Floodplain Resilience Plan Frequently Asked Questions (FAQ)

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Photo shows a neighborhood street and a mailbox surrounded by water.
Answers to common questions about floodplains, floodplain regulations, and the Floodplain Resilience Plan Project.
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What are floodplains?

Floodplains are the low-lying areas around rivers and streams; typically dry during normal conditions, they become inundated with water during flood events. Floodplains are generally categorized by how much they become inundated during specific flood events.

The City of Portland currently regulates two types of floodplains: the FEMA 100-year floodplain and the Metro Title 3 1996 Flood Inundation Area:

  • FEMA 100-year Floodplain includes areas near rivers and streams that the Federal Emergency Management Agency (FEMA) estimates have a 1% chance of flooding each year. The FEMA 100-year floodplain is also called the Special Flood Hazard Area.
  • Metro Title 3 1996 Flood Inundation Area includes most (but not all) the areas flooded in February of 1996, based on aerial photography, as well as the FEMA 100-year floodplain. The map and associated jurisdictional requirements in the region were adopted by Metro, Portland’s regional government, in 2000.

To develop a more accurate estimate of future flood risk in the area, City of Portland staff worked with the Army Corps of Engineers from 2020-22 to complete a new flood model for the Lower Willamette River. The new model estimates the land that would be flooded during a future flood comparable to the February 1996 flood. This model, called the Modeled Willamette River 1996 Flood Extent, incorporates current conditions, including development patterns and topography, to better estimate areas of future flooding compared to the existing Metro 1996 Flood Inundation Area.

The Floodplain Resilience Plan will update floodplain management regulations in all three floodplain areas (FEMA, Metro and Modeled Willamette River 1996 Flood Extent), referred to as the “combined flood hazard area.”

What is the FEMA National Flood Insurance Program (NFIP) Biological Opinion?

The National Flood Insurance Program (NFIP) offers federally backed insurance to homeowners, renters, and business owners if their local government meets FEMA’s program requirements. Flood insurance is required for all federally backed mortgages and loans in the FEMA 100-year floodplain. To take part in the NFIP, communities must implement FEMA’s minimum requirements. Current requirements include building and site development standards for properties in the floodplain and compliance with applicable federal laws, including the Endangered Species Act (ESA).

In 2009, several local and national environmental and fish conservation organizations (including Portland Audubon) sued FEMA, claiming that implementation of the NFIP in Oregon impedes the recovery of threatened and endangered salmon and steelhead. As a part of the settlement of the lawsuit, FEMA agreed to have the National Marine Fisheries Service (NMFS) assess the program to determine its potential impacts on threatened and endangered species in Oregon.

NMFS released its Biological Opinion (BiOp) in April 2016, concluding that the NFIP in Oregon does impact threatened and endangered species because it enables floodplain development, which reduces the habitat of these species. The BiOp directed FEMA to update its NFIP requirements (i.e., building and site development standards) to ensure that floodplain habitat and flood conveyance are maintained when development occurs in the floodplain. FEMA worked with Oregon jurisdictions and other stakeholders to develop the Oregon Implementation Plan for NFIP-ESA Integration, which lays out FEMA’s proposed approach to comply with the FEMA BiOp directives.

What is the Floodplain Management Update Work Plan?

In September 2019, directors of eight City bureaus approved a 5-year Floodplain Management Update Work Plan, which established the City’s overall approach to updating floodplain regulations and complying with the directives of the FEMA BiOp. City Council supported the implementation of the work plan through special appropriations funding in FY2018-19 and FY2022-23. Since then, staff at the Bureau of Planning and Sustainability, Bureau of Environmental Services and Bureau of Development Services have continued to move the work plan forward. To meet federal requirements and progress toward adopted City goals and policies as well as support existing bureau work plans, the Floodplain work plan aims to:

  • Update zoning code (Title 33) and building code (Title 24) regulations to preserve floodplain habitat and maintain flood storage when development occurs in the floodplain.
  • Restore and increase floodplain habitat and improve resilience through continued and ensured protection of natural areas and improvement of degraded areas over time.

Implementation of the work plan requires action by a number of City bureaus in a multi-phase effort. The timeline below summarizes the steps in the implementation process, along with FEMA’s compliance schedule.

Graphic showing a comparison of the FEMA BiOp timeline with the City work plan components and schedule.
This timeline summarizes the steps in the implementation process, along with FEMA's compliance schedule.

