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.