FEMA / Flood Maps

Flood Plain Mailing Map

Alameda's Flood Risk

Ninety percent of all natural disasters in California are flood related and most residential home insurance policies do not cover flood damage. Alameda’s flood risk is predominately due to high tides that can be further exacerbated by storm surges and heavy rainfall. Localized flooding, however, can occur in any location - and over 30% of flood losses nationally occur outside of mapped flood areas.

The Federal Emergency Management Agency (FEMA) has prepared Flood Insurance Rate Maps (FIRMs) within the City of Alameda and identified the areas with a one percent chance of flooding in any given year, known as the Special Flood Hazard Area (SFHA), and commonly referred to as the 100-year floodplain. Over 1000 properties within the City of Alameda are located within an SFHA.

Important: If you are planning to build new construction, planning a room addition, or are making a major structural renovation or other improvements to your home, please verify whether you are in the floodplain as the first step. All too often homeowners will invest funds in architectural or engineering design services only to realize afterward that they are limited in what can be done due to the provisions of the NFIP as described below. To verify if you are in the floodplain, please contact the Public Works Department, Land Development Engineering Division, by phone at (510) 747-7930 or by email: pwpermits@alamedaca.gov.

Is My Property Located within the Special Flood Hazard Area?

An easily viewable, unofficial Geographic Information System (GIS) based view of the current flood maps can be found on the City of Alameda’s Community View website at https://alamedaca.gov/permits/communityview,  click on the legend icon, then click on "FEMA 100-year" in the environmental pulldown. Community View provides property information including zoning, General Plan designation, flood zone data, and general property data provided by the County Assessor’s office in GIS format.

To view the official FIRMs, go to https://msc.fema.gov/portal.  In the search bar, type “Alameda.” You will now see an aerial map overlain with a green grid representing the FIRMs. You can dynamically zoom in to view your property and view/download/print the official FIRM your property is included on by clicking the “Map Image” button above the map. Paper copies of the FIRMs are also available for viewing at the City Hall Permit Center (2263 Santa Clara Ave, Room 190), Public Works Department (950 West Mall Square, Room 110), and the Main Library (1550 Oak St). 

City staff is available either in-person at the Permit Center or by calling the Public Works Department at (510) 747-7930 to assist interested individuals in determining whether a particular parcel of land and/or structure is within a SFHA. This service is based on a review of currently available FEMA maps, City GIS maps, Assessor’s Parcel Maps, and other documents or maps. Staff interprets this data to determine if any portion of a parcel (or structure) is in a SFHA. Note: this service does not determine whether or not flood insurance will be required by your lender. The City has no authority to change the flood zones as shown on the FIRM panels.

 

National Flood Insurance Program – Frequently Asked Questions

1. What is the National Flood Insurance Program?

 The National Flood Insurance Program (NFIP) provides insurance and federal disaster assistance in the event of floods within the City of Alameda. The program is administered by the Federal Emergency Management Agency (FEMA). Until recently, such coverage was generally unavailable from private sector insurance companies. In the absence of this program, the City's vulnerability to uninsured flood loss could be substantial and a threat to the public health, safety and welfare.

Federal flood insurance is made available as an option for Alameda residents including renters through our participation in the NFIP and our efforts to reduce flood risks to new construction in SFHAs. When the City of Alameda joined the program, the City agreed to require permits for all new development and substantial improvements to existing structures within SFHAs and ensure that construction materials and methods will minimize flood damage. As a result, building permits must contain documentation to substantiate how buildings are actually constructed.

2. Who needs flood insurance?

Floods can occur from various sources and are not covered on most homeowners insurance policies if the flood originates outside of the home.

If your property is in the floodplain, you are required to buy flood insurance if your lender is federally regulated or insured and it has become common practice for most lenders to require flood insurance. If flood insurance is not required by your lender or there is no mortgage on the property, flood insurance should still be considered for the building and contents within it. 

Renters may also purchase a separate policy to insure their contents within the home or apartment. Flood insurance is also available for owners and renters located outside of the mapped Special Flood Hazard Area.

3. How does the City participate in the National Flood Insurance Program?

FEMA worked closely with the State, County, and the City to identify flood hazard areas, flooding risks and to establish minimum floodplain management standards and when the City joined the NFIP, it adopted and began to enforce these standards. The floodplain management standards are designed to prevent new developments from increasing the flood threat and to protect new and existing buildings from anticipated flood events.

4. How does the National Flood Insurance Program benefit the community?

Flood insurance is available to Alameda residents and renters through the NFIP, a protection against flood losses which is generally not available through the private marketplace. Careful management of development in the floodplains results in construction practices that can reduce public and private flood losses. A major purpose of the program is to alert property owners to the danger of flooding and to assist them in reducing potential property losses.

