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CONVERSION FACTORS Multiply inch (in,) foot (ft) cubic foot per second (ft3/s) mile(mi) square mile (mi2) By 25.4 0,3048 0,02832 1.609 2,590 To obtain millimeter meter cubic meter per second kilometer square kilometer VERTICAL DATUM Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)-a geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea Level Datum of 1929. GLOSSARY OF TERMS Antidune: Bed forms of curved symmetrically shaped sand waves that may move upstream, remain stationary, or move downstream. Antidunes occur in trains that are in phase with and strongly interact with gravity water-surface waves. The water- surface waves have larger amplitudes than the coupled sand waves. At large Froude numbers, the waves generally move upstream and grow until they become unstable and break like surf (breaking antidunes), The agitation accompanying the breaking obliterates the antidunes, and the process of antidune initiation and growth is repeated. At smaller Froude numbers, the antidunes generally remain stationary and increase and decrease in amplitude without breaking (standing waves; Simons and Richardson, 1966, p, v), Backwater: Water backed up or retarded in its course as compared with its normal or natural condition of flow. In stream gaging, a rise in stage produced by a temporary obstruction such as ice or weeds, or by the flooding of the stream below. Bank, left and right: Reference terms used to specify the banks on the left and right when facing downstream. Bedform: Alluvial,channel bottom feature whose form depends on bed, material size, flow depth, and flow velocity, Bedforms include ripples, dunes, antidunes, and plane bed. Conveyance: A measure of the carrying capacity of a chmmel section and is directly proportional to channel discharge, Conveyance is that part of Manning.s equation that excludes the square root of the energy gradient or friction slope, Crest-stage gage: A device for recording the peak water,surface elevation during a flood by means of a cork line that adheres to a wooden rod placed in a 2,inch,diameter metal pipe that has been secured near the channel margins. Criticalllow: If the flow is critical, the Froude number is equal to unity, and the inertial forces balance the gravitational forces, This balance takes place at the depth at which flow is at its minimum energy. Dryland: Streams located in regions of semiarid to extremely arid climatic conditions. For the conterminous United States, this would apply to regions that accrue less than 20 in, of precipitation annually, Ephemeral: A stream or reach of a stream that flows briefly in direct response to precipitation or snowmelt in the immediate vicinity, and whose channel is at all times above the water table, Flood peak: The largest value of the runoff flow which occurs during a flood, as observed at a particular point in the drainage basin. Contents VII