothills 25.88% 0.86% 28 108 108
Forest Highlands 42.58% 4.85% 157 368 533
Glenmorrie 56.52% 3.08% 100 176 176
Hallinan 46.02% 2.89% 94 203 203
Holly Orchard 32.03% 0.93% 30 94 94
John's Woods 51.00% 0.45% 15 28 28
Lake Forest 44.21% 4.12% 133 301 647
Lake Grove 56.47% 5.60% 181 320 333
Lakeview-Summit 56.27% 2.75% 89 158 158
Lakewood 21.44% 0.77% 25 116 116
McVey-South Shore 41.91% 3.71% 120 286 286
Mountain Park 47.40% 9.58% 310 653 653
Oak Creek 40.00% 2.89% 94 234 311
Old Town 31.87% 0.50% 16 51 51
Palisades 50.40% 12.55% 405 804 804
Rosewood 50.12% 0.90% 29 58 435
Skylands 51.95% 0.33% 11 21 146
Stafford Tualatin 23.04% 0.61% 20 85 7189
Uplands 56.00% 5.35% 173 309 309
Waluga 41.81% 2.74% 88 212 212
Westlake 45.32% 4.23% 137 302 302
Westridge 52.31% 1.63% 53 100 116
Total - 93.06% 14,867 6424 3007
26 State of the Forest Report
38
Table 9. Value of annual benefits provided by street trees.
ECONOMIC BENEFITS OF
Benefits Citywide total ($) $/tree
THE URBAN FOREST Energy 106,112 2.63
CO2 27,965 0.69
Though there are many social benefits provided
by the urban forest that are not quantifiable, Air Quality 55,045 1.36
environmental services and property value Stormwater 877,702 21.76
increases due to trees can be translated into
economic terms. Urban trees save the City money Property value 1,906,836 47.28
by reducing the burden on public infrastructure Total 2,973,660 73.74
such as stormwater collection and transportation
systems. The reduced cost of heating and cooling
due to tree canopy directly affects both public and value due to trees is based on studies of actual
private buildings. These avoided costs can be housing prices influenced by the presence of
trees. Yet even these methods of quantification
quantified using energy and stormwater
management costs. Air quality improvement and cannot account for benefits such as crime
carbon sequestration are services provided by reduction, business district success, public health
trees that would otherwise cost money to improvement, and wildlife habitat.
artificially replicate. Based on a model for this
climate zone, these services are valued at a market The estimated value of benefits provided by Lake
price per unit of carbon or other pollutant Oswego's street tree population alone is nearly $3
million per year. With a total of 40,327 street
removed from the air. The increase in property
trees, each tree's annual benefit production
averages about$74 per tree (Table 9).
The energy savings are a result of avoided costs
for electricity in the summer and natural gas in the
winter. The total electricity saved throughout the
City annually is 1,239 MWh (megawatt hours),
' ',+ 1 ., ... . ter; which saves about $63,457. Natural gas savings is
S
A li n ;,; 37,221 therms worth$42,655.
4, �,, z r The calculation of benefits for atmospheric
t. `%:, -. '?4 carbon reduction takes into account total annual
1 may .n ! �` sequestered carbon, carbon release due to
�4a .70$ ;;, maintenance and decomposition, and avoided
�' ,� t� carbon emissions due to decreased energy use.
~ " , s' 4, y .,, The street tree population has a net uptake of
• �� 8,372,790 pounds per year, valued at $27,965,
� adding to the existing carbon storage of
.#_,' k ;. 102,559,800 pounds worth $342,550.
;''7�° Air quality improvement is calculated using the
q, f
'" values for removal of pollutants (including 03,
NO2, PMIo, SO2, and VOC) from the air, avoided
emissions due to energy reductions, and the
Trees provide energy savings through shade and windblock.
State of the Forest Report 27
39
Table 10. Average annual benefits of top 25 most abundant street tree species in,t/tree.
Species Energy CO2 Air Quality Stormwater Property value Total
Oregon white oak 8.35 1.85 4.53 68.46 128.86 212.03
Black cottonwood 3.87 1.45 1.37 34.85 88.63 130.16
Douglas-fir 4.10 0.79 2.29 51.30 67.98 126.46
Red maple 4.77 0.87 2.39 26.87 70.51 105.41
Western redcedar 2.92 0.54 1.72 36.94 58.51 100.63
Bigleaf maple 4.05 1.13 2.09 28.10 60.61 95.98
Norway maple 2.95 0.77 1.44 19.12 70.85 95.13
Sweetgum 3.96 0.86 1.42 25.60 60.90 92.74
Japanese maple 2.76 0.71 1.36 17.95 66.74 89.52
Red alder 3.13 0.67 1.12 19.76 55.72 80.39
Maple species 1.81 0.49 0.86 11.61 59.74 74.51
Vine maple 1.22 0.34 0.55 7.49 55.43 65.04
Willow species 2.30 0.50 0.83 14.40 45.56 63.59
Pear species 1.76 0.36 0.63 10.58 42.40 55.72
Incense-cedar 1.11 0.23 0.66 11.88 40.76 54.64
Kwanzan cherry 2.42 2.04 1.43 12.71 35.89 54.49
Purple leaf plum 2.04 0.49 1.23 12.86 35.80 52.42
Cherry species 1.39 0.97 0.75 5.93 23.96 33.00
Washington hawthorn 1.63 0.19 0.94 8.49 20.62 31.87
English hawthorn 1.52 0.15 0.88 8.24 15.20 25.99
Scotch pine 0.17 0.64 0.29 6.01 17.37 24.48
Filbert 0.88 0.55 0.47 3.54 16.09 21.53
Arborvitae 0.29 0.05 0.17 2.04 17.41 19.96
Pacific madrone 0.78 0.19 0.52 2.27 3.27 7.03
English laurel 0.57 0.11 0.38 1.78 1.49 4.33
emissions trees produce of biogenic volatile
organic compounds (BVOCs) that contribute to Lake Oswego's street tree canopy intercepts an
ozone formation and smog. The air quality estimated 31,581,200 gallons of water per year,
reduction due to BVOCs is relatively low decreasing the burden on streams and the
compared to benefits produced by most trees. stormwater conveyance and management system.
28 State of the Forest Report
40
This benefit represents the second largest Table 11. Total annual benefits, costs, and net benefits of
economic savings for the City at about $880,000 street trees.
per year. Total ($) $/tree $/capita
The largest annual benefit of the street tree Total benefits 2,973,660 73.74 81.82
population is the value added to property. This Total costs 277,568 6.88 7.64
benefit is calculated based on the average home
price for Western Washington and Oregon Net benefits 2,696,092 66.86 74.18
communities and the annual increase of LSA of
the tree population. In Lake Oswego, more than provide an annual return of $10.71 worth of
$1.9 million in property resale value per year is benefits for every dollar invested in them. This
due to the presence of trees located in the ROW. benefit-to-cost ratio far exceeds those of other
cities around the country that have derived ratios
The benefits provided by different trees vary using the STRATUM software.38 The high
depending on the age, LSA, and biological benefit-to-cost ratio may be due to low
characteristics of each species. Typically older expenditures on the Urban & Community
trees with more LSA provide the most benefits. Forestry program along with the minimal costs
Oregon white oak stands out as providing the for municipal tree planting due to Lake Oswego's
highest annual benefits, while trees such as high stocking rate. The net annual benefits
arborvitae, Pacific madrone (Arbutus menziesia), provided by street trees averages about $67 per
and English laurel produce very few annual tree and$74 per capita (Table 11).
benefits (Table 10).