5. How is flood risk determined?

Flood risk is determined through the use of historical flood information, rainfall topography, wind, velocity, tidal surge, flood control measures, development (existing and planned), community maps, and other data are all elements used in the Flood Insurance Study (FIS) prepared by FEMA. These factors are used to determine a predicted flood elevation also known as the Base Flood Elevation (BFE).  The BFE for Alameda is approximately elevation 10 feet (North American Vertical Datum 1988 or NAVD88) throughout the City.

Properties with adjacent grades or finish floor elevations below elevation 10 feet have a much higher flood risk than properties or buildings with elevations above 10 feet.

6. How are insurance premiums determined?

The City of Alameda has no direct involvement in the administration of the NFIP and insurance premiums are determined by FEMA. Buildings which are elevated above the Base Flood Elevation will generally have a lower insurance premium than those located below the BFE.

7. How can you qualify for a discounted insurance rate?

The Community Rating System (CRS) is a voluntary program in the NFIP that allows City residents to qualify for discounted flood insurance through implementation of floodplain management standards that exceed NFIP minimums. The City of Alameda is currently a Class 8 community under the CRS program which provides a 10% discount in flood insurance premiums.

In addition to the community discount, a property owner of a structure within the 100-year floodplain may choose to have their house surveyed to determine if either the improvements or the adjacent grade is above the BFE.  This process requires an Elevation Certificate (EC) for the existing structure to be completed by a licensed surveyor or registered civil engineer who is authorized to perform surveying.

If the Elevation Certificate verifies that the finish floor and/or adjacent grade is above the BFE the EC can be provided to your insurance agent to determine if it will lower the cost of insurance. If the EC verifies that the surrounding grades are above the BFE a property owner may apply for a Letter of Map Amendment (LOMA) directly through FEMA to remove the structure from the flood plain. Note that lenders have the option of waiving the flood insurance requirement if a LOMA has been approved by FEMA. 

All requests for a LOMA are done directly between the property owner and FEMA - the City is not involved (see the "How to Request a LOMA or LOMR-F" link at the bottom of this webpage for more information). However, the City will need a copy of your approved LOMA for our files for compliance with NFIP requirements. Please contact the Public Works Department at (510) 747 - 7930 so that we may receive a copy for our files.

8. Where can you get more information about Flood Risk?

More information regarding flood risk, insurance policies, opportunities to reduce insurance costs, and steps homeowners can take to prepare for a flood can be found at www.floodsmart.gov.

Residential Construction in Special Flood Hazard Areas – FAQs

A primary goal of the NFIP and floodplain management standards is to prevent new developments from increasing the flood threat and to protect new and existing buildings from anticipated flood events.

All new and "substantially improved" (see below definition) structures within the identified floodplain will be required to elevate the lowest floor of the structure one foot above the BFE in conformance with California Building Code (CBC). For nearly all of Alameda, this means the lowest floor must be elevated to or above 11 ft NAVD88. Substantial remodels, renovations, or building additions will likely require the entire structure to be elevated to or above 11 ft NAVD88.

Residents and Developers are strongly encouraged to speak with City Public Works Staff at the earliest conceptual stage of a project and before significant funds are spent on architects or engineers to complete a full set of construction plans.

1. How can a structure be protected in the SFHA?

There are two primary ways to protect a structure:

  • Placing fill to raise the site grade above the BFE. or
  • Elevating the building structure at least one foot above the BFE.

For a new structure, placing fill to raise the grade may be a viable option and can protect not only the building structure, but all other site improvements such as landscaping and hardscaping from flood damage. Nearly all new development taking place along the estuary and within Alameda Point are protected from flooding through this method of raising the surrounding grades well above the BFE.

Placement of fill is not always an option, particularly within an existing neighborhood. In these areas, the structure must be elevated one foot above the BFE.  For an example diagram of an elevated structure in Alameda’s flood zone, Click Here(PDF, 91KB) 

Building utility systems (including ductwork) must also be elevated to 1 foot above the BFE and properly secured to prevent flood damage. This includes all electrical, heating, ventilation, plumbing, air conditioning equipment, and other service facilities. See: Mechanical Equipment | FEMA.gov. and FEMA 348 - Protecting Building Utilities(PDF, 6MB) (begin at page 52).

2. What happens to the portion of the structure below the BFE?

Per National Flood Insurance Program requirements, all structural and building elements located below the BFE plus one foot are required to be unfinished and for unheated storage only, limited to that which is incidental to the residence. Any conversion of this area into a finished room or other use is a violation of floodplain regulations. 

This area must be constructed with flood resistant materials and have flood openings and design plans need to specify the acceptable materials being used for all flood damage-resistant construction. FEMA’s acceptable materials for construction below the BFE plus one foot are detailed in this document: FEMA Technical Bulletin 2. As noted in Table 2, only Class 4 and Class 5 materials are acceptable.

