FLOOD00155 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I Channel - A natural or artificial watercourse definite bed and banks to confine and periodically flowing water. Cloudburst - A sudden and extremely heavy downpour of rain that is small in areal extent; of short duration; and may be accompanied by lightning, thunder, and strong gusts of wind. of perceptible extent with conduct continuously or Flood Crest - The maximum stage or elevation reached by the waters of a flood at a given location. Flood Frequency - (see Probabi 1 ity) The average recurrence i nterva 1 of speciflc dlscharges or water stages which cause flooding. Flood Peak - The maximum instantaneous discharge of a flood at a given location. It usually occurs at or near the time of the flood crest. GLOSSARY Backwater Effect - The rise in surface elevation of flowing water upstream from and as a result of an obstruction to flow. Conveyance Capacity a. Channel conveyance capacity is the rate of discharge, in cubic feet per second, which can flow in a water course with the water surface not greater than the height of the channel banks. b. Floodway conveyance capacity is the rate of discharge in the overflow portion of the floodway which can pass through a specified area at depths and velocities governed by the hydraulic dimensions of the floodway. Designated Floodplain - The area designated as a floodplain by official act ion of the board of county commi ss ioners or city counc il with the prior concurrence of the Colorado Water Conservation Board. Flood - An overflow of lands nor normally covered by water and that are used or usable by man. Floods have two essential characteristics: the inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river or stream or an ocean, lake or other body of standing water. Floodplain - An area in and adjacent to a stream, which area is subject to floodlng as the result of the occurrence of a 100-year flood and which area thus is so adverse to past, current, or foreseeable construction or 1 and use as to constitute a significant hazard to public health and safety or to property. Flood Profile - A graph showing the relationship of water surface elevations to location, the latter generally expressed as distance above mouth for a stream of water flowing in an open channel. It is generally drawn to show surface elevation for the crest of a specific flood, but may be prepared for conditions at a given time or stage. Flood Stage - The stage or elevation at which overflow of the natural banks of a stream or body of water begins in the reach or area in which the elevation is measured. Floodway Zone - The channel of a stream and those portions of the adjoinlng floodplain which are reasonably required to carry and discharge the floodwaters of a lOO-year flood. It is the designated floodplain less than the low hazard zone, if any such low hazard zone has been ident ifi ed. If no low hazard zone has been i dent ified, then the terms "designated floodplain" and "floodway zone" shall be considered as being synonymous. Normally a flood is considered as any temporary rise in streamflow or stage, but not the ponding of surface water, that results in significant adverse effects in the vicinity. Adverse effects may include damages from overflow of land areas, temporary backwater effects in sewers and local drainge channels, creation of unsanitary conditions or other unfavorable situations by deposition of materials in stream channels during flood recess ions, use of ground water coi ncident with increased streamflow, and other problems. Flood, 100-Year - A type of flood, including the water surface elevation and territorial occupation thereof, which can be expected to occur at any time in a given area based upon recorded historical precipitation and other val id data, but with an average statistical one percent chance of being equalled or exceeded during anyone year. The term is used interchangeably with a one percent flood or Intermediate Regional Flood. (See definition for Intermediate Region Flood). Intermediate Regional Flood - A type of flood, including the water surface elevation and territorial occupation thereof, which can be expected to occur at any time in a given area based upon recorded historical precipitation and other valid data, but with an average statistical one percent chance of being equalled or exceeded during any one year. The term is used interchangeably with a one percent flood or one hundred year flood. (See definition for 100-year flood.) Left Bank - The bank on the left side of a river, stream or water course as the observer looks downstream. Low Hazard Zones - That area of the floodplain in which the waters of a lOD-year flow wi 11 not attain a max imum depth greater than one and one-ha 1f feet. Probabil ity - The annual chance of occurrence of specified hydrologic events, such as rainfall over a specified area of peak discharge at a specified location expressed in percent, e.g., 5 percent representing one chance in 20 of the event occurring in any year or an average recurrence of once in twenty years. 25