Flood Damage Prevention Code Update

The City of Sammamish participates in floodplain management, which under federal regulations means the operation of an overall program of corrective and preventive measures for reducing flood damage, including but not limited to emergency preparedness plans, flood control works, and floodplain management regulations.

The City also participates in the National Flood Insurance Program, which provides residents within the floodplain the opportunity to purchase affordable flood insurance policies. It requires the adoption of floodplain management regulations that meet federal requirements.

Currently, the City is working to complete a mandatory update to Chapter 15.10 SMC - Flood Damage Prevention to continue to meet federal requirements and qualify for the National Flood Insurance Program. The Washington Department of Ecology has provided the City with the necessary code updates to meet the eligibility requirements for National Flood Insurance Program which must be adopted by August 19, 2020.

What does this mean for me?

If your home is not within the floodplain, this code change will not affect you.

If your home is within the floodplain, your property will continue to be eligible to purchase affordable flood insurance through the Federal Emergency Management Agency, or FEMA.

Is my property within the floodplain?

The floodplain in Sammamish is limited to those properties on the eastern shore of Lake Sammamish. If you live along the lake, it is safe to assume your property is within the 100-year floodplain. If you would like to see the boundaries of the floodplain, and if your property lies within those boundaries, please use the King County iMap Tool and turn on the "Flood info" layer.

What is the process for updating the code?

City staff have outlined the mandatory changes, as identified by the Washington Department of Ecology, to Chapter 15.10 SMC and will present them to the City Council on May 12, 2020, during a Work Session. During that meeting, the City Council will provide staff with direction before holding a Public Hearing on June 16, 2020, to consider adopting the updated ordinance.

Public Comments and Questions

Is there a draft of the proposed changes to 15.10 SMC for review? Is there a link to them available? Will there be any public comments allowed at the public meeting? How would I sign up to submit public comments or make comments?

Hello and thank you for your question. The proposed changes markup and a table tracking those changes have been added to the document library. Additionally, you will find those items, along with the agenda bill for the City Council meeting. This link will also provide you will all the details necessary to attend the virtual meeting and how to provide written comments prior to the meeting or how to give verbal comments during the meeting.

I would appreciate seeing a markup of the staff proposed changes to Chapter 15.10.

A PDF of the proposed changes with markup and a table tracking those changes have been added in the document library. Additionally, you can find the agenda bill and relevant attachments for the proposed changes to Chapter 15.10.

The King County iMap Tool provides a broad brush view of the floodplain. The elevation contours appear to be NAVD 88 and are not very accurate at least in the vicinity of my home. What is the NGVD 29 elevation of the floodplain for Lake Sammamish? NGVD 29 is the elevation commonly used in Sammamish.

Thank you for your question. On Lake Sammamish, the minimum ordinary high water mark elevation is set at 28.18 NGVD29.

• The conversion between NGVD 29 to NAVD88 is +3.6 ft.
• As an example, if the NGVD 29 elevation is 31 feet, you would add 3.6 feet to get an NAVD88 elevation of 34.6 feet.
• The FEMA flood map(External link) from King County lists the flood elevation as 36 feet NAVD88. Converting that to NGVD 29 would be: 36 ft. - 3.6 ft. = 32.4 ft. NGVD 29.

What are the updates proposed for 15.10 SMC? Is there a new proposed draft of the update? Is there a link to the code updates that the Washington State Department of Ecology sent?

The north end of lake Sammamish has a fixed cement weir controlling the outlet of water from the lake. I've seen discussion of changing that to be dynamic - so it could be opened up more in the Fall and Winter to let more water out and leave more buffer in the lake to absorb big rain events to reduce flooding, and then restrict the flow more than now in the Spring and Summer to hold back more water in Lake Sammamish to allow for more outflow in the late August/September Salmon runs. Could the council push for doing that in Lake Sammamish? Exactly how they manage lake Washington - it is kept at 20 feet above sea level in the winter, and then raised to 22 feet in the spring and summer. Lower in the winter to eliminate flood damage - higher in the Spring and Summer to have more water to spill for Salmon in the late summer/early fall Salmon runs.

