Floodplain Maps Flashcards
As directed by the National Flood Insurance Act of 1968, FEMA conducts flood studies To determine what 2 things?
Map floodprone areas of the United States. Establish flood risk zones within those floodprone areas.
The base flood is a flood that has a _________ of occurring in any year.
1%
The base flood is also called the ________- year flood.
100
True or False
A 100-year flood will occur only once every 100 years.
False
True or False
A 100-year flood could occur 2 times in one year.
True
True or False
The 100- year flood might not occur in a 200- year period.
True
The base flood could occur two consecutive years in a row.
True
On NFIP maps, the base floodplain is called the _______ __________ ________ ____________.
One-percent annual chance flood
BFE is the acronym for what?
Base Flood Elevation
What are the components of a Flood Insurance Study?
Flood Insurance Study
Flood Insurance Rate Map
Prior to 1986- a separate flood boundary and Floodway map was included
For the purpose of a riverine flood study, ___________ is the study of the distribution and circulation of water in the environment, and _____ is the study of fluids in motion and how water will flow through the channel.
Hydrology
hydraulics
The rate at which runoff flows downstream is called the flood____________.
Flood Discharge measured in cubic feet per second
What probable effect dos increase in urbanization within a community or upstream of it have on the stream discharges within that community?
Increase flood discharge downstream (runoff volume and velocity)
What consequence on flood water level of a stream would usually occur when a bridge is constructed over a stream?
the bridge will constrict the stream channel and can elevate the water level behind the bridge
To locate the true elevation at a site, surveyors have established ______ marks also know as ______marks.
Reference or bench marks
Cross sections describe the _________of the floodplain
profile
What is the datum used for your FIS, FIRM, and profiles
NAVD88, NGVD 29
Flood profiles are developed by plotting the flood elevations at the ______ _______ and connecting the plotted points
Cross sections
To make a floodplain map, the base flood elevations are plotted on a ____ map or a _______map.
topographic or contour
The ______ is defined as the stream channel and that portion of the adjacent floodplain that must remain open to permit passage of the base flood.
Floodway
A floodway analysis conducted to the minimum NFIP standard allow the fringe to be obstructed until the base flood level is increased by how much.
One foot
What causes storm surge?
Air pressure changes and Wind from coastal storms causes the waves to pile up against coast
What is wave runup?
The additional sea level elevation created by the toe of waves advancing on the beach.
Instead of cross sections, coastal flood engineers survey ________.
Coast line transects.
The most hazardous part of the coastal floodplain is the ______ _________ ________ area, which is shown on the map as a _______ Zone.
Coastal High Hazard Area or V Zone
What differentiates shallow flooding from riverine flooding.
Where flooding occurs 1-3 feet deep and there is no channel or identifiable flow path.
shallow flooding occurs commonly, as sheet flow, ponding or as the result of poor urban drainage.
Flood studies that do not identifiy BFEs are called ______ _________.
Floodway maps, or old format FIRMs
Prior to 1986 the maps published with an FIS are the _________ and the _________.
Old format FIRM, FBFM, Flood boundary and Floodway map
Since 1986, the map published with an FIS is the_______
New format FIRM
Is your community’s FIRM a flat or Z-fold map
Z fold
How many panels does your FIRM have?
Varies
What is the map scale of your FIRM?
Varies
What does an elevation reference mark look like on a FIRM?
RM 15.2
What is an AO zone
Base floodplain with sheet flow, BFE are provided.
What is the FIRM effective date for your community?
Looks on the front of the FIRM title block
How is a floodway shown on the Flood Boundary and FLloodway Map?
White area bordered by grey shading of 100-year and 500-year flood boundary.
How is a floodway shown on the new format FIRM?
Floodways shown as diagonal hatched lines on new format FIRM
A Zone C on an old format FIRM is shown as a Zone ____ on the new format FIRM.
zone X
CRBS stands for what
Coastal Resource Barrier System
What community’s floodplains are shown on a countywide FIRM?
All geographic areas of that county
Floodways are shown along the _____ toe of a levee on the FIRM.
Landside toe of the dike or Levee
Area behind recognized levees are designated as _____ _______.
Zone X
The base flood elevation is the elevation of the ___ -year flood or the ___ % annual chance
100-year flood or the 1% annual chance.
The Special Flood Hazard Area or SFHA is what the _______ floodplain is called on FEMA maps.
Base floodplain
The SFHA is shown on a FIRM as a Zone that begins with the letter ___ or ____.
A or V
What are the components of a Flood Insurance Study?
The components of the Flood Insurance Study include:
FIS report
FIRM
Prior to 1986 a separate Flood Boundary and Floodway Map (FBFM) was issued as component of the FIS
List 3 things a FIRM is used to determine.
Extent of flood hazard
elevation of flooding
special flood conditions such as shallow coastal flooding.
___ is the study of a watershed’s behavior during and after a storm.
Hydrology
Most permanent FIR elevation reference marks are reference to what datum?