The annual benefits provided by street trees help
The City's annual expenditures on street tree us understand how much the urban forest
management, such as planting, watering, produces for the City every year. To quantify the
mulching, pruning, pest management, tree total value of the trees, not just the benefits they
removals, and Urban & Community Forestry produce, a replacement value estimates the full
Program costs are much less than the benefits cost of replacing trees in their current condition.
provided by the trees. Lake Oswego's street trees This form of appraisal attaches a compensatory
dollar value to each tree depending on the species,
1 ti condition, DBH, and tree location. The
replacement value of Lake Oswego's street tree
:* population is over$129 million (Table 12).
o
{ 1 The highest-valued tree species are Douglas-fir,
, I bigleaf maple, Oregon white oak, and Western
gr'r redcedar (Thuja plicata) (Table 12). These trees
. ir
reach large sizes at maturity, have large LSAs, and
j, are native to the region. Their replacement values
'J ! are high due to their dominance in the population
and the relative abundance of these trees in the
.. ll*
`' largest DBH classes. Of the 602 trees in the
� - - ,. largest two DBH classes, 80% of them are one of
these species.
j r 38 City of Portland. (2007).Portland's urban forest canopy:
Flowering dogwood in spring Assessment and public tree evaluation.Portland OR:Portland
Parks and Recreation Department.
State of the Forest Report 29
41
_
Table 12. Replacement value of street trees by DBH class. 'x.. �r. s ' iil r, �,..
DBH Total Number Replacemen -va.„,; •rj574*,:,:if ,..Ati , . ,r„.,- .*- :': ' ."..7-.:
t!e iv `'yk' }„ :' `
(in.) replacement of trees value $/tree irr -A,,,, +P rz'S' �?t Pe
l �rl '�F 'r' ,�41
value ($) ...,'ri{ `, t.
' ' � „• „jai"� '� - ��
0 5 3,932,381 16,641 236 .-: .4--* ` • .* wit °c(( �S -LP.
6 12 25,162,531 14,152 1,778 .44
�t" -:° ' "�� . �f r. .° ,E
13-18 29,651,473 5,560 5,333 ' � � " '- 44
19-24 19,925,719 1,927 10,340 4� •,:-, { '• + - : < 24
25-30 18,730,529 1,044 17,941 •
31-36 9,402,320 401 23,447 ti., . L ;+
37-42 8,973,830 261 34,382 # -
>42 13,355,964 341 39,167
Total 129,134,746 40,327 7,692
Bigleaf maple has a high replacement value and produces many
benefits.
Table 12. Replacement value for top 5 most valuable species in$.
DBH (in.) Douglas-fir Bigleaf maple Oregon white oak Western redcedar Red maple
0-5 282,048 225,581 19,875 92,790 53,159
6-12 1,905,315 4,293,908 581,204 959,417 980,394
13-18 6,024,813 4,330,870 1,347,369 1,023,707 2,380,612
19-24 4,995,394 3,400,664 1,777,805 978,925 0
25-30 10,548,058 4,632,232 641,838 0 0
31-36 3,892,474 3,211,778 557,435 0 0
37-42 4,111,293 1,965,193 1,320,801 822,259 0
>42 1,867,702 3,881,086 1,758,581 3,460,741 0
Total ($) 33,627,098 25,941,312 8,004,909 7,337,839 3,414,165
30 State of the Forest Report
42
planting spaces exist and can be utilized. Planting
MANAGEMENT new trees and planting mitigation trees should be
seen as opportunities to increase the diversity of
IMPLICATIONS AND the urban forest and to plant the right tree in the
right place.
RECOMMENDATIONS Ivy Removal
This study substantiates the importance of the The overwhelming presence of English ivy in
urban forest and establishes several management Lake Oswego's urban forest is a major problem.
priorities. The forest structure findings show areas More than 35% of the street trees in the City have
of potential improvement in urban tree ivy at the base of the tree or climbing along the
management and planting. Though the street tree mainstem into the crown. Used often in
resource already yields excellent returns, landscaping and roadside plantings, ivy is
opportunities exist to maximize environmental problematic in and around urban areas. Though it
and property value benefits. Due to the high is often planted on slopes due to its easy
stocking level and relatively high canopy cover, maintenance, uniform appearance and quick
management should focus on maintenance of establishment, ivy has a shallow root system that
existing trees and ivy removal. Though tree is ill-suited for erosion control.
planting is not an urgent concern, available
ill
`` V„ English ivy is a non-native, woody evergreen that
t„v,. ' ' # '' easily adapts to many growing conditions and
' thrives in the temperate climate of the Pacific` '` - ��` - Northwest. It grows rapidly year-round,
w +�. � t reproducing vegetatively and by seed. It can grow
c ,� in many soil types, in sun or shade, from sea level
"'� ' ' •' -,,-� , :.:„, 1` to 3300 feet in elevation, and is drought tolerant
:l ; : _ '• once established. English ivy can outcompete
4,-` __ • native grasses, herbs, and trees, significantly
r ,e, xIli w . ' s'.- altering ecosystems and reducing habitat. If left
, t , 1 ", ` �. ' -* - R. it - uncontrolled, open spaces and forests become
- ;' dominated by thick blankets of ivy that prevent
� 0, <. R regeneration of understory trees, shrubs and
t+t , , 4 , t :` it ' groundcovers, while providing minimal habitat
1 `t: , �t value.40 After habitat loss due to land
141
t , si • development, invasive species pose the greatest
'" �x• ; r „ 'r` threat to the survival of native biota in the United
�y�g 4 4. .. ,, States.'"
' r, s u 39 Written findings:Hedera,English iy. (2001). Olympia,WA:
•'' * Washington State Noxious Weed Control Board.
` , 40 Okerman,A. (2000). Combating the"ivy desert":The
. • ?'f y; r invasion of Hedera helix(English ivy)in the Pacific
1 1
Northwest United States.Restoration and Reclamation Review.
', 6(4).Retrieved from
http://hort.agri.umn.edu/h5015/rrr.htm
41 Hennings,Lori. (2006).State of the Watersheds Monitoring
English ivy growing in trees is a major problem in Lake Oswego. report Portland,OR:Metro Regional Government.
