News Details

Q&A About Flood Zones

 Is my property in a flood zone?

Yes. The entire city of Palo Alto is in a flood zone of one kind or another. But most of the city is in an "X" zone, which the Federal Emergency Management Agency (FEMA) describes as an area either lying outside the so-called 100year flood limit and inside the 500year flood limit, or as lying within the 100year flood limit but shallow enough to not represent a special hazard. The remainder of the city lies within Special Flood Hazard Areas (SFHA), which, roughly speaking, means the area of special hazard from a so-called "100year flood". (The Foothills area is a special case. It has not been studied and is Zone X by default.)

What's a "100year flood"?

"100year flood" is actually something of a misnomer: such a flood does not happen every 100 years. Rather, over a very long period of time such a flood occurs every hundred years on the average. To be accurate, such a flood has a 1% chance of occurring in any given year. This can be misleading as to the actual chances: by simple statistical math it can be calculated that such a flood has a 26% chance of occurring during the life of a 30year mortgage.

FEMA's choice of the 100year flood as the limit of the SFHA is quite arbitrary. A property lying just outside this area but within a 105year zone is almost equally likely to be flooded. And, like the Big Earthquake, the question is not "if" such a flood will occur but "when".

When was the last time we had a 100year flood?

No one's really sure. Historically, development in the area is relatively recent. It hasn't been that long since most of the floodprone areas were bayland or farmland and no one really cared whether a flood was a 100year flood. There have been major floods, though, with the 1950s being noteworthy: once, Baylands levees failed and a large area extending into Louis Road was flooded; another time the entire area from Middlefield Road at San Francisquito Creek to the Oregon Avenue/Bayshore area and beyond was flooded, with water flowing over the Bayshore Highway; this event was largely repeated in the disastrous flood of February 1998, considered roughly to have been a 70 or 80year flood.

What kinds of Special Flood Hazard Areas are there?

There are three basic types of SFHA in Palo Alto: areas where the flood waters are "ponded", with a more or less level surface like a lake (AE zone), areas where water flows down a gentle slope up to two feet deep (A0 zones), and the AH zones, which may be either.

The largest AE zone in Palo Alto is an area predicted to be flooded by extraordinary bay tides overtopping the levees around the Baylands and reaching a height of nearly 8feet above sea level. This AE zone covers a large area generally from Middlefield Road to the bay. Some properties within this area have an elevation as low as 2.1 feet above sea level, meaning the predicted flood would be some 6feet deep.

The largest AH zone lies along a wide strip from west of Middlefield Road from San Francisquito Creek to Hamilton Avenue and extending down to the Embarcadero Road/Bayshore interchange and between Channing Avenue and Hamilton Avenue, and is subject to flooding by overflow from San Francisquito Creek; this was roughly the area of the disastrous flooding of February 1998.

The next largest SFHAs lie west of the Southern Pacific/CalTrain tracks along Park Boulevard between Page Mill Road and Charleston Road.

These areas are shown on the Flood Insurance Rate Maps (FIRM) published by FEMA.

Didn't the work done on the creeks eliminate the flood zones?

The Santa Clara Valley Water District (not the City of Palo Alto) did extensive work on some of the creeks. This work was to eliminate or reduce the SFHAs lying west of the railroad tracks. It does not have any impact on the large AE zone caused by bay flooding. FEMA has already issued a Letter of Map Revision (LOMR) removing some areas from the SFHAs due to completion of some of the work along Adobe Creek and these are now incorporated into the latest Flood Insurance Rate Maps. Unfortunately, the work along Matadero and Barron Creeks did not go completely as planned and as of this writing there have been no further map changes due to creek work.

How can I find out for myself if I'm in a Special Flood Hazard Area?

Both the Public Works and Planning departments at the Palo Alto Civic Center have the flood maps available for viewing. Or Public Works will give that information over the phone at 3292151, by FAX at 3292240, or by CLICKING HERE. Public Works can also supply a letter stating the flood zone for a given property.  There is a fee associated with providing this letter.

Do I have to buy flood insurance if I'm in an SFHA?

No, not if you own the property outright. But federal regulations require that loans for property in an SFHA be protected by flood insurance, and lenders will require it. And given the aforementioned 26% chance of a 100year flood during the life of a typical mortgage, a lender would be less than prudent if it did not require flood insurance in any case.

When the flood occurs, FEMA will begin its emergency financial assistance on the premise that maximum insurance was carried on the property and that relief is only needed for an amount over that "deductible". As a practical matter, then, little or no disaster relief will be available for uninsured property.

There are only two ways out of an insurance requirement: assume the risk for yourself by paying off the mortgage, or get the property removed from the SFHA.

How can I get my property out of the SFHA?

