Floods and Grants Pass
The Rogue River is Grants Pass' best known scenic and recreational feature. But heavy rains and rain on snow events can turn our normally peaceful river into a raging current that can, and will, flood nearby low lands.
Flood impacts increase when permanent structures are built in the river’s path. The areas outside of the normal river channel, where high water spills over, are known as floodplains. Floodplains are nature’s nursery – providing slow moving waters for young fish and frogs, plenty of insects to feed birds and their young, new soils for plants to sprout from, and a natural water filtration system to recharge groundwater. The rich agricultural soils in and around the city would not exist if not for regular flooding of the Rogue River over thousands of years. Despite these environmental benefits, flooding devastates whole communities with destruction and suffering.
Major Historic Floods
The Rogue River has flooded Grants Pass more than a dozen times in the past 160 years, with the 1861 flood being the largest post-settlement event at an estimated 175,000 cubic feet per second (cfs). In comparison, the average monthly mean for Rogue River summer flows in 2018 was 1,825 cfs.
Photos of the December 1964 flood, which peaked at 152,000 cfs, show downtown rooftops peeking out from under floodwaters. The 1964 flood was caused by a combination of extended heavy rains (10 inches in 6 days) and mountain snow melting from warm rain coming in from the Pacific. Floodwaters swamped large areas of the city, extensively damaging homes, businesses, bridges, and the sewage treatment plant.
The most recent flood (on January 1, 1997) caused $10 million in damages to homes, businesses, agriculture, roads and bridges in Josephine County. Water in the Rogue rushed by at 90,100 cubic feet per second (cfs) during this event, significantly less than the 1964 flood waters due to construction of the Lost Creek Dam.
Flood Control and the Lost Creek Dam
The 1977 completion of Lost Creek Dam, 55 miles upstream on the Rogue River, began a new era for floodplains along the river. While the river does not regularly overflow onto floodplains to benefit fish and wildlife like it once did, human infrastructure gained a certain degree of protection. The dam will not prevent floods, as the 1997 flood attests to, but it 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. If a future flood event were to mimic the conditions and magnitude of the 1964 flood, the river would then crest at 7.5 feet over flood stage.
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 culverts and street crossings.
Floods Are a Fact of Life
As the past has shown, Grants Pass is vulnerable to flooding from both the Rogue River and Gilbert Creek. The Federal Emergency Management Agency (FEMA), along with the Oregon Department of Land Conservation and Development, have established guidelines for construction and other activities within floodplains. The City has adopted and enforces ordinances (rules) to support the federal and state regulations on a local level and continually works to protect citizens and infrastructure from floods.
FEMA has created categories for floods, based on the probability of flooding in any one year. The area with the highest likelihood of flood is the Floodway. It includes the actual channel of the river and the overbank areas immediately adjacent to the channel. This is the area where the water velocity and force are the most destructive.
The next floodplain category is the 100-year flood, which has a 1% chance of being flooded each year. Over the life of a 30-year mortgage, that translates to a 26% chance of being inundated. A 100-year flood is also referred to as a Base Flood. The height above sea level that it is expected to reach is called a Base Flood Elevation (BFE). Flood insurance rates are determined by the location of a structure within a floodplain, and the type of floodplain it occupies.
Nine percent of the land in Grants Pass is in the 100-year floodplain. The city maintains a flood zone map (PDF) which shows areas that are prone to flooding and their corresponding designations. Our interactive map allows you to search for your property. Expand the GP Map Viewer layers list, and select the ”Flood Zones." This layer shows the Flood Insurance Rate Map with the locations of the Floodway, 100-year floodplain and 500 year floodplain. It also contains Base Flood Elevation lines.
For more information on areas of special flood hazard please feel free to call our office at 541-450-6060 to speak with a floodplain specialist.
The state of Oregon also provides information on the National Flood Insurance Program (NFIP) and natural hazards on their website at: Department of Land Conservation and Development : National Flood Insurance Program (NFIP) in Oregon : Natural Hazards : State of Oregon
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.
Standard business, homeowner’s or renter’s insurance policies do not cover flooding. However flood insurance is available to Grants Pass residents through private insurance companies that operate under National Flood Insurance Program guidelines. Grants Pass residents receive a reduced flood insurance rate due to the City’s efforts to regulate development within Special Flood Hazard Areas.
All homes and structures in a Floodway or 100-year floodplain bought after 1970 with federally guaranteed funds (through a federally-insured bank) or with FHA, VA and SBA loans must carry flood insurance. However, that insurance only covers the building. You may want to purchase additional insurance to cover the building's contents. Any licensed insurance agent can help you find a plan that works for you.
Flood protection measures may be built-in during construction, or added to an existing building. The best protection is to build above the base flood level. All new commercial buildings, homes, garages, sheds and other structures constructed in the 100 year floodplain must be built 1 foot above the Base Flood Elevation (BFE). A surveyor can confirm if an existing building is above the BFE.
Other flood protection measures include:
- Examine your property for hazards that you might remedy prior to a flood.
- Place yard and garden supplies in the garage after the summer season is over.
- Electrical boxes, air conditioners, and water heaters can be elevated or relocated to a place that is less likely to flood.
- Improve drainage around your home or on your property.
- Keep nearby ditches and culverts clear of debris and obstructions to prevent water from backing up onto your property.
- Retrofit your home by installing flood vents, using flood-resistant materials, or even elevating your home above flood levels.
- Follow the permit guidelines established for development in floodplains. Stop by our office at 101 NW A Street, Suite 202 for more information, or call us at 541-450-6060.
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) Opens a New Window. as part of the building permit application.
How to Protect Our Community
Keeping creeks and drains clear of debris and garbage is one of the easiest ways to reduce flood risk. Gilbert Creek and other creeks carry rainwater out of the city to the Rogue River. When waterways become clogged with trash, debris or heavy vegetation, flooding and flood risk is increased. City ordinances protect our community by prohibiting the dumping of materials into waterways and the construction of structures and fences within 20 feet from the edge of the bank.
To report dumping, a blocked creek, or an illegal development, please call 541-450-6060.
What To Do in a Flood
- 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.
- 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.
- Stay calm. If you are forced to evacuate, use common sense. Panic can cause errors in judgment.
- 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.
- Do not drive through a flooded area. More people drown in their cars than anywhere else.
- Avoid downed power lines. Electrocution is a major killer in floods. Remember that electricity can travel through water.
- Stay away from waterways. Floods can weaken normally stable banks, which could give way under your weight.
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) Opens a New Window. . 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 viewing to the public during regular business hours.
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.
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.
Waterways and Potential Flood Areas Map