USEFUL INFORMATION IN DETERMINING BFE IN AN UNNUMBERED ZONE A
Requirements for Obtaining BFE Data
44 CFR 60.3 (b) (4)
Obtain, review, and reasonably utilize any base flood elevation and floodway data available
from a Federal, State, or other source…
Use of Draft or Preliminary Flood Insurance Study Data
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The data from a draft or preliminary flood insurance study constitutes “available data”
under Subparagraph 60.3 (b) (4).
Communities are given discretion concerning the use of draft or preliminary only if the data
is currently part of a valid appeal concerning the accuracy of the data.
Requirements for Obtaining BFE Data
44 CFR 60.3 (b) (3)
Require that all new subdivision proposals and other proposed development (including
proposals for manufactured home parks and subdivisions) greater than 50 lots or 5 acres, whichever is
the lesser, include within such proposals base flood information data…
Use of Draft or Preliminary Flood Insurance Study Data
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The data from a draft or preliminary flood insurance study constitutes “available data”
under Subparagraph 60.3 (b) (4).
Communities are given discretion concerning the use of draft or preliminary only if the data
is currently part of a valid appeal concerning the accuracy of the data.
Requirements for Obtaining BFE Data
44 CFR 60.3 (b) (3)
Require that all new subdivision proposals and other proposed development (including
proposals for manufactured home parks and subdivisions) greater than 50 lots or 5 acres, whichever is
the lesser, include within such proposals base flood information data…
FEMA publication Managing Floodplain Development in Approximate Zone A Areas (FEMA 265) is
useful for engineers.
Obtaining Existing Base (100-Year) Flood Elevations
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Watershed Concepts - FEMA’s Contractor for the Regional Mapping Center
U.S. Army Corps of Engineers
U.S. Department of the Interior, Geological Survey
U.S. Department of Agriculture, Natural Resources Conservation Service
New Jersey Department of Transportation
New Jersey Department of Environmental Protection
Whichever engineering firm originally studied your community.
If you need help determining the BFE, check with your community’s planning, engineering, or
permit office.
DOCUMENTATION: Whatever method you choose to use in determining the flood elevation for an
unnumbered A Zone, always document where the determination came from.
BFE Development
Zone A---The area that would be inundated by the base flood for which no BFEs
have been determined
Zone A Flooding: Various methods available:
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Existing high water profiles, aerial photographs of historic floods
Develop the BFE in-house using USGS quads, QUICK-2, National Flood
Frequency (NFF), and other programs, from determined cross-sections,
drainage area, precipitation, etc.
 Calculations submitted by registered professional engineers
 Federal, State or local agencies may have conducted detailed analyses not
incorporated into the effective NFIP maps. The results of these studies may
be used as “best available data” for LOMC determinations in Zone A
flooding.
What data can be used to determine BFEs?
• Any information that represents the best available data
• Any information that is known to be scientifically or technically correct
(including preliminary FIS)
Sources that provide existing BFE information
• FEMA
• Federal, State, or Local Agencies
• Corps of Engineers, USGS, NRCS, Flood Control Districts, etc.
Developing a BFE
• Simplified Methods
•Contour interpolation
•Data Extrapolation
• Detailed Methods
•Hand Calculations •Quick-2 •Hydraulic Models
Contour Interpolation
• Reduce or enlarge the topographic map of the site to the scale of the FIRM
• Superimpose the Zone A floodplain boundary onto the topographic map
• Determine if floodplain boundary conforms with contour lines within acceptable limits
• Elevations of the left and right overbanks must be within one half the contour
interval of the map
• If the method is reasonably accurate, determine the BFE
Data Extrapolation
Applicability
• Site must be within 500 feet of the detailed study area
• Site must have floodplain characteristics similar to the detailed study area
• Site must have no hydraulic structures
• Determine the location of the site on the flood profile for the detailed study area
• Extrapolate the last segment of the flood profile that has a constant slope to the
location of the site
• Determine the BFE from the extrapolated profile
DOCUMENTATION: Whatever method you choose to use in determining the flood elevation for
an unnumbered A Zone, always document where the determination came from.
INFORMATION FOR LOMCs (Letter of Map Changes):
To be eligible for a Letter of Map Amendment (LOMA) from FEMA, you must be able to prove that the
water elevation of the 100-year flood (or “base flood elevation”) is lower than the ground elevation at
the lowest exterior point around your foundation.
Why won't the lender take my surveyor's word?
