US Army Corps of Engineers
Portland District

New Start Feasibility Study of the Portland metropolitan area levee system

U.S. Army Corps of Engineers,
CENWP-PM
ATTN: Laura Hicks
P.O. Box 2946
Portland, OR 97208-2946

503-808-4510

PMLS-Feasibility@usace.army.mil

 

Click here to see slides from the
Corps and Levee Ready Columbia's open house meeting in August.

Portland Metro Levee System

PMLS feasibility study area along the Columbia River

New Start Feasibility Study

The U.S. Army Corps of Engineers has initiated a Feasibility Study focusing on Flood Risk Management of the Portland Metro Levee System in partnership with the Columbia Corridor Drainage Districts (CCDD) Joint Contracting Authority. CCDD consists of four drainage districts: Peninsula Drainage District #1, Peninsula Drainage District #2, Multnomah County Drainage District and the Sandy Drainage Improvement Company. The study area includes 27 miles of levees along the lower Columbia River within the Portland Metropolitan Area, running from Sauvie Island to the Sandy River.

The levee system is experiencing significant signs of structural vulnerabilities during high water, including sloughing, boils, and seepage. The three-year federal feasibility study process will lead to a recommendation to Congress for federal investment in addressing the problem areas in the Portland metropolitan area levee and drainage system.

The study will focus on developing an integrated plan to address potential system failures, meeting current levee safety standards, and identifying potential impacts from future changes including system consolidation, changing water flow conditions and potential operational changes to the Columbia River System.

The Non-Federal Sponsor on the project is the Multnomah County Drainage District (MCDD), which has been granted decision authority to act on behalf of the four drainage districts. The feasibility study is authorized in Section 216 of the Flood Control Act of 1970.

 

Public involvement

The U.S. Army Corps of Engineers, in partnership with Levee Ready Columbia, will hold an informational meeting on the Portland Metro Levee System feasibility study. The event, which is open to the public, will provide an update on the feasibility study including refinement of alternatives, technical information and analysis conducted to date, and the next steps in the feasibility study process.

When: Wednesday, August 28, 2019 at 6 p.m.
Where: Multnomah County Drainage District, 1880 NE Elrod Drive, Portland

Public input is critical to the development of this feasibility plan. The Corps wants to hear the concerns and ideas of community members regarding the Columbia River corridor levee system and managed floodplain. A draft report will be released for public review and comment at the end of 2019. 

Past public engagement: The Corps and MCDD held two scoping meetings in December 2018 to engage community members in discussing the study process, study milestones, and the development of preliminary alternative strategies for the reduction of flood risk in the Portland metropolitan area. Discussion also focused on modernization of the levees, flows and flood risk, geotechnical studies of the levees, and the economic risk and consequences posed by various flooding scenarios, as well as the effects on natural and cultural resources of alternatives considered. 

Our goals

  • Reduce flood damages, in particular critical infrastructure, in the Portland Metro Levee system over the period of analysis
  • Reduce threats to life safety from flooding and increase awareness of flood risk in the Portland Metro Levee system over the period of analysis
  • Increase resiliency of the flood management system over the planning period of analysis
  • Increase reliability of the flood management system over the planning period of analysis
  • To the extent practicable, provide opportunities for recreation, natural resources, and cultural resources
  • Improve operability of the flood management system and decrease flood response and recovery time

Understanding flood risk

Cross section of a river, a levee, and a building protected by the levee show the elements that make up flood risk: hazard, performance, exposure, vulnerability,

The primary goal of the feasibility study is to reduce the risk of flood damages to the Portland metropolitan area, thereby reducing threats to life and safety.

Flood risk is made up of a variety of factors, beyond exclusively the condition of the levees themselves. These factors include: the hazard, system performance, exposure, vulnerability, and consequences.

The essential questions in determining flood risk are:

  • What possible loading events could occur?
  • How well will the levee system perform when the event occurs?
  • What are the consequences if the levee does not perform as expected? What loss of life could occur?


In even simpler terms, flood risk is the probability of a flood multiplied by the consequences of that flood.