Welcome to the How to Use a Flood Insurance Study (FIS) course.

We are pleased to present this guide to the Flood Insurance Study (FIS). This course will describe the various information found in the FIS and explain how to use it. The sections are explained in detail for you to fully understand the information in the FIS. Using the information in the FIS in conjunction with the Flood Insurance Rate Map (FIRM) will enable you to determine the flood hazard for a property and allow you to take actions that may prevent flood damage and insure against losses caused by floods.

The National Flood Insurance Program (NFIP) requires that FIS flood profiles be used to determine an accurate Base Flood Elevation (BFE) in a riverine are with a detailed study. This course will show how to obtain an accurate BFE to the nearest tenth of a foot using the Flood profiles in the FIS. This is important information for floodplain management and flood insurance purposes and is one of the main uses of the FIS in the NFIP.

NOTE: This course presents the FIS sections in the order that they appear in most studies in the nation. The FIS format is updated and improved over time. If your community has a newer study, the same data will likely appear but the order in which the information is presented may have changed.

At the end of this course you will be able to:

• Identify information contained in a Flood Insurance Study (FIS)
• Explain what the information in a FIS means
• Describe how to use the information in the FIS

NOTE: If you have any problems with links in this course, please select the help button at the top of screen.

This is an overview of the course and an introduction to various course features and functionality.

At the end of this course overview and navigation introduction, you should be able to describe the:

• Course structure
• Screen features and navigation
• Knowledge Check functionality
• Course credit requirements

Take a moment to review the Lesson List located on the right side of your screen.

This course has seven (7) lessons. The lessons may be accessed sequentially or independently. The time to complete each lesson varies. A page tracker is displayed at the bottom middle of the screen to help you gauge your movement through the lesson. The estimated time required to complete each lesson will be stated on the lesson’s first screen.

After completing the course, take the Final Exam to:

• Gauge your knowledge of the topic
• Receive credit for taking the course

This course includes a glossary of terms used in this course. When you select the glossary link, the glossary will open in a new window.

NOTE: If you have any problems with links in this course, please select the help button at the top of screen.

At times during a lesson, there will be a Knowledge Check activity to review one of the concepts from the lesson. Instructions will appear at the top of the screen explaining how to complete the activity.

After you select the Check button, feedback on your answer selection will appear in a dialog box. To close the dialog box window, select the close link at the bottom of the window.

Try the sample Knowledge Check question below.

Slideshows are used in this course.

If you see a "Scroll down to see slideshow captions" message, the presence of a slideshow will be indicated by a shaded box with navigation buttons and a slide counter above it (see example below).

Select the slideshow's Next button (the gray right-facing arrowhead) to begin the presentation.

Some slideshow may have audio narration and/or captions that will explain the data entry procedure. Select the link to hear the audio narration. A media player window will appear when audio narration is activated.

This completes the Course Overview and Navigation. You learned:

• What this course is about
• How to complete this course
• How to receive credit for this independent study course

Select the next lesson from the main menu.

NOTE: If you have any problems with links in this course, please select the help button at the top of screen.

At the end of this lesson, you will be able to:

• Identify the purpose of a Flood Insurance Study (FIS)
• Recognize the authority behind an FIS

A Flood Insurance Study (FIS) is a report prepared by the Federal Emergency Management Agency (FEMA) that summarizes flood hazard data in a community. The analyses used to prepare a FIS are also used to produce the Flood Insurance Rate Map (FIRM).

The FIRM is a map set that graphically depicts identified flood hazards areas in a community. The FIRM is the basis for floodplain management, mitigation, and insurance activities in the National Flood Insurance Program. The FIS provides detailed information to supplement the FIRM.

Many students will find it helpful to download and view a FIS on a separate screen or printed. Student can then refer to each FIS Section while taking the course.

You can access the Flood County, USA sample FIS used for training classes at https://www.fema.gov/media-library-data/20130726-1554-20490-6003/dfm_dfft.pdf

If you would prefer to download the FIS for your community, advance to the next screen for instructions.

To get the most learning value out of this course, you may want to download your community’s Flood Insurance Study from the Map Service Center (MSC) website and follow along as you navigate this course. 

Steps to download a FIS.

1. Navigate to the FEMA Map Service Center available at https://msc.fema.gov/portal/home
2. Select the MSC Search All Products link form either the:
• Search All Products link in the web page text,
• Search All Products link in MSC Navigation bar.
3. Enter your Search information in one of the three search options:
• Jurisdiction (Note: When you select a State, County and Community options display)
• Jurisdiction Name or FEMA ID
• Product ID.
4. Select the Search button
5. Open the Effective Products folder
6. Find the FIS Report (#)
7. Select the Download All icon.
• The available FIS reports will list, showing Product ID, Effective Date, Size, and Download icon.
8. Select the Download icon for the FIS you want to retrieve.

The current effective, preliminary, and historic Flood Insurance Study (FIS) reports, Flood Hazard Boundary Maps (FHBM), Flood Boundary and Floodway Map (FBFM) and Flood Insurance Rate Map (FIRM) panels may be accessed, viewed and downloaded from FEMA's Map Service Center (MSC). Sometimes historic documents are not available for download and you will need to contact the MSC.

For more information or assistance,

• Contact a Flood Map Specialist by email at FEMAMapSpecialist@riskmapcds.com

or

• Call 1-877-FEMA-MAP (1-877-336-2627)

For more information on the publications available at the Map Service Center, open the MSC web site available at https://msc.fema.gov/

A Flood Insurance Study (FIS) includes the following sections and supporting information:

• Section 1.0: Introduction
• Section 2.0: Area Studied
• Section 3.0: Engineering Methods
• Section 4.0: Floodplain Management Applications
• Section 5.0: Insurance Applications
• Section 6.0: Flood Insurance Rate Map
• Section 7.0: Other Studies
• Section 8.0: Location of Data
• Section 9.0: Bibliography
• Section 10.0: Revisions (not in all FISs)

Supporting Data within the sections and appendices includes:

• Vicinity Map
• Summary of Discharges Table
• Floodway Data Table
• Summary of Stillwater Elevations Table
• Flood Profiles
• Flood Boundary and Floodway Map (FBFM) or Flood Insurance Rate Map (FIRM)
• Transect Data (in coastal and Great Lake communities)

Remember, this is a generalized structure. Individual studies may vary from this generic layout of FIS sections, but the study findings will still be conveyed in a similar format.

This section includes three sub-sections.