State of the Forest Report 31
43
In urban areas ivy also presents a serious danger efforts on public lands are implemented.
to people and infrastructure. English ivy grows Furthermore, restrictions on the general use of
from the ground up a tree and into the canopy, this plant would greatly aid in controlling its
depriving the tree of nutrients and sunlight. This spread.
weakens the tree while adding substantial weight
to the limbs. More than 2000 pounds of ivy has Maintain Existing Trees
been found on some trees in the Pacific
Northwest.42 Added weight increases the chance More than 40% of Lake Oswego's street trees are
that tree limbs will break during moderate to high young (smaller than 6" DBH). This percentage of
wind storms. small trees is larger than accepted urban forestry
standards, while the population of large mature
Two prominent methods of ivy removal are trees is less than recommended. Management of
herbicide application and physical removal. Ivy is the existing tree resource should have a twofold
not easily controlled with herbicides due to its focus: 1) preserving and pruning large mature
waxy cuticle, which allows the plant to resist trees to increase longevity and benefits, and 2)
herbicide uptake.43 Several combinations of pruning and maintaining young trees to maximize
herbicides have successfully killed ivy, but often health and future returns. The many young trees
result in regrowth, sometimes in higher in the City require little work now, but will require
concentrations than before herbicide application. an increasing amount of maintenance as they age.
Manual removal by cutting, pulling, and digging is However, investing in trees is worthwhile because
labor intensive, but effective. A combination of unlike other infrastructure, trees appreciate and
herbicide application, followed by manually provide more benefits as they age. Regular tree
removing resprouts may be the best technique for care and maintenance can increase benefits and
mass ivy removal. With a dedicated effort of avoid crisis-driven emergency care that is costly
removal followed by native replanting, ivy can be and risky to persons and property. Especially in
eradicated and soil better stabilized.44 street trees, providing maintenance during
Due to the spread, persistence, and detrimental —=—I. -, - ,; r" -
effects of ivy, this issue must be addressed with a - :mod / _
committed City-wide approach. This issue will not - /-
dissipate without being addressed and presents a -: ._�,
current and future threat to the community and "
the urban forest resource. The City presently has - - -,- ;,-, ; , _,' I
no systematic effort to control ivy on public lands -- ;' `^�'
or in private open spaces. Community education ,-.;� ""
and involvement are necessary to encourage ivy -. ' •`• `
control on private lands, while simultaneous + -I, 1 .i '. . t
42 Written findings:Hedera,English ivy. (2001). Olympia,WA:
Washington State Noxious Weed Control Board.
43 Okerman,A. (2000). Combating the"ivy desert":The _._
invasion of Hedera helix(English ivy)in the Pacific i R""`
Northwest United States.Restoration and Reclamation Review. ,
6(4).Retrieved from
http://hort.agri.umn.edu/h5015/rrr.htm }
44 Ibid.
43 City of Lake Oswego. (2007).Lake Oswego urban and
community foresty plan.Lake Oswego,OR:Lake Oswego Young trees will appreciate with age if they are properly maintained.
Planning Division.
32 State of the Forest Report
44
L o f'• aYy
o • at
c ,
4� x yC gl4y. 4 - e.
-
�Y, J'
r - rya, r.! to
r .
" _r?2•
i k rah..: .
35 ^ _ sr, 'C'• _ �+. .j'`sue •.-+''���'_..s ie ... _
444, v.
SCE .$,
K.
mow
- - f _
Street trees increase properly value,provide environmental services,and provide urban wildlife babiat.
establishment and lifelong regular pruning is vital likely return the widest variety of benefits since
to health and longevity. many environmental stressors are caused by
increasing urban hardening and pollution (both
The City of Lake Oswego's Tree Code highly associated with streets and cars).
emphasizes the importance of tree preservation. Maintaining ROW canopy cover will provide
The removal of trees is regulated by the City and stormwater benefits, urban heat island mitigation,
tree removal permits are contingent upon the CO, sequestration, and other air quality benefits
replanting of mitigation trees when possible.46 near the source of much pollution.
Comprehensive tree protection plans are required
for any development activities. The Heritage Tree Preserving canopy cover on private land should
Program gives special protection to landmark also be a focus since it will increase
trees to increase awareness and recognition of the environmental, property value, and habitat
important role trees play in the community. benefits. With redevelopment and densification,
preserving wildlife habitat connectivity relies on
Maintaining the existing tree cover is important stewardship in residentially zoned areas. In Lake
on public, private, and ROW property. Of these Oswego, land use primarily consists of residential
three land uses, however, the lowest canopy cover developments with some commercial and
is in the ROW. This is expected since the purpose industrial developments. The trend of replacing
of the ROW is to provide land for public smaller houses with large houses increases
conveyance and other infrastructure. However, impervious surfaces that contribute to increased
improving the canopy cover in the ROW would urban runoff. This trend also decreases available
planting space and encroaches on existing trees
and their root area. Though the value of wildlife
46 LOC 55.02.084
State of the Forest Report 33
45
habitat may not be easily quantified, the property trees are not well represented and several trees are
value benefit can be measured. This study shows over-represented. In the street tree population,
that the property value increase due to trees maples are over the recommended genus
represents the highest economic return. composition level of 12%, and Douglas-fir is over
Maintaining canopy cover in residential areas will the recommended species composition level of
maintain wildlife habitat while simultaneously 10%. While this is a valuable guideline, it is
increasing property values and tax returns° important to adjust recommendations to specific
communities. There is a need in Lake Oswego's
Though parks and open spaces were not ROW for long-lived, large growing species, like
specifically studied, the canopy cover on this land Douglas-fir. Broadleaf deciduous trees, like
is very high. Maintaining this canopy cover is maples, make up almost two thirds of the street
increasingly important as development reduces tree composition. An increase in coniferous or
stands of closed canopy forest and increases broadleaf evergreen trees would add diversity as
habitat fragmentation. The recreation value of well as increase annual benefits.
species-rich, healthy forests contributes to the
livability and character of Lake Oswego. In the ROW, though stocking is already high,
there are thousands of available planting spaces
Maintain Diversity that would require little or no preparatory work.
Utilizing these spaces to increase ROW canopy
Though maintaining the existing canopy cover is a cover would minimize planting costs, provide an
goal of the Urban & Community Forestry excellent opportunity to diversify street tree
Program, other land uses will undeniably compete species, and produce valuable future returns.
with trees. When trees are removed, mitigation
trees should be carefully selected to improve the Right Tree in the Right Place
urban forest. While the variety of species
represented in the urban forest is diverse, many Future tree plantings should also aim to maximize
.2
•
�•'yAJ�R�� �fgi'1 4
If*P ' "' �^r 5 �., 4 t.° ,,,.•'f' ;•i +'1*.W " .#;
n �" y ti J. 1 M1
'W�� `a'.. mod#_ N ,. ,} ✓
• ; V 1 4 '}` 4}., "f 101 • `=.rf 'e
ugh+• Y'?� I Y �` .- T} � .yw _ �+.� iA I" ' P J
Maintaining diversity in the urban forest is important for increasing the number of well-adapted tree species.
