Frequently Asked Questions
|Q: Who can prepare an Elevation
A: Elevation Certificates must be prepared and
certified by either a land surveyor, engineer, or
architect who is authorized by commonwealth, state, or
local law to certify elevation information. The Flood
Control District may also sign the certificate.
|Q: Which elevation datum do I use?
A: Flood Insurance Rate Maps (FIRMs) reference
the elevation datum used to compute flood elevations. In
completing elevation certificates, the same elevation
datum as that shown on the FIRM must be used to compute
lot and/or structure elevations and to compute flood
elevations that are not given on the FIRM.
|Q: What is fill and how does it
affect the floodplain?
A: For the National Flood Insurance Program (NFIP),
fill refers to soil that is brought in to raise the
level of the ground. Depending on where the soil is
placed, fill may change the flow of water or increase
flood elevations. Fill may be used to elevate a building
to meet the NFIP requirements. Sometimes fill is
combined with other methods of elevation such as pilings
or foundation walls. Placement of fill requires a
Floodplain Use permit from the Flood Control District
|Q: Why wasn't my Letter of Map
Change incorporated into the panel revision?
A: When a new National Flood Insurance Program
map becomes effective it supersedes all Letters of Map
Change (LOMCs) that have been issued for the affected
map panel. When the changes reflected in the LOMC can be
shown on the new FIRM, they are incorporated; however,
some LOMC changes cannot be shown on the new FIRM
because the change is too small to see on the map.
FEMA is in the process of developing procedures to
automatically revalidate the LOMCs that were not
|Q: When should I request a
conditional map revision?
A: FEMA's review and comment on a project that is
proposed within the Special Flood Hazard Area is
referred to as a Conditional Letter of Map Revision (CLOMR).
A CLOMR comments on whether the proposed project meets
the minimum floodplain management criteria of the
National Flood Insurance Program (NFIP) and, if so, what
revisions will be made to the community's NFIP map if
the project is completed as proposed.
There are only two situations where NFIP regulations
require a CLOMR to be obtained from FEMA before a
project can be built. The first is for a project on a
stream or river that has been studied through detailed
hydrologic and hydraulic analyses and for which base
flood elevations have been specified, but a floodway has
not been designated. If the community proposes to allow
development that would result in more than a 1.0 foot
increase in the base flood elevation, a CLOMR must first
The second situation requiring a CLOMR is for a
project on a stream or river for which detailed analyses
have been conducted and base flood elevations and a
floodway have been designated. If the community proposes
to allow development totally or partially within the
floodway that would result in any (greater than 0.0
foot) increase in the base flood elevation, a CLOMR must
Although the two situations described above are the
only equirements to obtain a CLOMR prior to permitting
development, FEMA will review and comment and, if
appropriate, issue a CLOMR for any proposed project when
requested by a participating community. All requests for
CLOMRs must be supported by detailed flood hazard
analyses prepared by a qualified professional engineer.
The specific data and documentation requirements are
contained in Part 65 of the NFIP regulations and in
FEMA's application/certification forms (MT-2). To defray
costs to NFIP policyholders, FEMA charges fees to
recover review costs. Specific information on the fee
schedule and exemption requirements are contained in the
|Q: When should I request a map
revision to the Flood Insurance Rate Map?
A: If physical changes to the floodplain have
changed the flood hazard information shown on the
effective National Flood Insurance Program (NFIP) map, a
revision should be requested. The request should be
accompanied by the appropriate portions of the MT-2
application/certification forms package and the required
|Q: How do I get a revision to the
Flood Insurance Rate Map?
A: A revision to the Flood Insurance Rate Map
(FIRM) may be requested by completing and submitting the
appropriate portions of the MT-2
application/certification forms package, entitled
"Revisions to National Flood Insurance Program Maps" (FEMA
Form 81-89 Series), and the required supporting
|Q: Where should I send my map
A: Revision requests should be sent to the
appropriate FEMA Regional Office.
|Q: Do I need to submit a fee with my
map revision request?
A: In most cases, yes. To ensure full
reimbursement of funds expended to review and process
most map change requests, FEMA established a standard
fee schedule. The fee schedule is published periodically
in the Federal Register and appears in the application/
certification forms package.
|Q: How long does it take to get a
A: FEMA typically responds in less than 30 days,
and must respond to a revision request within 90 days of
receipt of the application/certification forms and the
supporting information. The response may be a
determination, a request for additional information, or
a statement that additional time will be required to
complete the processing of the request.
|Q: How can I expedite my request?