1.1 – Purpose of Study

1.2 – Authority and Acknowledgements

1.3 – Coordination

This section details which communities are included in the FIS. It explains that flood risk data was developed to establish flood insurance zones and assist the communities in mitigating flood hazards.

44 CFR 60.1(d) explains that the Federal flood damage reduction criteria are the minimum. In some states and/or communities, floodplain management criteria or regulations may exist that are more restrictive than the minimum federal requirements. In such cases, the more restrictive criteria will take precedence, and the state and/or community (or other jurisdictional agency) will be able to explain them.

Communities adopt higher regulatory standards to:

• Reduce flood risk
• Make floodplain development safer
• Improve community resilience
• Allow flexibility for state or local conditions that require higher standards
• Encourage comprehensive floodplain management

Higher standards may reduce flood insurance premiums.

Authority for the NFIP, National Flood Insurance Act.

Identifies the National Flood Insurance Act (1968), the Flood Disaster Protection Act (1973), the National Flood Insurance Reform Act (1994), the Biggert-Waters Flood Insurance Reform Act (2012), and the Homeowner Flood Insurance Affordability Act (2014).

Identification of study contractor(s)

Identifies the companies or government agencies that developed the flood risk data incorporated into the FIS and flood map panels.

Contract Numbers

Identifies the contract numbers under which the work was accomplished.

Date work completed for each contract

Provides the date that the Study Contractor completed their work.

Initial Consultation and Coordination Officer’s (CCO) Meeting

In general, for each FIS an initial Consultation Coordination Officer’s (CCO) meeting is held with representatives from FEMA, the communities, and the study contractors to explain the nature and purpose of the FIS and to identify the streams to be studied by detailed methods. This subsection identifies which organizations, communities and Federal agencies were represented at the meeting.

Sources of Additional Information

Identifies sources of additional flood risk data that may have been incorporated into the FIS and Flood map but were not contracted or paid for by FEMA.

Final CCO Meeting

Provides date at which the results of the study were presented to representatives of the community and other interested parties. Also identifies the communities and agencies present at the meeting.

You have completed Lesson 1.

In this lesson, you:

• Identified the purpose of a Flood Insurance Study (FIS)
• Recognized the authority behind an FIS

At the end of this lesson, you will be able to:

• Identify two methods used to study flood sources
• Recognize information that would be included in the community description
• Recognize information that describes the Principal Flood Problems
• Recognize five examples of Flood Protection Measures

This section has four sub-sections.

2.1 − Scope of Study

2.2 – Community Description

2.3 – Principal Flood Problems

2.4 – Flood Protection Measures

This section may include information such as:

Identification of flood sources studied by detailed methods and the geographical limits of the study

Names the streams and any other bodies of water studied by detailed methods and the upstream and downstream limits of studied streams, including Base Level Engineering (BLE).

Identification of flood sources studied by approximate analyses

Names the streams and any other bodies of water studied by less than detailed methods.

Note: "studied by less than detailed methods" refers to areas subject to inundation by the 1-percent-annual-chance flood event generally determined using various approximate methodologies. Because sufficient detailed hydraulic analyses have not been performed, no Base Flood Elevations (BFEs) or flood depths are shown for these areas. See FEMA.gov Zone A page available at https://www.fema.gov/zone for more information.

Vicinity Map

Shows the location of the studied community in reference to County and/or State. Usually a portion of a USGS map shows the community by jurisdictional limits or a star.

Note: The FIS for most countywide studies will not contain a vicinity map. However, these studies will have a general map on the cover showing the location of the community or county.

This section describes the location, climate, and many of the physical characteristics of the community.

The types of information that may be included in this section are:

• Size and population of the community
• Average rainfall and temperature
• Soil types
• Names of the adjacent communities

This section may include information such as:

Causes of Major Floods

Identifies the causes of flooding within the community or region and identifies natural or man-made features that aggravate flooding within the community.

Past Major Floods

Provides the dates of the past major floods within the community.

Historical Flood Data

Provides brief historical accounts, usually from local newspapers, of the floods that have affected the community. Other sources include communities and organizations, such as, the Department of Transportation and State or Federal agencies. Details often include the magnitude of the storm, the amount of damage caused to personal property, real property and infrastructure and casualties. This information can be very helpful if the historic flood events are associated with a recurrence interval or flood frequency such as a 1% annual chance (100-year) or 0.2% annual chance (500-year) flood event.

Gage Station Locations

Provides location of stream or tide gages, dates of operation, intervals of continuous operation and name of Agencies that own, operate or maintain the gages. The type of gages might also be included.

This section will include a description of the flood protection measures in the area studied as well as a description of any regulations pertaining to the flood protection measures.

These measures can include:

• Channelization Projects
• Levees
• Dams
• Non-structural Flood Control Measures
• Flood Control Projects that do not provide protection to at least the 1% annual chance flood

Channelization Projects are man-made channels or waterways that are designed to increase the flood carrying capacity of a stream and, thereby, reduce flood elevations.

For a channelization project, the information in this section includes the:

• Type of channel (e.g., grass, concrete, gabion lined, etc.)
• Name of the agency or organization that constructed the channel
• Date of construction
• Name of the agency or organization that maintains the channel

Also, this section describes if the base flood is contained within the channel, and if not, the extent of flooding that will occur outside the channel.

Levees are man-made structures or engineered fill that extend above the flood elevation to prevent areas behind the levee from being inundated by floodwaters. For a levee, the information in this section includes the type of levee (e.g., flood control, agricultural, etc.), the name of the agency or organization that constructed the levee, the date of construction, the name of the agency or organization that maintains the levee, the level of protection provided by the levee (e.g., the magnitude of the flood that will overtop the levee) and the historical performance of the levee.

FEMA does not own, maintain, or set standards for how levees are built. However, in order for a levee to be accredited as providing flood protection, it must meet certain standards. It must:

• have a minimum of three feet of freeboard against the 1% annual chance flood event;
• be equipped with closure devices at every opening;
• be constructed with embankments and foundations that are certified not to fail due to erosion, seepage, or instability; and
• be certified against future loss of freeboard due to settling.

For additional requirements, refer to 44 CFR 65.10 available at https://ecfr.io/Title-44/se44.1.65_110.

Dams are man-made structures built across a watercourse to impound water and reduce the flow downstream.

Dams are often used to create retention/detention basins, reservoirs, and ponds. For each dam, the information in this section includes the type of dam (e.g., earthen, concrete, etc.), the name of the agency or organization that constructed the dam, the date of construction, the name of the agency or organization that maintains the dam, the purpose of the dam, and the historical performance of the dam.