34 State of the Forest Report
46
around buildings to provide windbreaks and
, - sunlight in the winter and shade in the summer
can provide energy savings. A comprehensive
street tree list for the City should be made and
:::
readily available to the public, City maintenance,
' : ;,„‘,1-'414*:'
A R' and any other party invested in ROW planting.
.... 771, . ---, ,,,ip,„..:
i./.,1 ,,r;
h , , ..-7-44, „..
�` : , To
",,,.„,:
+ b y '.. r. y. "'z 1
r a , ii
i' 7 • 'd
r s'±J i
' A• .,: dii 6yal,.o r, r
Planting large growing,long-lived, coniferous.species in the right place
will increase benefits of the urban forest.
benefits and minimize management costs by
planting the right tree in the right place. Where
appropriate, tree species that have the potential to
attain the greatest heights, diameters, and
longevity should be planted rather than
ornamentals that are comparatively small and
short-lived. In general, the larger the tree, the
greater the LSA, thus the more environmental
benefits produced. However, large trees in limited
spaces result in poor vigor and cause sidewalk
upheaval, wire conflicts, and other costly
problems. Tree species that present problems in
urban environments should be avoided, or
planted strategically. Sweetgums planted near
sidewalks cause twice the amount of sidewalk
damage than the second most problematic
species, Norway maple. Planting appropriate trees
State of the Forest Report 35
47
.
, r 'r
-4 .4'
. .„..,,,,„...., .
,, ...... , :„.„..,„),.. .z., ,, .,,, -
. I, ,,,. ..4.--t, .40V. "" • .' ..inr° --7'Srh.'W ' - ''‘'''',,:° ' "ti...:5".ty- 't.'3'' , ..„ .., • '
. .
r , ri
'k+,i. +` - # .. ...icy , ,F
l
-. 4- .: 01-FIE----e --- A
......- .i,000--
- - _ — ''-v , i
1.
Street trees provide shade that increase longevity of pavement and keep surrounding streams cool.
36 State of the Forest Report
48
CONCLUSION This study also establishes a need for continued
and improved support for the Urban &
The Urban & Community Forestry Plan, adopted Community Forestry Program. Comprehensive
in 2007, presents a series of interconnected goals and ongoing management of the urban forest is
to achieve sustainable and comprehensive urban necessary to maximize benefits. Increasing
outreach by educating and assisting the public in
forest management. Regarding the urban forest,
goals are to increase canopy cover, maintain a tree maintenance on privateproperty would aid
healthy and diverse forest, eradicate harmful this effort. The City's recent class offerings on
invasives that affect trees, and regularly assess and this topic have proved popular and demonstrate
the viability of a regular education program.
care for trees. Concerning the Urban &
Community Forestry Program, goals include Educating the public about the Tree Code, and
public engagement and education, integrated the reasoning behind the regulations, would also
planning involving all City departments, and lead to greater understanding and compliance.
Private cooperation and stewardship efforts,
funding to maintain the Program.
combined with a greater commitment to the
To meet the first set of goals to improve the state Program by the City are key components to
of the urban forest, an analysis of existing enhancing the urban forest.
conditions is necessary. This study provides
baseline data about the forest, from which plans, The street tree resource alone provides economic
goals, and action measures can arise. Future benefits worth more than ten times the money
spent on trees throughout the City. The City-wide
monitoring will allow managers to measure
canopy cover is high, yet there are areas where
progress and prioritize management actions.
1� - r111F7-. . .7'i
' Ali- .— itA
. , ..400.,... 7 : ,,
ar 4 — —1 t
1
. .X.
II
''''se:lift
-ar tax .+4 '.X ,, —
t
I I 1 .i -it. '4. 11 r ii�_34 4
17
,{ ; .�—
--'Y r s # 7rr✓!rc�.. r t r. a- f f"'iv i I 8.,•,•r s�-
Wooded residential lots along Oswego Lake.
State of the Forest Report 37
49
canopy cover can be improved. There are
thousands of spaces in the ROW that could be
planted to maximize benefits with minimal
preparation costs. Planting the right tree in the
right place is paramount to tree success and
minimizing maintenance costs. Future plantings
should also aim to diversify tree species in the
ROW.
Canopy cover near streams is relatively high, but
as distance from the stream increases canopy
cover decreases. While vegetation near streams is
important, the stream is affected well beyond the
100 foot buffer used in this study. Increased
vegetation on these sensitive lands provides water
quality and habitat benefits.
A major threat to the urban forest is the pervasive
presence of English ivy. Comprehensive
management and regulations to eradicate this
noxious weed should be a priority for the Urban
& Community Forestry Program and the City.
The age structure of street trees is varied, but
heavy on young trees and scare of large old trees.
To ensure a healthy urban forest and maximize
benefits as the population of young trees ages,
maintenance and outreach efforts should focus on
private property owners, who are responsible for
street trees adjacent to their property. The
majority of the land in Lake Oswego is zoned for
residential use, thus most of the urban forest
exists on private property. For holistic urban
forest management, public engagement and
education should be priorities.
To better understand the benefits provided by the
urban forest and the effects of current
management, future monitoring is necessary.
Current forest conditions will undoubtedly change
over time. Tracking these changes and managing
adaptively to best conserve and protect the urban
forest is an investment that would provide
economic, social, and environmental benefits for
future Lake Oswegans.
38 State of the Forest Report
50
GLOSSARY
Canopy cover—The amount of ground surface area covered by tree canopy or leaf cover.
D B H — Diameter and breast height, or the diameter of a tree measured 4.5 feet above ground. This is the
conventional tree measurement standard in the U.S.
Importance value —A tree's importance value reveals how reliant the community is upon that species.
It is determined using percent of total trees, percent of total LSA, and percent of canopy cover. Expressed
as a percentage.
LSA—Leaf Surface Area, or the measurement of area on one side of a tree's leaves. Higher LSA allows for
more benefit production.
ROW—Public right-of-way, or land designated to accommodate roads and public utility infrastructure. The
width of the ROW varies throughout the City, but will usually be at least as wide as the road and sidewalk,
usually several feet beyond. Often, the ROW extends into what people perceive as their front and back
yards.
Stormwater — The water that runs off impervious surfaces such as streets, sidewalks, parking lots, and
rooftops after precipitation events. It can also come from hard grassy surfaces like lawns and fields.
Stormwater that does not soak into the ground becomes surface runoff, which flows directly into surface
waters or is channeled into storm sewers,which eventually discharge to surface waters.
Stocking level — Tree stocking level indicates the amount of available planting space within the ROW
that is planted. Derived by dividing the total number of street trees by the available planting spaces.
STRATUM — Street Tree Resource Analysis Tool for Urban forest Managers, the iTree software created
by the U.S. Forest Service and other tree specialty organizations to scientifically quantify the structure,
function, and benefits of street trees.