A: Because FEMA receives many requests, they are
processed on a first-come, first-serve basis. The best
way to get a timely response is to make sure the forms
and supporting information are complete.
|Q: Why did I receive a Letter of Map
Revision and not a Physical Map Revision?
A: A Letter of Map Revision (LOMR) is a much
quicker revision than a Physical Map Revision (PMR).
PMRs can take up to two years to become effective. In
addition, a LOMR is a more cost effective means for FEMA
to revise a Flood Insurance Rate Map (FIRM). Due to
budget constraints, FEMA uses the LOMR process as much
as possible. You should keep a copy of the LOMR with
your valuable papers. It will be important to have when
you are ready to sell your property.
|Q: What is required to certify a
levee as providing protection from the base flood?
A: In order for FEMA to recognize a levee system
as providing protection from the base (1% annual chance)
flood, it must meet, and continue to meet minimum
design, operation, and maintenance standards established
in Section 65.10 of the NFIP Regulations. The design
criteria include, but may not be limited to,
requirements for freeboard, closure devices, embankment
protection, embankment and foundation stability,
settlement, and interior drainage. Public agencies must
have complete operation and maintenance plans. The
operation plan for the levee may include, but is not
limited to, procedures for closures, interior drainage
systems, and emergency measures. The maintenance plan
should detail responsibility and frequency of
maintenance necessary to ensure the integrity of the
levee system. All items necessary for a levee system to
be recognized as providing protection from the 1% annual
chance flood must be certified by a registered
professional engineer. The certification requirement is
different if a Federal agency has responsibility for the
|Q: Will rates be reduced when a
flood control project is partially completed?
A: The answer to this question depends on whether
the flood control project provides an adequate level of
protection and if it involves federal funding. If the
project is federally funded, then FEMA will revise the
FIRM to show changes in the floodplain if the critical
features of the project are under construction, 50% of
the total cost has been expended, and 100% of the
funding is authorized. When the FIRM is revised, the
protected area will be designated Zone A99, and the
flood insurance rate will be the same as in Zones B, C,
If a flood control project does not involve federal
funds, FEMA would handle a map revision request as a
Conditional Letter of Map Revision. The project sponsor
must submit engineering and technical information to
document the level of protection, how the floodplain is
modified, the structural adequacy of the project, and
operations and maintenance requirements. The FIRM would
be changed after the project is complete and "as built"
plans have been certified and submitted to FEMA. At that
time, the flood insurance rate in areas certified as
protected would be the same as in Zones B, C, and X.
|Q: The map shows that my lot is in
the mapped floodplain, but the ground my house is on is
higher. I believe I shouldn't be shown in the
floodplain. What are FEMA's requirements for being
removed from the 1% annual chance flood hazard area?
A: To be removed from the floodplain shown on the
Flood Insurance Rate Map, a structure must be on land
that is not subject to flooding by the 1% annual chance
flood. Remember, more severe floods can and do happen,
so even if your home is found to be on high ground, it
may still be damaged by an extreme flood event.
If your lot or building site is on natural ground
that is higher than the Base Flood Elevation (BFE) shown
on the FIRM, then you may request a Letter of Map
Amendment (LOMA). To support your request, you will have
to get a surveyor to determine the elevation of the
ground next to your building and complete an Elevation
Certificate. If the ground is higher than the BFE, then
FEMA will issue a LOMA. With a LOMA, your lender may
choose to not require flood insurance.
If your home was built on fill that was placed after
the FIRM was prepared, you may request a Letter of Map
Revision Based on Fill (LOMR-F). As with a LOMA, you
will need to get an Elevation Certificate completed by a
land surveyor. If the filled ground is higher than the
BFE, and if you do not have a basement, then FEMA may
issue a LOMR-F, and your lender may choose to not
require flood insurance.
|Q: What is a "floodway"? What does
it mean when homes or land are in the floodway?
A: Rivers and streams where FEMA has prepared
detailed engineering studies may also have designated
floodways. For most waterways, the floodway is where the
water is likely to be deepest and fastest. It is the
area of the floodplain that should be reserved (kept
free of obstructions) to allow floodwaters to move
downstream. Placing fill or buildings in a floodway may
block the flow of water and increase flood heights.
Because of this, your community will require that you
submit engineering analyses before it approves permits
for development in the floodway.
