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Floodplain Management

Corte Madera CreekThe Floodplain Management Ordinance of the Mill Valley Municipal Code (Title 18) regulates development within the floodplain by requiring new structures to comply with the regulations of the flood zone; and also by requiring any existing structures to comply with the Code, if a substantial improvement is proposed. The ordinance, which has been part of the Municipal Code since 1979, is a requirement for the City’s participation in the federal flood insurance program through the Federal Emergency Management Agency (FEMA). Periodically, FEMA updates the Flood Insurance Rate Maps (FIRM). These maps identify the boundaries of the 100-year floodplain and divide the floodplain into various “zones” based on the estimated depth of flood waters. A 100-year flood is the statistical probability, based on the review of historic rainfall and flood data, that there is a one percent chance in any given year that a flood of this magnitude will occur. Property located within designated “Special Flood Hazard” areas or within the “Regulatory Floodway”, as shown on the Flood Insurance Rate Maps, are subject to additional development restrictions and regulations based on the City’s Floodplain Management Ordinance and are also required to have flood insurance. The City’s participation with FEMA in regulating development in the floodplain can affect the availability of and rates for flood insurance for individual property owners.

2012-13 FEMA Map Updates

The City of Mill Valley hosted a Community Meeting with FEMA and the County of Marin regarding these updates on Thursday, October 11, 2012. At this meeting, FEMA summarized the process of conducting a flood study and spoke about the revision of the Flood Insurance Risk Maps, including the creation of a regulatory floodway. A schedule of activities and milestones was reviewed regarding the timeline of this work. A flood insurance representative from FEMA was at the meeting to discuss the National Flood Insurance Program and review benefits to adding flood insurance coverage before map changes occur to a flood risk area, otherwise known as “grandfathering”. FEMA also conducted a question and answer period for general questions, with a following break out session where local officials answered more specific property related questions using the draft maps. If you missed the October 11th meeting, the presentation made by FEMA can be found here.  Another community meeting will be held regarding the maps in early 2013; a notice will be sent out prior to the next meeting.

Further information regarding these updates can be found on FEMA’s website

 Will your property be affected by the 2012-13 Map Updates?

You can check to see if your property is within a FEMA designated floodplain or within a regulatory floodway by clicking here. Remember the maps are in the draft form at this time and will not be final until spring of 2013. Note: If your property is currently in a FEMA designated floodplain and does not appear on the spreadsheet please contact the Planning Department to confirm it is no longer in a flood zone. Some properties have not been affected by these map changes and will remain in the same floodplain as they previously were.

What is a Regulatory Floodway?

A regulatory floodway means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation by more than one foot. Structures located within Regulatory Floodways have additional development restriction beyond those imposed by being located within a floodplain. Note: All properties within the regulatory floodway are also in a floodplain and must follow the requirements of both designations.

Substantial Improvements in the Floodplain

A substantial improvement is defined in the Municipal Code as, “any repair, remodel, rehabilitation, addition, or improvement the cost of which equals of exceeds 50 percent of the “depreciated market” value of the existing structure either, before the improvement is started, or if the structure has been damaged and is being restored, before the damage occurred.” If a structure is located in the floodplain, proof of the depreciated market value “reflected in an appraisal prepared by an independent professional appraiser” as well as the value of the proposed improvements (verified by the Cost Evaluation worksheet), must be provided to the Planning and Building Department along with the initial submittal for a building permit.

The Substantial Improvement worksheet must be accompanied by a current appraisal for the structure (from within one year), the Cost Evaluation worksheet, an itemized breakdown of the valuation of the project. The Substantial Improvement worksheet must be signed by both the property owner and the appraiser certifying that the information provided is accurate. The Planning and Building Department will then review the forms to ensure they have been filled out correctly and determine if the project is a substantial improvement. Over the counter permit applications to the Building Department will not have to complete the worksheet, unless it is the second over the counter building permit that has been submitted within a two year time period. Projects on structures within the floodplain are cumulative within two years.

Substantial Improvement FAQ’s:

Why am I required to fill out this worksheet?

The property on which you are proposing to do work is located within a Federal Emergency Management Agency (FEMA) designated floodplain determined by the latest FEMA map, which went into affect on May 4, 2009. All properties located within a floodplain must follow Chapter 18: Floodplain Management, of the Mill Valley Municipal Code.

What is the definition of a substantial improvement?

Substantial improvement means any repair, remodel, rehabilitation, addition, or improvement, the cost of which equals or exceeds 50 percent of the "depreciated market" value of the existing structure either, before the improvement is started, or if the structure has been damaged and is being restored, before the damage occurred.

What is the definition of the depreciated market value of a structure?

Depreciated value means the value of the structure only and does not include the land or any other accessory buildings or site improvements. It is the replacement cost of the existing structure less any depreciation that results from age or condition. For the purposes of the City’s floodplain management regulations the “market value” of a structure shall mean the same as “depreciated market value”.

How do I determine the valuation of my project?

To establish the value of any proposed improvements, a contractor shall submit an itemized breakdown of estimated material/labor costs and the Cost Evaluation form (attached to this packet). The contractor shall use the attached Material Receipts/Estimates handout to help them determine the valuation of the proposed project. These submitted documents and the project valuation will then be reviewed and approved by the Building Official in comparison to market value rates within Marin County and the City of Mill Valley.

What if the scope of work increases after my building permit is pulled?

The valuation of the project is cumulative. Therefore, if during construction changes are made to the permit; those valuations must be added to the total valuation submitted for the project. If during construction the project increases to over 50% of the depreciated market value of the structure, it must conform to the City’s current floodplain management regulations. Project valuations are cumulative for two years, meaning that all open permits for a structure are totaled together. A permit must be finaled for two years before a new project can begin to avoid it having a cumulative effect on valuation.

Do I need to fill out this form for a permit that is done over the counter?

Substantial improvements are typically not triggered by over-the-counter types of permits, so the first over-the-counter permit submitted for a property will not require these documents. However, since the valuation is cumulative for two years, if you pull an additional over-the-counter permit within that time frame you will need to fill out the form and include the total valuation of all the permits pulled in that two year period of time.

What if my project is a Substantial Improvement?

If the proposed repair, remodel, rehabilitation, addition, or improvement, equals or exceeds 50 percent of the depreciated market value of the existing structure it is considered a substantial improvement and you will be required to conform to Chapter 18 of the Mill Valley Municipal Code. Depending on the zoning and floodplain designation you may be required to flood proof the structure (commercial zones) or elevate the finished floor of the structure above the base flood elevation. If the proposed project is a substantial improvement you should speak to the Planning Department for more information and requirements.

Where can I get more information?

Chapter 18.04 of the Mill Valley Municipal Code

Additionally, for information on the Floodplain, Regulatory Floodway, or the Map Updates for properties within the City of Mill Valley you can contact the Planning Department at (415) 388-4033.

Last updated: 10/25/2012 3:03:27 PM