Street tree—Trees located within the public ROW. For this inventory, trees whose bases were located at
least halfway in the ROW were considered street trees. Street trees are the responsibility of the abutting
property owner.
Urban heat island —An urban area that is significantly warmer than a rural area. This effect is caused
largely by increased paved or built surfaces. Urban impervious surfaces absorb and store thermal energy,
particularly during warm summer months, causing surface temperatures to rise.
State of the Forest Report 39
51
- ''''..'VI; _.,.-..-.
, ,. ..10,006. . , ,,,,,, ..,..,,, ,..,,.: ;,,„
---72:___ _ . se 1„
.41
�:. IL , tiL "Y xi
,.,y1'.LM r I4a n
w<Q.. { - 1 'ate, 7 F' y a
', • _
Ly ` �. - --
._ -' •"r. .. a�cr�•.ems_: - c. s' �I' � - _ y-
x - -'_'
xP
- .-_ .-: '- . tom - —.t-
•
Planting a mix of both broadleaves and deciduous trees will create a diverse urban forest in the future.
40 State of the Forest Report
52
property value increase. With the input of annual
APPENDIX A citywide costs of street tree care and data from
the street tree inventory, STRATUM produced
Methods cost-benefit analyses. The estimation of benefits
produced was based on tree biomass using a
growth model specifically adapted to the Pacific
This study consisted of two parts: a street tree Northwest climate zone in conjunction with
inventory and a City-wide canopy analysis. regional models approximating energy use, air
The street tree inventory was conducted over a quality, and carbon sequestration. Total annual
randomly generated sample of 5% of the street costs were determined by combining several
expenditures including planting, pruning, tree and
segments in Lake Oswego. Due to the population stump removal, pest and disease control,
of Lake Oswego, a 5% sampling yields a standard establishment and irrigation, sidewalk and
error of +/-10, thereby making it a statistically infrastructure repair, litter and storm cleanup,
significant sample of the street tree composition litigation for tree related claims, and program
in the City. Using Tiger LINE IDs provided by administration.
the US Census Bureau, 109 segments out of 2,188
street segments within the boundaries of Lake The City-wide canopy analysis was conducted
Oswego were randomly selected using ArcGIS. using one foot resolution aerial infrared photos
The width and location of the ROW on selected taken in 2007 from Metro's Regional Land
streets was determined for each street using a Information System (RLIS). The data was
combination of plat maps, "as-built" diagrams,
prepared using ERDAS Imagine software to
GIS-generated maps and field surveying provide 5 land cover classes including Forest,
techniques. Herbaceous, Bare Ground, Impervious, and
Water. These classes were created using a
Tree data collection along 109 street segments supervised classification process whereby the
was conducted from July to November 2008. The computer was "taught" to differentiate the
AmeriCorps Community Forestry Coordinator, infrared reflectance signature of each land cover.
with help from the AmeriCorps Natural Resource
Technician, collected data detailing attributes of Due to the similarity in signatures between the
all the street trees and available planting spaces Herbaceous and Forest land cover classes, a
within the ROW along the 109 selected street feature space image displaying graphs of signature
segments. Numerical data recorded in the field statistics was created. These graphs are displayed
was entered into iTree's STRATUM software for as a set of ellipses which are based on the mean
analysis. and a standard deviation of 4 for each land cover
color signature. The overlap in ellipses shows
The U.S. Forest Service, in collaboration with where signatures represent similar pixels. For this
private and non-profit organizations, developed analysis the ellipses demonstrated little overlap
the iTree suite, which includes several indicating unique spectral variance for each class
scientifically based computer programs that can and satisfactory classification (Figure 1). An
be used to quantify structure, function, value and accuracy assessment was done creating an error
management needs of the urban forest resource. matrix with a Kappa coefficient of .88, showing
STRATUM (Street Tree Resource Analysis Tool an 88 percent error reduction in the classification
for Urban forest Managers) was used in this study
process.
to quantify the value of annual environmental and
property value benefits such as energy Each land cover class was assigned a total pixel
conservation, air quality improvement, carbon count with each pixel equaling one square foot.
dioxide reduction, stormwater control and The pixel count of the forested area was weighted
State of the Forest Report A-1
53
against the total count of pixels within the image
to yield a 44.4% percent cover within the City of
Lake Oswego. All further analysis was performed
using ArcGIS 9.3. Canopy coverages over specific
geographical areas or zones in Lake Oswego were
derived by extracting the vegetation data with
e g City data.
!ill t• Lir
•
e: ,L
.46
ic
AIRIMMr—
Figure 1. Herbaceous and forest class.spectral signature
ellipses.
A-2 State of the Forest Report
54
APPENDIX B
Table B-1. Percent canopy cover for Metro regions in 2007.From Metro's State of the Watersheds 2008 Environmental
Indicators.Metro's study resulted in higher estimated canopy cover for Lake Oswego and Portland,and possibly other
jurisdictions (however this cannot be verified without more detailed canopy analysis by individual jurisdictions).
Acres of canopy Percent canopy
cover within Acres within cover within Percent of region's
Jurisdiction jurisdiction jurisdiction* jurisdiction total canopy cover
Beaverton 3,020 11,910 25.4% 3.4%
Clackamas 11,762 36,162 37.5% 13.2%
Cornelius 235 1,281 18.4% 0.3%
Damascus 3,711 9,924 37.4% 4.2%
Durham 144 265 54.3% 0.2%
Fairview 429 2,280 18.8% 0.5%
Forest Grove 858 3,704 23.2% 1.0%
Gladstone 441 1,591 27.7% 0.5%
Gresham 4,064 14,996 27.1% 4.6%0
Happy Valley 1,531 4,503 34.0% 1.7%
Hillsboro 3,384 14,798 22.9% 3.8%
Johnson City 7 43 15.1% 0.0%
King City 60 447 13.5% 0.1%
Lake Oswego 3,405 7,234 47.1% 3.8%
Maywood Park 47 107 44.0% 0.0%
Milwaukie 757 3,168 23.9% 0.9%
Multnomah 8,115 26,218 37.2% 9.1%
Oregon City 1,697 6,280 27.0% 1.9%
Portland 27,231 92,768 29.4% 30.7%
Rivergrove 57 117 48.3% 0.1%
Sherwood 541 2,739 19.8% 0.6%
Tigard 1,920 7,545 25.4% 2.2%
Troutdale 773 3,862 20.0% 0.9%
Tualatin 1,028 5,186 19.8% 1.2%
Washington 10,432 33,141 31.5% 11.7%
West Linn 1,977 5,111 38.7% 2.2%
Wilsonville 1,176 4,723 24.9% 1.3%
Wood Village 87 608 14.3% 0.1%
Total 88,889 291,521 30.5% 100.0%
*Excludes area for which no 2007 aerial photographs were available.