This section includes key dimensions and elevations of the dam; width, height, top elevation, spillway crest elevation, normal pool elevation, and emergency spillway elevation. In addition, details on operation or emergency plans may be included in this section.

Non-structural Flood Control Measures include various regulations, such as:

• Higher Floodplain regulatory standards than the NFIP minimum requirements.
• Regulations that reduce runoff potential by restricting watershed or floodway development.
• Regulations requiring use of future conditions, hydrology, etc.

This section may also contain information on platted conservation tracts, or projects such as designing easements and increasing open space in the floodplain.

You have completed Lesson 2.

It covered Section 2.0: Area Studied and its four sub-sections.

2.1 – Scope of Study

2.2 – Community Description

2.3 – Principal Flood Problems

2.4 – Flood Protection Measures

In this lesson, you learned to:

• Identify two methods use to study flood sources; (1) detailed methods and (2) approximate analyses.
• Recognize information that describes the community; e.g., size and population of the community, average rainfall and temperature, soil types, and names of the adjacent communities.
• Recognize information that describes the Principal Flood Problems; e.g., causes of flooding and features that aggravate flooding, historical flooding data, and gage station locations and information regarding the gages.
• Recognize five examples of Flood Protection Measures, e.g., channelization projects, levees, dams, non-structural flood control measures, and flood control projects that do not provide protection to at least the 1% annual chance flood.

At the end of this lesson, you will be able to:

• Describe the difference between hydrologic and hydraulic studies
• Recognize four Riverine Hydrologic methods of analyses
• Recognize three sources of data used in Riverine Hydraulic analyses
• Recognize how the Base Flood Elevation (BFE) is calculated for Coastal Areas
• Recognize information that would be included in the Coastal Hydraulic Analyses
• Indicate why the FIS identifies the vertical datum used in the study

This section includes five sub-sections.

3.1 – Riverine Hydrologic Analyses

3.2 – Riverine Hydraulic Analyses

3.3 – Coastal Hydrologic & Hydraulic Analyses

3.4 − Flood Protection Measures

3.5 − Vertical Datum

Some of the sub-sections have additional layers of detailed information.

Identification and explanation of flood frequencies

Section 3.0 provides a brief explanation of probability and recurrence intervals for floods.

It explains how a 1-percent annual chance, or more severe flood event, can occur more than once over a short time interval.

Important terms used in this section:

• Hydrologic = amount of water
• Hydraulic = flood height or elevation

Hydrologic analyses are studies of the amount of water flowing in a stream during flood events.

Generally, FISs are concerned with the peak rates of flow or discharges in streams for the 10-percent (10 year), 4-percent (25 year), 2-percent (50 year), 1-percent (100 year), and 0.2-percent (500 year) annual-chance exceedance flood events. Peak discharges are typically measured in cubic feet per second (cfs).

The 4-percent annual chance (25-year) flood event may not be calculated in older Flood Insurance Studies.

In newer Flood Insurance Studies a 1-percent-plus annual chance profile may also be included to communicate uncertainty in estimated discharge due to factors such as saturated ground conditions. It can also reflect uncertainty for other parameters or future hydrologic conditions.

Example: The 1-percent annual chance flow is assumed to be under typical conditions, however the soil in the watershed may be saturated because of higher than average rainfall. The 1-percent-plus profile reflects the potential higher base flood elevation under those conditions. It can also provide more information for communities to predict future flooding conditions in areas under heavy development or when considering higher standards like freeboard.

The major items addressed in this section are:

• Sources of Data
• Methods of Analysis (Riverine)
• Summary of Discharges Table

This section identifies the data used to determine peak discharges or the agency from which the discharges were obtained.

The data used in determining discharges may include:

• Topographical maps
• Gage data
• Land use maps
• Soil information

This section provides detailed explanations on the methods used to determine the peak discharges, and why that methodology is appropriate for the watershed.

Typical methodologies are:

• Drainage Area-Discharge Curves
• Gage Data Analysis
• Regression Equations
• Rainfall-runoff Models

Drainage Discharge Curves are graphs relating peak discharges to the drainage areas. They are developed from known peak discharges and drainage areas for other streams in the area.

Using the graphs, the peak discharges at any location on the stream can be determined by simply knowing the drainage area to that location.

A separate curve is used for each flood frequency.

Gage data analysis involves statistical computations performed using a historical record of flood data at a stream gage to determine the peak discharge on the stream for a flood event of a given probability (e.g., a flood that has a 1-percent annual chance).

For gage data analysis, this section provides information about the stream gage, which includes the:

• Location of the gage
• Name of the agency or organization that owns, operates, and maintains the gage
• Length of historical record used in the analysis

Any changes in the watershed that could influence the peak discharges recorded at the gage may also be discussed in this section.

These are mathematical equations based on statistical analysis that calculate the peak discharge based on watershed characteristics.

This section indicates:

• From what publication the equation was obtained,
• Who developed the equation, and
• What variables are required for the equation.

Typical variables used in regression equations include:

• Drainage area
• Rainfall
• Watershed slope.

Any limitations on the use of the equation, such as size of watershed or region, are also included in this section.

The United States Geological Survey (USGS) is a major source of stream flow data from gages. This data is then used to develop regression equations. Other agencies and researchers may develop their own peak discharge analyses. The FIS describes the techniques, agencies, and contractors that developed the peak discharge data used in the study.

Rainfall-runoff models are computer models that calculate the peak discharges for given rainfall events and watershed characteristics.

For the hydrologic model(s) used, the information in this section includes the:

• Name of the computer program,
• Name of the agency that created the program, and
• Major parameters of the program.

Rainfall events that may have been used to calibrate the model are also identified in this section.

This table briefly summarizes the drainage areas and peak discharges at locations along the streams. The locations chosen for the table are generally at physical features shown on the maps.

Not all discharges used in the analyses are shown on the table. Typically, discharges for the 10-percent (10 year), 4-percent (25 year), 2-percent (50 year), 1-percent (100 year), and 0.2-percent (500 year) floods are shown in the tables.

Note: Peak discharges for 25-year flood events are shown on newer studies

Hydraulic analyses are studies that determine the flood height or water surface elevations (WSELs) on streams or rivers.

FISs are primarily concerned with the 1-percent annual chance (100-year) flood WSELs. These are known as Base Flood Elevations (BFEs).

