City of Canby Addendum
to the Clackamas County Multi-Jurisdictional
Natural Hazard Mitigation Plan
Prepared for
The City of Canby
Updated:
Date, 2024, (Resolution # 24-xx)
September 18, 2019, (Re
solution # 1327)
2013
2009
Photo Credit: City of Canby
Effective:
April XX, 2024-April XX, 2029
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This material is a result of tax-supported research and, as such, is not copyrightable.
It may be freely reprinted with the customary crediting of the source.
This Natural Hazard Mitigation Plan was prepared by:
Planning grant funding provided by:
Federal Emergency Management Agency (FEMA)
Project Award Number: DR-4562-39-P-OR
Additional Support Provided by:
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Table of Contents
PURPOSE .................................................................................................................................................................. 3
NHMP PROCESS, PARTICIPATION AND ADOPTION ............................................................................................................ 3
NHMP IMPLEMENTATION AND MAINTENANCE ................................................................................................................ 4
CAPABILITY ASSESSMENT ............................................................................................................................................. 5
Existing Authorities ........................................................................................................................................................ 5
Public Works .................................................................................................................................................................. 6
City Administration ........................................................................................................................................................ 7
Policies and Programs .................................................................................................................................................... 7
Personnel ....................................................................................................................................................................... 8
Capital Projects .............................................................................................................................................................. 8
Federal or State Funded Mitigation Successes ............................................................................................................... 9
Capital Resources ........................................................................................................................................................... 9
Findings .......................................................................................................................................................................... 9
MITIGATION PLAN MISSION ....................................................................................................................................... 10
MITIGATION PLAN GOALS .......................................................................................................................................... 10
MITIGATION STRATEGY .............................................................................................................................................. 12
RISK ASSESSMENT..................................................................................................................................................... 15
Hazard Analysis ............................................................................................................................................... 15
Community Characteristics ............................................................................................................................. 16
Community Lifelines ........................................................................................................................................ 20
Critical Facilities ............................................................................................................................................................ 20
Critical Infrastructure ................................................................................................................................................... 21
Essential Facilities ......................................................................................................................................................... 21
Environmental Facilities ............................................................................................................................................... 21
Vulnerable Populations ................................................................................................................................................ 21
Hazardous Materials .................................................................................................................................................... 21
Economic Assets/Population Centers .......................................................................................................................... 22
Cultural and Historic Assets.......................................................................................................................................... 22
Hazard Characteristics .................................................................................................................................... 22
Drought ........................................................................................................................................................................ 22
Earthquake (Cascadia Subduction Zone) ...................................................................................................................... 23
Earthquake (Crustal) .................................................................................................................................................... 25
Flood ............................................................................................................................................................................ 30
Landslide ...................................................................................................................................................................... 32
Severe Weather............................................................................................................................................................ 34
Extreme Heat ............................................................................................................................................................. 34
Windstorm ................................................................................................................................................................. 35
Winter Storm (Snow/Ice) ........................................................................................................................................... 36
Volcanic Event .............................................................................................................................................................. 37
Wildfire......................................................................................................................................................................... 38
ATTACHMENT A: ACTION ITEM CHANGES ........................................................................................................ 41
ATTACHMENT B: PUBLIC INVOLVEMENT SUMMARY ........................................................................................ 42
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List of Tables
TABLE CA-1 ACTION ITEMS ............................................................................................................................................ 13
TABLE CA-2 HAZARD ANALYSIS MATRIX ........................................................................................................................... 16
TABLE CA-3 COMMUNITY CHARACTERISTICS ...................................................................................................................... 19
TABLE CA-4 CRITICAL FACILITIES IN CANBY ........................................................................................................................ 20
TABLE CA-5 RAPID VISUAL SURVEY SCORES ....................................................................................................................... 27
TABLE CA-6 EXPECTED DAMAGES AND CASUALTIES FOR THE CSZ FAULT AND PORTLAND HILLS FAULT:
EARTHQUAKE, SOIL MOISTURE, AND EVENT TIME SCENARIOS ......................................................................................... 28
TABLE CA-7 STATUS OF ALL HAZARD MITIGATION ACTIONS IN THE PREVIOUS PLAN .................................................................. 41
List of Figures
FIGURE CA-1 UNDERSTANDING RISK ................................................................................................................................ 15
FIGURE CA-2 CASCADIA SUBDUCTION ZONE EXPECTED SHAKING ........................................................................................... 24
FIGURE CA-3 ACTIVE CRUSTAL FAULTS, EPICENTERS (1971-2008), AND SOFT SOILS ............................................................... 25
FIGURE CA-4 FEMA FLOOD ZONES ................................................................................................................................. 30
FIGURE CA-5 LANDSLIDE SUSCEPTIBILITY EXPOSURE ............................................................................................................ 33
FIGURE CA-6 WILDFIRE RISK .......................................................................................................................................... 38
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Purpose
This is an update of the Canby addendum to the Clackamas County Multi-Jurisdictional Natural Hazard
Mitigation Plan (NHMP). This addendum supplements information contained in Volume I (Basic Plan)
which serves as the NHMP foundation and Volume III (Appendices) which provide additional
information. This addendum meets the following requirements:
• Multi-Jurisdictional Plan Adoption §201.6(c)(5),
• Multi-Jurisdictional Participation §201.6(a)(3),
• Multi-Jurisdictional Mitigation Strategy §201.6(c)(3)(iv) and
• Multi-Jurisdictional Risk Assessment §201.6(c)(2)(iii).
Updates to Canby’s addendum are further discussed throughout the NHMP and within Volume III,
Appendix B, which provides an overview of alterations to the document that took place during the
update process.
Canby adopted their addendum to the Clackamas County Multi-jurisdictional NHMP on [DATE TBD,
2024]. FEMA Region X approved the Clackamas County NHMP on [DATE TBD, 2024] and the City’s
addendum on [DATE TBD, 2024]. With approval of this NHMP the City is now eligible to apply for the
Robert T. Stafford Disaster Relief and Emergency Assistance Act’s hazard mitigation project grants
through [DATE TBD-1, 2024].
NHMP Process, Participation and Adoption
This section of the NHMP addendum addresses 44 CFR 201.6(c)(5), Plan Adoption, and 44 CFR
201.6(a)(3), Participation.
In addition to establishing a comprehensive community-level mitigation strategy, the Disaster
Mitigation Act of 2000 (DMA2K), and the regulations contained in 44 CFR 201, require that jurisdictions
maintain an approved NHMP to receive federal funds for mitigation projects. Local adoption, and
federal approval of this NHMP ensures that the city will remain eligible for pre- and post-disaster
mitigation project grants.
The Oregon Partnership for Disaster Resilience (OPDR) at the University of Oregon’s Institute for Policy
Research, and Engagement (IPRE) collaborated with the Oregon Office of Emergency Management
(OEM), Clackamas County, and Canby to update their NHMP.
The Clackamas County NHMP, and Canby addendum, are the result of a collaborative effort between
citizens, public agencies, non-profit organizations, the private sector, and regional organizations. The
Canby HMAC guided the process of developing the NHMP.
Convener
The Canby Economic Development Director and Communications Specialist serves as the NHMP
addendum convener. The convener of the NHMP will take the lead in implementing, maintaining and
updating the addendum to the Clackamas County NHMP in collaboration with the designated convener
of the Clackamas County NHMP (Clackamas County Resilience Coordinator).
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Representatives from the City of Canby HMAC met formally and informally, to discuss updates to their
addendum (Volume III, Appendix B). The HMAC reviewed and revised the City’s addendum, with focus
on the NHMP’s risk assessment and mitigation strategy (action items).
This addendum reflects decisions made at the designated meetings and during subsequent work and
communication with the Clackamas County Resilience Coordinator and the OPDR. The changes are
highlighted with more detail throughout this document and within Volume III, Appendix B. Other
documented changes include a revision of the City’s risk assessment and hazard identification sections,
NHMP mission and goals, action items, and community profile.
The Canby HMAC was comprised of the following representatives:
• Convener Jamie Stickel, Economic Development Director & Communications Specialist
• Jerry Nelzen, Public Works Director
• Jorge Tro, Canby Police Chief
• Eileen Stein, City Administrator
The HMAC served as the local review body for the NHMP update.
NHMP Implementation and Maintenance
The City Council will be responsible for adopting the Molalla addendum to the Clackamas County
NHMP. This addendum designates a HMAC and a convener to oversee the development and
implementation of action items. Because the City addendum is part of the County’s multi-jurisdictional
NHMP, the City will look for opportunities to partner with the County. The City’s HMAC will convene
after re-adoption of the Molalla NHMP addendum on an annual schedule. The County is meeting on a
semi-annual basis and will provide opportunities for the cities to report on NHMP implementation and
maintenance during their meetings. The convener will serve as the conveners and will be responsible
for assembling the HMAC. The HMAC will be responsible for:
• Reviewing existing action items to determine suitability of funding;
• Reviewing existing and new risk assessment data to identify issues that may not have been
identified at NHMP creation;
• Educating and training new HMAC members on the NHMP and mitigation actions in general;
• Assisting in the development of funding proposals for priority action items;
• Discussing methods for continued public involvement;
• Evaluating effectiveness of the NHMP at achieving its purpose and goals (use Table 26,
Volume I, Section 4, as one tool to help measure effectiveness); and
• Documenting successes and lessons learned during the year.
The HMAC will be responsible for the following activities described in detail in Volume I, Section 4:
The jurisdiction will utilize the same implementation and maintenance process identified in Volume I,
Section 4.
The jurisdiction will provide continued public participation during the plan maintenance process
through periodic presentations to elected officials, public meetings, postings on social media, and/or
through interactive content on the jurisdiction’s website (for more information see Volume I, Section
4).
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The jurisdiction will utilize the same action item prioritization process as the County (for more
information see Volume I, Section 4 and Volume III, Appendix E).
Implementation through Existing Programs
This NHMP is strategic and non-regulatory in nature, meaning that it does not necessarily set forth any
new policy. It does, however, provide: (1) a foundation for coordination and collaboration among
agencies and the public in the city; (2) identification and prioritization of future mitigation activities;
and (3) aid in meeting federal planning requirements and qualifying for assistance programs. The
mitigation plan works in conjunction with other city plans and programs including the Comprehensive
Land Use Plan, Capital Improvements Plan, and Building Codes, as well as the Clackamas County NHMP,
and the State of Oregon NHMP.
The mitigation actions described herein (and in Attachment A) are intended to be implemented
through existing plans and programs within the city. Plans and policies already in existence have
support from residents, businesses and policy makers. Where possible, Canby will implement the
NHMP’s recommended actions through existing plans and policies. Many land-use, comprehensive and
strategic plans get updated regularly, allowing them to adapt to changing conditions and needs.
Implementing the NHMP’s action items through such plans and policies increases their likelihood of
being supported and applied. Implementation opportunities are further defined in action items when
applicable.
Capability Assessment
The Capability Assessment identifies and describes the ability of the City of Canby to implement the
mitigation strategy and associated action items. Capabilities can be evaluated through an examination
of broad categories, including: existing authorities, policies, programs, funding, and resources.
Existing Authorities
Hazard mitigation can be executed at a local scale through three (3) methods: integrating hazard
mitigation actions into other local planning documents (i.e., plan integration), adopting building codes
that account for best practices in structural hardening, and codifying land use regulations and zoning
designations that prescribe mitigation into development requirements. The extent to which a
municipality or multi-jurisdictional effort leverages these approaches is an indicator of that
community’s capabilities.