What is the Floodplain Resilience Plan and what does it propose to do?

The Floodplain Resilience Plan specifically refers to zoning code (Title 33) amendments that aim to reduce the impacts of future flooding on those who live or work in, or close to, Portland’s floodplains. The plan also aims to protect floodplain habitat for endangered and threatened fish species.

The plan, along with current and future updates to the building code and expanded mitigation banking options, will continue the City’s implementation of the Floodplain Management Program Work Plan. This citywide effort responds to FEMA guidance to update rules that apply to new development along the edges of Portland’s rivers and streams.

To achieve these goals, the Floodplain Resilience Plan will:

  • Apply new floodplain development and vegetation management requirements to maintain fish and wildlife habitat through the application of Environmental or River overlay zones.
  • Apply additional protections within 170 ft of ordinary high water to expand habitat.
  • Incorporate the results from new modeling of a 1996 flood-like event into the City’s regulated floodplain (or “combined flood hazard area”).

Read more about the floodplain proposals in different parts of the city

What amendments did the Planning and Sustainability Commission (PSC) make to the Proposed Draft?

After holding a public hearing on the Proposed Draft of the Floodplain Resilience Plan on September 27, 2022, and conducting work sessions in October and November, the PSC made a recommendation to City Council to adopt the plan, with a few minor amendments that fall into two categories:

  1. Map Amendments – Updated maps of the proposed River Environmental overlay and riparian buffer area along the Willamette River, based on new information received on a few sites in the study area.
  2. Technical Zoning Code Amendments – Clarified proposed language in several code sections that addressed measuring of top of bank, dredging in the waters along South Waterfront, the application of the River Environmental overlay zone on public streets and sidewalks, and proposed tree removal standards in South Waterfront.

What is the building code (Title 24) project and what potential updates will be evaluated as a part of the project?

The Bureau of Development Services (BDS) is leading a separate project focused on building code updates. Primarily, the proposed building code updates will address the placement of soil and structures in the floodplain. This project is another step in the implementation of the City’s Floodplain Management Program Work Plan.

The project is proposing to increase the volume of excavation required to offset the volume of soil or structures placed in the floodplain. The current excavation ratio is 1:1 for removal/addition of soil only (known as “balanced cut/fill”). The BDS project proposes to increase the excavation ratios in some portions of the FEMA 100-year floodplain up to a ratio of 1.5:1 or 2:1, depending on how close proposed development is to the waterway. The excavation ratio for the developed floodplain is proposed to stay at 1:1, but the placement of buildings in the FEMA 100-year floodplain must be included in the calculation. The purpose of these changes is to ensure that the movement of flood waters is maintained with new development, and there is no increased risk of flooding on nearby properties.

This building code project will be considered by City Council starting in August 2023, similar to when the Floodplain Resilience Plan will be at City Council.

Read more about the BDS building code update project

What is the relationship between the Floodplain Resilience Plan and the Economic Opportunities Analysis (EOA)?

The next phase of implementation for the Floodplain Management Update Work Plan will focus on the Columbia River and Columbia Slough floodplains and be coordinated with the Economic Opportunities Analysis (EOA) project.

The purpose of the EOA is to analyze and forecast business and job growth in Portland’s industrial and other business districts, then designate an adequate 20-year supply of developable land for that economic growth. The EOA update will align 2040 growth expectations with current market trends and incorporate community input. The EOA considers a number of indicators in its estimate of developable land, including employment forecasts, economic development objectives, environmental considerations, such as floodplain requirements, increased tree canopy and other natural resource protections, and equity goals.

To ensure that the EOA analysis appropriately considers and responds to the FEMA BiOp directives, the Floodplain Resilience Plan Proposed Draft does not propose amendments to existing environmental regulations in the following industrial/employment zones: Heavy Industrial (IH), General Industrial 2 (IG2) and General Employment 2 (EG2). Changes in these areas will be considered as part of the EOA update, along with the Columbia Corridor and Industrial Land Ezone Project (CCIL Ezone Project), to provide adequate protection for natural resources in this key area of employment within the city.

During the EOA process, City staff will evaluate floodplain and environmental protections in conjunction with the updated economic growth forecast and buildable land inventory, in order to optimize natural resource protection, reduce natural hazard risks, and promote economic opportunity. The Economic Opportunities Analysis update is expected to be adopted in 2024.