State of the Forest Report B_1
55
Table B-2. Complete population summary of street trees by functional type,species,and DBH class.
DBH class (in)
Species 0-5 6-12 13-18 19-24 25-30 31-36 37-42 >42 Total SE
Broadleaf Deciduous Large(BDL)
Bigleaf maple
Acer macrophyllum 984 2,389 823 361 281 141 60 100 5,139 (±1,722)
Oregon white oak
Quercusgarryana 80 301 281 161 40 20 40 40 964 (±416)
Black cottonwood
Populus trichocarpa 80 161 141 20 60 40 0 0 502 (±218)
Oregon ash
Fraxinus latifolia 80 161 80 20 0 0 0 0 341 (±137)
Pin oak
Quercuspalustris 20 100 60 0 20 0 0 0 201 (±113)
Northern red oak
Quercus rubra 20 20 60 0 0 0 0 0 100 (±58)
Japanese zelkova
Zekkova serrata 60 40 0 0 0 0 0 0 100 (±58)
Ginkgo
Ginkgo biloba 60 20 0 0 0 0 0 0 80 (±62)
Honeylocust
Gleditsia triacanthos 0 20 40 0 0 0 0 0 60 (±34)
Silver maple
Acer saccharum 0 40 0 0 0 0 0 0 40 (±39)
European beech
Fagus sylvatica 40 0 0 0 0 0 0 0 40 (±39)
American elm
Ulmus americana 0 20 0 20 0 0 0 0 40 (±28)
Horsechestnut
Aesculus hippocastanum 20 0 0 0 0 0 0 0 20 (±20)
Northern catalpa
Catalpa speciosa 20 0 0 0 0 0 0 0 20 (±20)
Other BDL 0 0 20 0 0 20 0 0 40 (±28)
BDL Total 1,465 3,272 1,506 582 401 221 100 141 7,688 (±1,899)
Broadleaf Deciduous Medium(BDM)
Norway maple
Acerplatanoides 241 823 120 20 0 0 0 0 1,204 (±367)
Red alder
Alnus rubra 161 783 161 40 20 0 0 0 1,164 (±422)
Red maple
Acer rubrum 221 442 361 0 0 0 0 0 1,024 (±402)
Maple species
Acer species 522 341 20 20 0 0 0 0 903 (±281)
Willow species
Salix species 361 422 100 0 20 0 0 0 903 (±393)
Sweetgum
Liquidambar styraciflua 120 422 221 60 0 0 0 0 823 (±298)
Pear species
Pyrus species 261 261 40 0 0 0 0 0 562 (±181)
Birch species
Betula species 100 40 60 20 0 0 0 0 221 (±107)
Flame ash
Fraxinus oxycarpa 100 80 20 20 0 0 0 0 221 (±130)
B_2 State of the Forest Report
56
Green ash
Fraxinus Penn ylvanica 120 40 0 0 0 0 0 0 161 (±99)
European plum
Prunus domestica 60 40 40 20 0 0 0 0 161 (±77)
Paper birch
Betula papyrifera 100 20 0 0 0 0 0 0 120 (±100)
Pacific dogwood
Cornus nuttallii 100 20 0 0 0 0 0 0 120 (±67)
European white birch
Betula pendula 0 40 20 20 0 0 0 0 80 (±48)
Cascara
Rhamnus purshiana 60 0 0 0 0 0 0 0 60 (±34)
Katsuratree
Cercidiphyllum japonicum 20 20 0 0 0 0 0 0 40 (±28)
Bigtooth aspen
Populusgrandidentata 40 0 0 0 0 0 0 0 40 (±39)
Black locust
Robinia pseudoacacia 0 20 0 20 0 0 0 0 40 (±28)
Hornbeam
Carpinus caroliniana 20 0 0 0 0 0 0 0 20 (±20)
Weeping willow
Salix x sepulcralis 0 0 0 20 0 0 0 0 20 (±20)
Other BDM 60 201 141 0 0 0 0 0 401 (±122)
BDM Total 2,670 4,015 1,305 261 40 0 0 0 8,290 (±1,144)
Broadleaf Deciduous Small(BDS)
Cherry species
Prunus species 783 1,204 281 20 0 0 0 0 2,288 (±692)
Beaked hazelnut
Corylus cornuta 662 381 60 0 0 0 0 0 1,104 (±403)
English hawthorn
Crataegus laevigata 602 261 161 0 0 0 0 0 1,024 (±397)
Cherry plum
Prunus cerasifera 161 602 60 40 0 0 0 0 863 (±253)
Vine maple
Acer circinatum 522 201 0 0 0 0 0 0 723 (±233)
Kwanzan cherry
Prunus serrulata 161 221 40 120 0 0 20 0 562 (±177)
Washington hawthorn
Crataegusphaenopyrum 221 301 20 0 0 0 0 0 542 (±368)
Japanese maple
Acerpalmatum 201 241 80 0 0 0 0 0 522 (±136)
European hazelnut
Corylus maxima 161 120 0 0 0 0 0 0 281 (±274)
Flowering dogwood
Cornus jlorida 141 100 0 0 0 0 0 0 241 (±109)
Laceleaf Japanese maple
Acerpalmatum Dissectum' 141 20 0 0 0 0 0 0 161 (±66)
Alder species
Alnus species 100 0 0 0 0 0 0 0 100 (±98)
European mountain-ash
Sorbus aucuparia 20 40 20 0 0 0 0 0 80 (±48)
Apple species
Malus species 20 20 20 0 0 0 0 0 60 (±34)
Saucer magnolia
Magnolia x soulangiana 20 0 0 0 0 0 0 0 20 (±20)
State of the Forest Report B-3
57
Red elderberry
Sambuucus racemosa 20 0 0 0 0 0 0 0 20 (±20)
Other BDS 301 100 0 0 0 0 0 0 401 (±118)
BDS Total 4,235 3,814 743 181 0 0 20 0 8,993 (±1,562)
Broadleaf Evergreen Medium(BEM)
English laurel
Prunus laurocerasus 903 80 0 20 0 0 0 0 1,004 (±304)
Pacific madrone
Arbutus meniesii 562 381 0 0 0 0 0 0 943 (±666)
Southern magnolia
Magnoliagrandora 321 0 40 0 0 0 0 0 361 (±240)
American holly
Ilex opaca 141 40 0 0 0 0 0 0 181 (±158)
BEM Total 1,927 502 40 20 0 0 0 0 2,489 (±985)
Broadleaf Evergreen Small(BES)
Rhododendron species
Rhododendron species 120 0 0 0 0 0 0 0 120 (±54)
European holly
Ilex aqufolium 20 20 0 0 0 0 0 0 40 (±28)
BES Total 141 20 0 0 0 0 0 0 161 (±60)
Conifer Evergreen Large (CEL)
Douglas-fir
Pseudotsuga menziesii 1,586 923 1,004 422 542 161 100 40 4,777 (±1,284)
Western redcedar
Thujaplicata 381 442 161 80 0 0 20 80 1,164 (±342)
Incense-cedar
Calocedrus decurrens 462 20 40 20 0 0 0 0 542 (±345)
Austrian pine
Pinus nigra 0 100 161 80 0 0 0 0 341 (±134)
Sitka spruce
Picea sitchensis 120 20 40 0 0 0 20 0 201 (±90)
Grand fir
Abiesgrandis 60 20 0 40 0 0 0 20 141 (±75)
Pine species
Pinus species 0 60 60 20 0 0 0 0 141 (±85)
Ponderosa pine
Pinus ponderosa 0 60 40 40 0 0 0 0 141 (±75)
Deodar cedar
Cedrus deodara 20 0 0 40 60 0 0 0 120 (±47)
Blue spruce
Picea pungens 40 40 0 40 0 0 0 0 120 (±47)
Redwood
Sequoia sempervirens 20 20 0 40 0 20 0 0 100 (±58)
Western hemlock
Tsuga heterophylla 40 20 0 0 0 0 0 0 60 (±34)
Noble fir
Abies procera 0 0 20 0 0 0 0 20 40 (±28)
Atlas cedar
Cedrus atlantica 0 0 40 0 0 0 0 0 40 (±28)
Red pine
Pinus resinosa 40 0 0 0 0 0 0 0 40 (±39)
Port-Orford-cedar
Chamaecyparis lawsoniana 0 0 20 0 0 0 0 0 20 (±20)
B_4 State of the Forest Report
58
Alaska-cedar
Chamaecyparis nootkatensis 0 20 0 0 0 0 0 0 20 (±20)
Norway spruce
Picea abies 0 0 20 0 0 0 0 0 20 (±20)
Giant sequoia
