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Flood of fi'ecord -- The greate:,t flood recorded for a location. Floodplain n The low lands adjoining the- channel of a river, creel<;, Btream or other watHr course, lake, or body of standing water which may b~~ or has been covmed by a floodwater.- Floodplain Delineation n The process of Showing in grapl,ic form on a map or photo mo:saic, areas which may be or have been inundated by a specific or predicted flood. Floodplain Information Stucfy -- A study prepared using detailed methods to determinE> water surface profiles and floodplain delineations including delineaticn of the 1 DO-year floodplain. F/oodway" The channel of a stream and the portions of the adjoining flood- plain reqLired to pass the discharge of the 1 DO-year flood with an insignifi- cant increase in flood levels. As used in the National Flood Insurance Program. Iloodways must be large enough to pass the 1 <lO-year discharge without causing the flood elevation to increase more than a specified amount (usually one-foot), Freeboarcf -- A factor of safety usually expressed in feet above a design flood level for flood protection or control works. Gauge -.. }\n instrument for measuring precisely the flow of water past a given point on c:l stream. Gauged u Measured by onH or more strHam gauges which provide data about his':oric volumes of water t11rough a particular stream reach. Horizontal Datum -- An assumed set of lines in the two horizontal dimensions used as a reference in surveying or mapping and expressed as longitudinal and latitudinal coordinates, Hydraulic Analysis n The study of determining water levels for particular flood events. Hydraulic Loading -- Pressure from the forces of water at rest or moving water. Hydrodynamic u Resulting from water in motion pressinn against adjacent surfaces.ialso Dynamic) Hydrodynamic Loads n Forces imposed on structures by flood waters due to the impact of moving water on the upstream side of a structure, negative pressures on the downstream side, and drag along the sides. Hydrolog.'c Analysis n The study of determining rainfall run-off (flood waters) for a specific watershed, Hydrosta.'ic n Resulting from the weight of water at rest.(also Static) Hydrosta'ic Loads -- Forces imposed on structures due to the weight of the flood water. Intermitt"nt Stream (or Stmam fleach) .,. A stream (or stream reach) which has surface discharge generally betweEln 10 and 80 percent of the time. Because an intermittent stream channel is at or near the water-table surface, discharge can be the result of a disconUnous suppiy from springs or ground water senpage, a discontinuous supply from surface sources, including runoff or rainfall and seasonal snowmelt, or both. If a channel has a sustained period of no streamflow interrupted by a seasonal period of continous streamflc,w, at least 1 month in length, the stream or streams is intermittent. Levee -- lID artifical barrier constructed to prevent a river or stream from overflowing. Liquefacr/on -- The process of becoming liquid. Log-Pearson III Technique ,.- A statistical distribution technique which is used in analyz ng observed peal, flows in order to calculate projected peak flows for varioes flood frequenCies considered in a floodplain study. Magnitucle n The largest measured volume of flow during a particular flood. Master Drainageway Planning Study.. A study prepared using detailed methods to determine water surl'ace profiles and floodplain delineations, including delineation of the 100-year floodplain, and to determine alternative structural and non-structural plans for dealing with 1 OO"year flows and drainage problems. Mean Sea Level n The avera!Je height of the sea for all stages of the tide over a 19-yea - period. 55