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Flood Protection Information
Special Flood Hazard Areas (SFHA)
Devastating storms, runoffs from early snowmelt, and rising rivers can happen when you least expect them. Floods are the most common natural disaster in the North Bend, and many properties have some risk of flooding. Being prepared now could not only save lives, but also reduce the emotional toll and property damages that may come with disaster.
In North Bend, potential flooding comes from five water bodies: South Fork Snoqualmie River, Middle Fork Snoqualmie River, Ribary Creek, Gardner Creek, and Silver Creek.
North Bend has two types of common flooding: groundwater flooding and river flooding. River flooding is when the streams and rivers overtop their banks due to excess runoff or snow melt. This type of flooding can occur gradually or quickly. Groundwater flooding typically occurs with moderate-to high-intensity rain storms. as rainfall of 3 inches or more in a 24-hour period. In normal rain storms, water has some opportunity to infiltrate into the ground along ditches or landscaped areas. During extended rain storms, the ground becomes saturated and unable to absorb more water, and water begins to pond in ditches and low areas. Groundwater flooding generally occurs gradually and allows time for property owners to identify an impending flood situation and prepare for it, but is can also last for several weeks. Both groundwater and river flooding events generally occur during the winter months.
There have been 15 damaging floods from the Snoqualmie River in the North Bend vicinity since 1975. The City of North Bend, like many other jurisdictions in King County, was founded close to the banks of a river because the river environment provided opportunities for navigation, commerce, fishing, logging, and agriculture. Thus, older and in some cases historical portions of the City, including North Bend’s downtown core, are located in areas that are vulnerable to flooding. Approximately 42 percent of North Bend’s land area is mapped or identified as the special flood hazard area (SFHA) also known as the 100-year floodplain, or the area with a 1% chance of flooding every year.
To find out if your property is within the SFHA you can view King County iMap, visit Floodsmart.gov or call the Public Works Department. The Public Works Department can also help you find additional flood insurance information and help with Flood Insurance Rate Map Zone Determination.
Build Responsibly
A floodplain development permit is required prior to beginning any development within the SFHA. Development is defined as "manmade alteration of unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations, storage of equipment and materials and subdivision of land. For properties within the floodplain, development also includes the removal of more than 5% of the native vegetation on the property, or alteration of natural site characteristics."
"Substantial improvement and substantial damage" is when the cost of any repair or alteration of a structure is valued at more than 50% of the assessed value of the structure. If a structure is being repaired, the structure's value is based on the pre-damage value. In North Bend, the cost of repair or alteration is the current project value combined with the cost of all projects over the prior 5-year period. If a project is considered a substantial improvement or substantial damage, the structure must be brought into compliance with current floodplain regulations. For older structures, this may require elevation of the structure, floodproofing, installation of additional foundation vents or modifications to the crawlspace.
Landowners can apply for a floodplain development permit at Public Works. Regulations for development within the SFHA are found within NBMC 14.08.
Natural & Beneficial Floodplain Functions
The floodplain is the area adjacent to rivers and streams that periodically flood. Floodplains are hydrologically important, environmentally sensitive, and ecologically productive areas that perform many natural functions. In addition to the scenic and recreational value of the floodplain, they also provide habitat, food, and protection to fish and wildlife, recharge aquifers, improve water quality, and created the rich farmland for which the area is known.
Values and functions supporting high diversities of plants and animal life include:
Biological Productivity
• Support high rate of plant growth
• Maintain biodiversity
• Maintain health and integrity of the ecosystem
Fish and Wildlife Habitat
• Provide breeding and feeding grounds
• Create and enhance waterfowl habitat
• Protect habitats for rare/endangered species
North Bend is located within the Snoqualmie Watershed. The Snoqualmie Watershed is the largest and most forested in King County, encompassing almost 700 square miles. North Bend participates in the Snoqualmie Watershed Forum which has a goal of protecting and restoring the health of the watershed. Snoqualmie Watershed Map.
To protect and improve the natural and beneficial function of the floodplain, all development within the floodplain must:
- Consider effects to threatened and endangered species pursuant to the National Flood Insurance Program Puget Sound Biological Opinion (BiOP). More information about the BiOP can be found on FEMA's website https://www.fema.gov/national-flood-insurance-program-endangered-species-act. Except for exempt projects as described in NBMC 14.12.210(B), all projects must complete a habitat assessment and demonstrate the projects will be able to demonstrate this through compliance with the city code and can document it using the city's Habitat Assessment Worksheet.
- Comply with the city's critical areas regulations. The State of Washington designates the SFHA as a critical area, and all projects within the critical area must comply with the city's critical areas provisions within NMBC.14.05.
- Comply with the city's Shoreline Master Program (SMP), if applicable. Shorelines within the city are associated with the South Fork and Middle Forks Snoqualmie Rivers. More information about the SMP including a map of potential shoreline jurisdiction can be found on the city's SMP website https://northbendwa.gov/226/Shoreline-Master-Program.
For More Information
If you have any questions or would like more details, please review our helpful resources, refer to the FEMA website, contact your local insurance agent, or download the 2022 Fall/Winter Floodplain News (PDF).