Sequoiadendron giganteum 0 0 0 0 0 0 0 20 20 (±20)
CEL Total 2,770 1,746 1,606 823 602 181 141 181 8,049 (±1,615)
Conifer Evergreen Medium(CEM)
Scotch pine
Pinus ylvestris 0 201 241 40 0 0 0 20 502 (±173)
Eastern redcedar
Juniperus virginiana 20 261 40 0 0 0 0 0 321 (±275)
Lodgepole pine
Pinus contorta 40 161 40 20 0 0 0 0 261 (±87)
Mugo pine
Pinus o 20 40 40 0 0 0 0 0 100 (±51)
CEM Total 80 662 361 60 0 0 0 20 1,184 (±357)
Conifer Evergreen Small(CES)
Arborvitae
Thuja occidentalis 3,232 20 0 0 0 0 0 0 3,252 (±1,339)
Hinoki falsecypress
Chamaecyparis obtusa 100 20 0 0 0 0 0 0 120 (±67)
Chinese juniper
Juniperus chinensis 20 60 0 0 0 0 0 0 80 (±48)
English yew
Taxus baccata 0 20 0 0 0 0 0 0 20 (±20)
CES Total 3,352 120 0 0 0 0 0 0 3,473 (±1,350)
Grand total 16,641 14,152 5,560 1,927 1,044 401 261 341 40,327 (±6,248)
State of the Forest Report B-5
59
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‘17----v7, COUNCIL REPORT
OREGON
TO: Jack Hoffman, Mayor
Members of the City Council
Alex D. McIntyre, City Manager
FROM: Jonna Papaefthimiou, AICP, Natural Resources Planner
SUBJECT: Sensitive Lands Program Update
DATE: June 5, 2009
ACTION
No action is required at this time.
INTRODUCTION/BACKGROUND
This memo provides an update of the Planning Division's recent efforts related to public
education and outreach regarding the Sensitive Lands Zoning Overlay chapter of the
Community Development Code.
The City recently adopted housekeeping changes to the Sensitive Lands chapter of the
Code (Ordinance 2527), and the Planning Division anticipated undertaking an update to
the Sensitive Lands Atlas this year. Together these efforts have raised the profile of the
Sensitive Lands program in the community. This has in turn highlighted a need for
more public outreach about the program, and elicited staff willingness to re-examine
some aspects of the code, particularly to determine if the City can provide greater
flexibility to landowners while maintaining environmental quality.
In response to public interest in this issue, staff has undertaken two new initiatives
related to the Sensitive Lands Code: a partnership with Friends of Tryon Creek State
Park (FOTCSP) and Tryon Creek Watershed Council (TCWC) to provide education and
resources related to conservation, and a "Second Look Work Group," to review the
Sensitive Lands Code and seek opportunities for greater flexibility for landowners.
These initiatives are described in more detail below.
In support of both these initiatives, staff has also outlined a general public outreach
effort. This program will include a mailing to inform current Sensitive Lands owners of
the resources available to them, hosting an information booth at the Farmer's Market,
61
Council Report
06/05/2009
Page 2
and providing informational talks at other community meetings and events. It will also
include development of improved informational publications and a website.
Staff has postponed work on the update to the Sensitive Lands Atlas until later this year,
to allow time for the Second Look Work Group to complete its work, and time to launch
the Tryon Creek partnership and general outreach efforts. The atlas update phase will
additionally include public outreach targeting the 450 landowners potentially impacted
by the changes. If the effort of the Second Look Work Group proves successful, staff
will also recommend utilizing a similar work group to review and make
recommendations on proposed changes to the Sensitive Lands Atlas.
DISCUSSION
Tryon Partnerships
Voluntary landscaping improvements are one of the most attractive and cost-effective
ways to improve environmental quality in residential areas. However, the City it is not
presently able to offer assistance to landowners who are interested in making voluntary
environmental enhancements outside the formal development-review process. The
City's Sensitive Lands chapter sets minimum standards for development adjacent
streams and wetlands and within the boundaries of tree groves, but the program is more
focused on requirements than incentives.
Friends of Tryon Creek State Park (FOTCSP) and Tryon Creek Watershed Council
(TCWC) currently offer a watershed restoration mentoring program, where a paid staff
person and a volunteer mentor work with a property owner to improve watershed
function and wildlife habitat. The program helps landowners identify opportunities and
constraints, develop a plan and timeline to make changes, and secure resources to
perform the work. The work with landowners may span a period of a year or more to
implement changes in the appropriate season. Their focus is primarily on removing
invasive species, preventing erosion, and installing native and drought-resistant plants.
This mentoring program is now available only to residents of the Tryon Creek
watershed, a minority of Lake Oswego homes. Through a partnership with FOTCSP
and TCWC, this opportunity will soon be available to all Lake Oswego residents. In FY
20010-11, FOTCSP and TCWC will provide six introductory "Landscaping for
Conservation" workshops free to Lake Oswego residents, and up to 50 home landscape
audits, free to Lake Oswego residents who attend the workshop and would like
assistance in implementing projects.
The Tryon Creek Watershed Council has been successful in its voluntary restoration
efforts in large part because it is able to act as a neutral convener, engaging public and
non-profit funders, community partners, and residents across a diverse spectrum.