The Flood Insurance Rate Maps (FIRMs) and Flood Hazard Boundary Maps (FHBM) portray the
Special Flood Hazard Area (SFHA), or what is more commonly known as the gray shaded area,
within which the purchase of flood insurance is required as a condition for granting a mortgage
from a federally-backed or federally-regulated lending institution. The lender or insurance
agent must use the boundaries of the SFHAs shown on the Flood Insurance Rate Maps to
determine if mandatory flood insurance applies. The area between the flooding source and the
flood hazard boundary is commonly shaded gray. Thus, even though a site survey or an
elevation certificate indicates the homesite is above the Base Flood Elevation (BFE) and is
technically outside the floodplain, if the homesite is within the gray shaded area (the SFHA) on
the map, the bank will say flood insurance is required.
Are the flood maps wrong?
The general lack of detailed topographic mapping throughout this nation means that the
floodplain boundaries in most communities cannot be accurately mapped. Since, FEMA
(Federal Emergency Management Agency) cannot afford to field check all floodplain
boundaries, some areas of high ground are shown as floodplain, and some low areas are not.
What is FEMA going to do about flood maps being wrong ?
In short, nothing. However, FEMA created the Letter of Map Amendment and Revision
(LOMA/R) process to correct or change flood maps [FIRMs and FHBMs] to reflect actual ground
surveys or better topographic mapping. Letters are issued by FEMA officially removing lots or
portions of lots (by legal description) from the SFHA or changing the boundaries of the SFHA.
These are dated and sent to the homeowner applicant and are also filed with the municipality
or county within which the property is located. The building site is removed from flood zone AE,
AI-30, A, etc and placed in flood zone B, C, or X, which are not part of the SFHA [Special Flood
Hazard Area].
When a LOMA/R is issued removing a building site from the SFHA, the mandatory flood
insurance purchase requirement is lifted. However, the lender always has the option of
requiring flood insurance anyway. For example, the homesite might be just a few inches above
BFE, so the lender feels that there is still a threat of flood damage to their "secured property".
Once the flood zone has been changed to B, C, or X, the building qualifies for a PREFFERRED
RISK POLICY, the least expensive flood insurance available.
Letter of Map Amendment (LOMA): This is used to revise the SFHA boundary based on detailed
elevation surveying and/or topographic mapping of the site. If the homesite and the lowest floor of the
building (including basement or garage) is the BFE, FEMA can the map to remove the homesite and
other land area from the SFHA. (The map will not actually be physically changed or revised, but the
structure or homesite will be certified as being outside the SFHA)
Letter of Map Revision, based on fill (LOMR-F): When FILL dirt is placed on property to raise
the building site above the BFE FEMA can remove the raised area from the boundaries of the
SFHA, thus revising the FIRM. This is a man-made change to the floodplain.
How do I get a LOMA or LOMR-F?
A homeowner may apply for a LOMA or LOMR-F. However, a Site Plan & Boundary Survey and
Elevation Information or Elevation Certificate must accompany each application. These must
be prepared, sealed and certified by a Professional Land Surveyor. The applicant is responsible
for paying for this survey information.
To be eligible for a Letter of Map Amendment (LOMA) from FEMA, you must be able to prove that the
water elevation of the 100-year flood (or “base flood elevation”) is lower than the ground elevation at
the lowest exterior point around your foundation. Part 70 of the NFIP Regulations requires that the
lowest ground touching the structure be equal to or higher than the BFE
How long does it take to get FEMA to approve a LOMA or LOMR-F?
It normally takes 6-12 weeks from the time an application is received until a letter of
determination is issued. Applications are processed on a first come, first served basis.
What if there is no flood elevation on the flood map?
If the property is in Flood Zone A, without a letter or number after the "A", the flood zone is
"approximate". [FEMA calls it an "unnumbered A Zone"] No Base Flood Elevation (BFE) has
been determined for the area. However, FEMA can only approve a LOMA/R if a BFE has been
established using standard engineering methodology or using the simplified method.
Sometimes another government agency has done a flood study and determined flood
elevations, or perhaps the lot is in a fairly recent subdivision for which flood elevations were
determined as part of the land development process. Check with your local building inspector
or code enforcement officer. However, it is unlikely in this area to find such information.
If there is no existing flood study, one will have to be developed in order to process a LOMA/R,
either by the simplified methodology or by a watershed study, which is very costly.
LOMAs or LOMR-Fs in Flood Zone A are usually more complicated. Be prepared!
LAG - Lowest Adjacent Grade: The elevation of the lowest ground
touching the structure’s foundation
For LOMC submittals removal of a structure from SFHA is based on the LAG, not
the finished floor.
Obtaining FIS Back-up Data
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Must request in writing -- Approximately 2 to 4 weeks to process requests
Typically costs $100-$200
Can fax request to (703) 751-7391
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 A Flood Insurance Study (FIS) is a book that contains information
regarding flooding in a community and is developed in conjunction with
the FIRM and FHBM
 The FIS contains flood profiles, floodway data tables, summaries of
elevations as well as a narrative of the flood history of a community and
discusses the engineering methods used to develop the FIRMS
 If the flooding is conveyed by the street, provide the highest top of curb
or crown of street elevation along the property line and add the depth of
flooding to determine the BFE .