However, the water surface elevations for the 10-percent (10 year), 4-percent (25 year), 2-percent (50 year), 1-percent-plus (100 year), and 0.2-percent (500 year) flood events may also be determined.

The major items addressed in this section are:

• Sources of Data
• Methodologies

This section identifies the sources of data used in the analysis to calculate the flood elevations, which include:

• Cross Sections
• Roughness Coefficients
• Starting Water Surface Elevations for riverine studies

A cross section is an elevation view of the floodplain taken perpendicular to the flow at a given point. Cross sections are typically determined using aerial and field survey information, topographic maps or Digital Elevation Models (DEMs), or some combination of the two.

This section will contain pertinent information about the cross sections, such as how they were determined; the date of any field survey; and the scale, contour interval, and date of topographic maps or accuracy of DEMs that may have been used.

Exact BFEs are determined at each cross section. The flood elevation is then interpolated between cross sections to develop the flood profiles.

Cross sections are commonly located at regular intervals, additional cross sections are typically incorporated into the model upstream and downstream of bridges, culverts, weirs and other stream crossings or impediments to flow or at locations where floodplain characteristics change.

Some of the locations of the cross sections used in the analyses will be shown on the flood map in detailed study riverine areas.

Commonly referred to as Manning's “n” coefficients, these coefficients are used in the hydraulic calculations to reflect the resistance to flow in the channel and overbanks. Resistance to flow is typically due to the composition of surfaces (cement vs boulders, etc.) and type of vegetation that is present in these areas. This section lists the range of Manning's “n” coefficients used in the study for the channel and overbanks.

Example of how the Manning's “n” coefficients may be used in a FIS

Channel and overbank roughness coefficients (Manning's “n”) were assigned by field inspection, photographs, and textbook resources (References 6 and 7).

In Sampleville, the “n” coefficients for the Mud River and Mud River East Channel range from 0.025 to 0.028 for the channel and 0.038 to 0.055 for the overbanks. For Sandy Creek, the “n” coefficients range from 0.035 to 0.040 for the channel and from 0.040 to 0.065 for the overbanks. For Southside Road Drainage Ditch, the channel “n” coefficient is 0.035 and the overbank “n” coefficient is 0.04.

Select USGS Surface-Water Field Techniques, available at https://wwwrcamnl.wr.usgs.gov/sws/fieldmethods/Indirects/nvalues/index.htm to see examples of some typical channels whose roughness coefficients are known.

This section describes how the starting water surface elevations (WSELs) were determined in a study.

Starting WSELs are the flood elevations used at the first downstream cross section in the step-backwater computations for riverine studies.

For Starting WSELs, absent established downstream elevations or a control cross section, FEMA generally uses normal depths, which are computed using the channel slopes and cross-sectional areas (also known as slope-area method).

This section lists the methodologies used to compute the flood elevations and the various components used in the calculations. The most common methodology used to calculate flood elevations for a stream is a step-backwater computer program, such as HEC-2 or HEC-RAS. For more complex flooding situations, a computer program that models two-dimensional flow may be used.

HEC indicates the model was developed by the US Army Corps of Engineers Hydrologic Engineering Center (HEC). RAS is an acronym for their “River Analysis System”.

When coastal flood hazard areas (V Zones) have been determined, subsection 3.1 and 3.2 of the FIS explains how they were determined. In addition to coastal areas along the Atlantic, Pacific, and Gulf coasts, some areas of the Great Lakes are also considered to be at risk of coastal flooding.

Stillwater elevations are calculated for lakes, ponds and similar bodies of water. Stillwater elevations for Large bodies of water such as the oceans or the great lakes typically include the effects of storm surge.

The FIS typically includes the Summary of Stillwater Elevations that reflect coastal hydrology and coastal transect data information used in coastal hydraulic analyses. Transects for coastal analyses are similar to cross sections for Riverine analyses.

In coastal areas, BFEs are calculated by taking into account the:

• storm surge Stillwater Elevation,
• wave height above the storm surge Stillwater Elevation, 
• amount of wave setup, and
• wave runup (where present).

The factors involved in a typical coastal Hydrologic and Hydraulic analysis include:

Coastal Storm Surge Analysis—Storm surge is the amount of water, combined with the effect of normal tides, that is pushed towards the shore during a storm. The height of the surge is driven by many variables, including the strength and size of the storm, and the speed and direction in which the storm moves. A storm surge Stillwater Elevation (SWEL) model is used in a coastal analysis when supported by the history of storms in the area.

Wave Setup Analysis—Is the increase in water level caused by waves breaking ashore during a storm. This is affected by the height of the waves, the speed at which waves approach the shore, and the slope of the underwater ground near the shore.

Wave Runup - Overland Wave Modeling —Typically, the Wave Height Analysis for Flood Insurance Studies (WHAFIS) model is used which considers water depth, wind speed, vegetative cover, building density, and other factors to predict how the waves run up on the shore and help determine accurate coastal BFEs and flood zone boundaries.

This section includes a general explanation of how tropical and extra-tropical cyclones, such as hurricanes, nor’easters and gales or “Freshwater Furies” on the Great Lakes are reflected in coastal flood studies.

Storm Surge Analyses are used when historical data indicate that storm surges should be incorporated into the Stillwater Elevation (SWEL) for a coastal area.

The “forcing functions” of these large storms (wind speed, central pressure depression, radius to maximum winds, forward speed, and direction of approach to the shoreline) are discussed.

The type and specific name or version of the computer program used to establish the storm surge Stillwater Elevation (SWEL) as well as the sources of data used in the storm surge program that generated the model are included.

Finally, an explanation of the storm surge model and identification of the storm(s) that were used to calibrate the model are included. Storm surge analyses and parameters may include:

• Storm intensity (central pressure depression)
• Radius from storm center to maximum winds
• Forward speed of storm
• Direction of storm path approaching shoreline
• Frequency of the storm occurrence
• Astronomic tide effects
• Joint probability analysis
• Determination of Stillwater Elevation (SWEL)

This table reflects coastal hydrology. The Stillwater Elevation table will also include lacustrine (lake) flooding sources.

The Summary of Stillwater Elevations Table lists stillwater elevations (without waves) for selected recurrence intervals at certain locations.

The general term Stillwater Elevation (SWEL) is used in this table and in this course to include typical Stillwater Elevation and storm surge Stillwater Elevation when used in coastal analyses.

This section provides details of the Coastal Hydraulic studies and findings.