Comprehensive Plan
Oregon’s Statewide Planning Goal 7 requires comprehensive planning within every jurisdiction that is
designed to reduce risks to people and property from natural hazards. Canby addresses Statewide
Planning Goal 7 Natural Hazards as part of their Comprehensive Plan Element, Natural Hazards. This
plan was originally adopted in 1984. Chapter 4, Environmental Concerns, includes findings related to
natural hazards. This chapter establishes the H overlay zone, which restricts development in areas of
identified flood hazards. Other hazards discussed are steep slopes (along riverbanks), expansive soils,
high water tables, and shallow topsoil.
The City of Canby is pursuing updating this Comprehensive Plan in 2023-2024, following the adoption of
new Housing Needs and Economic Opportunity analyses in 2023.
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Planned updates to the jurisdiction’s Goal 7 element or its broader comprehensive plan will reflect the
data and findings within this NHMP and integrate analyses of future climate and natural hazard impacts
into the community’s long-range plans.
Land Use Regulations
Existing land use policies that define zoning and address hazardous conditions provide another source
of mitigation capability. 
Canby Development Code
Chapter 16.40 Hazard Overlay Zone (H) assures that the development will not result in an unacceptable
level of risk because of hazardous conditions. It is intended to be applied only to those specific
properties which have been identified as having steep slopes or potential for flooding. It utilizes the
flood insurance study, including the flood insurance rate map, dated June 17, 2008.
Chapter 15.12 Flood Hazard Protection Ordinance c
omplies with federal and state regulations related
to flood hazard protection. It was last updated in 2008 and is based upon the Oregon Model Flood
Hazard Prevention code of that time and includes provisions addressing substantial
improvement/substantial damage.
The Planning Division is responsible for processing all land use applications within the City of Canby
wh
ich includes subdivisions, partitions, and site and design review. We also provide development
services, zoning reviews, and provide the public with information on all property-related issues within
the City limits. City approval is required before Clackamas County can issue a building permit. 
They work closely with the County and neighboring jurisdictions to ensure plans are aligned.
Structural Building Codes
The Oregon Legislature recently adopted updated building codes for both residential (2023 adoption)
and commercial structures (2022) since the last update of this Plan. These building codes are based on
the 2021 version of the International Building Code, International Fire Code, and International Existing
Building Code.
Clackamas County 
currently issues all building, plumbing, and electrical permits for the City of Canby.
The Clackamas County Building Department administers and enforces the 2022 Oregon Structural
Specialty Code and the 2022 Oregon Fire Code. As a result, both new residential and commercial
structures will be required to build according to the latest seismic and wind hardening standards in
addition to requiring fire resistant building materials for those structures constructed in proximity or
within the WUI.
Public Works
The City of Canby Public Works Department is responsible for streets, including street lighting, storm
drains, parks, building maintenance, Zion Memorial Cemetery, and the Wastewater Treatment Plant.
Water and electric are administered by Canby Utility.
Much of their work is associated with the reduction of hazards to the community and the
implementation of resilience measures.
2019 Canby Public Works Standards
The Canby Public Works Standards provide guidance for the development of public infrastructure
(streets, sanitary sewer, and storm drainage).
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City Administration
The City Council of Canby has the responsibility of developing and adopting the annual city budget.
Integrating hazard mitigation goals and projects into the annual budget is key to implementing the plan.
The City Council tries to broadly address resilience planning needs while it determines city and
departmental priorities and looks for multiple-impact projects wherever possible. They also work with
staff to apply for federal and state grant funding to pursue larger projects that are outside of general
fund capacity.
Policies and Programs
This Plan directs Canby and Clackamas County to explore integration into other planning documents
and processes. Canby has made progress in integrating the NHMP into its portfolio of planning
processes and programs over the last five years.
Housing Needs Analysis, 2023
The Housing Needs Analysis deducted the following lands from the residential land inventory:
• Open water of at least one-half acre in size.
• Land within the 100-year floodplains. This includes lands in flood-hazard areas as identified by
the Flood Prone classification of Canby’s Comprehensive Plan
• Wetlands identified by the City and identified in the Comprehensive Plan as a barrier for
future development
• Land within Metro’s ORCA (Outdoor Recreation & Conservation Areas) data set
• Land in public ownership with no development potential
• Land with slopes greater than 25%
The Housing Need Analysis found that population growth in Canby will require the addition of 2,286
new dwelling units between 2023 and 2043. After removing constrained lands from the vacant land
inventory, the current Canby UGB is not sufficient to accommodate these future housing needs.
Urban Growth Boundary Expansion
The City has identified a need for a potential Urban Growth Boundary (UGB) expansion in the next five
years, to add approximately 100 acres for housing and 440 acres for employment to the City’s planning
area. The Preliminary UGB expansion study area includes 1,600 acres of land surrounding the current
UGB. Known hazards will be reviewed as part of this study to help determine the most resilient areas
for expansion/development.
Stormwater Master Plan Update, 2023
This Stormwater Master Plan updates Canby’s guiding principles for stormwater system design, the
2014 Capital Improvement Plan, and all project costs, and provides guidance for compliance with the
Water Pollution Control Facility Permit issued to the City of Canby. The existing conveyance systems
throughout the City are comprised of gravity storm drainage pipes, open drainage ways or ditches,
trench drains, and UICs.
The City of Canby does not currently have stormwater water quality treatment requirements and the
City is not a “regulated” small Municipal Storm Sewer System (MS4) subject to the EPA Phase II
Stormwater Rule. The primary basis for adopting a Capital Improvement Plan for the City of Canby is to
improve stormwater collection and disposal deficiencies in the system.1 This plan identifies stormwater
areas of concern, including localized/urban flooding, and recommends projects to address these issues
(through 2043), including some long-range projects in anticipation of future classification as an EPA
regulated MS4.
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Parks and Recreation Master Plan, 2022
This update to the 2002 Parks Master Plan addresses a growing need for recreational resources within
the community. It includes acquisition and development goals that include protection and restoration
of sensitive riparian resources and wetlands along the Molalla River (“Molalla River Greenway”
concept).
Community Wildfire Protection Plan (2024)
The Clackamas County Community Wildfire Protection Plan (CWPP) will be incorporated into this Plan
as a functioning annex. The NHMP will also be integrated into the City’s Capital Improvement Plan, to
be adopted by early 2024.
Personnel
The following Canby personnel have assignments related to natural hazard mitigation planning and
implementation:
Emergency Management: Jorge Tro, Police Chief
Public Information Officer: Jamie Stickel, Economic Development Director | Communications Specialist
Floodplain Manager: Planning Director
Grant writing (for Public Works or emergency management): Jamie Stickel, Economic Development
Director | Communications Specialist
Capital improvement planning: Jerry Nelzen, Public Works Director
Capital improvement execution: Jerry Nelzen, Public Works Director
Canby does not have any employees solely designated to Emergency Management or Mitigation. These
personnel integrate hazards and resilience planning into their greater work programs to the best of
their abilities. However, there is limited capacity to expand upon their capabilities or workloads.
Capital Projects
Canby has implemented recommendations from the last NHMP into its capital improvement projects
over the last 5 years, including:
The following mitigation-related or resilience projects have been completed since 2018:
Ongoing projects that enhance the City’s resilience include:
• Emergency Operations Plan Update (expected 2024)
Proposed projects that relate to hazard mitigation and resilience within the next five years include:
• Wastewater Treatment Plant site improvements
• New wastewater treatment pump station
• Storm water system upsizing/capacity projects
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Federal or State Funded Mitigation Successes
The community has several examples of mitigation success including the following projects funded
through FEMA Hazard Mitigation Assistance and the Oregon Infrastructure Finance Authority’s Seismic
Rehabilitation Grant Program
1
.
FEMA Funded Mitigation Successes
• 2014: PDMC-PJ-10-OR-2011-001, Canby Water Reservoir Seismic Retrofit
• 2007: DR-1510-0005-R, Highway 99E Undergrounding Project, Canby Utility Board
• 2004: PDMC-PJ-10-OR-2003-003, City of Canby/Canby Telephone Central Offices Seismic
Upgrade
Seismic Rehabilitation Grant Program Mitigation Successes
• none identified.
Capital Resources
Canby maintains several capital resources that have important roles to play in the implementation of
the natural hazard mitigation plan.
Critical facilities with power generators for use during emergency blackouts: Canby Public Works, Canby
Police Department, and Canby Fire Station (main station and northside station). NOTE: Planned
upgrades to emergency power to the Canby Civic Center and the Canby Adult Center.
Schools: Trost Elementary School, Baker Prairie Middle School, and Canby Highschool
Warming/Cooling Shelters: Canby Public Library, Zoar Lutheran Church, the Canby Center, Canby Adult
Center, Denny’s Restaurant – open hours and days vary by location.
Food pantries: The Canby Center serves as the food pantry in Canby. NOTE: The Canby Center is
expanding and the plans are consolidate the food pantry to a single location at the Canby Center, so I
have removed St. Patrick’s Church
Fueling storage: Public Works has plans to upgrade the City of Canby’s fueling storage in 2024 to
include 12,000 gallons of diesel, 12,000 gas.
Findings
Several important findings from this capability assessment informed the design of the Plan’s mitigation
strategy and aided in prioritizing action items.
Staffing Limitations and Capacity
Canby staff are assigned hazard mitigation responsibilities as a (small) part of their larger job
responsibilities. Restricted capacity reduces the breadth of the programming the community can
undertake in any year. The city relies upon its relationships with the County and other cities within its
region to expand its operations.
Reliance upon outside funding streams and local match requirements
Canby operates on a limited budget with many conflicting priorities. This leaves few opportunities for
using local financial resources to implement hazard mitigation work. They lean heavily upon state and
1
The Seismic Rehabilitation Grant Program (SRGP) is a state of Oregon competitive grant program that provides funding for
the seismic rehabilitation of critical public buildings, particularly public schools, and emergency services facilities.
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federal grant funds as the primary means for securing mitigation funding. Hazard mitigation grants such
as HMGP and BRIC require 10-25% local funding match, as well as extra staff capacity and expertise to
navigate the application process and manage the funding.
Leveraging Partnerships with Public and Nonprofit Entities
Regional planning displayed in Community Wildfire Protection Planning process demonstrates the City’s
ability to effectively share information and identify priority needs.
Mitigation Plan Mission
The 2024 HMAC reviewed the previous NHMP Mission and Goals in comparison to the State NHMP
Goals and determined that they would make necessary updates to include references to community
lifelines and to advance equity and inclusion in hazard mitigation.
The NHMP mission states the purpose and defines the primary functions of NHMP. It is intended to be
adaptable to any future changes made to the NHMP and need not change unless the community’s
environment or priorities change.
The mission of the NHMP is to:
Enhance county resiliency and capacity to address natural hazards by promoting sound public policy
and effective mitigation strategies designed to equitably reduce risk and impacts on community
members, community lifelines, historic and cultural resources property, and ecological systems.
This can be achieved by increasing public awareness, documenting the resources for risk reduction and
loss-prevention, and identifying activities to guide the county towards building a safer, more
sustainable community.
Mitigation Plan Goals
Mitigation plan goals are more specific statements of direction that residents and public and private
partners can take while working to reduce the risk from natural hazards. These statements of direction
form a bridge between the broad mission statement and action items. The goals listed here serve as
checkpoints as agencies and organizations begin implementing mitigation action items.
Meetings with the HMAC, previous hazard event reports, and the previous NHMPs served as methods
to obtain input and identify priorities in developing goals for reducing risk and preventing loss from
natural hazards.
