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Summary of Floodplain Resilience Plan proposals

Photo shows an open space holding flood water with dry winter grasses and split-rail fencing
Summary of the Floodplain Resilience Plan and its proposals, including updates to the plan since the Proposed Draft, and how the proposals will affect different geographic areas of Portland.
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The purpose of the Floodplain Resilience Plan is to reduce the impacts of future flooding and degradation of floodplain habitat on endangered and threatened fish species, bring City regulations into compliance with federal regulations, and advance the City’s own climate resiliency goals. Read more about the Floodplain Resilience Plan.

Summary of plan proposals by area

The Floodplain Resilience Plan includes different proposals depending on the location within the city:

Willamette River Central Reach

  • Require floodplain development within 170 ft of the ordinary high water mark (known as the riparian buffer area) to address natural resources impacts and incorporate measures to improve fish habitat along the riverbank, such as removal of structures or rip rap, creation of shallow water habitat and other strategies. Improvements to fish habitat are approved through land use review.
  • Apply the River Environmental overlay zone to encompass the proposed riparian buffer area and any undeveloped floodplain landward of the riparian buffer area.

Willamette River South Reach

  • Update the boundaries of the existing riparian buffer area and River Environmental overlay zone to include the areas identified in the Modeled 1996 Willamette River Flood Extent and FEMA 100-year Floodplain.
  • Remove the River Environmental overlay zone from developed floodplains landward of the riparian buffer area.

South Waterfront

  • Add new standards for tree and vegetation removal and maintenance, similar to those in the River Overlay Zones chapter (33.475).
  • Clarify that exterior lighting standards apply to all of the Greenway overlay zone, which was the original intent of the code, but currently apply only within 100 ft of the top of bank.
  • Change the process for South Waterfront Greenway Review from a Type III procedure to a Type II procedure, consistent with the approval process in other environmental overlay zones in the city. A Type II procedure allows for a determination on a proposed development to be made by Bureau of Development Services staff.

Fanno Creek and Tryon Creek

  • Expand the Environmental Conservation overlay zone to cover undeveloped floodplains along Fanno and Tryon creeks.

Elsewhere in the city (including Fanno Creek, Tryon Creek, Johnson Creek, Columbia River and Columbia Slough)

  • Update 33.430, Environmental Zones, to limit (in some cases) when a tree can be removed through an exemption and establish a requirement that at least three trees are planted whenever a tree is removed in the floodplain.

Key PSC amendments to the Proposed Draft

During the fall of 2022, the Floodplain Resilience Plan Proposed Draft went before the Planning and Sustainability Commission (PSC). The PSC approved a small number of amendments to the plan in two categories:

  1. Map Amendments – Updated maps of the proposed River Environmental overlay and riparian buffer area along the Willamette River.
  2. Zoning Code Amendments – Clarified proposed language in several code sections that addressed measuring 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.

Key updates made in the Proposed Draft

The Floodplain Resilience Plan Discussion Draft was released in early November 2021. Public comments were gathered on the draft through the end of January 2022. The Proposed Draft incorporated changes in response to those comments, as well as additional research and evaluation by project staff. Updates prior to release of the Proposed Draft included:

  • Separate building regulations (Title 24) update process – Several proposed updates to Building Regulations Chapter 24.50, Flood Hazard Areas, were included in the Discussion Draft, along with zoning code (Title 33) proposals. City staff subsequently decided to split the updates to titles 33 and 24 into separate projects. The Bureau of Development Services is leading the Chapter 24.50 Flood Hazard Areas Code Update Project, which addresses excavation requirements in floodplains and other considerations. Find more information on Title 24 update project.
  • Incorporated Modeled Willamette River 1996 Flood extent – In collaboration with the U.S. Army Corps of Engineers, City staff completed a new model of a Willamette River flood event similar to the February flood of 1996, which is expected to be more common due to climate change. This modeled flood event is incorporated into the “combined flood hazard area,” which is used to refine the boundaries of environmental overlay zones along the Willamette River.
  • Apply environmental zoning to undeveloped floodplains – The Discussion Draft proposed the application of environmental regulations to all floodplains along the Willamette River Central Reach, Fanno Creek and Tryon Creek that are not already in an environmentally focused overlay zone. The River Environmental overlay zone is currently applied to all Willamette River South Reach floodplains. To simplify the approval process and avoid unnecessary development costs, the Proposed Draft applied the environmental regulations only to undeveloped floodplains. Environmental regulations are still proposed for all floodplains in the riparian buffer area (where applicable). The riparian buffer area includes floodplains within 170 feet of the ordinary high-water mark in the Central and South reaches of the Willamette River.
  • Update requirements in the Willamette River South Reach – The River Environmental overlay zone and the riparian buffer area boundary were modified to apply to the updated combined flood hazard area, which includes the new Modeled Willamette River 1996 Flood Extent. In some cases, this resulted in an expansion of the River Environmental overlay zone and/or riparian buffer area and, in others, the extent of these areas was reduced. Additionally, the removal of the River Environmental overlay zone is proposed for developed floodplains not in the riparian buffer area.
  • Remove proposed Environmental Conservation Overlay expansions in Columbia Corridor – The Discussion Draft included some targeted expansion of the Environmental Conservation overlay zone on floodplains along the Columbia River and Columbia Slough not in the Heavy Industrial (IH), General Industrial 2 (IG2) and General Employment 2 (EG2) zones. After further evaluation, these proposed expansions were not included in the Proposed Draft. Instead, they will be included in a package of future zoning code updates that will be part of the Economic Opportunities Analysis. Find more information on the Economic Opportunities Analysis.


Jeff Caudill

City Planner II, Planning and Sustainability

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