Topics in this section include:

• Wave setup, runup and height analysis
• Storm erosion and effects of shoreline profiles
• Identification of computer programs, field surveys, and topographic maps used during the study
• Transect descriptions

This section discusses how erosion was considered in the coastal flood hazard analysis. Generally, erosion is considered using geographically appropriate methods in determining the equilibrium profile on which the nearshore hydraulics were analyzed.

For example, FEMA’s approach in some east coast areas is to remove 540 square feet of the dune area above the stillwater elevation and adjust the transect profile accordingly. The 540 square-foot criteria is based on the national average.

In order to be considered as a topographic feature during the base flood, the primary frontal dune must have at least 540 square feet of area in cross section above the stillwater elevation.

In order to be considered intact, the eroded profile must be included into the wave height and wave runup analysis.

This section identifies the maps used to delineate the flood zones, explains how transects were used, and lists the date(s) the transects were surveyed.

A transect is a line taken perpendicular to the shoreline. They are similar to the cross sections used in Riverine Hydraulic Analyses and represent a specific portion of the shoreline in which ground cover and ground elevations will have similar hydraulic characteristics during a storm event.

Map data includes:

• Location of Transects
• Numbering of Transects

Note: Newer studies will show transect locations on the FIRM panels as well as on a transect location map in the FIS.

The Transect Descriptions table includes:

• Transect Number
• Description of Transect
• Stillwater Elevation at each Transect
• Maximum Wave or Runup Elevation at each Transect

The transect data table includes:

• Flood Source
• Transect Number
• Stillwater Elevations for All Recurrence Intervals
•  Range of Wave Height and Runup Elevations along the transect

All of the flood elevations, including those listed in the tables in the FIS, are referenced to a specific vertical datum

A datum is an abstract coordinate system with a reference surface that serves to provide known elevations to begin surveys. If a report says that a flood will rise 100 feet, and the datum being used is sea level, it means that the flood will rise 100 feet above the sea level reference surface. Over time, technology has enabled ever more accurate ways to establish a datum that accounts for factors like gravitational pull.

This section indicates the vertical datum used for the information in the hydraulic analysis and presented in the FIS. The vertical datum used in the FIS should not be confused with local vertical datum historically used for navigation, etc. in many areas.

Vertical datum is important to ensure that like values are being used when the information in the FIS, such as the BFE, is being compared to other vertical data. There is a potential for error if the datums representing the height of the flood and height of the grade (ground) are mixed.

As our National Spatial Reference Systems are improved over time, the datum FEMA uses when developing FISs and FIRMs changes with it. For example, FEMA had primarily used the National Geodetic Vertical Datum of 1929 (NGVD 29) in the original FIRMs and FISs for most communities, but began using the North American Vertical Datum of 1988 (NAVD 88) after that new datum was established. In the future, the FISs and FIRMs will likely continue to utilize improvements in this and other aspects of flood hazard mapping

For more information on conversion factors and datums, see NGVD -> NAVD available at https://pubs.usgs.gov/sir/2010/5040/section.html.

Is sea level rise included?

• No, sea level rise is not included because it considers a future condition. The NFIP is not currently permitted to base flood insurance rates on future conditions. Communities are officially encouraged to consider higher regulatory standards. When changes to existing flood hazards occur, the area is re-studied.

Is erosion included?

• Some erosion is included. Where sandy dunes exist, erosion is evaluated to determine how the dune will be affected by a storm event.

Is bluff failure included?

• No, bluff failure and long-term erosional processes are not included. Bluff erosion is usually the result of many factors including, but not limited to, precipitation, irrigation, and undercutting by wave action. Because bluff failure is episodic, a constant rate of change cannot be assumed or applied in the analysis. Assumptions would have to be made to estimate a future condition. When changes to existing flood hazards occur, the area is re-studied.

You have completed Lesson 3.

It covered Section 3.0: Engineering Methods and its five sub-sections:

3.1 – Riverine Hydrologic Analyses

3.2 – Riverine Hydraulic Analyses

3.1 and 3.2 – Coastal Hydrologic & Hydraulic Analyses

3.3 − Vertical Datum

In this lesson, you learned to:

• Describe the difference between hydrologic and hydraulic studies
• Recognize four Riverine Hydrologic methods of analyses
• Recognize three sources of data used in Riverine Hydraulic analysis
• Recognize how the Base Flood Elevation (BFE) is calculated for Coastal Areas
• Recognize information that would be included in the Coastal Hydraulic Analyses
• Indicate why the FIS identifies the vertical datum used in the study

At the end of this lesson, you will be able to:

• Identify floodplain boundary information included in a Flood Insurance Study (FIS)
• Identify floodway information included in a FIS

This section includes two sub-sections:

4.1 – Floodplain Boundaries

4.2 − Floodways

Floodplain boundaries show the areas that would be inundated by a flood of a given frequency. The Flood map shows the floodplain boundaries for the flood having a 1-percent annual chance (100-year flood) and, in some areas, the flood having a 0.2-percent annual chance (500-year flood).

This section indicates the scales, contour intervals or topographic accuracy, and dates of the topographic model or maps used to delineate the floodplain boundaries.

The floodplains are delineated using flood elevations at cross sections or transects and by interpolating between cross sections or transects using topographic maps.

For newer flood maps, digital elevation models are typically derived from LiDAR and are used to develop digital cross sections to improve flood elevation accuracies.

A "Regulatory Floodway" means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.

Communities must regulate development in these floodways to ensure that there are no increases in flood elevations.

For streams and other watercourses where FEMA has provided Base Flood Elevations (BFEs), but no floodway has been designated, the community must review floodplain development on a case-by-case basis to ensure that increases in water surface elevations beyond a certain amount do not occur, or identify the need to adopt a floodway if adequate information is available. 

This section defines the floodway and explains how it is used for floodplain management.

Also, this section lists which streams have floodways and describes how floodways were determined.

You have completed Lesson 4.

It covered Section 4.0: Floodplain Management Applications and its two sub-sections. .

4.1 – Floodplain Boundaries

4.2 − Floodways

In this lesson, you learned to:

• Identify floodplain boundary information included in a Flood Insurance Study (FIS)
• Identify floodway information included in a FIS

At the end of this lesson, you will be able to:

• Identify what is defined and identified in FIS Section 5.0: Insurance Application
• Identify what is described in FIS Section 6.0: Flood Insurance Rate Map (FIRM)
• Identify information included in FIS Section 7.0: Other Studies
• Identify the locations provided in FIS Section 8.0: Locations

The remaining sections of the FIS are:

Section 5.0: Insurance Application

Section 6.0: Flood Insurance Rate Map

Section 7.0: Other Studies

Section 8.0: Location of Data

Section 9.0: Bibliography and References

Section 10.0: Revisions (not in all Flood Insurance Studies)

For insurance applications, areas on Flood Maps are designated by zones based on the flood risk potential computed in the analysis.