All the NHMP goals are important and are listed below in no order of priority. Establishing community
priorities within action items neither negates nor eliminates any goals, but it establishes which action
items to consider implementing first, should funding become available.
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Goal 1: Protect Life and Property
• Develop and implement mitigation and climate adaptation projects and policies that aid in
protecting lives by making homes, businesses, community lifelines, and other property more
resilient to natural hazards and impacts from climate change.
• Establish mitigation projects and policies that minimize losses and repetitive damages from
recurring disasters while promoting insurance coverage for severe hazards.
• Improve hazard identification and risk assessment information to inform and provide
recommendations for enhanced resilience in new development decisions and promote
preventative measures for existing development in areas vulnerable to natural hazards.
Goal 2: Enhance Natural Systems
• Incorporate natural hazard mitigation planning and activities into watershed planning, natural
resource management, natural systems enhancement, and land use planning to protect life,
property, and ecological system.
Goal 3: Augment Emergency Services
• Strengthen emergency operations by enhancing communication, collaboration, and
coordination of natural hazard mitigation activities and policies across agencies at all levels and
regions of government, sovereign tribal nations, and the private sector.
Goal 4: Encourage Partnerships for Implementation
• Improve communication, coordination, and participation among and with public agencies,
community members, community lifelines, and private sector organizations to prioritize and
implement hazard mitigation activities and policies.
• Enhance efforts toward identifying and optimizing opportunities across state agencies,
surrounding communities, and private entities for resource sharing, mutual aid, and funding
sources/support.
Goal 5: Promote Public Awareness
• Build community resilience and awareness and reduce the effects of natural hazards and
climate change through community-wide engagement, collaboration, resource-sharing,
learning, leadership-building, and identifying mitigation project-related funding opportunities.
Goal 6: Advance Equity and Inclusion
• Mitigate the inequitable impacts of natural hazards by prioritizing the directing of resources
and efforts to build resilience and engagement in the most vulnerable communities least able
to prepare, respond, and recover.
• Strengthen efforts aimed at increasing engagement, outreach, and collaboration with
community and cultural organizations and agencies that are dedicated to providing services
and support to vulnerable and underserved communities.
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Mitigation Strategy
This section of the NHMP addendum addresses 44 CFR 201.6(c)(3(iv), Mitigation Strategy.
The City’s mitigation strategy (action items) were first developed during the 2003 NHMP planning
process and revised during subsequent NHMP updates. During these processes, the HMAC assessed the
City’s risk, identified potential issues, and developed a mitigation strategy (action items). During the
2023 update process the City re-evaluated their mitigation strategy (action items). During this process
action items were updated, noting what accomplishments had been made and whether the actions
were still relevant; any new action items were identified at this time (see Attachment A for more
information on changes to action items).
Action Items
Table CA-1 documents the title of each action along with, the lead organization, partners, timeline,
cost, and potential funding resources. The HMAC decided to modify the prioritization of action items in
this update to reflect current conditions (risk assessment), needs, and capacity. High priority actions are
shown with orange highlight. The City will focus their attention, and resource availability, upon these
achievable, high leverage, activities over the next five years. Although this methodology provides a
guide for the HMAC in terms of implementation, the HMAC has the option to implement any of the
action items at any time. This option to consider all action items for implementation allows the
committee to consider mitigation strategies as new opportunities arise, such as capitalizing on funding
sources that could pertain to an action item that is not currently listed as the highest priority. Refer to
Attachment A for changes to actions since the previous NHMP.
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Risk Assessment
This section of the NHMP addendum addresses 44 CFR 201.6(b)(2) - Risk Assessment. In addition, this
chapter can serve as the factual basis for addressing Oregon Statewide Planning Goal 7 – Areas Subject
to Natural Hazards. Assessing natural hazard risk has three phases:
• Phase 1: Identify hazards that can impact the jurisdiction. This includes an evaluation of
potential hazard impacts – type, location, extent, etc.
• Phase 2: Identify important community assets and system vulnerabilities. Example
vulnerabilities include people, businesses, homes, roads, historic places and drinking water
sources.
• Phase 3: Evaluate the extent to which the identified hazards overlap with or have an impact
on, the important assets identified by the community.
The local level rationale for the identified mitigation strategies (action items) is presented herein and
within Volume I, Section 3 and Volume III, Appendix C. The risk assessment process is graphically
depicted in Figure CA-1. Ultimately, the goal of hazard mitigation is to reduce the area of risk, where
hazards overlap vulnerable systems.
Figure CA-1 Understanding Risk
Source: USGS- Oregon Partnership for Disaster Resilience Research Collaboration, 2006
Hazard Analysis
The Canby HMAC developed their hazard vulnerability assessment (HVA), using their previous HVA and
the County’s HVA as a reference. Changes from their previous HVA and the County’s HVA were made
where appropriate to reflect distinctions in vulnerability and risk from natural hazards unique to
Molalla, which are discussed throughout this addendum.
Table CA-2 shows the HVA matrix for Molalla
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listing each hazard in order of rank from high to low. For local governments, conducting the hazard
analysis is a useful step in planning for hazard mitigation, response, and recovery. The method provides
the jurisdiction with a sense of hazard priorities but does not predict the occurrence of a hazard. Two
catastrophic hazards (Cascadia Subduction Zone earthquake and Crustal earthquake) and two chronic
hazards (winter storm and flood) rank as the top hazard threats to the City (Top Tier). Landslide,
wildfire, extreme heat, and drought comprise the next highest ranked hazards (Middle Tier), while
windstorm and volcanic event comprise the lowest ranked hazards (Bottom Tier).
Table CA-2 Hazard Analysis Matrix
Source: Canby HMAC, 2023.
Community Characteristics
Table CA-3 and the following section provides information on City specific demographics and assets.
Many of these community characteristics can affect how natural hazards impact communities and how
communities choose to plan for natural hazard mitigation. Considering the City specific assets during
the planning process can assist in identifying appropriate measures for natural hazard mitigation.
Canby has grown substantially since its incorporation in 1893 and has an area today of about 4 square
miles. Canby lies in the heart of very productive agricultural lands.
Canby’s climate is consistent with the Marine west coast climate zone, with warm summers and cool,
wet winters. Canby receives most of its rainfall between October and May, and averages 45 inches of
rain.
2
Snowfall is rare but can occur annually.
The City of Canby is located on a relatively flat terrain and, with few exceptions, has only gentle changes
in the topography of less than 30 feet within the city limits and Urban Growth Boundary (UGB),
between 140 to 170 feet above mean sea level. The southwest portion of the city drops abruptly at the
Molalla River to an elevation of approximately 80 feet. At the northern border of the UGB, the
topography gradually slopes to the Willamette River, dropping from an elevation of approximately 130
feet to 100 feet at the city’s wastewater treatment facility. To the east of Canby, the topography
changes very little until beyond the urban growth boundary, where the ground has undulating gentle
hills in the southeastern areas and steep rocky cliffs in the northeastern areas along the Willamette
River.
2
“Monthly Average for Canby, OR” The Weather Channel Interactive, Inc. Retrieved April 11, 2019.
Hazard History Vulnerability
Maximum
Threat
Probability
Total
Threat
Sc
ore
Hazard
Rank
Hazard
Tiers
Earthquake - Cascadia 4 45 100 49 198 1
Earthquake - Crustal 6 50 100 21 177 2
Winter Storm 18 30 70 49 167 3
Flood 16 20 70 56 162 4
Landslide 14 35
30 63 142 5
Wildfire 12 25 70 21 128 6
Extreme Heat Event 16 15
40 56 127 7
Drought 10 15 50 42 117 8
Windstorm 14 15 30 42 101 9
Volcanic Event 2 15 50 7 74 10
Bottom
Tier
Top
Tier
Middle
Tier
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Clackamas County NHMP: Canby Addendum Page| 17
Population, Housing, and Income
Between 2016 and 2022 the City grew by 2,559 people (16%; as of 2022 the population was 18,979).
Between 2022 and 2045 the population is forecast to grow by 22% to 23,104.
Most of the population is White/Caucasian (76%) and about 18% of the population is Hispanic or Latino.
The poverty rate is 9% (8% of children under 18, 7% for people 65 and older), 9% do not have health
insurance, and 51% of renters pay more than 30% of their household income on rent (35% for owners).
About 29% of the population has a bachelor’s degree or higher (10% do not have a high school degree).
Approximately 14% of the population lives with a disability (34% of population 65 and older), and 22%
are either below 15 (24%) or over 65 (19%) years of age. About 11% of the population are 65 or older
and living alone and 9% are single parents.
The City includes a diversity of land uses but is zoned primarily residential. About 72% of housing units
are single-family, 23% are multifamily, and 5% are mobile homes. Less than one-fifth of homes (16%)
were built before 1970 and 52% were built after 1990. Newer homes are more likely to be built to
current seismic, flood, wildfire, and other hazard standards. Two-thirds (66%) of housing units are
owner occupied, 32% are renter occupied, and 2% are vacant.
Transportation/Infrastructure
Canby is accessible by state highway 99E, running north to south on the city’s west side. Congestion on
99E can result in the diversion of traffic onto City streets. Canby is also bisected by the Union Pacific
Railroad main line, which separates the North side from the South; passenger service is provided by
Amtrak.
Motor vehicles represent the dominant mode of travel through and within Molalla. Ten percent (10%)
of renters and 2% of owners do not have a vehicle. Most workers drive alone to work (73%); 6%
carpool, 2% use public transit, 4% either walk or use a bicycle, and 10% work at home.
The City’s public transit is provided by the Canby Area Transit system, which provides shuttle
transportation to scheduled route locations within Canby. The Canby Ferry, one of three ferries still in
operation on the Willamette River, can transport nine vehicles per trip across the Willamette River. The
availability and quality of pedestrian and bicycling facilities (sidewalks, bike lanes, and pathways) is
inconsistent, generally newer neighborhoods have facilities.
Economy
Canby is a relatively self-sufficient city that operates its own electric and water service (uncommon in
Oregon). The business district includes a thriving downtown core as well as flourishing businesses along
Highway 99E. The Canby area has a multitude of attractions tied to the bountiful nursery industry,
which attract thousands of visitors annually. In Clackamas County, 75% of the nursery acreage is in the
vicinity of Canby.
To a certain extent, Canby has been a “bedroom” community for Portland and Salem, though the City
hopes to moderate this trend by increasing industrial development. The City is accessible by rail and
highway and is located outside of the Portland Air Quality Maintenance area (AQMA). About 49% of the
resident population 16 and over is in the labor force (8,873 people) and are employed in a variety of
occupations including management, business, and financial (19%), professional and related (16%),
office and administrative (12%), construction, extraction, and maintenance (11%), and sales related
(10%) occupations.
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Most workers residing in the city (84%, 7,049 people) travel outside of the city for work primarily to
Portland and surrounding areas.
3
A significant population of people travel to the city for work, (82% of
the workforce, 6,277 people) primarily from Portland and surrounding areas.
4
3
U.S. Census Bureau. LEHD Origin-Destination Employment Statistics (2002-2021). Longitudinal-Employer Household
Dynamics Program, accessed on December 19, 2023 at https://onthemap.ces.census.gov.
4
Ibid.
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Clackamas County NHMP: Canby Addendum Page| 19
Table CA-3 Community Characteristics
Source: U.S. Census Bureau, 2016-2021 American Community Survey; Portland State University, Population Research Center,
"Annual Population Estimates", 2016 & 2022; Portland State University, Population Research Center, "Population Forecast
Tables", (2023, Preliminary).