If your home is already in the floodway, you may want
to consider what you will do if it is damaged. If it is
substantially damaged (the costs to repair equal or
exceed 50% of the market value of the building) your
community will require that you bring it into
compliance. In most cases, this means you will have to
elevate it above the base flood elevation. Because
placing fill dirt in the floodplain can make flooding
worse, you'll probably have to elevate on columns,
pilings or raised foundation walls. If your land is
large enough to have a site outside of the floodway or
even out of the floodplain, you may want to think about
moving your home to a safer location.
|Q: What is the 100-year floodplain?
A: The 100-year floodplain is defined as the area
that would be covered by floodwater during a 100-year
storm event. In stormwater managements, floods are
classified by statistical probability of occurrence.
When we speak of a 100-year flood, we are referring to a
flood event that has a one percent chance of occurring
in any given year. The magnitude of a 100-year flood is
determined from historical data and precipitation
patterns within the watershed.
Q: What is a Floodplain
Floodplain boundaries vary along a channel depending
on such factors as topography, soils and vegetation, the
size of the watershed, and the condition of the channel.
These boundaries may also change over time as the
watershed is developed or the channel is altered. In
addition, the floodplain may be redefined as new or
revised statistical data becomes available.
|Q: What do I need to know if my
building is in the floodplain?
A: Buildings in special flood hazard areas shown
on FIRMs may be damaged when flooding occurs. Some
buildings flood frequently, while others get damaged by
only the more severe events.
If your home is in the 1% annual chance floodplain,
it has a 26% chance of getting flooded over a 30-year
period. This means it is about five times more likely to
get damaged by flood than by a severe fire!
You should know that usually you can get flood
insurance, if available, by contacting your regular
homeowners insurance agent. FEMA and others recommend
that everyone in special flood hazard areas buy flood
insurance. If you buy a home or refinance your home,
your mortgage lender or banker may require flood
insurance. But, even if not required, it is a good
investment especially in areas that flood frequently or
where flood forces are likely to cause major damage.
Another thing you should know is that your community
may require permits for remodeling, improving,
expanding, or rebuilding your building. In order to
reduce long-term flood damage, the NFIP requires that
buildings that are substantially improved or
substantially damaged become compliant. This means if
the cost of the improvements or repairs is more than 50%
of the market value of the building, you will have to
make it compliant with the rules for floodplain
construction. Usually, this means lifting it off the
foundation and elevating it above the predicted flood
level. If you carry a flood insurance policy and have
major flood damage, you may be eligible for up to
$20,000 to help pay for the cost of this work.
|Q: Can floodway or floodplain
boundaries be changed?
A: Under current Floodplain Regulations, the
channel and/or adjacent lands may be modified to reduce
the water surface elevation during a 100-year flood,
thus, narrowing the floodway boundaries
|Q: What is sand and gravel mining?
A: Flood Control is primarily concerned with
aggregate extraction activities within delineated
floodplains and floodways. The industry of aggregate
production involves excavating loose alluvial material
from the river bed or its banks, sorting and grading the
material and hauling it in trucks from the site.
|Q: Who do I contact about dust,
noise, or traffic impacts from a sand and gravel
A: We only regulate the impacts on stormwater
conveyance of sand and gravel mining. Dust is regulated
by the Mohave County Department of Environmental
Services. Noise and traffic complaints can be sent to
the Mohave County Department of Transportation.
Potential zoning conflicts arising as a result of sand
and gravel mining should be referred to the Mohave
County Department of Planning and Zonning
|Q: What are the major impacts of
sand and gravel mining within floodplains?
A: The impact of a sand and gravel operation
depends primarily upon where the pit is located within a
floodplain and the depth and area of excavation. The
effects of excavating deep pits in the floodplain are
generally not recognized by the public until after a
major flooding event. The most recent major flood events
occurred in 1993, 1979 and 1978, so the frequency of
such events is relatively rare. If not excavated
properly, sand and gravel pits can induce changes in the
river bed which endanger life and property by changing
the depth, velocity, or path of floodwaters.
|Q: How does Flood Control prevent
adverse impacts from sand and gravel pits?
A: We minimize the chance of sand and gravel
mining damage by requiring that a
Floodplain Use Permit (FUP) be issued for each sand
and gravel operation. We require that applicants address
concerns about bank stability and erosion by engineering
analysis of the site activities and how they will affect
the river morphology when floods occur.
|Q: How do sand and gravel pits cause
impacts that can endanger life or property?