3. Can I have a basement in the Special Flood Hazard Area?

No. Basements, defined as an area of a building below the adjacent grade on all sides are strictly prohibited for residential structures within a SFHA.

4. What is a Substantial Improvement?

Substantially Improved structures are existing buildings whose cost of proposed project improvements (including cost of contractor labor, overhead, and profit) equals or exceeds 50% of the current appraised market value of the existing building (value of the building only; land and any other structure that is physically detached from the building may not be included in the market appraisal).

This 50% figure is cumulative and tracked over a 5-year rolling period by the Permit Department. While it is possible to do multiple improvement projects without being subject to NFIP provisions within a 5-year period, so long as the total cost does not equal or exceed the 50% threshold, property owners are advised to consider the potential flood risk to their new investment and are encouraged to elevate their home at least one foot above the BFE.

If you meet/exceed the 50% threshold, the lowest floor for the entire structure must be raised to at least one foot above the BFE. 

5. How can the existing market valuation be determined?

The NFIP states that acceptable estimates of market value for the existing building can be obtained from these sources:

  • An independent appraisal by a professional appraiser. The appraisal must exclude the value of the land and not use the "income capitalization approach" which bases value on the use of the property, not the structure.
  • Detailed estimates of the structure's actual cash value - the replacement cost for a building, minus a depreciation percentage based on age and condition. For most situation, the building's actual cash value should approximate its market value.
  • Property values used for tax assessment purposes, using only the value for the improvements and not the land itself.
  • The value of buildings taken from NFIP claims data (usually actual cash value).

It is common to start with the most recent tax assessment from the Alameda County Assessor’s Office. Due to Proposition 13, the tax assessment for homes that were purchased more than 5-10 years ago may considerably undervalue the current structural value. In these instances, an independent appraisal by professional appraiser will likely be needed.

6. What must be included in the project cost?

The Building Permit valuation for a specific building permit application may not fully include all items which must be included in the project cost when determining if the scope of work is a substantial improvement.   

See here(PDF, 68KB) for what the NFIP states is to be included and excluded in the calculation for cost of proposed project improvements.  You or your contractor may be asked to provide a detailed estimate to substantiate the project cost.

 

Non-Residential Construction in Special Flood Hazard Areas -FAQs

Non-residential or commercial construction in the SFHA generally follows the same requirements as for residential structures (see above section) with two primary differences:

1. Basements are allowed for commercial buildings within the SFHA provided they are floodproofed.

2. Substantially improved non-residential structures must either a) have the lowest floor elevated at least one foot above the BFE, or b) be designed so that the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. This means dry-floodproofing the structure up to one-foot above the BFE in lieu of elevating the structure if the 50% threshold is met/exceeded. See FEMA-TB-3-Reqts-for-Dry-Floodproofed-Non-Res-Buildings.pdf(PDF, 3MB).

 

Building Permit Requirements in the Special Flood Hazard Area

All Building Permit applications within the SFHA are routed to the Public Works Department for review of the floodplain requirements.  Renovations, remodels, and additions are first screened to determine if the project constitutes a Substantial Improvement as noted in the residential FAQs above. Projects which are determined to not constitute a Substantial Improvement are approved by Public Works with no further flood protection requirements.

All new and substantially improved structures, including accessory dwelling units, garages, trash enclosures and all other structures larger than a 120 square foot shed must fully comply with the City’s Municipal Code, California Building Code, and NFIP requirements.  The regulations do not apply to gazebos, carports, and other structures without walls.

A pre-construction Elevation Certificate based on the proposed construction drawings is required prior to building permit issuance to verify existing and proposed site grades and the proposed building finish floor elevation and other design elements for compliance with City and NFIP requirements.  Elevation Certificates must be prepared by a licensed land surveyor or registered civil engineer who is authorized to perform surveying.

Additionally, a second, post-construction Elevation Certificate based on actual construction must be submitted and approved by the Public Works Department prior to the issuance of a Certificate of Occupancy.

 

Sea Level Rise

The National Flood Insurance Program does not take future sea level rise into account and is based on current flood risk. As result of climate change, we know that sea levels will rise in the future and increase the flood risk throughout Alameda. For more information about Alameda’s Climate Action and Resiliency Plan, click here

Helpful Documents

The City has created a PDF document to answer frequently asked questions and to serve as a guide to residential construction within the Special Flood Hazard Area. Download the PDF here:  FAQ and Construction Guide(PDF, 66KB)

FEMA Documents:

 

City of Alameda Floodplain Management Ordinance:

        
 
For More Information:
 
Please contact the Public Works Department, Land Development Engineering Division, by phone at (510) 747-7930 or by email: pwpermits@alamedaca.gov.