Note: ACS 5-year estimates represent average characteristics from 2012-2016 or 2017-2021. Sampling error may result in low
reliability of data. This information or data is provided with the understanding that conclusions drawn from such information
are the responsibility of the user. Refer to the original source documentation to better understand the data sources, results,
methodologies, and limitations of each dataset presented.
2016 Population Estimate 16,420
2022 Population Estimate 18,979 16% Single-Family (includes duplexes) 4,882 72%
2045 Population Forecast* 23,104 22% Multi-Family 1,567 23%
Mobile Homes (includes RV, Van, etc.) 374 5%
< 1%
1% Family Household 4,814 72%
1% Married couple (w/ children) 1,696 25%
0% Single (w/ children) 623 9%
76% Living Alone 65+ 737 11%
0%
4% Pre-1970 1,109 16%
Hispanic or Latino/a (of any race)
18% 1970-1989 2,188 32%
Limited or No English Spoken 1,430 8% 1990-2009 2,867 42%
2010 or later 659 10%
Less than 5 Years 745 4%
Less than 15 Years 3,211 18% Owner-occupied 4,478 66%
65 Years and Older 3,010 17% Renter-occupied 2,183 32%
85 Years and Older 371 2% Seasonal 0 0%
0.52 Vacant 162 2%
Total Disabled Population 2,485 14% No Vehicle (owner occupied) 73 2%
Children (Under 18) 136 3% Two+ vehicles (owner occupied) 3,680 82%
Working Age (18 to 64) 1,346 12% No Vehicle (renter occupied) 219 10%
Seniors (65 and older) 1,003 34% Two+ vehicles (renter occupied) 976 45%
Less than $15,000 485 7% In labor Force (% Total Population) 8,873 49%
$15,000-$29,999 673 10% Unemployed (% Labor Force) 259 3%
$30,000-$44,999 522 8%
$45,000-$59,999 818 12% Management, Business, & Financial 1,637 19%
$60,000-$74,999 488 7% Professional & Related 1,446 16%
$75,000-$99,999 1,295 19%
Office & Administrative
1,023 12%
$100,000-$199,999 1,831 28%
Construction, Extraction, & Maint.
941 11%
$200,000 or more 549 8%
Sales & Related
917 10%
$83,948
0.40 No Health Insurance 1,597 9%
Public Health Insurance 6,472 36%
Total Population 1,647 9% Private Health Insurance 12,364 69%
Children (Under 18) 348 8%
Working Age (18 to 64) 1,088 10% Drove Alone 6,388 73%
Seniors (65 and older) 211 7% Carpooled 565 6%
Public Transit 158 2%
Owners with a Mortgage 1,101 35% Motorcycle 0 0%
Owners without a Mortgage 263 20% Bicycle/Walk 313 4%
Renters 1,105 51% Work at Home 853 10%
Housing Cost Burden (Cost > 30% of household income)
Some Other Race
Two or More Races
Gini Index of Income Inequality
Poverty Rates (Percent age cohort)
Occupation (Top 5) (Employed 16+)
Health Insurance
Transportation to Work (Workers 16+)
Population Characteristics
Population
Growth
Age Dependency Ratio
Median Household Income
Asian
Black/ African American
Native Hawaiian and Other Pacific Islander
White
American Indian and Alaska Native
Income Characteristics
Households by Income Category
Household Characteristics
Employment Characteristics
Race
Vulnerable Age Groups
Disability Status (Percent age cohort)
Housing Units
Household Type
Year Structure Built
Housing Tenure and Vacancy
Vehicles Available (Occupied Units)
Labor Force (Population 16+)
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Community Lifelines
This section outlines the resources, facilities, and infrastructure that, if damaged, could significantly
impact the public safety, economic conditions, and environmental integrity of the city. Community
Lifelines are the most fundamental services in the community that, when stabilized, enable all other
aspects of society to function. Mitigating these facilities will increase the community’s resilience.
The community lifelines identified below were identified by the City of Molalla. This integrated network
of assets, services, and capabilities are used day-to-day to support the recurring needs of the
community and enable all other aspects of society to function. Decisive intervention (e.g., rapid re-
establishment or employment of contingency response solutions) is required to maintain/reestablish
these facilities and services following a hazard incident.
Critical Facilities
Facilities that are critical to government response, and recovery activities (i.e. life, safety, property, and
environmental protection). These facilities include: 911 Centers, Emergency Operations Centers, Police,
and Fire Stations, Public Works facilities, sewer, and water facilities, hospitals, bridges, roads, shelters,
and more.
Table CA-4 includes critical facilities identified in the DOGAMI Risk Report (2024) and
assumed impact from individual hazards.
Table CA-4 Critical Facilities in Canby
Critical Facilities by Community
Flood 1%
Annual
Chance
CSZ 9.0 Earthquake
Moderate to
Complete Damage
Canby-Molalla
Fault Mw-6.8
Moderate to
Complete
Damage
Landslide High
and Very High
Susceptibility
Wildfire
High or
Moderate
Risk
Exposed
>50% Prob.
>50% Prob.
Exposed
Exposed
Ackerman Middle School
-
X
X
-
-
Baker Prairie Middle School
-
X
X
-
-
Canby Fire District 62
-
-
X
-
-
Canby Fire District Northside Station - X X - -
Canby High School
-
X
X
-
-
Canby Police Department
-
-
-
X
-
Canby Public Works
-
X
X
-
-
Canby Sewage Treatment - X X - -
Cecile Trost Elementary School
-
-
X
-
-
Howard Eccles Elementary School
-
X
X
-
-
Legacy Medical Group - Canby - X X - -
Philander Lee Elementary School
-
X
X
-
-
Willamette Falls Health Center
-
-
X
-
-
William Knight Elementary School
-
-
X
-
-
Source: DOGAMI, Multi-Hazard Risk Report for Clackamas County, Oregon (O-24-XX, September 2023 Draft), Table A-14.
Highlighted cells are tentative to be confirmed by DOGAMI in their final Risk Report.
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Clackamas County NHMP: Canby Addendum Page | 21
Additional Critical Facilities not included in the DOGAMI Risk Report
Critical Infrastructure
Infrastructure that provides necessary services for emergency response include:
• 4 Power Substations
• Canby Area Transit (CAT)
• Canby Utility Business Offices
• City Hall Complex/Library
• Public Works Building (EOC #3)
• Telephone Central Station
• Wastewater Treatment Facilities
• Canby Police Department (EOC #2)
• Fire Station #362 (EOC #1)
• Fire Station #365 (south of Canby)
Essential Facilities
Facilities that are essential to the continued delivery of key government services, and/or that may
significantly impact the public’s ability to recover from the emergency. These facilities may include:
community gathering places, churches, and other public facilities such as school fields.
• Ackerman Elementary School
• Baker Prairie School
• Canby High School
• Canby Adult Center
• Canby Christian Church
• Clackamas County Event Center
• Four Square Church
Medical Clinics
• Old Canby Library Building
• St. Patricks Church
• United Methodist Church
• Student Transportation
Environmental Facilities
Environmental assets are those parks, green spaces, wetlands, and rivers that provide an aesthetic, and
functional ecosystem services for the community include:
• Canby City Parks
• Canby Utility Bottom Lands
• Emerald Park
• Molalla River State Park
• Willow Creek
Vulnerable Populations
Vulnerable populations, including seniors, disabled citizens, women, and children, as well those people
living in poverty, often experience the impacts of natural hazards and disasters more acutely.
Populations that have special needs or require special consideration include:
• Adult Foster Homes
• Canby Adult Center
• Countryside Living (assisted living)
• Hope Village (senior living and rehab)
• Providence Health Center
• Rackleff House (assisted living)
• Riverside RV Park
• Village on the Lochs
Hazardous Materials
Facilities that, if damaged, could cause serious secondary impacts may also be considered “critical.”
Hazardous materials sites are particularly vulnerable to earthquake, landslide, volcanic event, wildfire,
and winter storm hazards. A hazardous material facility is one example of this type of critical facility.
Those sites that store, manufacture, or use potentially hazardous materials include:
• American Steel
• BBC Steel
• Johnson Controls Inc.
• JV Northwest
• Pacific Pride Fuel Storage Tanks
• Railroad
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Clackamas County NHMP: Canby Addendum Page | 22
• SR Smith
• Wastewater Treatment Facility
• Water Treatment Facility
• Wilco
Economic Assets/Population Centers
Economic assets include businesses that employ large numbers of people and provide an economic
resource to the city of Canby. If damaged, the loss of these economic assets could significantly affect
economic stability, and prosperity. Population Centers usually are aligned with economic centers and
are a concern during evacuation/notification.
Cultural and Historic Assets
The cultural and historic heritage of a community is more than just tourist charm. For families that have
lived in the city for generations and new resident alike, it is the unique places, stories, and annual
events that makes the community an appealing place to live. The cultural and historic assets are both
intangible benefits and obvious quality-of-life- enhancing amenities. Because of their role in defining
and supporting the community, protecting these resources from the impact of disasters is important.
An example of the types of properties that should be considered before, during, and after an event
include the following properties identified on the National Register of Historic Places within Canby:
• William Knight House, 525 SW 4
th
Avenue
• Kraft-Brades-Culbertson Farmstead, 2525 N Baker Drive
• Macksburg Lutheran Church, 10190 S Macksburg Road
• Herman Anthony Farm, 10205 S New Era Road
Other important historic resources:
• Canby Chapel
• Canby Depot Museum
• Canby Ferry
• Cemeteries
• Clackamas County Event Center
Hazard Characteristics
Drought
The HMAC determined that the City’s probability for drought is moderate and that their vulnerability to
drought is
low. The probability rating did not change and the vulnerability rating decreased since the
previous version of this NHMP.
Volume I, Section 2 describes the characteristics of drought hazards, history, as well as the location,
extent and probability of a potential event. Due to the climate of Clackamas County, past and present
weather conditions have shown an increasing potential for drought.
The City of Canby currently obtains its potable water from the Molalla River with an intake pump
station capacity of 7.9 million gallons a day (mgd). The primary groundwater source is the Springs
Gallery with a seasonally varied capacity up to 1.4 mgd, though low pH and
moderate nitrate
concentrations limit the use of it as the primary source. The Canby Utility water system includes surface
and groundwater sources, treatment facilities, 66 miles of piping, four storage reservoirs with total
usable capacity of 5.5 million gallons, and three pump stations. The Water System Master Plan was last
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updated in Summer 2023 to provide long-term guidance for the development of the City’s water
system, which is a supporting
document for the Comprehensive Plan.
Vulnerability Assessment
Due to insufficient data and resources, Canby is currently unable to perform a quantitative risk
assessment, or exposure analysis, for this hazard. For a list of facilities and infrastructure vulnerable to
this hazard see the Community Assets Section and
Table CA-4.
Mitigation Activities
Canby Utility has a Water Supply Shortage Contingency Plan that details voluntary and non- voluntary
actions to be taken in the event of a water shortage. Additional drought hazard mitigation activities are
conducted at the county, regional, state, and federal levels and are described in the Clackamas County
NHMP.
Future Projections
According to the Oregon Climate Change Research Institute “Future Climate Projections, Clackamas
County,”
5
drought, as represented by low summer soil moisture, low spring snowpack, low summer
runoff, and low summer precipitation, is projected to become more frequent in Clackamas County by
the 2050s.
Increasingly frequent droughts will have economic and social impacts upon those who depend upon
predictable growing periods (ranches, farms, vineyards, gardeners) as well as upon the price and
availability of fresh vegetables. It may also stress local jurisdiction’s ability to provide water for
irrigation or commercial and household use.