A: There are three potential impacts of sand and
gravel mining: (1) When floodwaters enter a pit, erosion
occurs or the upstream lip of the pit and moves upstream
in a process known as "headcutting." Floodwaters in
natural streams in Mohave County contain huge quantities
of sand and gravel in motion. When these sediment-rich
waters enter a large pit, the solids settle out, and the
water leaving the pit is relatively clean. (2) This
cleaner water tends to pick up more sediment after
leaving the pit and causes downstream erosion, or "tailcutting."
(3) Deep pits with steep slopes and inadequate
embankment stabilization tend to collapse into the pits
as floodwaters pass, causing lateral migration of the
|Q: Why is a permit required from
Flood Control District for sand and gravel mining?
A: Flood Control District requires permits to
ensure that sand and gravel mining operations do not
have any adverse impacts on adjacent properties, such as
diverting floodwaters or causing river bed changes which
alone or cumulatively can put other properties at risk
of inundation or erosion hazards.
|Q: Under what authority does the
Flood Control District permit sand and gravel
A: Flood Control District permits sand and gravel
operations in floodways under the authority of the
Floodplain Regulations, Section 902(7). Operations
within the floodway fringe are permitted under the
authority of Section 1002(12).
|Q: What permits are required for
sand and gravel mining?
A: In addition to the Floodplain Use Permit from
FCD, permits are required from Mohave County for dust
control and construction, and from
Arizona Department of Environmental Quality for
water quality. If the excavation involves disturbance of
vegetation that provides a wildlife habitat or enters
into an area designated as a "Water of the US" by the US
Army Corps of Engineers, the operation must obtain a 404
permit as well. See the links to other permits.
|Q: Where can I learn more about sand
and gravel mining?
Arizona Rock Products Association maintains a
website to promote the interests of the aggregate
extraction industry in Arizona.
|Q: What are the penalties for
violation of the regulations for sand and gravel
A: Violation of the Floodplain Regulations is a
class 2 misdemeanor, punishable by a fine of $10,000.
Violation of the Drainage Regulation is also a class 2
misdemeanor, punishable by a fine of $10,000, with each
day of violation constituting a separate offence.
|Q: Can I get rainfall, streamflow
and weather data that is not available on the web page?
A: Yes. Nearly all the data for the rain and
stream gages are available via the web access tools.
Weather data is generally available for the past few
months via the web.
Flood Warning & Data Collection
|Q: Why do most of the rain gages
appear to read in increments of 0.04 inches?
A: Because most of the rain gages actually read
in millimeters. One millimeter is equal to 0.03937
inches, and it is this number that is used by the
computer to do calculations. For example, 7mm will read
as 0.28 inches, but 8mm will round to 0.31 inches when
reported in hundredths of inches. A few of the raingages
read in increments of 0.01 inches, and there are no
rounding errors in calculations for these gages.
|Q: Why are there more raingages in
some areas of the County than in others?
A: The density of raingages and the placement of
individual gages are based on many factors. Some of
these are: flood hazard or potential, District projects,
location of channels, permitting requirements,
environmental factors, watershed boundaries and the
proximity of existing gages.
Sometimes two gages appear very close to each other on a
map, but have very different roles.
|Q: How do the streamgages work?
A: The majority of our streamgages use a sensor
called a "pressure transducer". This device senses the
pressure exerted by water (or any fluid) above it. Only
the density of the fluid need be known to calculate the
depth of the fluid above. Once the depth is known, the
flow rate (usually cubic feet per second, or cfs, also
known as discharge) can be calculated by application of
a rating curve.
|Q: OK, so what is a rating curve?
A: A rating curve is a graph of depth (usually in
feet) versus discharge (usually cfs). It is created
through application of a mathematical formula in the
case of weirs and engineered channels, or through a
process of channel surveying and mathematical modeling
for natural channels. In either case, the channel slope,
area and roughness determine the capability of a channel
to transmit water.
|Q: Why do stream gages sometimes
show a depth value but no corresponding discharge?
