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I I I I I I I I I I I I I I I I I I I SECTIONFIVE GLOSSARY OF RRMS Flood An overflow on lands that are not normally covered by water,and that are used or usable by man. Floods have two essential characteristics: (1) the inundation of land is temporary; and (2) the land is adjacent to and inundated by overflow from a river, stream, an ocean, a lake, or other body of standing water. 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 drainage channels, creation of unsanitary conditions or other unfavorable situations by deposition of materials in stream channels during flood recessions, rise of ground water coincident with increased streamflow, and other problems. Flood Crest The maximum stage or elevation reached by the waters of a flood at a given location. FloodDlain The relatively flat area or low lands adjoining the channel of a river, stream, water course, ocean, lake, or other body of standing water which has been or may be covered by flood-water. Flood Profile A graph showing the relationship of water surface elevation 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. Floodwav The regulatory floodway, which is adopted into the community's floodplain management ordinance, is the stream channel plus that portion of the overbanks that must be kept free from encroachment in order to discharge the I-percent-annual-chance flood without increasing flood levels by more than LO foot (some states specify a smaller allowable increase). Head Loss The effect of obstructions, such as narrow bridge openings or buildings, that limit the area through which water must flow, raising the surface of the water upstream from the obstruction. URS 5-1 Left Bank The bank on the left side of a river, stream, or water course looking downstream. Reference Point . A numbered point identifying a specific location used for correlating the data shown in various forms throughout the report. , 1 " Right Bank The bank on the right side of a river, stream, or water course looking downstream. 10%.5%.1%. and 0.2% 00-. 50-.100-, and 5oo-Year) Probability Flood A flood having a 10, 2, 1, or 0.2 percent probability (chance), respectively, of occurrence in any year or an average frequency of occurrence in the order of once in 10, 50, 100, or 500 years, respectively. The flood may occur in any year. It is based on statistical analyses of streamflow records and analyses of rainfall and runoff characteristics in the general region of the watershed. Top ofWaterwav This is the roof of the opening in a stream crossing through which water flows under normal conditions. It is the underside of the deck span - sometimes called "low steel," the roof of a box culvert, or the crown of an arched or circular cui vert.