Earthquake (Cascadia Subduction Zone)
The HMAC determined that the City’s probability for a Cascadia Subduction Zone (CSZ) earthquake is
moderate and that their vulnerability to a CSZ earthquake is high. These ratings did not change since
the previous version of this NHMP.
Volume I, Section 2 describes the characteristics of earthquake hazards, history, as well as the location,
extent, and probability of a potential event. Generally, an event that affects the County is likely to affect
Canby as well. The causes and characteristics of an earthquake event are appropriately described
within the Volume I, Section 2 as well as the location and extent of potential hazards. Previous
occurrences are well documented within Volume I, Section 2 and the community impacts described by
the County would generally be the same for Canby as well.
Within the Northern Willamette Valley/Portland Metro Region, three potential faults and/or zones can
generate high-magnitude earthquakes. These include the Cascadia Subduction Zone, Portland Hills
Fault Zone, and Gales Creek-Newberg-Mt. Angel Structural Zone (discussed in the crustal earthquake
section). Figure CA-2 displays relative shaking hazards from a Cascadia Subduction Zone earthquake
event. As shown in the figure, most of the city is expected to experience very strong shaking (orange),
while areas near rivers and streams will experience severe (light red) to violent (dark red) shaking in a
CSZ event.
Cascadia Subduction Zone
The Cascadia Subduction Zone is a 680-mile-long zone of active tectonic convergence where oceanic
crust of the Juan de Fuca Plate is subducting beneath the North American continent at a rate of 4 cm
5
Oregon Climate Change Research Institute, Future Climate Projections, Clackamas County, Oregon. February 2023.
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Clackamas County NHMP: Canby Addendum Page | 24
per year. Scientists have found evidence that 11 large, tsunami-producing earthquakes have occurred
off the Pacific Northwest coast in the past 6,000 years. These earthquakes took place roughly between
300 and 5,400 years ago with an average occurrence interval of about 510 years. The most recent of
these large earthquakes took place in approximately 1700 A.D.
6
The city’s proximity to the Cascadia Subduction Zone, potential slope instability and the prevalence of
certain soils subject to liquefaction and amplification combine to give the city a high-risk profile. Due to
the expected pattern of damage resulting from a CSZ event, the Oregon Resilience Plan divides the
State into four distinct zones and places the city predominately within the “Valley Zone” (Valley Zone,
from the summit of the Coast Range to the summit of the Cascades). Within the Northwest Oregon
region, damage and shaking is expected to be strong and widespread - an event will be disruptive to
daily life and commerce and the main priority is expected to be restoring services to business and
residents.
Figure CA-2 Cascadia Subduction Zone Expected Shaking
Source: Map created by Oregon Partnership for Disaster Resilience.
Data: Oregon Department of Geology and Mineral Industries. Preparedness Framework Implementation Team (IRIS v3).
Note: To view hazard detail click this link to access Oregon HazVu
6
The Cascadia Region Earthquake Workgroup, 2005. Cascadia Subduction Zone Earthquakes: A magnitude 9.0 earthquake
scenario. http://www.crew.org/PDFs/CREWSubductionZoneSmall.pdf
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Earthquake (Crustal)
The HMAC determined that the City’s probability for a crustal earthquake is low and that their
vulnerability to crustal earthquake is
high. These ratings did not change since the previous version of this
NHMP.
Volume I, Section 2 describes the causes and characteristics of earthquake hazards, history, as well as
the location, extent, and probability of a potential event. Generally, an event that affects the County is
likely to affect Canby as well.
Figure 3 shows a generalized geologic map of the Canby area that
includes the areas for potential regional active faults, earthquake history (1971-2008), and soft soils
(liquefaction) hazard. The figure shows the areas of greatest concern within the City limits as red and
orange.
There are two potential crustal faults and/or zones near the City that can generate high- magnitude
earthquakes. These include the Gales Creek-Mt. Angel Structural Zone and Portland Hills Fault Zone
(discussed in greater detail below). Other faults include the Canby- Molalla fault (running through the
city’s east edge intersecting Highway 99E) and Oatfield fault (just to the east of the city on the eastern
side of the Willamette River), and the Mt. Hood Fault in eastern Clackamas County. Historical records
count over 56 earthquakes in the Portland-metro area. The more severe ones occurred in 1877, 1880,
1953 and 1962. The most recent severe earthquake was the March 25, 1993 Scotts Mills quake. It was a
5.6 magnitude quake with aftershocks continuing at least through April 8.
Figure CA-3 Active Crustal Faults, Epicenters (1971-2008), and Soft Soils
Source: Map created by Oregon Partnership for Disaster Resilience.
Data: Oregon Department of Geology and Mineral Industries. Preparedness Framework Implementation Team (IRIS v3).
Note: To view hazard detail click this link to access Oregon HazVu
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Canby-Molalla Fault Zone
The Canby-Molalla Fault Zone is a series of NE-trending fault that vertically displace the Columbia River
Basalt with discontinuous aeromagnetic anomalies that represent significant offset of Eocene basement
and volcanic rocks. The fault zone extends for 31 miles from the vicinity of Tigard south through the
towns of Canby and Molalla in northern Oregon.
Portland Hills Fault Zone
The Portland Hills Fault Zone is a series of NW-trending faults that vertically displace the Columbia River
Basalt by 1,130 feet and appear to control thickness changes in late Pleistocene (approx. 780,000 years
ago) sediment. The fault zone extends along the eastern margin of the Portland Hills for 25 miles and
lies about 11 miles northeast of Canby.
Vulnerability Assessment
In 2018 the Department of Geology and Mineral Industries (DOGAMI) completed a regional impact
analysis for earthquakes originating from the Cascadia Subduction Zone and Portland Hills faults (O-18
-
02). Findings from that report are provided at the end of the crustal earthquakes hazard section.
The city has overall moderate vulnerability to an earthquake, which includes the essential and critical
facilities. Canby’s infrastructure is particularly vulnerable to earthquake damage. All of the city’s water
facilities are all within the moderate hazard zone. Highway 99E crosses over the Molalla River and runs
along the Willamette River, which are seismically vulnerable areas and might affect the ability of
outside assistance in the case of an earthquake. During a major earthquake, emergency responders
may have difficulty performing their duties because their buildings could be impacted by the event. The
Canby Fire District 62 Station, and the Police Department’s headquarters are in the moderate to high
hazard zones. Areas near the Willamette and Molalla Rivers are likely comprised of softer soils prone to
liquefaction. This can be very destructive to underground utilities such as water and sewer lines.
Buildings and water lines can sink into the liquefied ground while sewer pipes, manholes and pump
stations (assets partially filled with air) may float to the surface. After the earthquake, the liquefied soil
will re-solidify, locking tilted buildings and broken pipe connections into place. In 2017, the Canby Fire
District Station #62 was awarded a Seismic Rehabilitation Grant for $233,256 and retrofitted their main
fire station. For a list of facilities and infrastructure vulnerable to this hazard, see the Community Assets
Section and
Table CA-4.
Vulnerable populations such as children could be significantly impacted, as many schools lie in the
moderate hazard zone. The data gathered from the statewide DOGAMI inventory should be used to
prioritize school buildings in Canby for seismic hazard retrofitting.
Seismic building codes were implemented in Oregon in the 1970s; however, stricter standards did not
take effect until 1991 and early 2000s. As noted in the community profile, approximately 48% of
residential buildings were built prior to 1990, which increases the City’s vulnerability to the earthquake
hazard. Information on specific public buildings’ (schools and public safety) estimated seismic
resistance, determined by DOGAMI in 2007, is shown in
Table CA-5; each “X” represents one building
within that ranking category. Of the facilities evaluated by DOGAMI using their Rapid Visual Survey
(RVS), none have a very high (100% chance) or high (greater than 10% chance) collapse potential. Note:
one fire station has been rebuilt and the police department moved to a newly constructed location.
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Table CA-5 Rapid Visual Survey Scores
Facility
Site ID*
Level of Collapse Potential
Low
(<1%)
Moderate
(>1%)
High
(>10%)
Very High
(100%)
Schools
Ackerman Center
(350 SE 13
th
Ave)
Clac_sch54
X
Eccles Elementary
(562 NW 5
th
Ave)
Clac_sch55
X
Knight Elementary
(501 N Grant St)
Clac_sch53
X
Lee Elementary
(1110 S Ivy St)
- Not assessed as part of the 2007 RVS
Trost Elementary
(800 S Redwood St)
Clac_sch76
X
Baker Prairie Middle
(1859 S Township Rd)
- Not assessed as part of the 2007 RVS
Canby High
(721 SW 4
th
Ave)
Clac_sch66
X
Fire Facilities
Canby Fire District Main Station 62
(221 S Pine St)
See Mitigation Successes
Clac_fir39
X
Canby Fire District Station 65
(26815 S Hwy 170) (Outside City)
Clac_fir48
X
Law Enforcement Facilities
Canby Policy Department
(1175 NW 3
rd
Ave)
- Built at current site in 2012
Source: DOGAMI 2007. Open File Report 0-07-02. Statewide Seismic Needs Assessment Using Rapid Visual Assessment.
“*” – Site ID is referenced on the RVS Clackamas County Map
In addition to building damages, utility (electric power, water, wastewater, natural gas) and
transportation systems (bridges, pipelines) are also likely to experience significant damage. There is a
low probability that a major earthquake will result in failure of upstream dams.
Utility systems will be significantly damaged, including damaged buildings and damage to utility
infrastructure, including water treatment plants and equipment at high voltage substations (especially
230 kV or higher which are more vulnerable than lower voltage substations). Buried pipe systems will
suffer extensive damage with approximately one break per mile in soft soil areas. There would be a
much lower rate of pipe breaks in other areas. Restoration of utility services will require substantial
mutual aid from utilities outside of the affected area.
Earthquake Regional Impact Analysis
In 2018 DOGAMI completed a regional impact analysis for earthquakes originating from the Cascadia
Subduction Zone and Portland Hills faults (O-18-02). Their s
tudy focused on damage to buildings, and
the people that occupy them, and to two key infrastructure sectors: electric power transmission and
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emergency transportation routes. Each earthquake was studied with wet and dry soil conditions and for
events that occur during the daytime (2 PM) and night time (2 AM). Impacts to buildings and people
were tabulated at the county, jurisdictional (city), and neighborhood unit level. Estimated damaged
varied widely across the study area depending on local geology, soil moisture conditions, type of
building, and distance from the studied faults. In general, damage from the Cascadia Subduction Zone
scenario was greater in the western portion of the study area, however, damage could still be
significant in some areas east of the Willamette River. The report found that damage to high-value
commercial and industrial buildings was high since many of these facilities are in areas of high to very
high liquefaction hazard. Casualties were higher during the daytime scenario (generally double) since
more people would be at work and occupying non-wood structures that fare worse in an earthquake.
The Portland Hills fault scenario created greater damages than the Cascade Subduction Zone scenario
due primarily to its placement relative to population centers and regional assets; however, at distances
15 or more miles from the Portland Hills fault the damages from the Cascadia Subduction Zone scenario
generally were higher. In both the Cascadia Subduction Zone and Portland Hills Fault scenarios it is
forecasted that emergency transportation routes will be fragmented, affecting the distribution of goods
and services, conditions are worse under the Portland Hills Fault scenario. Portions of the electric
distribution system are also expected to be impacted under both scenarios, however, the impact is
considerably less than it is to the transportation routes. Additionally, capacity or redundancy within the
electric distribution network may be beneficial in select areas that are likely to have greater impacts.