A: Because frequently the instrument is not at
the "bottom" or zero point in the channel or the pool
area of a dam. It is often necessary to locate the
instrument above or below this point. In these cases
there will either be some positive or negative depth
displayed when discharge numbers begin to register. In
neither case will flow actually be happening at the site
unless the discharge value is non-zero.
|Q: How is the Contoured Rainfall Map
A: The Contoured Rainfall Map is produced using a
remote-shell login to the ALERT database and ARCview GIS
software. A program takes information from a form, such
as the ending date/time and the desired map duration,
and produces from the ALERT database a table of rain
gage values to be plotted. This is then read into
ARC view, and a plug-in called Spatial Analyst
interpolates a surface, much like a topographic map. A
contoured map is produced, and the operator can choose
to add other coverage's like highways, boundaries, and the
rain gage locations. The image is then copied to a paint
program where the scale and time period text are added.
Finally, the image is sent via FTP to the web site.
|Q: Why do the "Wind Speed" sensors
appear to read so low?
A: Sensors of the "Wind Speed" type do not
transmit the instantaneous wind velocity but rather an
average wind speed over a time period. That period
happens to be the time it took for the last 1 km of wind
(wind run) to "blow" past the sensor, so the period is
shortened as the wind speed increases. The average wind
speed reported is the distance (1 km) divided by the
time (seconds), converted to miles per hour.
|Q: What is a "Water-Year"?
A: The water-year is used by the USGS and other
federal agencies to define a period of data collection.
It runs from October 1st through September 30th.
Water-year 2003 began on 10/01/02 and ended on 09/30/03.
|Q: How do I get drainage clearance?
A: A Drainage Clearance is issued as part of the
Building Permitting process. A site plan has to be
submitted to the FCD Permitting Desk. The Plan is taken
in and a decision is made whether a site investigation
is required. If not, then the plan is either issued over
the counter or sent to Durango for further review. If a
site investigation is required, the applicant is told to
stake the property corners of the building location and
call the FCD for the site inspection. Once the
inspection is performed the decision is made as to
whether an engineer needs to be retained to provide
hydrology and/or hydraulic information, or can we issue
the Drainage Clearance only based upon minimal
information such as drainage arrows and cross-sections.
Once the final plans are prepared and sent to the FCD,
they are reviewed and if all of the requirements are met
they are approved. When all of the reviewing agencies
are satisfied that the plan meets their requirements, a
Drainage Clearance is issued as part of the County’s
Permitting Process. For information call (928) 757-0925.
|Q: What needs to be shown on the
A: Review the section “Plan Submittal
|Q: When do I call for a stem
A: Prior to pouring the stem walls. Have the
contractor set up the height of the stemwalls for our
inspector’s site visit. This should happen after the
initial site plan has been approved. Call our inspection
line at (928) 757-0925. Inspections for the next day
need to be called in prior to 2:30 p.m. (This is an
automated system). You can also request an inspection
|Q: When do I call for a final
A: After everything has been completed, all the
concrete has been poured, all trenches have been filled,
stockpiles/berms removed and the site has been rough
|Q: Do I need a site inspection?
A: Whether a site inspection is needed or not
depends on the location of the site and if the Flood
Control District already has drainage information for
the site. The Flood Control District Representative
downtown will determine if a site inspection is needed
at the time of the plan submittal.
|Q: Am I in a floodplain?
A: Check the Federal Emergency Management
Agency’s Flood Insurance Maps or if the property is
located in the Unincorporated Areas of Mohave County you
can call the Flood Control District’s at (928) 757-0925 and ask for floodplain
determination. Prior to calling make sure you have the
Tax Assessor Number.
|Q: Do I need an engineer to prepare
A: An Arizona Registered Engineer is needed if
there is extensive grading, a wash is to be rerouted or
encroached upon, the proposed house is adjacent to a
significant wash, or if the finished floor is to be set
lower than the allowed finished floor criteria (see
requirements for finished floors and grading on-site on
the following page).
|Q: How far away from the wash does
my house need to be?
A: The location of the structure in proximity to
a wash is dependent on the size of the wash, the amount
of flow the wash carries, and if any bank stabilization
is required. The Flood Control District Plan Reviewer
will determine if a location is acceptable during the
plan review. In general, stay away from all major
washes. A good rule for proposed structures within
twenty feet would be to provide bank protection and set
the footers below the bottom elevation of the wash. For
larger washes, a civil engineer will need to determine
appropriate erosion control. Erosion control may need to
meet Arizona State Standard 5-96.
|Q: How do I report a violation of
the Drainage Regulations?
A: Call (928) 757-0925. Be
prepared to provide as much detail as possible,
including the address or parcel number involved and a
description of the suspected violation. If you choose to
provide your name and phone number, efforts will be made
to keep that information confidential.