This section identifies and defines all flood insurance zone designations shown on the effective Flood Map. These typically include Zones, A, AE, AH, AO, AR, A99, V, VE, X and D.

Older Flood Insurance Studies may include a Flood Insurance Zone Data Table. This is where you find information on Zones A1–A33 or Zones V1–V33. These zones are now all considered to be either Zone AE or Zone VE. This table presents information that was used for insurance applications but is not used any longer.

This section briefly describes the purpose of the FIRM for flood insurance and floodplain management applications. The FIRM itself is a graphic representation of data summarized in the FIS.

For flood insurance applications, the FIRM designates flood insurance rate zones as described in Section 5.0 and, in the 1-percent-annual-chance floodplains studied by detailed methods, the FIRM will show selected whole-foot BFEs or average flood depths. The Rounded BFE's on the FIRM should never be used when accurate BFEs are required for permitting development or insurance rating purposes.

Insurance agents use zones and BFEs in conjunction with information on structures and their contents to assign premium rates for flood insurance policies.

For floodplain management applications, the map shows by tints, screens, and symbols, the 1- and 0.2-percent-annual-chance floodplains, floodways, and the locations of selected cross sections used in the hydraulic analyses and floodway computations.

FIS Section 7.0: Other Studies

This section includes a list of previous FISs that are superseded by the publication of the new FIS.

FIS Section 8.0: Location of Data

This section identifies the FEMA Regional Office and the Community Map Repository (i.e., the local community office that keeps a copy of the FIS) and gives their addresses.

FIS: Section 9.0: Bibliography and References

This section lists References, including engineering references and earlier FEMA studies.

This section is included in some Flood Insurance Studies and provides brief information on revisions to the FIS.

The information provided may include:

• the development or project that necessitated the revision,
• the name of the agency or engineering firm that preformed the analyses,
• descriptions of the hydrologic and hydraulic analyses, and
• identification of the maps used to determine the floodplain boundaries.

You have completed Lesson 5.

It covered Flood Insurance Study:

Section 5.0: Insurance Application

Section 6.0: Flood Insurance Rate Map

Section 7.0: Other Studies

Section 8.0: Location of Data

Section 9.0: Bibliography and References

Section 10.0: Revisions

 

In this lesson, you learned to:

• Identify what is defined and identified in FIS Section 5.0: Insurance Application
• Identify what is described in FIS Section 6.0: Flood Insurance Rate Map (FIRM)
• Identify information included in FIS Section 7.0: Other Studies
• Identify the locations provided in FIS Section 8.0: Locations

At the end of this lesson, you will be able to:

• Identify the information contained in the Flood Profiles in a Flood Insurance Study (FIS)
• Identify what floodplain determination must be made by using the flood profile

The Flood profiles are important supporting data in the FIS.

Other Supporting Data within the FIS sections and appendices includes:

• Vicinity Map
• Summary of Discharges Table
• Floodway Data Table
• Summary of Stillwater Elevations Table
• Flood Boundary and Floodway Map (FBFM) or Flood Insurance Rate Map (FIRM)
• Transect Data (in coastal and Great Lake communities)

Remember, this is a generalized structure. Individual studies may vary from the Flood County generic FIS in format but will convey the study findings in a similar format.

A flood profile is a graph of the flood elevations along the centerline of a stream. The horizontal scale is the length of the stream. The vertical scale is the elevation of ground, water surfaces, etc.

The flood profile in the FIS always shows the profiles for the base or 1% annual chance (100-year) flood event. The flood profile also typically shows the 10-percent (10 year), 4-percent (25 year), 2-percent (50 year) and 0.2-percent (500 year) annual chance flood event profiles. Note: The 4-percent (25 year) flood profile is more typical on newer studies.

Other information shown on the flood profile includes the cross sections shown on the flood maps, the elevation of the stream bed, the location of stream crossings such as bridges and culverts along with other hydraulic structures like dams or weirs.

In accordance with NFIP requirements, flood profiles must be used to determine an accurate Base Flood Elevation (BFE) for a location in a riverine floodplain. BFE information displayed with a wavy line on the Flood Insurance Rate Maps are approximate BFEs rounded to the nearest foot.

The flood profile graph shows flood events, stream bed, cross sections, and road crossings.

In this example, the Y axis (vertical) is Elevation (Feet NGVD) and the X axis is distance, Stream distance in feet above confluence with Lake Hightower.

Floodway data tables are part of the FIS supporting data. Data for the Cross sections shown on the FIRM, including accurate BFE's, are listed on the Floodway data tables. To find the Base Flood Water-Surface Elevation find the cross-section ID and the corresponding elevation in the Regulatory column.

Select Floodway Data Table to open in a new window an image of the Floodway Date table that includes the following BFEs for cross section AJ, AK, and AL outlined to show the Regulatory intersection on the data table.

There are three common elements between the FIS Flood Profile and the Flood Insurance Rate Map. They are:

1. centerline of stream (stream bed)
2. road crossings
3. cross section locations

There are three common elements between the FIS Flood Profile and the Flood Insurance Rate Map. They are:

1. centerline of stream (stream bed)
2. road crossings
3. cross section locations

This slideshow presents the 7 steps for identifying an accurate BFE for a specific property using the flood profile. This is the most common and important use of the FIS, especially for Surveyors and Floodplain Administrators. Note: The rounded BFE's shown on a FIRM panel were used by insurance agents to rate flood insurance policies.

Scroll down to see captions.

There can be some variance in the BFE calculations using the FIS and FIRM methods.

In our example, a correct BFE could have easily ranged from 454.4 to 454.8 feet with pencil sharpness and other factors accounting for the range. Because of this, it is recommended that you use the top of the profile line to be conservative and add a little safety margin.

Remember:

• Flood Profiles are not necessarily “smooth” or a straight line between cross sections. These drops and rises between Cross Sections are represented in the Flood Profile.
• The NFIP requires using the FIS document to determine the BFE for permitting development.
• The Floodway Data Table can be used to help eliminate large errors. Look at the regulatory BFE's of the cross section immediately above and below the site and make sure the accurate BFE you determined from the flood profile falls between those two numbers.