Table CA-6 shows the permanent resident population that are vulnerable to injury or death (casualty)
and the buildings in the City that are susceptible to liquefaction and landslides, it does not predict that
damage will occur in specific areas due to either liquefaction or landslide. More population and
property are exposed to higher degrees of expected damage or casualty under the Portland Hills Fault
“wet” scenario than in any other scenario.
Table CA-6 Expected damages and casualties for the CSZ fault and Portland Hills fault: earthquake, soil
moisture, and event time scenarios
Source: DOGAMI, Earthquake regional impact analysis for Clackamas, Multnomah, and Washington Counties, Oregon (2018, O-
18-02), Tables 12-8, 12-9, 12-10, and 12-11.
"Dry" Soil
"Wet"
Saturated Soil
"Dry" Soil
"Wet"
Saturated Soil
Number of Buildings
5,559 5,559 5,559 5,559
Building Value ($ Million)
1,890 1,890 1,890 1,890
Building Repair Cost ($ Million)
58 61 159 231
Building Loss Ratio
3% 3% 8% 12%
Debris (Thousands of Tons)
34 36 76 103
Long-Term Displaced Population
78 159 202 874
Total Casualties (Daytime)
38 40 109 172
Level 4 (Killed)
1 1 5 8
Total Casualties (NIghttime)
14 20 41 93
Level 4 (Killed)
0 0 1 2
Cascadia Subduction Zone (M9.0)
Portland Hills Fault (M6.8)
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Cascadia Subduction Zone Scenario
The City of Canby is expected to have a 3% building loss ratio with a repair cost of $58 million under the
CSZ “dry” scenario, and a 3% building loss ratio with a repair cost of $61 million under the CSZ “wet”
scenario.
7
The city is expected to have around 38 daytime or 14 nighttime casualties during the CSZ
“dry” scenario and 40 daytime or 20 nighttime casualties during the CSZ “wet” scenario. It is expected
that there will be a long-term displaced population of around 78 for the CSZ “dry” scenario and 159 for
the CSZ “wet” scenario.
8
(See Risk Report content for additional information.)
Portland Hills Fault Scenario
The City of Canby is expected to have a 8% building loss ratio with a repair cost of $159 million under
the CSZ “dry” scenario, and a 12% building loss ratio with a repair cost of $231 million under the CSZ
“wet” scenario. The long-term displaced population and casualties are greatly increased for all the
Portland Hills Fault scenarios. The city is expected to have around 109 daytime or 41 nighttime
casualties during the Portland Hills Fault “dry” scenario and 172 daytime or 93 nighttime casualties
during the Portland Hills Fault “wet” scenario. It is expected that there will be a long-term displaced
population of around 202 for the Portland Hills Fault “dry” scenario and 874 for the Portland Hills Fault
“wet” scenario.
Recommendations from the report included topics within Planning, Recovery, Resiliency: Buildings,
Resiliency: Infrastructure Improvements, Resiliency: Essential and Critical Facilities, Enhanced
Emergency Management Tools, Database Improvements, Public Awareness, and Future Reports. The
recommendations of this study are largely incorporated within this NHMPs mitigation strategies (Table
MO-1 and Volume I, Section 3). For more detailed information on the report, the damage estimates,
and the recommendations see: Earthquake regional impact analysis for Clackamas, Multnomah, and
Washington Counties, Oregon (2018, O-18-02
).
Natural Hazard Risk Report for Clackamas County
The Risk Report (DOGAMI, O-24-XX)
9
provides hazard analysis summary tables that identify populations
and property countywide that are vulnerable to the earthquake hazard. According to the Risk Reports
the following population and property within the study area may be impacted by the profiled events:
Cascadia Subduction Zone event (M9.0 Deterministic): 477 buildings, and (8 critical facilities), are
expected to be damaged for a total potential loss of $186 million (a loss ratio of 7%). About 516
residents may potentially be displaced.
Crustal event (Canby-Molalla fault M6.8 Deterministic): 2,210 building are expected to be damaged (12
critical facilities), for a total potential loss of $811 million (a loss ratio of 31%). About 3,017 residents
may be displaced (17% of population).
Future Projections
Future development (residential, commercial, or industrial) within Clackamas County will be at risk to
earthquake impacts, although this risk can be mitigated by the adoption and enforcement of high
development and building standards. Reducing risks to vulnerable populations should be considered
during the redevelopment of existing properties.
7
DOGAMI, Earthquake regional impact analysis for Clackamas, Multnomah, and Washington Counties, Oregon (2018, O-18-
02), Tables 12-8 and 12-9.
8
Ibid, Tables 12-8 and 12-9.
9
DOGAMI, Multi-Hazard Risk Report for Clackamas County, Oregon (O-24-XX, September 2023 Draft), Table A-13.
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Flood
The HMAC determined that the City’s probability for flood is high and that their vulnerability to flood is
moderate. The probability rating did not change and the vulnerability rating decreased since the
previous version of this NHMP.
Volume I, Section 2 describes the characteristics of flood hazards, history, as well as the location,
extent, and probability of a potential event.
Figure CA-4 illustrates the flood hazard area for Canby.
Portions of Canby have areas of floodplain (located in the Hazard Overlay Zone). The Federal
Emergency Management Agency (FEMA) regulatory floodplains for the Molalla and Willamette Rivers
are depicted as relatively narrow areas on each side of the channels. On the Willamette River, the
floodway is generally confined within high stream banks. On the Mollala River, the floodways cover a
somewhat larger area that is usually located on the outside bank from Canby. Floods can have a
devastating impact on almost every aspect of the community, including private property damage,
public infrastructure damage, and economic loss from business interruption. It is important for the City
to be aware of flooding impacts and assess its level of risk.
Figure CA-4 FEMA Flood Zones
Source: Map created by Oregon Partnership for Disaster Resilience.
Data: Oregon Department of Geology and Mineral Industries. Preparedness Framework Implementation Team (IRIS v3).
Note: To view hazard detail click this link to access Oregon HazVu
The economic losses due to business closures often total more than the initial property losses that
result from flood events. Business owners, and their employees are significantly impacted by flood
events. Direct damages from flooding are the most common impacts, but indirect damages, such as
diminished clientele, can be just as debilitating to a business.
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For mitigation planning purposes, it is important to recognize that flood risk for a community is not
limited only to areas of mapped floodplains. Other portions of Canby outside of the mapped floodplains
may also be at relatively high risk from over bank flooding from streams too small to be mapped by
FEMA or from local storm water drainage. City staff has identified sites where local drainage facilities
are taxed during high flows, especially where open ditches enter culverts or go underground into storm
sewers and works to mitigate the stormwater flood risks in these areas (see the City’s Stormwater
Master Plan for more information).
The largest flooding event to affect Canby was the February 1996 flood. The high-water level meant
tributaries could not drain into the Molalla and Willamette River, which led to localized flooding on
several backed-up creeks. Recently in December 2015, the Molalla River flooded low lying areas around
Canby’s South Pine Street.
The extent of flooding hazards in Canby primarily depends on climate and precipitation levels.
Additionally, withdrawals for irrigation and drinking water, as well as stream and wetland modifications
or vegetation removal can influence water flow.
Vulnerability Assessment
The City completed an analysis, using the best available data, as a component of the vulnerability
assessment in 2009, updated in 2012, and reviewed and updated, as appropriate, in 2018. This analysis
looked at identified hazard areas in conjunction with available data on property exposed to the hazard.
Exposure of community assets to natural hazards was determined by manually comparing community
assets with each hazard and identifying where assets and hazards intersected.
Approximately 4% percent of the total land area in Canby is exposed to the flooding hazard, and in
some areas this hazard presents potential life safety hazards. Multi-family housing structures, including
Redwood Terrace Apartment Complex and Canby Grove, may be affected by flooding. Critical facilities
exposed to the flood hazard include the water treatment facility main river intake structure, the
wastewater treatment facility, backwash ponds, and the city’s public works facility. In flooding events
these facilities may be exposed to high waters and services can be interrupted.
Bridges and culverts are also vulnerable to flooding because debris and sediment can choke culverts
and undermine bridges, causing surface water drainage problems. Canby relies on bridges for
transportation and connection to other main highways. Canby could potentially be isolated if the
bridges were to fail. Knights Bridge and Goods Bridge are particularly exposed. Roadways exposed
include S. Ivy (Hwy 170) and SW/SE 1st Ave (Hwy 99E). Disruption to this infrastructure could result in
transportation issues, power outages, sewage back-up, and affect overall community and
environmental health.
Many older buildings will have difficulty sustaining pressure from flooding events and should be
targeted for floodplain retrofitting. For a list of facilities and infrastructure vulnerable to this hazard see
the Community Assets section and
Table CA-4.
Natural Hazard Risk Report for Clackamas County
The Risk Report (DOGAMI, O-24-XX)
10
provides hazard analysis summary tables that identify
populations and property countywide that are vulnerable to the flood hazard. The Risk Report did not
identify population or property within the study area that may be impacted by the profiled flood
hazard.
10
DOGAMI, Multi-Hazard Risk Report for Clackamas County, Oregon (O-24-XX, September 2023 Draft), Table A-13.
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Future Projections
According to the Oregon Climate Change Research Institute “Future Climate Projections, Clackamas
County,”
11
winter flood risk at mid- to low elevations in Clackamas County, where temperatures are
near freezing during winter and precipitation is a mix of rain and snow, is projected to increase as
winter temperatures increase. The temperature increase will lead to an increase in the percentage of
precipitation falling as rain rather than snow. The projected increases in total precipitation, and in rain
relative to snow, likely will increase flood magnitudes in the region. Vulnerable populations adjacent to
floodways (including the unhoused, manufactured home communities, and campground occupants)
will be more at risk as the winter flood risk increases.
National Flood Insurance Program (NFIP)
FEMA’s Flood Insurance Study (FIS), and Flood Insurance Rate Maps (FIRMs) are effective as of June 17,
2008. The City complies with the NFIP through enforcement of their flood damage prevention
ordinance and their floodplain management program. The last Community Assistance Visit (CAV) for
the city was November 19, 1993. Canby does not participate in the Community Rating System (CRS).
Canby has no Repetitive Loss or Severe Repetitive Loss Properties.
Landslide
The HMAC determined that the City’s probability for landslide is high and that their vulnerability to
landslide is
moderate. The probability and vulnerability ratings increased since the previous version of
this NHMP.
Volume I, Section 2 describes the characteristics of landslide hazards, history, as well as the location,
extent, and probability of a potential event within the region. Although catastrophic landslides have not
occurred in Canby, steep slopes do exist along the banks of the Molalla River and extends south from
6th Street up to the northern city limits. Highway 99E, north of Canby, is especially vulnerable to
landslides with multiple incidents of rockslides shutting down lanes in 2007, 2010, and 2015. As an
example, on January 7, 2009, two slides occurred in private yards after an intense winter storm. About
three feet of earth fell 30 to 50 feet from the back yard of a home on North Baker Drive. Another home
on Alder Creek Lane in Knights Bridge Estates lost approximately 10 feet of its back yard.
Landslide susceptibility exposure for Canby is shown in
Figure CA-5. Most of Canby demonstrates a
low to moderate landslide susceptibility exposure. Approximately 2% of Canby has very high or high,
and approximately 9% moderate, landslide susceptibility exposure.
12
However, most of the areas that
are identified to exhibit dangerous potential rapidly moving landslides are vacant and often preserved
in wooded and dedicated open space.
Note that even if a jurisdiction has a high percentage of area in a high or very high landslide exposure
susceptibility zone, this does not mean there is a high risk, because risk is the intersection of hazard,
and assets.
