Floodplain Information

Muddy Creek 2012 Flood

Floodplain Management in Benton County

Benton County has approximately 57,000 acres of land located within its floodplains and nearly 3,200 individual parcels that are partially or entirely located within a floodplain. Here is a link to Benton County Zoning Map.

Benton County participates in a program called the Community Rating System (CRS) which is part of the Federal Emergency Management Agency’s (FEMA) National Flood Insurance Program (NFIP).  The NFIP’s Community Rating System provides discounts on flood insurance premiums to property owners in those communities that establish floodplain management programs that go beyond national minimum requirements.  CRS communities receive credit towards premium reductions for floodplain management programs that:

  • Protect public health and safety;
  • Reduce the risk of flood-related hazards, damage, and erosion;
  • Prevent increases in flood damage due to new construction;
  • Encourage and incorporate measures that protect natural and beneficial floodplain functions;
  • Preserve open space areas in and around floodplains;
  • Inform community residents and agencies of floodplain hazards and benefits;
  • Encourage acquisition of flood-prone properties and relocation of structures to reduce the risk of flooding;
  • Facilitate accurate insurance rating; and
  • Promote the awareness of flood insurance.

The current Class 7 designation authorizes the following flood insurance premiums for Benton County property owners:

  • 15% for properties located in a floodplain (high-risk flood hazard area) and
  • 5% for properties located outside of a high-risk flood area.

Benton County is one of only eight communities to maintain Class 7 ratings in Oregon. Rural Benton County residents have enjoyed at least a Class 7 level discount of 15% on their flood insurance premiums for over 15 years, due to the county’s maintenance of that classification. Statewide only seven government agencies – including the cities of Albany, Central Point, Corvallis, Medford, Portland, and Salem, as well as Marion County – have lower ratings, ranging from Class 5 to Class 6.

In order to maintain the current level of participation in the CRS program and help ensure county property owners continue receiving flood insurance at a discounted rate, Benton County is required to continue doing various things:

  • Maintain records of all development activity approved in the floodplain.  Benton County does this through approval of Floodplain Development Permits.  These records document the county’s commitment to responsible floodplain management.
  • Provide floodplain and flood hazard related information.  Typical types of information available at the Benton County Community Development office include:
    • The location of a property in relation to the floodplain shown on the current and historic Flood Insurance Rate Maps (FIRM) for the county;
    • Additional flood insurance data for a site, such as the flood zone designation shown on the FIRM panel and, if available, an approximate base flood elevation;
    • Land use and building code regulations that apply to properties in a floodplain;
    • A copy of FIRMs showing flood hazard boundaries and, when available, mapped floodway locations;
  • Maintain a record of all elevation certificates submitted to the Community Development office.  Elevation certificates are required for all new construction and are typically available for structures constructed or improved since 2002.  Additional floodplain worksheets are sometimes available for structures constructed as early the late 1980s.
  • Provide outreach information to property owners whose land is in or near a floodplain.  The county sends out a yearly Flood Facts mailing identifying high flood risk areas and providing reminders about development requirements in floodplains, information about how to prepare for and respond to flood events, helpful contact information, significant flood events that have occurred in the past, benefits of floodplain functions, and actions that help reduce damage caused by flooding.
  • Provide information regarding flood mitigation options.  The county Floodplain Manager can provide information about possible retrofitting options that can be helpful to reduce the risk of structural damage from flood events and potentially reduce flood insurance premiums.

Planning a Project in the Floodplain?