You have completed Lesson 6.

It covered Flood Profiles.

In this lesson, you learned to:

• Identify the information contained in the Flood Profiles in a Flood Insurance Study (FIS)
• Identify what floodplain determination must be made by using the flood profile

You also learned the seven steps to finding the BFE for a specific property using the Flood Profile and FIRM

Step 1 of 7: Find the location of the property and structure on the FIRM.

Step 2 of 7: Draw a site specific “BFE line” perpendicular to the flow of the stream.

Step 3 of 7: Identify the FIRM/FIS common element nearest to the intersection of the BFE line and Centerline.

Step 4 of 7: Measure the distance from closest common element to the property BFE line.

Step 5 of 7: Add up the measurements from the FIRM to use with the FIS Flood Profile.

Step 6 of 7: Identify the 1% Flood Profile for the property.

Step 7 of 7: Identify the BFE for the property.

This lesson helps you reviews the key points for each lesson before taking the course exam.

Lesson 0 presented the course objectives.

Participants will be able to:

• Identify information contained in a Flood Insurance Study (FIS)
• Explain what the information in a FIS means
• Describe how to use the information in the FIS

This lesson discussed the following topics:

• A Flood Insurance Study (FIS) is a report prepared by FEMA that summarizes an analysis of the flood hazards in a community.
• The study used to prepare a FIS is also used to prepare a flood map that shows the flood hazards areas in a community.
• The general structure of a FIS has ten sections and supporting data.
• FIS Section 1.0: Introduction, has three subsections.
• 1.1 Purpose of Study identifies the communities involved and explains that flood risk data was developed to establish flood insurance zones and assist the communities in mitigating flood hazards.
• 1.2 Authority and Acknowledgements identifies NFIP authority, the study contractors, contract numbers and the date work was completed for each contract.
• 1.3 Coordination documents the Initial and Final Consultation and Coordination (CCO) meeting, identifies sources of information, and provides the dates the study was presented to the community and other stakeholders.

In this lesson we discussed the following topics:

• Section 2.0 Area Studied, has four subsections:
• 2.1 Scope of Study names streams and identifies if the method of study used, detailed or approximate.
• 2.2 Community Description describes the location, climate, and many of the physical characteristics of the community.
• 2.3 Principal Flood Problems includes historical data of major floods and identifies gage locations.
• 2.4 Flood Protection Measures includes information about channelization projects, levees, dams, non-structural flood control measures, and flood control projects that do not provide protection to at least the 1% annual chance flood.

In this lesson we discussed the following topics:

• Hydrologic analyses study the amount of water and Hydraulic analyses study the flood height or elevation of water.
• Newer FISs will contain hydraulic models with multiple frequencies: 10-percent (10 year), 4-percent (25 year), 2-percent (50 year), 1-percent (100 year), and 0.2-percent (500 year) annual chance exceedance events.
• FIS Section 3.0 Engineering Methods has three Subsections.
• 3.1 Riverine Hydrologic Analyses includes:
• Sources of data (topographical maps, gage data, land use maps, and soil information)
• Methods of analysis (drainage areas-discharge curves, gage data analysis, regression equations, and rainfall-runoff models)
• Summaries of the drainage areas and peak discharges.
• 3.2 Riverine Hydraulic Analyses includes:
• Sources of data (cross sections, roughness coefficients, starting water surface elevations), and
• Methodologies describe how the flood elevations and the various components were calculated.

In this lesson we discussed the following topics:

• FIS Section 3.0 Engineering Methods has three Subsections.
• 3.1 & 3.2 Coastal Hydrologic and Hydraulic Analyses
• Explains how the coastal flood hazard areas are determined.
• Discusses factors involved in coastal Hydrologic and Hydraulic analysis (coastal storm surge analysis, wave setup analysis and overland wave modeling from wave runup).
• Includes the Summary of Stillwater Elevations that reflects coastal hydrology.
• 3.2 Coastal Hydraulic Analyses:
• Discusses factors effecting wave setup, runup and height analysis.
• Explains FEMA’s approach to storm erosion and effects of shoreline profiles.
• Identifies the computer program(s) used during the study.
• Explains how transects are used and the date surveyed.
• 3.3 Vertical Datum identifies the specific vertical datum used so that users can ensure they don’t mix datum.

In this lesson we discussed the following topics:

• Section 4.0 – Floodplain Management Applications has two sections.
• 4.1 Floodplain Boundaries:
• Explains that floodplain boundaries show the areas that would be inundated by a flood of a given frequency.
• Indicates the scales, contour intervals or topographic accuracy, and dates of the topographic model or maps used to delineate the floodplain boundaries.
• 4.2 Floodways:
• Defines the floodway.
• Explains how it is used for floodplain management.
• Lists which streams have floodways.
• Describes how floodways were determined.

In this lesson you learned:

• Section 5.0 Insurance Applications explains that areas on Flood Maps are designated by zones based on the flood risk potential computed in the analysis and defines all the zones shown on the effective Flood Map.
• Section 6.0 Flood Insurance Rate Map (FIRM) explains the purpose of the FIRM for flood insurance and floodplain management.
• Section 7.0 Other Studies includes a list of previous FISs that are superseded by the publication of the new FIS.
• Section 8.0 Location of Data identifies the location of the FEMA Regional Office and Community Map Repository.
• Section 9.0 Bibliography and References lists references used in the FIS.
• Section 10.0 Revisions, if included in the FIS, provides information on revisions to the FIS.

In this lesson, you learned:

• A flood profile is a graph of the flood elevations along the centerline of a stream.
• The flood profiles in the FIS show the profiles for the 100-year flood event, and often show the profiles for the 10-, 25-, 50-, and 500-year flood events. These equate to the 10%, 4%, 2%, 1% and 0.2% annual probability events.
• Other information shown on the flood profiles include:
• Cross sections shown on the flood maps.
• The elevation of the stream bed.
• The location of stream crossings such as bridges and culverts along with other hydraulic structures like dams or weirs.
• The flood profiles must be used to determine an accurate Base Flood Elevation (BFE) for a location in a riverine floodplain.

You have completed Lesson 7.

You can go back and review any portion of the course or continue to the course exam.

100-year flood: The flood having a 1-percent chance of being equaled or exceeded in any given year; also known as the base flood. The 1-percent annual chance flood, which is the standard used by most Federal and state agencies, is used by the National Flood Insurance Program (NFIP) as the standard for floodplain management and to determine the need for flood insurance. A structure located within a special flood hazard area shown on an NFIP map has a 26 percent chance of suffering flood damage during the term of a 30-year mortgage.