Your concerns regarding the management of Lake Sammamish's water level and floodplain will be forwarded to the City Council for their consideration during the June 16th meeting. A draft of the proposed updates will be posted on this page on June 5, for review. Those materials will include what changes were required by the Department of Ecology.

This is a repeat of a question asked on 5/12 for which I have not received an answer: In the iMap tool, selecting the layer, Flooding info, and under that, FEMA preliminary 100-year floodplain, causes Lake Sammamish to overlaid with light blue and darker blue layers (I presume that’s what they are). But it is not clear what the distinction is. What do the two colors of blue represent?

Thank you for your question and my apologies for the slow response! The darker of the blue layers within the FEMA preliminary 100-year Floodplain layer is the one you should pay attention to as it's also the regulatory floodplain for Lake Sammamish. Another way to see this is to un-check the two FEMA layers and check the "Regulatory floodplain" layer, which will also show you the boundary of the floodplain. Unfortunately, I am not seeing a second, lighter blue layer within the FEMA 100-year Floodplain layer; The only light blue I see is just the color of the lake. Sorry I cannot be of more help with that.

Will the new ordinance take into account: 1. King County's obligation to correctly manage the Lake Sammamish weir, and keep the Sammamish River waterway clear, and 2. Recognize the individual elevations of structures. The map shows the flood plain as a straight line, whereas, on the ground, it's lumpy due to how much the individual properties were built up before the construction of improvements. We may not be able to join the 6/16 meeting but hope that these matters will be addressed in the new ordinance.

Thanks for your question and comment. The draft ordinance does not specifically address your first and second points, but I will include your comment in the packet that goes before the City Council for their consideration on June 16.

How can I become "in the loop" in terms of what exactly the City of Sammamish is doing, changing, and processing as it relates to compliance with this Flood Damage Prevention Ordinance Update? I would like to stay current on the proposals and recommendations that are being made by all stakeholders.

Hello and thank you for your question. The best way to stay in the loop is by subscribing to notifications on this page. We will be posting any project updates and posting materials here as they become available. Please keep an eye out on June 5th when we will be posting the draft code with the changes the Department of Ecology and FEMA are requiring.

99.9% of the real flood risk to Sammamish residents along Lake Sammamish is due to King County's mismanagement of the weir. This last Winter lake water levels were at their highest in living memory resulting in significant damage. If, as you say, this ordinance is directed at "reducing flood damage" then the City needs to take an active effort to make sure King County manages the weir and lake outflow so that winter lake levels are properly managed.

Thank you for your comments. Your concerns regarding the Lake Sammamish Floodplain will be forwarded to the City Council with their consideration of these code changes. The City Council is scheduled to discuss this topic as part of their regular meeting on 06/16/2020.

The currently proposed update of the City of Sammamish Flood Damage Prevention Code (Sammamish Municipal Code Chapter 15.10) is required by FEMA as part of the City’s NFIP program. For properties located within the FEMA-mapped floodplain (mapped by FEMA, not the City of Sammamish) to be eligible for the Federal Government’s FEMA hazard insurance benefits, the City must participate in the NFIP and we are required to make adjustments to our Flood Damage Prevention Code to match FEMA’s requirements. If we do not make these changes, the City may not be eligible to participate in the NFIP program and property owners within the FEMA-mapped floodplain will not be eligible for the insurance benefits that go along with the City’s participation in this program.

Regarding the Lake Sammamish Weir (AKA the Willowmoor Floodplain) at the Sammamish River transition zone, the City is aware of the outlet concerns of lakefront property owners and we are tracking the King County Flood Control District efforts to research options and develop solutions. Information on this effort is available on the King County website. The property where the lake outlet and floodplain transition area are located is not City property. King County is the lead agency in developing a solution and in implementing construction. For more information about the Willowmoor Floodplain Restoration Project, please contact Kate Akyuz, Project Manager, King County River and Floodplain Management Section.