Recognizing this, the City is also partnering with the Tryon Creek Watershed Council
and Friends of Tryon Creek State Park to initiate efforts to form a watershed council for
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Council Report
06/05/2009
Page 3
the Oswego Lake watershed. In the coming fiscal year, the TCWC and FOTCSP will
work to identify stakeholders, convene a working group, and develop a mission
statement and bylaws. The purpose of the Council will be to promote voluntary,
community-based actions and education to protect water quality in the City's largest
watershed. The expectation is that when the Council becomes established, the City will
be a member, but other community stakeholders and volunteers will also hold
leadership positions.
Second Look Work Group
In addition to providing greater support for voluntary restoration efforts, staff is also
seeking opportunities to improve the functioning of the City's current Sensitive Lands
code. Staff has proposed creating a five-member work group of residents and technical
experts to review the entire code and search for opportunities to streamline and provide
flexibility, with alternative options for compliance within the framework of the code.
The group's charge would be to take a "second look" at the Sensitive Lands code and
recommend changes that maintain or improve the current level of environmental
protection and maintain compliance with Metro and State standards. Within this
framework, the work group will be asked to identify changes that:
• Make the code more clear; and / or
• Simplify the application process; and / or
• Provide flexibility for landowners; and / or
• Eliminate any element that does not provide an environmental benefit.
At least one Planning Commission member and one Sensitive Lands owner should be
members of the work group. The majority of members should also have professional
backgrounds in environmental or land-use planning fields.
Staff suggests that the Second Look Work Group review Metro requirements and
examples from several other local cities at the outset, and then review Lake Oswego's
Sensitive Lands chapter, section by section, in a series of weekly meetings. The
intended outcome is a suite of recommendations for changes to the Code. The process
would be structured so that the group could maintain the focus and momentum required
to review the entire Sensitive Lands chapter in a reasonable amount of time. A well-
defined, efficient process would make economical use of staff and consulting resources.
An important initial element of the Second Look Work Group's schedule would be a
review of the environmental overlay zones from other Oregon cities, to provide
benchmarks of good practice. Council has also expressed an interest in this
information. The table on the following page makes a summary comparison of other
cities' protections for water resources, habitat areas, and individual trees.
63
a
Has
Water environmental Has
Width of water What resources are ordinance Where does tree
Jurisdiction resource buffers zoning
protected? limitingtree ordinance apply?
overlay? overlays other
than water? removal?
35-40'from Significant tree groves
Lake Oswego Yes topographic Yes shown on Sensitive Yes All trees 5 DBH or
break Lands Map greater
50'from edge of
Metro water, flat Yes; significant
Title 3 model code) Yes streams, 200' No habitat areas (Title No -
edge of water, 13).
ravines
50' from ed e of Trees removed during
Tigard g Slopes of 25% or development for
water, flat reater and significant subdivison, partition,
streams, up to g g
(Uses Clean Water Yes streams,
from ed e Yes fish and wildlife habitat Yes site development
200'
Services standards for g areas on Significant review, PD, CUP;
water resources) of water, Habitat Areas Maptrees in Sensitive
ravines.
Lands.
Historic trees/groves;
Landscape trees as a
Beaverton part of approved
Uses Clean Water See Tigard Trees and tree groves
g landscape plan; Street
Yes Yes shown on the zoning Yes
Services standards for above trees; Trees in SNRA
water resources) map (significant natural
resource area), and
Community trees.
Council Report
06/05/2009
Page 5
Has Has
Water Width of water environmental What resources are ordinance Where does tree
Jurisdiction resource buffers zoning protected? limiting tree ordinance apply?
overlay? overlays other ?
than water? removal.
Regional
conservation Trees 12" DBH or
show greater if lot has: (1)
plansno single family
protection areas dwelling, (2) not in a
based on
single family zone, (3)
topography; not used solely as
usually 30-200 Forested areas shown Yes single family
Portland Yes feet from Yes on the environmental g y
streams, with no zones mapresidence, and (4)
Can be further
set standard; divided. More
updating plans stringent tree removal
now and
50' regs apply in
proposing environmental
minimum overlays.
standard.
50'from edge of Permit required for
water, flat removal of 6" DBH
West Lin Yes streams, up to No - Yes native oaks,
n 200' from edge dogwoods, and
of water, madrones, 12" DBH
ravines. for other trees.
0)
UI
As the table shows, it is difficult to compare among jurisdictions because the boundaries
of a "significant resource" are defined differently. However, some similarities do emerge
from this comparison: most cities require buffers of at least 50 feet for year-round
streams, and 200 feet for streams in ravines. Most cities also appear to set stream
buffers according to the amount of flow or the area drained rather than the
environmental condition of the stream. Lake Oswego, in contrast, regulates according
to the condition of streams (habitat quality), and requires buffers of just 35-40 feet from
streams, unless they are in a ravine, in which case the buffer is 35-40 from the top of
the ravine. Many cities do also provide some protections to trees as well as to stream
and wetland buffers. However, Lake Oswego's tree protections are likely the strongest
in the region.
General Community Outreach
In addition to the two specific initiatives mentioned above, staff are also undertaking
some general outreach work to inform residents about these initiatives, to let them know
about the content of the housekeeping changes that were recently completed, and to be
available to answer questions and allay concerns about the Sensitive Lands program.
This effort will include a mailing to all current Sensitive Lands owners.
The City is also developing a more user-friendly webpage on environmental topics and
several brochures that explain the purposes and the application of the Sensitive Lands
program for ordinary readers. The materials and information about the free resources
available to residents will be available around the City this summer, with an information
table at community events.
The main messages of the City's Sensitive Lands outreach are:
• The City of Lake Oswego's sensitive lands program protects resources that are
important to water quality, land values, and community well-being,
• Environmental overlays are a part of a regional strategy for conservation, and all
Metro cities are participating with similar programs.
• The City's goal is to work with property owners to ensure that they can use, develop,
and enjoy their properties within the guidelines of the code.
ALTERNATIVES VES & FISCAL IMPACT
The City's contribution to the TCWC and FOTCSP partnership, for landscaping for
conservation workshops, home visits, and watershed council work is $10,000. This
amount is already included in the Planning budget, funded partly in the 2008-2009 fiscal
year and partly in 2009-2010.
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Council Report
06/05/2009
Page 7
The general public outreach effort is expected to add approximately $3,000 for
consulting and publication design. This amount is included in the budget for the current
fiscal year.
There are no other anticipated fiscal impacts from this initiative.
RECOMMENDATION
Staff recommends that Council provide informal clarification and feedback to inform next
steps on the Second Look Work Group and the TCWC / FOTCSP partnership. No
formal action is required at this time.
ATTACHMENTS
None
Sustainabilityhas been considered as part of this recommendation. .re
Reviewed by:
Department ector
f 1 a
Fi nce Dir ctor
Ale . I my e
City Manager
67