Flood Management

Floods: A Part of Grants Pass
The Rogue River is Grants Pass’ best known scenic and recreational feature. But heavy rains can turn our normally peaceful river into a raging current that can, and will, reclaim nearby low lands as its own. The Rogue has flooded the city more than a dozen times in the past 130 years. The most recent flood (in January 1, 1997) caused $10 million damage to homes, businesses, agriculture, roads and bridges in Josephine County.

Although water in the Rogue rushed by at 90,100 cubic feet per second (cfs), the New Year’s flood was nothing compared to the county’s largest recorded flood. In 1861, the Rogue River swept by at 175,000 cfs. (In comparison, the 1997 average summer flow was 2,431 cfs.)
1964 Flood
The December 1964 flood rages through Grants Pass. Caveman and 7th Street bridges can be seen in the middle of the photo, taken facing west.
Recent Flood
Our most recent major flood occurred December 23, 1964, when the river peaked at 152,000 cfs. Floodwaters swamped large areas of the city, extensively damaging homes, businesses, bridges, and the sewage treatment plant. The 1964 flood was caused by a combination of extended heavy rains (10 inches in 6 days) and snowmelt from upstream mountains. The 1997 New Year’s flood was caused by 4 inches of rain over a 48-hour period onto ground that was already saturated by heavy December rains.

Dam
The 1977 completion of Lost Creek Dam, 55 miles upstream on the Rogue River, will not prevent floods. The dam, however, will reduce the severity of floods. For example, in 1964 the river crested 15 feet above flood stage. Engineers estimate that Lost Creek Dam will reduce floodwaters by 7.5 feet. So in a storm the magnitude of 1964, the river now would crest at 7.5 feet over flood stage.

Gilbert Creek
The Rogue River isn’t the only Grants Pass waterway that has a history of flooding. Gilbert Creek provides drainage for 5.6 square miles of the city. The creek has flooded many times after heavy storms, overflowing streets at various culverts around the city.
1964 Flood house
1964 flood: Three feet deep and rising was the water around this home along the Rogue River Highway. The river was expected to crest at 32 feet and cover this house above the main floor windows.
Floods Are a Fact of Nature
Flooding is a problem only where humans compete with nature for the use of low lands along rivers and streams. These low lands are called floodplains, the most common being a base level called the 100-year floodplain (which has a 1% chance of being flooded each year). 9% of the land in Grants Pass is in the city’s 100-year floodplain, which is based on the flood of 1861. The city maintains a flood zone map (PDF) which shows areas that are prone to flooding and their corresponding designations.

Floodplains are helpful in many ways. They reduce the severity of floods by allowing floodwaters to spread out and slow down. They filter sediment from streams and rivers to improve water quality, and they recharge groundwater. Floodplains also are home to many plants and animals, some of which cannot live anywhere else.

Waterways and Potential Flood Areas Map

Waterways and Potential Flood Areas Map
How to Protect Your Property
People living in floodplains are 27 times more likely to experience a flood than a fire during a 30-year mortgage. However, buildings can be protected through insurance and physical alteration.

Insurance
Standard homeowners insurance policies do not cover flooding, but flood insurance is available to Grants Pass residents through the National Flood Insurance Program. You might already have flood insurance through your mortgage escrow, because all homes bought after 1970 with federally guaranteed funds (through a federally-insured bank) or with FHA, VA and SBA loans must be insured. However, that insurance only covers the building and you may want to purchase additional insurance to cover the building’s contents. Any licensed insurance agent can sign you up.
Physical Alteration
Flood protection measures may be built in during construction, or added to an existing building. The best protection is to build above the flood level. All new homes constructed in the floodplain must be built 1 foot above the 100-year flood level. A surveyor can tell if an existing building is above the flood level.

Additional Flood Protection
Other flood protection measures include:
  • Anchoring manufactured homes with a hold-down bracing system.
  • Applying a sealant to walls and floors to reduce seepage.
  • Installing backwater valves and backflow prevention devices to protect plumbing.
  • Raising a building and extending the original foundation above the flood level.
  • Raising electrical connections and appliances above expected flood levels.
  • Sealing off unused doors and windows.
All new building and substantial improvements to property in the floodplain must meet National Flood Insurance Program regulations. City permits are required before one can build, fill, or substantially improve buildings or property in the 100-year floodplain. Development on property located in a flood zone are required to submit a Flood Elevation Certificate (PDF) as part of the building permit application.

How to Protect Our Community
Gilbert Creek and other creeks are drains that carry rainwater out of the city to the Rogue River and on to the ocean. When the creeks and the river become clogged with trash, debris or heavy vegetation, flooding is increased. City ordinances protect our drainage ways by prohibiting the dumping of materials into waterways and the construction of buildings and fences less than 20 feet from the top of the bank.

To report dumping, a blocked creek, or an illegal development, please call 541-450-6060.

What To Do in a Flood
  1. Turn your radio on. Stay informed by tuning in local radio broadcasts. The U.S. Weather Service notifies all radio stations when a flood is forecast. Keep a battery-powered radio on hand in case the electricity goes out.
  2. Protect your home. Turn off the electricity and gas. If there is time, sandbags can divert water away from your home, and furniture and appliances can be moved to higher ground or a second floor.
  3. Stay calm. If you are forced to evacuate, use common sense. Panic can cause errors in judgment.
  4. Do not walk through flowing water. Six inches of moving water can knock you off your feet, and drowning is a major cause of flood deaths.
  5. Do not drive through a flooded area. More people drown in their cars than anywhere else.
  6. Avoid downed power lines. Electrocution is a major killer in floods. Remember that electricity can travel through water.
  7. Stay away from waterways. Floods can weaken normally stable banks, which could give way under your weight.
Regulations
Regulations governing development and construction of structures in the floodplain are located in Article 13 Section 13.200 of the City of Grants Pass Development Code (PDF). The Parks and Community Development office has copies of the Federal Emergency Management Agency’s Flood Insurance Study for the County of Josephine, State of Oregon and Flood Insurance Study for the City of Grants Pass, with the accompanying Flood Insurance Rate Maps, available for view to the public during regular business hours.