 If the entire property is inundated by the SFHA and the flow is not
conveyed by the street, add the depth of flooding to the average lot
elevation
 If the property is partially inundated by the SFHA and the street does not
convey the flow, add the depth of flooding to the lowest lot elevation
 Along with the information required above, sufficient certified
topographic information, including flow paths, to show that the structure
is located on high ground relative to the depth of flooding is required
FEMA may calculate the BFE for A-Zone properties
 For single lot less than 5 acres
 Will require additional survey data (river cross-section)
INFORMATION FOR ELEVATION CERTIFICATE (EC):
Elevation Certificate (EC)
 Administrative tool of the NFIP
 Used only to certify building elevations
 Required to properly rate post-FIRM buildings
 Provides a way for communities to record elevation information &
document compliance
 Can be used to support a LOMA or LOMR-F request
 Does not provide a waiver of insurance purchase requirements
 Only a LOMA or LOMR-F can remove the Federal mandate for insurance
requirement
Highlights of Section D
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This section must be certified by a surveyor, engineer, or architect
Section needs to contain a signature
Stamp/Seal is not required by FEMA but check with local and state
regulations
 Comment Section
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Can be used to list the Lowest Lot Elevation, Top of Curb elevation for Zone A and
AO cases
o Further clarification of how the BFE was determined
When do I have to do a conversion from NGVD to NAVD?
Answer) If there is anything on the Elevation Certificate (EC) to indicate that a different datum has been used for
the Base Flood Elevation (BFE) and the Lowest Floor Elevation (LFE), the data conversion process must be used to
ensure that all numbers reflect the same datum. The Underwriting Bulletin dated July 27, 2009, states that when
an existing EC provides the building elevations referenced to NGVD 29, and the BFEs on the Flood Insurance Rate
Map (FIRM) are referenced to NAVD 88, the NGVD 29 elevations must be converted to NAVD 88.
http://www.nfipiservice.com/stakeholder/pdf/bulletin/w-11025.txt
If I have dual foundations, which have not been specifically addressed, how do I rate the building?
Answer) If part of the building is slab-on-grade and part is elevated by posts, piers, piles, or foundation walls, use
the lowest part of the building in determining the correct building description. This means that if the slab-on-grade
part of the building is lower than the elevated portion of the building, you must describe the building as a nonelevated building.
If there is a shed outside of the footprint of the main structure, it will not be considered an enclosure or an
obstruction. The shed will be considered an appurtenant structure, and contents coverage will be available if the
shed meets the definition of a building (including being tied down or permanently affixed to the site.) Note: Except
for a detached garage, appurtenant structures must have building coverage purchased separately.
Effective October 1, 2011, an EC will be required to obtain flood insurance for all buildings in
unnumbered A, AO, and AH zones.
When there is no BFE, the EC must provide the distance from the reference floor to
“highest adjacent grade.” This is the highest natural grade, immediately adjacent to the
building, prior to construction. If the structure is slab-on-grade on a fill pad, the highest
adjacent grade is beneath the fill. This distance can be determined from the grading and fill
information filed with the building plans and/or by using a hand soil bore to obtain a core of
soil from alongside the structure. A practical alternative is to locate the highest natural
grade adjoining the base of the fill pad out away from the house. The distance from the top
of the core to the original soil level can be measured and placed on the EC. Highest grade is
not the top of the fill pad.
Flood insurance rates are based on actuarial risk. Rates are lower when a BFE has been established
or estimated in an “A” Zone. When no BFE is estimated or available, the rates are based on distance
above highest adjacent grade. The higher above grade, the lower the rates. Houses raised on fill will
be inadvertently penalized if the top of the fill pad is used as highest grade, rather than the original
natural grade.
If you need help determining the BFE, check with your community’s planning, engineering, or permit
office.
LIABILITY ISSUES
Professional Liability
Bodin v. Gill, 117 S.E.2d 325 (Ga., 1960) in which the court stated the broad rule of law which applies to
not only architects and engineers but other professional services. The court stated that “The law imposes
upon persons performing architectural, engineering, and other professional and skilled services the
obligation to exercise a reasonable degree of care, skill, and ability, which generally is taken and
considered to be such a degree of care and skill as, under similar conditions and like surrounding
circumstances, is ordinarily employed by their respective professions.” However, the standards of care and
the proof required differ. Design professionals are held to a standard of care consistent with the minimum
standard of care in their profession and expert testimony must usually be used to establish this standard of
care. See Lochrane Eng v. Willingham Realgrowth, 552 So.2d 228 (Fla., 1989) This may or may not be
true for others who perform services but lack professional status.