Vulnerability Assessment
DOGAMI completed a statewide landslide susceptibility assessment in 2016 (O-16-02), general findings
from that report are provided above and within
Figure CA-5. Additionally, the City completed an
analysis, using the best available data, as a component of the vulnerability assessment in 2009, updated
in 2012, and reviewed and updated, as appropriate, in 2018. This analysis looked at identified hazard
areas in conjunction with available data on property exposed to the hazard. Exposure of community
11
Oregon Climate Change Research Institute, Future Climate Projections, Clackamas County, Oregon. February 2023.
12
DOGAMI. Open-File Report, O-16-02, Landslide Susceptibility Overview Map of Oregon (2016)
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Clackamas County NHMP: Canby Addendum Page | 33
assets to natural hazards was determined by manually comparing community assets with each hazard
and identifying where assets and hazards intersected.
Natural Hazard Risk Reports for Clackamas County
The Risk Report (DOGAMI, O-24-XX)
13
provides hazard analysis summary tables that identify
populations and property countywide that are vulnerable to the landslide hazard.
According to the Risk Report 11 buildings are exposed to the high and very high landslide susceptibility
hazard (1 critical facilities) for a total exposure of $19.5 million (a building exposure ratio of 0.7%).
About 20 residents may be displaced by landslides (a population exposure ratio of 18.1%).
Figure CA-5 Landslide Susceptibility Exposure
Source: Map created by Oregon Partnership for Disaster Resilience.
Data: Oregon Department of Geology and Mineral Industries. Preparedness Framework Implementation Team (IRIS v3).
Note: To view hazard detail click this link to access Oregon HazVu
Two critical facilities are exposed to the landslide hazard —Canby Utility’s main river intake, Springs
Gallery, and pump houses as well as the Police Department (EOC #2). The critical infrastructure is
especially exposed to the landslide hazard. In addition, economic centers, cultural or historic assets,
environmental assets, and hazardous material sites are exposed to the landslide hazard. Hazardous
materials sites would also suffer damage, resulting in threats to environmental and human health,
while disrupting the availability of gasoline for vehicle transport and furthering economic loss because
such sites are also sources of employment. For a list of facilities and infrastructure vulnerable to this
hazard see the Community Assets section and Table CA-4.
13
DOGAMI, Multi-Hazard Risk Report for Clackamas County, Oregon (O-24-XX, September 2023 Draft), Table A-13.
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This exposure means that large scale and simultaneous landslides triggered by an earthquake could
substantially disrupt City operations buildings, police, fire stations and key pieces of infrastructure
(bridges, sewage pump stations, water reservoirs) that would hinder the ability of the City to respond
to emergency situations created by such an event.
As a result, it will be important for the City to pursue opportunities for retrofitting and mitigating
important structures and infrastructure, such that said facilities can withstand and survive landslides,
particularly simultaneous landslides generated by an earthquake. Business continuity planning shall also
be an important factor, given the number of economic centers and employment facilities that are
threatened by the landslide hazard.
Potential landslide-related impacts are adequately described within Volume I, Section 2, and include
infrastructure damages, economic impacts (due to isolation, and/or arterial road closures), property
damages, and obstruction to evacuation routes. Rain-induced landslides, and debris flows can
potentially occur during any winter, and thoroughfares beyond City limits are susceptible to obstruction
as well.
The most common type of landslides are slides caused by erosion. Slides move in contact with the
underlying surface, are generally slow moving, and can be deep. Rainfall-initiated landslides tend to be
smaller; while earthquake induced landslides may be quite large. All soil types can be affected by
natural landslide triggering conditions.
Future Projections
Landslides are often triggered by rainfall when the soil becomes saturated. As a surrogate
measure of landslide risk, the Oregon Climate Change Research Institute report presents a threshold
based on recent precipitation (cumulative precipitation over the previous 3 days) and antecedent
precipitation (cumulative precipitation on the 15 days prior to the previous 3 days). By the 2050s under
the higher emissions scenario, the average number of days per year in Clackamas County on which the
landslide risk threshold is exceeded is not projected to change substantially. However, landslide risk
depends on multiple factors, and this metric, which is based on precipitation, does not reflect all
aspects of the hazard. Additional triggers, such as earthquakes, wildfires, or development, can increase
risks of landslides. Future development along slopes or adjacent to riverbanks will be a greater risk of
impact from this hazard.
Severe Weather
Severe weather can account for a variety of intense, and potentially damaging hazard events. These
events include extreme heat, windstorms, and winter storms. The following section describes the
unique probability, and vulnerability of each identified weather hazard.
Extreme Heat
The HMAC determined that the City’s probability for extreme heat events is high and that their
vulnerability is
low. The probability rating increased and the vulnerability rating decreased since the
previous NHMP.
Volume I, Section 2 describes the characteristics of extreme heat, history, as well as the location,
extent, and probability of a potential event within the region. Generally, an event that affects the
County is likely to affect the City as well.
A severe heat episode or "heat wave" occurs about every two to three years, and typically lasting two
to three days but can last as many as five days. A severe heat episode can be defined as consecutive
days of upper 90s to around 100. Severe heat hazard in the Portland metro region can be described as
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the average number of days with temperatures greater than or equal to 90-degrees, or 100-degrees,
Fahrenheit. On average the region experiences 13.6 days with temperatures above 90-degrees
Fahrenheit, and 1.4 days above 100-degrees Fahrenheit, based on new 30-year climate averages (1981-
2010) from the National Weather Service – Portland Weather Forecast Office.
The City of Canby has not experienced any life-threatening consequences from the few historical
extreme heat events, although changes in climate indicate that the area should expect to see more
extreme heat events.
Future Projections
According to the Oregon Climate Change Research Institute “Future Climate Projections, Clackamas
County,”
14
the number, duration, and intensity of extreme heat events will increase as temperatures
continue to warm. In Clackamas County, the number of extremely hot days (days on which the
temperature is 90°F or higher) and the temperature on the hottest day of the year are projected to
increase by the 2020s and 2050s under both the lower (RCP 4.5) and higher (RCP 8.5) emissions
scenarios. The number of days per year with temperatures 90°F or higher is projected to increase by an
average of 12 (range 3–21) by the 2050s, relative to the 1971–2000 historical baselines, under the
higher emissions scenario. The temperature on the hottest day of the year is projected to increase by
an average of about 7°F (range 2–11°F) by the 2050s. Higher temperatures and longer/more extreme
heat events will have negative impacts upon vulnerable populations such as those over 65+, children,
those living in older or temporary housing, and field workers.
Windstorm
The HMAC determined that the City’s probability for windstorm is moderate and that their vulnerability
to windstorm is
low. The probability and vulnerability ratings decreased since the previous version of
this NHMP.
Volume I, Section 2 describes the characteristics of windstorm hazards, history, as well as the location,
extent, and probability of a potential event within the region. Because windstorms typically occur
during winter months, they are sometimes accompanied by flooding and winter storms (ice, freezing
rain, and very rarely, snow). Other severe weather events that may accompany windstorms, including
thunderstorms, hail, lightning strikes, and tornadoes are generally negligible for Canby. In July 2016,
two funnel clouds were spotted due to a low-pressure system and no damage was reported. While five
miles east of Canby, a tornado touched down at Aurora State Airport in October of 2017.
Volume I, Section 2 describes the impacts caused by windstorms, including power outages, downed
trees, heavy precipitation, building damages, and storm-related debris. Additionally, transportation and
economic disruptions result as well.
Damage from high winds generally has resulted in downed utility lines, and trees usually limited to
several localized areas. Electrical power can be out anywhere from a few hours to several days.
Outdoor signs have also suffered damage. If the high winds are accompanied by rain (which they often
are), blowing leaves, and debris clog drainage-ways, which in turn may cause localized urban flooding.
Future Projections
Limited research suggests little if any change in the frequency and intensity of windstorms in the
Northwest as a result of climate change. Those impacted by windstorms at present, including older
residential or commercial developments with above-ground utilities, poor insulation or older
14
Oregon Climate Change Research Institute, Future Climate Projections, Clackamas County, Oregon. February 2023.
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Clackamas County NHMP: Canby Addendum Page | 36
construction, heavy tree canopies, or poor storm drainage, will continue to be impacted by windstorms
in the future.
Winter Storm (Snow/Ice)
The HMAC determined that the City’s probability for winter storm is moderate and that their
vulnerability to winter storm is
moderate. The probability rating decreased and the vulnerability rating
did not change since the previous version of this NHMP.
Volume I, Section 2 describes the characteristics of winter storm hazards, history, as well as the
location, extent, and probability of a potential event within the region. Severe winter storms can consist
of rain, freezing rain, ice, snow, cold temperatures, and wind. They originate from troughs of low
pressure offshore that ride along the jet stream during fall, winter, and early spring months. Severe
winter storms affecting the City typically originate in the Gulf of Alaska or in the central Pacific Ocean.
These storms are most common from November through March.
Most winter storms typically do not cause significant damage, they are frequent, and have the potential
to impact economic activity. Road closures due to winter weather are an uncommon occurrence but
can interrupt commuter and commercial traffic.
Future Projections
According to the Oregon Climate Change Research Institute “Future Climate Projections, Clackamas
County,”
15
cold extremes will become less frequent and intense as the climate warms. In Clackamas
County, the number of cold days (maximum temperature 32°F or lower) per year is projected to
decrease by an average of 6 (range -3– -8) by the 2050s, relative to the 1971–2000 historical baselines,
under the higher emissions scenario. The temperature on the coldest night of the year is projected to
increase by an average of 6°F (range 0– 11°F) by the 2050s.
The intensity of extreme precipitation is expected to increase as the atmosphere warms and holds
more water vapor. In Clackamas County, the number of days per year with at least 0.75 inches of
precipitation is not projected to change substantially. However, by the 2050s, the amount of
precipitation on the wettest day and wettest consecutive five days per year is projected to increase by
an average of 15% (range 0–31%) and 10% (range -1–26%), respectively, relative to the 1971–2000
historical baselines, under the higher emissions scenario.
Vulnerable populations will be more likely to experience the negative impacts of winter storms in the
future, particularly the unhoused and the elderly.
Vulnerability Assessment
Due to insufficient data and resources, Canby is currently unable to perform a quantitative risk
assessment, or exposure analysis, for the extreme heat, windstorm, and winter storm hazards.
The areas of the City that are often most at risk to severe winter storms are residential areas on steeper
slopes, where roads may be icy and, thus, difficult to climb and descend. Road corridors leading to
residential areas with fuller tree canopies are susceptible to downed tree limbs, and those areas that
are above 500 feet in elevation are particularly vulnerable. However, some weather systems are
characterized by a temperature inversion, where the valley floor is colder than the nearby hills.
Consequently, severe winter storms affect the entire city.
15
Oregon Climate Change Research Institute, Future Climate Projections, Clackamas County, Oregon. February 2023.
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The major risk to property results from exposed utilities, especially power lines and water pipes that are
damaged by wind, broken tree limbs and cold temperatures. Businesses also suffer economic losses
when they must close as the result of the inclement weather and/or the loss of power, which, in turn,
disrupts the local supply chain of goods and services. Periods of extended ice coverage hinder
emergency response services and limit the mobility of residents, which could result in serious life safety
issues.
Telcom Central Station and City Hall Complex are critical facilities located adjacent to vulnerable power
lines. Canby Utility, Public Works, and Canby Telephone would be strained during a severe storm event
as they work to clear roads and repair or replace power distribution and/or transmission lines and
maintain telephone lines for communication. Additionally, the area along 99E from South Elm to South
Ivy St. is particularly vulnerable to damaged power lines from fallen tree limbs.
