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8 II. GLOSSARY This section defines terms encountered frequently in flood plain management. The definitions are simplified to meet the needs of those who are not specialists in the field, More detailed and scientific definitions of these and other terms can be found in several of the publications listed in the bibliography. Backwater Effect - The rise in water surface elevation caused by some obstruction such as a narrow bridge opening, buildings or fill material that limits the area through which the water must flow. Also rE:.ferred to as "heading up". Base Flood Elevation (BFE) - A term used by the State of Colorado and FEMA to indicate the minimum flood elevation to be used by a community as a basis for its flood plain managE:.- ment rE:.gulations; presently required by regulation to be that flood which has a one-percent chance of being E:.qualed or exceeded in any given year. Also known as a 1 DO-year flood or one-percent chance flood. Base Flood Plain - The flood plain that would be inundated by a 1 DO-year (one-percent chance) flood. Basement Floor - The lowest floor level below thE, main floor of a building, Basin - The total area from which surface runoff is carried away by a drainage system. Other comparable terms are "drainage area", "catchmE,nt area", and "watershed". Building Code - RE:.gulations adopted by a governmental body which set forth standards for the construction of buildings and other structUrE" for the purpose of protecting the health, safety and general welfare of the public. C.F,S, - Cubic feet per second, Used to describe the amount of flow passing a given point in a stream channel. One cubic foot per second is equivaent to approximately 7.$ gallons per second, Channel - A natural or artificial watercourse with definite bed and banks to confine and con- duct flowing water. Channel Capacity - The maximum flow which can pass through a channel without overflowing the banks. Cross Section - A graph or plot of ground elevation across a stream valley or a portion of it, usually along a line perpendicular to the stream or direction of flow, Designated Flood Plain - The flood plain boundary delineated by the base flood elevation after it has been approved by Colorado Water Conservation Board and adopted by the local community. Designated Floodway - The channel of a stream and that portion of the adjoining flood plain designated by a regulatory agency to be kept free of further development to provide for unobstructed passage of flood flows. The designated f100dway is within the designated flood plain. Design Flood - Commonly used to mean the magnitude of flood used for design and opera- ion of flood control structures or other protective measures. It is sometimes used to denote the magnitude of flood used in flood plain regulations Erosion - The process of the gradual wearing aWay of land masses due to friction forces created between flowing water and the ground surface.