NAVD88
A hydraulic study uses the hydrology, cross section information and stream characteristics to determine the flood _____.
elevation
Cross sections are shown on which map?
The FIS flood profiles map
Flood profiles are used to determine what?
The flood elevations in the stream channel
In riverine situations, the floodplain is divided into two separate parts for floodplain management purposes. These parts are the _______ and the _________.
stream channel and the fringe
Based on minimum NFIP standard, if the flood fringe were completely filled, how high could the base flood elevation go up.
One foot
What FIRM zone has wave heights greater than three feet?
V zone
Instead of using a base flood elevation, some shallow flooding areas are defined using a base flood ______.
Depth
An approximate study shows the base _______ but does not show the base flood __________.
flood hazard extent, base flood elevation
How many digits are there in the NFIP community identification number
6 digits such as 99009C
What is an AH Zone?
Shallow flooding base floodplain due to ponding, includes BFEs
What was the problem with the way the floodway was shown on the old format Flood Boundary and Floodway Maps?
Made without detailed studies or hydraulic analysis
The new format FIRMs include what three elements?
Floodways, cross sections, simplified flood zone insurance information,
Do Q3 Flood Data show base flood elevations if they are available.
Q3 flood data product is FEMA software to use with desktop mapping and GIS. They do NOT include base flood elevations
Rivers and coastlines each have its own probability of flooding, how is probability defined?
Probability defines the size of the storm and the odds of that size of flood occurring in any year.
How is 100-year flood used by NFIP?
Used to require purchase of flood insurance and regulating new development.
What is the recurrence interval calculation for 100 year flood?
1 divided by .01 = 100. One percent annual chance flood
What is calculation for 500 year flood?
1 divided by .002 = 500 year flood or .2 percent annual chance flood
A flood with a on- percent chance of occurring in a year can be called one of these three terms:
.
Base flood
100- year flood
one-percent annual chance flood.
Define the base floodplain?
The land area covered by the base flood.
What is the Special Flood Hazard Area or SFHA
The area covered by the base flood designated by zones
A,AE,AA1-30, AO, AH, V, VE or VE-30 depending on the amount of flood data available.
What is the significance of site located in the SFHA?
NFIP floodplain management regulations must be enforced by the community as a condition of participation in the NFIP. Mandatory flood insurance required.
Define Base Flood Elevation.
The calculated elevation to which floodwater is expected to rise.
What is the chance of flooding in any one year from a 10,25, 50 and 100-year storm?
10%, 4%, 2%, and 1%
What is the chance in flooding in 30 years from a 10, 25, 50, and 100-year flood?
96%, 71%, 45%, 26%
What were the mapping directives to Federal Insurance Agency under the 1968 National Flood Insurance Act?
Identify all floodprone areas in the US and establish flood- risk zones within the floodprone areas.
What is purpose of flood studies?
Analyze the terrain and factors that affect flood hazards.
How is the flood study information used?
To draw the maps that delineate the flood plain boundaries.
What elements are included in the maps and studies
Projected flood elevations Flood velocities Floodway dimensions Insurance rating zones Describe how study was done and how maps were prepared
What are uses of the flood studies and maps
Flood insurance
Floodplain management
What were the initial early maps called.
Flood Hazard Boundary Maps- base on approximate studies
What are maps with more detailed studies called?
FLood Insurance Rate Maps or FIRMs. Based on published Flood Insurance Study reports or FIS, also called Detailed Studies.
What does the FIS and FIRMS provided for communities
Data needed to adopt and implement more comprehensive floodplain manage the regulations and entire regular phase of the NFIP.
What information is contained in the Flood Insurance Study report
Flooding issues narrative
Community map and photos
Tables with flood Hazard data
Flood profiles for recurrence intervals (10-, 50-, 100-and 500- yr flood)
What Zone is defined by the Floodway plus the flood fringe?
Zone AE or A1-30
How do communities permit development in the flood fringe area?
If structure is elevated or will not cause the base Flood Elevation to rise.
How do communities allow development in the Floodway?
Building discouraged due to high Hazard, but is allowed if building does not obstruct flows, or cause BFE to rise more than one foot.
How is the floodway boundary extent determined.
Model fill in the edges of the floodplain until the flood water rises one foot.
How are surge elevations predicted for a certain recurrence interval?
Based on data from past storms, model include wind speeds, wind direction, and atmospheric pressure to calculate surge elevations.
What is the Stillwater Flood Elevation based on?
Historic storm surge elevations not including the waves.
How does coastal flood study account for waves?
Study analyzes the wave crest Elevation above Stillwater, wave run up, and wave setup- the additional Elevation over normal surge Elevation.
Define shallow flooding
Flooding with an average depth of one to three feet
List types of shallow flooding?
Pounding, or urban drainage, sheet flow, coastal flooding from wave run up that is trapped behind dunes or structures
what is an AO zone?
Shallow flooding due to sheet flow, usually with established depth.