There is a misconception that all that's necessary to be considered out of the SFHA is to demonstrate to the City of Palo Alto that a structure's lowest floor is above the flood height. This is not true: a structure is in the SFHA as long as any aboveground part of the structure or its foundation lies below the flood height. However, you may have been incorrectly included in the SFHA even though your land is high enough to be above the flood height. Only FEMA has the authority to decide whether you were improperly included in an SFHA. There are two basic ways to do this:

FEMA can publish new maps. This would require a new areawide study and would only be done if there were major changes which might affect the SFHA. For instance, the work on the creeks will justify a future study. Or, if the levees around the Baylands were raised, a new study would probably eliminate the large AE SFHA.

FEMA can issue you a Letter of Map Amendment (LOMA) which states that your specific property is so situated and configured that when the 100year flood comes your house would, in effect, be sitting on its own little island. To obtain a LOMA you must submit data to FEMA showing that you would indeed be high and dry during the flood. Some of this data will require the hiring of a licensed surveyor or registered professional engineer. Public Works Engineering has an information sheet on LOMAs available on request.
FEMA does have one other method available: the Letter of Map Revision (LOMR). A LOMR is used when fill is to be added to the site to elevate the property above the Base Flood Elevation, or has been added since 1980. It is not as useful as a LOMA in getting out of some of the flood requirements.

I've been issued a LOMA and it says the structure isn't in the Special Flood Hazard Area. What's that mean?

All the rules and insurance requirements apply to structures, not land (there isn't any flood insurance for damage to the land). If FEMA determines that during a 100year flood a structure will sit on its own little island, no matter how small, it will issue a LOMA for the structure, even though the rest of the property may still be low enough to be in the flood. This LOMA is then valid until either the flood map is revised or some sort of remodeling expands the footprint of the house.

Who decided we had to have flood zones? It doesn't seem like floods are all that big a deal.

In the past, insurance companies have been unable or unwilling to provide flood insurance for the simple reason that one flood could bankrupt an insurance company; the risk of flood damage is too high and tends to happen all at once; it might not be covered by distributed premiums already collected. In fact, the 1% per year chance of a flood in an SFHA is higher than the risk of fire. However, fire damage happens singly, here and there, at random, and can be covered as it occurs. This is not true of floods.

In order to make flood insurance available, Congress provided for the National Flood Insurance Program (NFIP) with the government acting pretty much as the insurer. But flood insurance was made available only on a community basis, and a community wishing to have flood insurance available had to join the NFIP and enforce the federal regulations by implementing them with local ordinances.

I understand that there are special requirements for construction in an SFHA. What are they?

As a community participating in the National Flood Insurance Program, Palo Alto is required to impose the federal rules regarding construction in an SFHA. These rules are spelled out in Section 16.52 of the Palo Alto Municipal Code and apply to "substantial improvement" and new construction in an SFHA, and to any improvement, no matter how small, to a structure in an SFHA built or "substantially improved" since 15 February 1980. Excerpts from the Code are contained in the Public Works Engineering Information Sheet "Requirements Applicable to Special Flood Hazard Areas", available on request.

The requirement that hurts the most is that the lowest floor be elevated above the flood level. This effectively prohibits basements (which are defined as any enclosed area below grade on all sides). Because of zoning requirements which limit building height and prohibit building beyond a specified "daylight plane", the need to elevate the lowest floor can create a "squeeze" which might prevent the building of a second floor.

Other provisions require openings in areas below flood level to allow water to enter and exit, flood proofing of utilities below the flood level, etc.

Wait a minute. First you say the lowest floor must be above flood level, and then you say that areas below flood level require openings. Isn't that a contradiction?

The exception to the elevation requirement is that any enclosed area used only for storage or parking does not have to be elevated (but it can't be below grade). Such an area may not be used for any other purpose. That means that crawl spaces and garages can be below flood level, but would require the openings.

So how do I know how high to make the lowest floor?

That information comes from the Flood Insurance Rate Maps (FIRM). For AE and AH zones the Base Flood Elevation is given as an absolute elevation "above sea level", and the lowest floor must be at or above that elevation. For A0 zones the depth of the water is given, and the lowest floor must be at least that amount above the highest point of adjacent grade. For A0 zones, then, the absolute elevation of the lowest floor must be determined, and, for the adjacent grade, the highest point on the perimeter of the projected final "footprint" of the structure has to be determined. The difference between the two absolute elevations must be equal to or greater than the depth given on the FIRM.

Obviously, this can be important information in making your decision as to whether to proceed with your plans. In order to help keep your costs down during the preliminary planning stages, the City Surveyor has been instructed to cooperate in establishing a benchmark near your property for your surveyor to work from. Unfortunately, the City Surveyor can't survey on private land for private purposes.

If you do proceed with plans for a new structure or a "substantial improvement" you will have to hire a surveyor to complete an "as built" certification of these elevations once construction is advanced enough to determine the final elevation of the lowest floor.

I think my lowest floor is already high enough. Is there any way to document this ahead of time?

The FEMA elevation certificate can be used. For a substantial improvement it would be required in any case if you proceed with your plans. It may also be useful if you might be selling your house in the near future. The elevation Certificate must be completed by a licensed surveyor. Public Works engineering has a supply of blank forms available.

