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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.


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 has only a 1% probability of occurring in any given year. The agency that owns a levee must certify that a levee provides 100-year flood protection before FEMA can "accredit" a levee. FEMA's flood insurance program requires this level of protection in order to provide insurance at preferred risk (lower) rates.

Base Flood
This stands for the design flood event with a 1% probability of occurring in any given year. Also sometimes referred to as a 100-year flood. Note: the term "100-year flood" is inaccurate, as it infers that a base flood can only occur once every 100 years. In fact, a base flood can occur in any given year.

This stands for Base Flood Elevation, and refers to the anticipated water surface elevation during a Base Flood for a specific location.

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.

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.

Another FEMA term, this stands for Flood Insurance Rate Maps. It refers to the official maps of floodplain limits, features and related data. The FIRMs are issued by FEMA to identify risk "zones" for setting flood insurance rates. DFIRM refers to a digital such map. The available FIRMs for Sutter County are posted on this website.

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 providing at least 100-year flood protection. FEMA cannot accredit a levee unless and until the levee owner certifies that the levee meets all current FEMA standards.

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.

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.

For Floodplain Management purposes a structure is defined as a building with at least two walls and a roof, said building being principally above ground. This includes a gas or liquid storage tank, and also includes manufactured homes.