Courts have applied the term “design professional” primarily to architects, engineers,
landscape architects,
and surveyors.
http://www.state.me.us/spo/flood/docs/asfpm_professional_liability_construction.pdf
Liability Based on Negligence
A design professional may also be held liable because he or she has been “negligent”. As
common law, all members of society (not just design professionals) must act reasonably
so as not to injure other members of society. If they do not act reasonably and injuries
result, they may under certain circumstances be sued for negligence.
Negligence in design or failure to provide contracted services can be based on incomplete
design specifications or services as well as complete but erroneous ones. It is not
sufficient for a design professional to perform as well as he or she could. The design
professional must have done what the reasonable design professional of ordinary prudence in the
profession would have done. The standard is usually one of the design community as a whole, but a
higher standard may be applied where the design professional has made special representations, where
statutes or ordinances establish a higher standard than is customarily used, or in cases in which a
particularly great or grave risk of harm is involved.
See, e.g., Trusky v. Holoway, 14-04-00196-CV (Texas, 2205) in which the court held a surveyor liable
on negligence and Deceptive Trade Practices Act causes of action to a landowner for failing to tell the
landowner that a property was in a floodway. He did indicate that the property was in a floodplain.
Regulations. An architect or engineer is, in general, responsible for acquainting himself
or herself with all applicable regulations. This means that the architect or engineer should
investigate not only local zoning, subdivision control and building codes but applicable
state and federal regulations (e.g., the Section 404 permitting program). Negligence may
“arise from breach either of a common law duty or one imposed by statute or regulation
since the conduct of a “reasonable man” may be prescribed by legislative enactment.”36
In general, violation of a statute or ordinance creates, at a minimum, a presumption of
negligence or evidence of negligence.
Government Liability
Although design professionals employed by governments are not liable as individuals,
their government units (local, state, federal) may be. Governments may be sued for
negligence if public employees negligently design or construct a structure with resulting
injury to a member of the public. They may be liable if their employees provide
inadequate flash flood warnings to members of the public on public lands. They may
be sued for negligence, trespass, nuisance or under another common law theory or for a
taking of private property without payment of compensation under a state or the federal
Constitution if they increase flood or erosion damage on nongovernmental lands.136
Governments are particularly vulnerable to suits for negligence based upon “ministerial”
acts of employees such as improper maintenance of a drainage ditch. In general,
governments are not liable for “discretionary” acts such selecting the flood passage
design capacity for a bridge.
STATE OF VERMONT – A ZONE (UNNUMBERED) CROSS SECTION
SURVEY EXAMPLE -- Surveying for a LOMA in “Zone A”
http://www.anr.state.vt.us/dec//waterq/rivers/docs/nfip/rv_azonesurv
ey.pdf
Regions labeled as “Zone A” on your floodplain map indicate those areas where FEMA has designated the
approximate floodplain, but has not done the detailed river studies necessary to establish a base flood elevation.
If your parcel is less than 5 acres in size, FEMA will calculate the base flood elevation for you IF you provide the
appropriate survey information with your LOMA application:
- The surveyor must establish a cross-section of the stream. This cross-section should begin at the upstream edge of
your structure, and should extend perpendicular to the stream. The cross-section should extend on the opposite
bank of the stream to the point where the relative ground elevation on the opposite bank equals or exceeds the
ground elevation of your structure.
- Several survey points should be established along this cross-section. A survey point should be included at every
point where there is a significant break in slope or change in topography along the cross-section. Elevation and
distance along the cross-section should be measured for each survey point. Elevation can be measured using an
“assumed datum”, where the surveyor establishes an arbitrary elevation at a nearby landmark and records relative
elevations compared to that point. Distance along the cross-section can be made starting from the corner of your
structure.
- All distance and elevation measurements should be recorded in a table. The surveyor should include a scaled
diagram of the cross-section that includes each of the survey points (see “cross-section view” ). An “overhead
view” of the cross-section (including the survey points) that shows the home in relation to the stream should also
be included.
- Include all other information relevant to the survey. You should include several photos of the banks on either side
of the stream. Knowing the type of ground cover nearby is necessary for FEMA to model the base flood elevation.
- Your LOMA application should also include the ground elevation at the lowest point around your foundation (also
called the “lowest adjacent grade”), using the assumed datum.
This survey information should allow FEMA to calculate a base flood elevation for your site, and compare that
information to the lowest adjacent grade. PLEASE NOTE: the investment of time and money needed to obtain this
survey information does not guarantee that the outcome will be favorable, and there is always the possibility
that the base flood elevation will be higher than your lowest adjacent grade.
If you have questions regarding Letters of Map Amendment from FEMA please visit the FEMA Map
Assistance Center (http://www.fema.gov/plan/prevent/fhm/fmc_main.shtm), or contact a FEMA
Map Specialist at “FEMAMapSpecialist@mapmodteam.com” or 1-877-FEMA-MAP (1-877-3362627).