If you plan to use the certificate as a selling point, be cautioned that the certificate is valid only for the current flood map revision and only for the current configuration of the house; it would not necessarily permit future expansion. Nor does the certificate indicate that the house is "not in a flood zone": it remains in the SFHA and the certificate only documents that one of several SFHA construction requirements are met.

I want to do some remodeling and the city says I have to jack up my house and fill in my basement. What's going on?

For "substantial improvements" these rules apply to both the new work and the existing structure even if only a second floor is to be added. So, yes, you may be required to jack up your house and fill in the basement.

There's an exception though, if your "substantial improvement" is a so-called "horizontal" or "vertical" addition. If your addition is either a "wing" attached to the existing house through just a new doorway, or your addition is pure second story, without altering the structural integrity of the existing house or doing any additional remodeling in the existing house, the existing house may not have to be modified to meet current flood requirements. However, the new addition itself must meet current requirements, so for "horizontal" additions you may end up with a splitlevel.

You put "substantial improvement" in quotes, why?

Because the term has a special definition for flood zone development:

Substantial Improvement

"Any improvement to an existing structure for which the total cost of all improvements to be made exceeds 50% of the current market value of the existing structure, exclusive of land, improvements to the land, swimming pools, detached structures, decks not a part of the structure, etc."

This calculation also applies to any house built since 1980 which was built in accordance with requirements but where FEMA has adjusted the flood elevation upward. For instance, the flood elevation for the large AE area subject to bay flooding was changed to 8feet from 7feet in September 1989.

So if my remodeling is small enough I won't have to raise my house?

No. If it's obviously not a "substantial improvement", or if the "substantial improvement" requirement appears to apply but you can demonstrate that your improvements will actually be less than 50%, then no requirements would have to be met.

How do I prove what I'm doing isn't a "substantial Improvement"?

The "proof" would consist of the submittal of a reasonably detailed estimate by a qualified person of the cost of all the work to be done to the structure, and a professional appraisal of the current value of the structure.

The estimate must include all work to be done to any addition to the existing house, and any work to be done in the existing house. In other words, all the work covered by your anticipated building permit, except for the cost of permit, license, architect, design, or other fees, and the cost of any improvements not part of the structure, such as pools, landscaping, and detached structures.

The cost estimate must also include minor work such as painting and flooring, built-in appliances, and the fair market value of any free or donated labor or materials.

The appraisal must be by a practicing appraiser (of a stature acceptable to lenders) of the current market value of the structure to be improved. This value cannot include the value of the land or any improvements not a direct part of the structure. For instance it cannot include the value of pools, guest houses or detached garages (although an attached garage can be included).

The documents will be compared to the submitted building plans and reviewed for reasonableness by Public Works Engineering to determine whether the figures supplied justify the conclusion that the proposed work is not a "substantial improvement". If not, that conclusion will be documented and the applicant will be able to proceed without needing to meet the flood zone requirements.

If my house were damaged by fire or earthquake, do the repairs count towards "substantial improvement"?

Damage is handled a little differently. The requirements depend on the concept of "substantial damage":

Substantial Damage

". . . damage of any origin . . . where the cost of restoring the structure to its before damaged condition would equal or exceed 50 per cent of the market value of the structure before the damage occurred." [44CFR59.1]

The regulations go on to require that the "substantial improvement" rules apply to "substantial damage" even if the structure is not restored fully to its predamage condition. Scope of current repair work is not what counts, but rather what it would cost to do the complete restoration. For instance, if it would cost 55% of the predamage market value of the structure to fully repair the damage, it will be necessary to meet the elevation and basement requirements even if the current repair work will only be 5% of the predamage market value.

Variances are available for relief from other zoning requirements. How about the flood zone requirements?

Theoretically, variances are available for cases of sufficient hardship. In the past, the city issued a number of variances based on a misunderstanding of the degree and nature of hardship required. Subsequently, FEMA issued more detailed interpretations that the hardship had to be due to the peculiar nature of a single piece of land compared to other land in the area and that personal or economic hardship was insufficient. Thus far, FEMA has provided a number of examples of hardship that do not qualify for a variance, but none that demonstrate what does qualify. For all practical purposes, variances are extremely difficult to justify.

My property is commercial. Does it have to meet all of the requirements?

Nonresidential construction and improvement must meet all of the requirements, with one significant exception: it is not necessary to construct the first floor level at or above the flood height as long as the structure is "dry" floodproofed up to the flood level. Such "flood proofing" must be certified as meeting the requirements by a registered professional engineer.

This publication is intended to be an informal means of informing the public about a City process. Although it is assumed the information provided is accurate, this publication only provides an overview and is not intended to create any sort of legal obligation on the City's part. The actual process is governed by City ordinances, regulations and procedures which implement relevant provisions of the Code of Federal Regulations. The reader should make specific inquiry for specific cases.

Last Updated: March 14, 2007