Benton County, Oregon

Making Benton County a Better Place to Live
Printed on Aug 31, 2015 @ 8:17 AM

Benton County Emergency Management – Flood Resources

Know Before You Go: Road & Weather Info

Oregon Department of Transportation Trip Check. Dial 5-1-1 from your cell phone, and in Benton County, call 541-757-4211.

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Flood Terminology

Bankfull: the point at which the river level has reached the top of its bank. For some rivers this may not be well defined.

Crest: the point at which the river is at its greatest flow or height.

Flood Stage: the level at which the flooding begins to create damage to property.

Flow: the volume of water flowing in the river, measured in cubic feet per second. River levels for our area may be monitored at

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County Floodplain Information Services

The County can determine the relationship of a particular property to the floodplain including:

  1. Whether the property is located within the Special Flood Hazard Area;
  2. Flood Insurance Rate Map (FIRM) Zone for property;
  3. Base Flood Elevation for property, if available; and
  4. Whether the property is located within the Floodway.

Contact Benton County Community Development Department at 541-766-6819 for further information.


Understanding & Regulation

Maintaining the flow capacity in streams which cross County properties requires cooperation and assistance to prevent flooding and bank erosion.

The County regulates the floodplain in order to protect the lives and property, while affording County property owners the ability to obtain floodplain insurance.

A number of important measures will help all of us protect our valuable water resource and natural environment:

Recognize the natural beneficial functions of floodplains to help reduce flooding. Floodplains are a natural component of the Benton County environment. When flooding spreads across the floodplain, its energy is dissipated, which results in lower flood flows downstream, reduced stream bank and channel erosion, increased sediment deposition and improved groundwater recharge. Floodplains are scenic, valued wildlife habitat, suitable for farming. Poorly planned floodplain development can lead to stream bank erosion, property loss, downstream flooding and degradation of water quality.

Never dump or throw anything into ditches or streams. A plugged channel cannot carry water and when it rains, the excess water must go somewhere. Trash and vegetation dumped or accumulated in a stream degrades water quality of the stream and its receiving waters. Every piece of trash debris contributes to flooding. It is important to keep waterways clear of debris at all times to ensure clear flow and cleaner water.

Report any observations of debris dumping or activity that may damage streams, drainages or rivers to Benton County Community Development Department, 541-766-6819.

Remove debris, trash and loose branches. Keep banks clear of debris to help maintain an unobstructed flow of water in stream channels. Do not remove vegetation that is actively growing on a stream bank. Streamside vegetation is strictly regulated by local, state and federal rules. Before undertaking any removal of growing streamside vegetation, contact Benton County Community Development Department and the Division of State Lands at 503-378-3805. Report any clearing of live vegetation or trees on stream banks to Benton County Community Development.

Obtain a floodplain development permit and/or building permit if required. To minimize damage to structures during flood events the County requires all new floodplain construction to be anchored against movement by floodwaters, resistant to flood forces, constructed with flood-resistant materials and flood-proofed or elevated so that the first floor of living space is at least one foot above the elevation of the 100-year flood. All service facilities (electrical, heating, ventilation, plumbing, heat pumps, air-conditioning equipment, water heaters, etc.) must also be elevated above the 100-year flood or designed to prevent water from entering or accumulating within the components during flooding.

The floodplain construction standards apply to all new structures and substantial improvements of existing structures. The County defines a substantial improvement as any repair, reconstruction, or improvement of a structure the cost of which equals or exceeds 50% of the actual cash value of the structure.

Most other types of development within the floodplain such as grading, cut and fill, installation of riprap and other bank stabilization techniques also require a floodplain development permit. County staff is available to schedule site visits and review flood, drainage and other related issues. Contact Development Department staff prior to undertaking any activity within the floodplain.

Reduce risk of damage to homes. There are practical and cost effective methods for reducing or eliminating the risk of flooding to property owners whose homes have experienced previous flood damage or potential future damage. Such techniques include elevation or relocation of the structure to higher ground, constructing floodwalls or berms, flood proofing and protecting utilities.

During times of flooding, homes that have not been retrofitted can be protected during emergencies by the installation of sandbags.

More Resources

Types of flood information available on the Emergency Management website:

FEMA Links:

More Information

For more information on flooding, see:

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