Remember to get a Floodplain Development Permit before you begin your project.  A Floodplain Development Permit is required for all development in the floodplain – even if the work does not require a regular building permit or land use approval. All new development within the floodplain must comply with current floodplain development standards, which may include elevating a structure or the utilities serving the structure to the Benton County design flood elevation.  New construction and additions to existing structures require that a licensed surveyor complete three elevation certificates:

  • A pre-construction elevation certificate for the building site to verify flood elevation and existing ground elevation. 
    • This certificate is submitted with the application for a permit. 
    • Note:  Prior to applying for a permit it is helpful to submit this certificate to the Floodplain Manager and discuss the proposed project.
  • A mid-construction elevation certificate to verify floor elevation. 
    • For a site-built dwellings and accessory structures, this certificate is submitted after placement of the lowest floor and prior to vertical wall construction; approval of the certificate is required prior to approval of the underfloor inspection.  For manufactured dwellings, this certificate is submitted after the dwelling has been placed on the property; approval of the certificate is required prior to approval of the set-up inspection.
  • A finished construction elevation certificate for the completed structure. 
    • This certificate is prepared after all of the utilities have been placed and all finished grading is completed.  The certificate must be submitted and approved prior to final inspection approval for the structure.

Other permits may require submission of an elevation certificate completed by a licensed surveyor as well.  A Floodplain Development Permit is also required for all work to repair a structure that has been damaged by any type of event.

What Counts as "Development"?

In a floodplain, this term has a very broad definition.  Examples of typical types of “development” in a floodplain include:

  • Structural projects – new structures, additions, demolitions, repairs, fences, and retaining walls
  • Electrical, plumbing and mechanical projects – replacing or installing electrical wiring, heat pumps, irrigation pumps, etc.
  • Remodeling projects – hanging drywall, replacing or installing windows, flooring, and roofs
  • Ground disturbing projects – filling, excavating, or grading your property
  • Riparian projects – stream restoration and habitat enhancement

Some of the projects listed above may not require a separate building permit or land use approval but they all require a Floodplain Development Permit.  If someone else will be doing the project for you, remind them to get floodplain development approval first.

Why is a Floodplain Development Permit Required?

As part of Benton County’s participation in the Community Rating System, the county is required to maintain records of all development activity approved in the floodplain.  These records are kept in the form of Floodplain Development Permits.  They document the county’s commitment to responsible floodplain management and help ensure county property owners continue receiving flood insurance at a discounted rate.

Where Can I Get an Application Form?

The application form is available in the Supporting Documents section below and at the Benton County Community Development office. There is also a link to a set of step-by-step instructions detailing how to determine whether or not your project is located in a floodplain and how to obtain the floodplain information requested on the form.

For more information, contact the Community Development office at 541-766-6819

What Types of Development Are Most Often Affected by Floodplain Regulations?

Here is a quick list of structure-related floodplain development regulations that are most likely to affect you:

  • Dwellings – New dwellings, substantially improved dwellings, substantially damaged dwellings must have the first habitable floor elevated 18 inches above Base Flood Elevation;
  • Accessory structures – New accessory structures, substantially improved accessory structures, substantially damaged accessory structures must also have the first habitable floor elevated 18 inches above Base Flood Elevation;
  • Additions to, or replacement of, existing dwellings or other primary structures – The existing footprint of a primary structure, such a dwelling, may only be increased or shifted by a maximum of 10% unless the structure is elevated 18 inches above Base Flood Elevation on posts, piers, or piles;
  • Electrical, mechanical, heating, ventilation, plumbing and comparable equipment – When providing service to a structure, installation and replacement of these types of equipment typically must be elevated 12 inches above Base Flood Elevation or must be water tight during flood conditions; some exceptions to these requirements are available for structures built prior to 1986; and
  • Crawlspaces – Crawlspaces in a floodplain must be adequately vented to allow for automatic flow of flood water through the crawlspace during flood events.  Flood vents must be installed below the Base Flood Elevation and not more than 12 inches above the adjacent grade.  Flood vents may be screened but must remain uncovered at all times.
  • New primary structures – New primary structures, such as dwellings and commercial structures, are not allowed to be constructed in the floodplain unless no other option exists on the property.  When allowed within a floodplain, these structures must be sited on land that is the least susceptible to flood hazard and must be adequately elevated as stated above.

Remember:  A free floodplain development permit is required for all development in the floodplain, even if the work does not require a regular building permit or land use approval.

For more information, including the full text of the floodplain development regulations, visit https://www.co.benton.or.us/planning/page/development-code and click on the link for Chapter 83.