All schools and one adult community center that are considered essential facilities are also exposed to
the severe weather hazards. In addition, critical infrastructure, economic centers, cultural or historic
assets, environmental assets, and hazardous material sites are exposed to severe weather hazards. For
a list of facilities and infrastructure vulnerable to these hazards see the Community Assets section and
Table CA-4.
The exposure of these facilities and infrastructure means that severe weather events could
substantially disrupt the operations of City government buildings and fire stations, impairing key City
functions, while hindering the ability of emergency response personnel to respond to emergency
situations that are created by a severe storm event.
Volcanic Event
The HMAC determined that the City’s probability for a volcanic event is low and that their vulnerability
to a volcanic event is
low. These ratings did not change since the previous version of this NHMP.
Volume I, Section 2 describes the characteristics of volcanic hazards, history, as well as the location,
extent, and probability of a potential event within the region. Generally, an event that affects the
western portion of the County is likely to affect Canby as well. Several volcanoes are located near
Canby, the closest of which are Mount Hood, Mount Adams, Mount Saint Helens, Mount Rainier, and
the Three Sisters.
Vulnerability Assessment
Due to Canby’s relative distance from volcanoes, the city is unlikely to experience the immediate effects
that eruptions have on surrounding areas (i.e., mud and debris flows, or lahars). Depending on wind
patterns and which volcano erupts, however, the city may experience ashfall. The eruption of Mount St.
Helens in 1980, for example, coated the Willamette Valley with a fine layer of ash. If Mount Hood
erupts, however, the city could experience a heavier coating of ash.
Natural Hazard Risk Reports for Clackamas County
The Risk Report DOGAMI, O-24-XX) provides hazard analysis summary tables that identify populations
and property countywide that are vulnerable to the volcanic event (lahar) hazard. The Risk Report did
not identify population or property within the study area that may be impacted by the profiled volcanic
event (lahar) hazard.
Future Projections
Although the science of volcano predictions is improving, it remains challenging to predict a potential
volcanic event. Ash fall, which will be the greatest impact, will impact the entire County. Impacts will be
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felt hardest by property managers (ranches, farmers, etc.) and by those relying upon clean surface
water (for drinking water production and irrigation).
Wildfire
The HMAC determined that the City’s probability for wildfire is low, and that their vulnerability to
wildfire is
moderate. These ratings did not change since the previous version of this NHMP.
The Clackamas County Community Wildfire Protection Plan (CWPP) is hereby incorporated into this
NHMP addendum by reference, and it will serve as the wildfire section for this addendum. The
following presents a summary of key information; refer to the full CWPP for a complete description,
and evaluation of the wildfire hazard. Information specific to Canby is found in the following chapter:
Chapter 9.2: Canby Rural Fire Protection District #62.
Volume I, Section 2 describes the characteristics of wildland fire hazards, history, as well as the location,
e
xtent, and probability of a potential event within the region. The location, and extent of a wildland fire
vary depending on fuel, topography, and weather conditions.
Figure CA-6 shows overall wildfire risk in Canby. Weather, and urbanization conditions are primarily at
cause for the hazard level. Canby has not experienced a catastrophic wildfire within City limits.
Figure CA-6 Wildfire Risk
Source: Map created by Oregon Partnership for Disaster Resilience.
Data: Oregon statewide wildfire risk map created by Oregon State University (unpublished).
Note: To view additional wildfire risk information click this link to access Oregon Explorer’s CWPP Planning Tool
Clackamas County has two major physiographic regions: the Willamette River Valley in western
Clackamas County and the Cascade Range Mountains in eastern and southern Clackamas County. The
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Willamette River Valley, which includes Canby, is the most heavily populated portion of the county and
is characterized by flat or gently hilly topography. The Cascade Range has a relatively small population
and is characterized by heavily forested slopes. Eastern Clackamas County is at higher risk to wildfire
than western portions of the county due to its dense forest land. Human caused fires are responsible
for most fires in Clackamas County.
The forested hills within, and surrounding Canby are interface areas including the following High
Priority Communities at Risk (CARs): Adkins Circle, Dutch Vista/Madrona, Public Works Infrastructure,
Sundowner, and the following Medium Priority CARs: N Side Molalla River Bluff, Molalla River State
Park, and South End.
16
The City is characterized by lush parks, neighborhoods surrounded by mature trees and under story
vegetation and development intermingled with the natural landscape. One area of wildland-urban
interface is the northeast portion of Canby. A heavily wooded area borders the north and south
boundaries of the sewage treatment facility and Public Works Building (EOC #3). Most of the woodlands
are surrounded by urban development that are a concern in the case of a wildfire event.
Most of the city has less severe (moderate or less) wildfire burn probability that includes expected
flame lengths less than four feet under normal weather conditions, except in a small, wooded area new
the Willamette River on North Holly Street that has the probability of four to eight feet expected flame
lengths. However, conditions vary widely and with local topography, fuels, and local weather (including
wind) conditions. Under warm, dry, windy, and drought conditions expect higher likelihood of fire
starts, higher intensity, more ember activity, and a more difficult to control wildfire that will include
more fire effects and impacts.
Vulnerability Assessment
Due to insufficient data and resources, Canby is currently unable to perform a quantitative risk
assessment, or exposure analysis, for this hazard. However, the City completed an analysis, using the
best available data, as a component of the vulnerability assessment in 2009, updated in 2012, and
reviewed and updated, as appropriate, in 2018. This analysis looked at identified hazard areas in
conjunction with available data on property exposed to the hazard. Exposure of community assets to
natural hazards was determined by manually comparing community assets with each hazard and
identifying where assets and hazards intersected.
Residences and businesses that border occluded woodlands with slopes greater than 25% are at the
greatest risk of loss or damage from wildfires. A great deal of infrastructure is exposed to the wildfire
hazard, including Canby’s primary water source, water treatment facilities, and Public Works Building
(EOC#3). This could affect the efficiency of fire protection professionals during a large-scale wildfire.
Vegetation along roadways is also highly dangerous, as negligent motorists provide ignition sources by
tossing cigarette butts out car windows. A variety of historic landmarks are also included in the high
wildfire zone.
Natural Hazard Risk Reports for Clackamas County
The Risk Report (DOGAMI, O-24-XX)
17
provide hazard analysis summary tables that identify populations
and property countywide that are vulnerable to the landslide hazard.
According to the Risk Report 9 buildings are exposed to the high and (or) moderate (medium) risk
wildfire hazard (no critical faclities) for a total exposure of $2.9 million replacement value (a building
16
Clackamas County Community Wildfire Protection Plan, Canby Rural Fire Protection District #62 (2018), Table 10.13-1.
17
DOGAMI, Multi-Hazard Risk Report for Clackamas County, Oregon (O-24-XX, September 2023 Draft), Table A-13.
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replacement value exposure ratio of 0.1%). About 8 residents may be displaced by wildfires (a
population exposure ratio of 0.04%).
Future Projections
According to the Oregon Climate Change Research Institute “Future Climate Projections, Clackamas
County,”
18
wildfire frequency, intensity, and area burned are projected to continue increasing in the
Northwest. Wildfire risk, expressed as the average number of days per year on which fire danger is very
high, is projected to increase in Clackamas County by 14 (range -6– 34) by the 2050s, relative to the
historical baseline (1971–2000), under the higher emissions scenario. Similarly, the average number of
days per year on which vapor pressure deficit is extreme is projected to increase by 29 (range 10–44)
by the 2050s. Communities at risk to wildfire include those within the urban wildfire interface or along
river or creek corridors, where fire can travel quickly. Communities will need to address growing
wildfire risks if populations are not restricted from expanding further into higher risk areas.
18
Oregon Climate Change Research Institute, Future Climate Projections, Clackamas County, Oregon. February 2023.
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Attachment A:
Action Item Changes
Table CA-7 is an accounting of the status (complete or not complete) and major changes to actions
since the previous NHMP. All actions were renumbered in this update to be consistent with other
jurisdictions that are participating in the multi-jurisdictional NHMP. All actions marked not complete are
ongoing, are still relevant, and are included in the updated action plan (Table CA-1).
Previous NHMP Actions that are Complete:
Severe Weather #1, “Obtain funding to bury power lines subject to frequent failures to reduce power
outages from the windstorm and severe winter storm hazard, where possible.” Complete. This is part of
normal operations.
Previous NHMP Actions that are Not Complete and No Longer Relevant:
None identified.
Table CA-7 Status of All Hazard Mitigation Actions in the Previous Plan
2018 Action Item
2024
Action
Item
Status
Still Relevant?
(Yes/No)
Multi-Hazard #1 #1 Not Complete Yes
Multi-Hazard #2 #2 Not Complete Yes
Multi-Hazard #3 #3 Not Complete Yes
Multi-Hazard #4 #4 Not Complete Yes
Multi-Hazard #5 #5 Not Complete Yes
Earthquake #1 #6 Not Complete, revised Yes
Flood #1 #7 Not Complete, revised Yes
Flood #2 #8 Not Complete Yes
Landslide #1 #9 Not Complete Yes
Severe Weather #1 - Complete No
Wildfire #1 #10 Not Complete Yes
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Attachment B: Public Involvement
Summary
Members of the steering committee provided edits and updates to the NHMP prior to the public review
period as reflected in the final document.
To provide the public information regarding the draft NHMP addendum, and provide an opportunity for
comment, an announcement (see below) was provided from January XX through January XX on the
City’s website. The plan was also posted and announced on the County’s website. There were X
comments provided that have been reviewed and integrated into the NHMP as applicable. Additional
opportunities for stakeholders and the public to be involved in the planning process are addressed in
Volume III, Appendix B.
A diverse array of agencies and organizations were provided an opportunity to provide input to inform
t
he plan’s content through a variety of mechanisms including the opportunity for comment on the draft
plan. The agencies and organizations represent local and regional agencies involved in hazard
mitigation activities, those that have the authority to regulate development, neighboring communities,
representatives of businesses, academia, and other private organizations, and representatives of
nonprofit organizations, including community-based organizations, that work directly with and/or
provide support to underserved communities and socially vulnerable populations. For more
information on the engagement strategy see Volume III, Appendix B.
Website Posting
To be added following posting
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HMAC
The Hazard Mitigation Advisory Committee (HMAC) members possessed familiarity with the community
and how it is affected by natural hazard events. The HMAC guided the update process through several
steps including goal confirmation and prioritization, action item review and development, and
information sharing, to update the NHMP and to make the NHMP as comprehensive as possible. The
steering committee met formally on the following dates:
Meetings #1 and #2: March 20 and May 24, 2023 (via remote conference)
During these meetings, the HMAC:
• Reviewed the previous NHMP, and were provided updates on hazard mitigation planning, the
NHMP update process, and project timeline.
• Updated recent history of hazard events in the city.
• Reviewed and confirmed the County NHMP’s mission and goals.
• Reviewed and provided feedback on the draft risk assessment update including community
vulnerabilities and hazard information.
• Reviewed and updated their existing mitigation strategy (actions).
• Reviewed and updated their implementation and maintenance program.
• Discussed the NHMP public outreach strategy.
Meeting #3: December 14, 2023 (via remote conference)
During this meeting, the HMAC:
• Confirmed and provided feedback on the final draft risk assessment update including
community vulnerabilities and hazard information provided by DOGAMI (Risk Report).
• Reviewed and confirmed the city’s capabilities assessment.
• Reviewed, confirmed, and prioritized the city’s mitigation strategies.
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