Flood Protection Glossary of Terms
Acronyms, technical, and bureaucratic terms abound in presentations and reports regarding
flood protection. The following was compiled to help sort out and simplify some of the more
frequently used terms.
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100-year flood protection
This is a measure of strength and stability of levees used by the Federal Emergency Management
Agency. It refers to a level of strength sufficient to withstand a flood so serious that it
is likely to occur only once in 100 years. It is the standard
FEMA requires before they will certify,
or accredit a levee.
FEMA's flood insurance
program requires this level of protection in order
to provide insurance at preferred risk (lower) rates.
BFE
This stands for Base Flood Elevation, and refers to the elevated water level expected in that
once-in-100-years flood event.
Closure structure
All openings in levee structures are required to be equipped with sufficiently strong,
stable closures, such as gates or stoplogs.
Core sampling
This is a process by which levee strength is tested. Equipment drills deep into the levees
at various points to test the stability of the soil and other materials. Core samples help
determine whether levee sections meet the 100-year-standard.
DWR
This acronym refers to the State Department of Water Resources, which owns the Yuba City
basin levees, has primary responsibility for funding levee projects in California, and has
oversight responsibilities to the local levee districts, which manage and maintain the
levees on a day-to-day basis.
FIRM
Another FEMA term, this
stands for Flood Insurance Rate Maps. It refers to the official
maps of flood plain limits, features and related data. The maps are issued by
FEMA to
identify risk “zones” for setting flood insurance rates. Only properties within zones
on the map where levees are accredited as meeting the 100-year-protection level
will be able to buy insurance at preferred risk (lower) rates. DFIRM refers to a
digital such map. Among FEMA's
objectives is to provide internet access to the maps.
Freeboard
Freeboard refers to the vertical distance from the water’s surface to the top of the levee.
Interior drainage
The term refers to the ability to get water from the dry side of the levee to the wet side of the levee.
Interior flooding/exterior flooding
The terms simply refer to flooding on the dry side or wet (river) side of a levee, respectively.
Levee accreditation
Often referred to as levee certification, this status is given to a levee when it is accepted by
FEMA as meeting all current
FEMA standards, including the
100-year-protection level.
Levee districts/reclamation districts
Local levee or reclamation districts are government entities responsible for the
day-to-day operation, management and maintenance of levees, with oversight by
the State Department of Water Resources.
Proposition 1E
This is one part of the statewide infrastructure bond measure approved by the voters in
November, 2006. Most of 1E includes the bond funds earmarked for flood control and
related improvements.
Seepage
Where levees or their foundations are not watertight, seepage occurs through or under the levee.
Excessive seepage can weaken the structure’s stability or physically erode the structure from the inside out.
Settlement analysis
Core sampling and other tests help engineers determine how much the soil and other
materials in a levee have settled or can be anticipated to settle.
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