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An ~pproximate depth of flooding can bo established by sub- tracting the ground elevatibn estimated from the contour map from the previously determined water surface elevation. To locate the edge of the flood plain by simple scaling methods, neasure the distance on the map from two or more physical features that can be identified both on the map and ih the field to the edge of the flood plain. The flood plain limits can then be es- tablished by laying out the measured distances in the field. GLOSSARY Backwater Effect - The rise in surface elevation of flowing water upstream from and as a result of an obstruction to flow. Basin _ An enclosed or partly encl~sed water area or de- pression on the surface of the earth. Channel - A natural or artificial watercourse with definite bed and banks to ~onfinc and convey flowing water. Designated Flood Plain - The area designated as a flood plain by ofhCl.al actl.on of the (board of county commissioners) (city council) with the prior concurrence of the ColoradO Water Conserva- tion Board. Flood basin that A temporary rise in the water level of stre~m or results in inundation. Flood frequency - The average frequency, statistically de- termined, for WhlCh a specific flood flow magnitude may be equalled or exceeded. (Frequency, expressed as an occurrence within a speci- fied number of years, is the equivalent of recurrence interval which is the average time interval between actual occurrences of a flood event of a given or greater magnitude of flow). Flood profile - a graph or a plotting of water surface ele- vations of a specl.fic flood frequency of a stre~~ or basin. Flood Plain (general definition) An area along and adjacent to a stream or basl.fi whl.ch l.S subJect to flooding. Flood Ph.in (re "laLol: .Jefinition) - I,:,. ;:lrcJ. i:-:: ;:l;';C il.cjil.cent to a stream, W ~c area l.S su Ject to Tooding as the result of the occurrence of an intermediate regional flood and which area thus is so adverse to past, current, or foreseeable construction or land use <1S to constitute a significant hazard to public health and safety or to property. Intermediate Re?iOnal Flood- A type of flood, including the water surface elevatl.on and terrl.torial occupatio:1 thereof, which can be expected to occur at any time in a given area based upon recorded historical prccipit<<l.ion "nu oLhe!: v"lid d"til, Zut ;.:i':h an average statistical one percent chancQ of being equalled or ex- ceeded during anyone year. The t.,rm is used intercha.ngeably with a one percent flood or one hundred year flood. Obstruction - Any dam, wall, wharf, emb~nkment, levee, dike, pile, abutment, projection, exc~v~tion, channel rectification, bridge, conduit, culvert, building, wire, fence, rock, gravel, -15- -16-