by Jessica Rojas, NECN
The Multnomah County Drainage District (MCDD), located between NE Columbia Blvd and Marine Drive, is a system of four districts, charged with the objective of protecting lives and property from flooding. This is done through the operation and maintenance of a stormwater and flood management system for over 1200 acres of land along the Columbia Slough and lower Columbia River. The system that MCDD is responsible for includes 27 miles of levees, 13 pump stations, and 45 miles of ditches, sloughs, streams, and culverts.
The flood control levees managed by the district were created in 1917 to manage water-saturated areas adjacent to the river. The districts run from Portland Boulevard in the west all the way to the Sandy River in the east.
The 12,000 acres that MCDD manages are originally a part of the natural floodplain of the Columbia River and the districts were created to develop the floodplain as farmland. Shortly after construction of the levees began in the 1930’s, significant flooding occurred and in 1948 the Vanport flood happened.The federal government authorized the United States Army Corps of Engineers (ACE) to build out the Levee system here. Over time land uses have changed but the desire to keep the area drained has stayed the same.
“If the drainage district was to lose accreditation of the levees, many businesses and homeowners would be required to have their own flood insurance.”
MCDD maintains an area that provides employment in the Northeast area, including many middle-income jobs that can be accessed with only a high school education. What is also important to understand is that this system is required to meet federal standards in order for those who operate and live in that area to receive program benefits.
The main benefit is receiving national flood insurance protection through accreditation of the levees. FEMA requires that the levees are maintained to a certain standard- meaning, the ability of the levees to withstand the 1% annual chance of what is known as the 100 year flood. Wikipedia describes the concept as a “flood event that has a 1% probability of occurring in any given year.” If the levees can be reasonably expected to protect against that 1% annual chance of a flood, then protected areas are considered by FEMA to be outside of the floodplain.
If the drainage district was to lose accreditation of the levees, many businesses and homeowners in the district would be required to have their own flood insurance, which would drastically affect the economy of the area.
Another program benefit is through the support of the ACE, called The Rehabilitation and Inspection program. The ACE built this system and the district is under agreement with them that MCDD will maintain the infrastructure, with ACE inspections every few years. If significant damage was found, due to an event like a 100 year flood, such as in 1996, ACE will provide those repairs and cover 80% of the costs with the district.
MCDD is evaluating the levees to make sure they’re ready for the future as required for maintenance. Communities all around the country are going through a similar process as all federally authorized levies are required to evaluate as needed.
MCDD has also been engaging with the broader community as stakeholders. They have engaged with local industries, neighborhood associations, business groups and environmental advocates to greater understand what the community feels is the right level and protection from such events, like a 100 year flood or megathrust earthquake from the Cascadia Subduction zone.
If you were driving along Marine Drive this past February and noticed some unfamiliar equipment, it was likely one of the big drill rigs taking soil samples out of the Levee, which will be used by engineers to evaluate its health. MCDD will provide those geotechnical reports back to the community to inform stakeholders of what kind of risk-based decisions will need to be considered.
Read MCDD’s annual reports and more on their website, mcdd.org.