Laserfiche WebLink
<br />Appendix 1 <br /> <br />Glossary of Floodplain Analysis Teras <br /> <br />1-Percent Annual Chance Flood: the flood that has a one-percent chance of being <br />equaled or exceeded on the average in any given year; equivalent to the 100-year <br />flood. <br /> <br />100-Year Flood: the flood that is equaled or exceeded once in 100 years on the <br />average; equivalent to the one percent annual chance flood. <br /> <br />Alluvial Streaa: a stream that has formed its channel by the process of <br />aggradation. The sediment in the stream is similar to the material in the bed <br />and banks. <br /> <br />Ba.e Flood. the flood having a one percent chance of being equalled or exceeded <br />in any given year (the 100-year flood). <br /> <br />Ba.e Flood Elevation (BPE). the water-surface elevation associated with the base <br />flood. <br /> <br />COnveyance: a measure of the carrying capacity of the channel section. Flow <br />(Discharge (Q)) is directly proportional to conveyance (K). The pro~rtional <br />factor is the square root of the energy slope; expressed as Q = K * S . <br /> <br />Cross Section: a vertical profile of the ground surface taken perpendicular to <br />the direction of flood flow. The profile is defined by coordinates of ground <br />elevation and horizontal distance (station). <br /> <br />Discharge: a measure of flow volume per unit of time. <br />flow are usually cubic feet per second (cfs). <br /> <br />In hydrology, units of <br /> <br />Exceedence Frequency: the frequency that a flood of a certain discharge will be <br />equaled or exceeded in any given year; equal to the inverse of the recurrence <br />interval. <br /> <br />Flood: (a) a general and temporary condition of partial or complete inundation <br />of normally dry land areas from: (1) the overflow of inland or tidal waters; (2) <br />the unusual and rapid accumulation or runoff of surface waters from any source; <br />(3) mudslides (Le., mudflows), which are proximately caused by flooding as <br />defined in (a)(2) above and are akin to a river of liquid and flowing mud on the <br />surfaces of normally dry land areas, as when earth is carried by a current of <br />water and deposited along the path of the current. (b) The collapse or <br />subsidence of land along the shore of a lake or other body of water as a result <br />of erosion or undermining caused by waves or currents of water exceeding <br />anticipated cyclical levels or suddenly caused by an unusually high water level <br />in a natural body of water, accompanied by a severe storm, or by an unanticipated <br />force of nature, such as flash flood or abnormal tidal surge, or by some <br />similarly unusual and unforeseeable event, which results in flooding as defined <br />in (a) (1) above. <br /> <br />Flood Crest: the maximum height of a flood, usually measured as an elevation or <br />depth. <br /> <br />Flood Bazard: the potential for inundation that involves the risk to life, <br />health, property, and natural floodplain values. <br /> <br />Al-l <br />