Primary Mission of the Districts - Manage Floodplain

The districts' flood protection and drainage infrastructure was constructed or improved by the Corps of Engineer.  As the designated local sponsors, the districts must meet Corps standards for operation and maintenance of the facilities.

The ‘special purpose’ or primary mission of the drainage districts is to manage the Columbia River floodplain to prevent flooding of landowners from high water levels in the Columbia River and from stormwater runoff. The drainage districts are designated by the Corps as the local sponsors for the federally authorized flood protection structures within their respective boundaries. As such, the districts must adhere to the Corps engineering standards for operation, maintenance, repair, replacement and rehabilitation (OMRR&R) of the levees, associated drainage structures, and pumping plants that make up each districts infrastructure.

In addition, the districts are responsible for flood protection in the floodplains designated by the Federal Emergency Management Agency (FEMA) as special flood hazard areas (SFHAs). The districts do this by maintaining water levels below the base flood elevation (BFE) established by FEMA to prevent flooding of usable or developed land, which provides the assurance needed for residents and developers obtain flood insurance. The BFE is the 100-year flood elevation.

The FEMA-approved BFE for the MCDD is at elevation 14.0 feet NGVD; PDD-1 is at elevation 11 feet NGVD; and PDD-2 is at elevation 5 feet NGVD Although the SDIC currently does not have a FEMA-approved BFE, studies are underway to determine it (possibly at elevation 16 feet NGVD). The districts’ water level management occurs 24-7 during storms and high water events. State regulations and local zoning codes concerning floodplain management and flood protection also are tied into the FEMA-designated flood hazard areas and the BFEs maintained by the drainage districts to prevent flooding. The interrelationships between the drainage districts’ activities and allied governments as related to flood protection are shown graphically in Figure 6 (see below).

The drainage districts are a special purpose local government organized under ORS Chapter 547, Drainage Districts (see Appendix A, Summary of Oregon Laws and Regulations, Drainage Districts). Each drainage district provides a service or “benefit” to the landowners inside its boundaries: protection from flooding and therefore, beneficial use of the land. Sections in ORS 547 of particular importance are excerpted below and include the authority to form a drainage district and the importance of flood protection (§547.005); rights of access (§547.305); provisions for districts west of the Cascades (§547.405); maintaining improvements (§547.410 and §547.415); and prohibited practices (§547.425). The complete text for ORS 547 can be found at http://www.leg.state.or.us/ors/home.html.

Figure 6. Interrelationships between Drainage District Activities and Allied Governments