Base Flood: The flood having a 1-percent chance of being equaled or exceeded in any given year; also known as the 100-year flood. The base flood, which is the standard used by most Federal and state agencies, is used by the National Flood Insurance Program (NFIP) as the standard for floodplain management and to determine the need for flood insurance. A structure located within a special flood hazard area shown on an NFIP map has a 26 percent chance of suffering flood damage during the term of a 30-year mortgage.

Base Flood Elevation: The height of the base flood, usually in feet, in relation to the National Geodetic Vertical Datum of 1929, the North American Vertical Datum of 1988, or other datum referenced in the Flood Insurance Study report, or depth of the base flood, usually in feet, above the ground surface.

Cross Section: A line developed from topographic information, across a floodplain at which a computation of flood flow has been made to establish a potential flood elevation. Cross sections are shown on the Flood Boundary Floodway Map, Flood Insurance Rate Map, and/or Flood Profiles of a Flood Insurance Study.

Cubic feet per second (cfs): Typical units used to express the rate of flow of surface water in open channels. One "cfs" is approximately equal to 7.5 gallons per second.

Datum: FEMA's 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. The National Geodetic Vertical Datum (NGVD) is the national standard reference datum for elevations, formerly referred to as Mean Sea Level (MSL) of 1929. NGVD is used as the reference datum on most FIRMs.

Discharge: The volume of water that passes a given location within a given period of time. Usually expressed in cubic feet per second.

Federal Emergency Management Agency (FEMA): An independent agency of the Federal government, founded in 1979, which reports directly to the President. FEMA is responsible for identifying and mitigating natural and man-made hazards. The agency's mission is: to reduce loss of life and property and protect our nation's critical infrastructure from all types of hazards through a comprehensive, risk-based, emergency management program of mitigation, preparedness, response and recovery.

Flood (also Flooding): A general and temporary condition of partial or complete inundation of normally dry land areas. For flood insurance claim purposes, two or more structures must be inundated before flood damage will be covered.

Flood Hazard Boundary Map (FHBM): Initial map issued by FEMA to identify approximate Special Flood Hazard Areas (SFHAs) within a community.

Flood Insurance Rate Map (FIRM): A map on which the 100-year (1% annual chance) and 500-year (0.2% annual chance) floodplains, Base Flood Elevations, and risk premium zones (and floodway information on Map Initiatives FIRMs) are delineated to enable insurance agents to issue accurate flood insurance policies to homeowners in communities participating in the National Flood Insurance Program.

Flood Insurance Study (FIS): An examination, evaluation, and determination of flood hazards and, if appropriate corresponding water-surface elevations. The resulting reports are used to develop Flood Insurance Rate Maps. Also known as a flood elevation study.

Flood Profile: A cross-sectional drawing showing the contiguous cross sections along a stream, with ground elevations and potential flood elevations plotted.

Floodplain or Flood-Prone Area: Any land area susceptible to inundation by water from any source.

Floodway: Channel of a stream plus any adjacent floodplain areas that must be kept free of encroachment so that the 100-year flood discharge can be conveyed without increasing the elevation of the 100-year flood by more than a specified amount (1 foot in most states).

HEC-2: A step-backwater program developed by the U.S Army Corps of Engineers Hydrologic Engineering Center for use in calculating water-surface profiles for steady, gradually varied flow in natural or man-made channels. Levee Levees are man-made structures or fill that extend above the flood elevation to prevent lower areas from being inundated by the flood.

Manning’s “n” Roughness Coefficient: Coefficient used to account for the friction caused by earthen, vegetative, and/or man-made surfaces within a floodplain cross section. The coefficient, n, is commonly used to represent flow resistance for hydraulic computations of flow in open channels. The procedure for selecting n values is subjective and requires judgment and skill that is developed primarily through experience. The expertise necessary for proper selection of n values can be obtained in part by examining characteristics of channels that have known or verified roughness coefficients. A table of Manning's "n" values is available from the "Help" pull-down menu in the Quick-2 program.

Map Repository: The location where a community's flood maps are kept; usually the local zoning and planning office.

Map Service Center (MSC): The Map Service Center distributes National Flood Insurance Program (NFIP) materials to a broad range of customers, including Federal, State, and local government officials; real estate professionals; insurance providers; appraisers; builders; land developers; design engineers; surveyors; lenders; and the public. MSC products include: Digital Flood Insurance Rate Maps, Flood Insurance Rate Maps, Flood Insurance Study reports, Digital Q3 flood data, Community Status Book, Flood Map Status Information Service, Letters of Map Change, and NFIP Insurance Manuals.

National Flood Insurance Program (NFIP): Federal insurance program under which flood-prone areas are identified and flood insurance is made available to residents of participating communities that agree to adopt and enforce floodplain management ordinances to reduce future flood damage.

Normal Depth: The depth expected for a stream when the flow is uniform, steady, one dimensional, and is not affected by downstream obstructions or flow changes. This is the usual calculation that is utilized to determine Base Flood Elevations for property or structures in approximate (Zone A) areas.

Overbank: The area of a cross section that is found outside of the channel bank stations on either side of the stream channel.

Peak Discharge: The peak volume of water that passes a given location within a given period of time. Usually expressed in cubic feet per second.

Perpendicular to Flow Path: Cross sections should be plotted so that they are oriented in a manner that is perpendicular to the flow path. Plotting cross sections in this manner requires that the user examine the topography to determine the direction in which the water is most likely to flow in relation to different points along the proposed cross section line. Typically, this can be achieved by ensuring that the cross section line crosses each contour on the topographic map at or near a 90° angle.

Scale: A representative fraction of map distance to ground distance. Example: 1:12,000 is the representative fraction in which one unit of measure on the map is equal to 12,000 of the same units of measure on the ground. Federal Emergency Management Agency map scales are expressed in a ratio of 1" of map distance equal to a given number of feet on the ground.

Step-Backwater Analysis: Method used in Quick-2 (and other modeling programs) to analyze multiple cross sections. Water-surface elevations are determined for all sections based on a given discharge. The initial water-surface elevation is automatically determined by the normal depth method or by direct input of a water-surface elevation or depth.

Water-Surface Elevation: The height, in relation to the National Geodetic Vertical Datum of 1929 (or other datum, where specified) of floods of various magnitudes and frequencies in the identified floodplains of coastal or riverine areas