NAMEseddisch - Computation of fluvial sediment dischargeABSTRACTSEDDISCH computes fluvial sediment discharge by allowing the user to choose between five described bedload formulas and eight described bed-material formulas. The bedload discharge formulas are those of Schoklitsch (1934), Kalinske, Meyer-Peter and Muller (1948), Rottner, and Einstein. The bed-material formulas are those of Laursen, Engelund and Hansen, Colby, Ackers and White, Yang sand formula, Yang gravel formula, Einstein, and Toffaleti.METHODNumerous sediment-discharge formulas have been proposed in literature. Selection of the thirteen formulas used in SEDDISCH was based on: (1) theoretical background, (2) extent of testing by original author and independent investigator(s), and (3) extent of use by engineers and researchers. The user is asked to choose from these formulas based on which field data are available. Bedload Discharge Formulas Bedload discharge is the discharge of sediment that moves in essentially continuous contact with the bed. Schoklitsch developed a bedload formula based mainly on Gilbert's (1914) flume data with median sediment sizes ranging from 0.3 to 5 mm. The basis for this formula is that bed material begins to move at some critical discharge and that the bedload discharge is proportional to the rate of work done by the part of the tractive force in excess of that needed to overcome the resistance along the wetted perimeter. The formula developed by Kalinske for computing bedload discharge of unigranular material is based on the continuity equation which states that the bedload discharge is equal to the product of the average velocity of the particles in motion, the weight of each particle, and the number of particles. Meyer-Peter and Muller developed an empirical formula for the bedload discharge in natural streams. The computer program computes the effective diameter of the bed-material mixture from the entered sediment size-fraction data. However, the program does not compute the bedload discharge by size fractions. Rottner developed an equation to express bedload discharge in terms of the flow parameters based on dimensional considerations and empirical coefficients. In his derivation, wall and bed form effects were excluded, and Rottner stated that the equation may not be applicable when small quantities of bed material are being moved. The bedload relation developed by Einstein is derived from the concept of probabilities of particle motion. Bed-Materal Discharge Formulas Bed-material discharge is the discharge of sediment which is derived from and readily exchanges with the particles in the bed material; particles comprising the bed-material discharge move both as bedload and in suspension. The equation developed by Laursen to compute the mean concentration of bed-material discharge is based on empirical relations using natural sediments with a specific gravity of 2.65, and medium diameters that range from 0.011 to 4.08 mm. Engelund and Hansen applied Bagnold's (1966) stream power concept and the similarity principle to derive a sediment transport equation. This equation can be used with moderately sorted bed materials having mean fall diameters larger than 0.15 mm. Colby presented a graphical method to determine the discharge of sand-size bed material that ranged from 0.1 to 0.8 mm in water at a temperature of 15.6 degrees Celsius. This program uses a set of equations derived by Carl Nordin (U.S. Geological Survey) that represent Colby's curves at 0, 5, 10, 15.6, 20, 30, and 40 degrees Celsius. Ackers and White developed a general sediment-discharge function in terms of three dimensionless groups: size, mobility, and discharge. Yang derived an equation to compute concentration of the bed- material discharge, for sand-bed streams, based on dimensional analysis and the concept of unit stream power. He defined unit stream power as the rate of potential energy dissipated per unit weight of water, which is expressed by the velocity and slope product. Yang, using the same dimensional analysis and multiple regression methods as was used to derive discharge rates in sand-bed streams, derived an equation to compute the bed-material discharge concentration, in gravel-bed streams. The same definition of unit stream power is used in both the sand and gravel transport equations. Einstein's method combines his computed bedload discharge with a computed suspended bed-material discharge to yield the total bed- material discharge. Toffaleti's method is based on the concepts of Einstein with three modifications: (1) velocity distribution in the vertical is obtained from an expression different from that used by Einstein; (2) several of Einstein's correction factors are adjusted and combined; and (3) the height of the zone of bedload transport is changed from Einstein's two grain diameters. Toffaleti defines his bed-material discharge as total river sand discharge even though he defines the range of bed-size material from 0.062 to 16 mm.HISTORYVersion 1.2 1998/01/16 - First release of original program as ported and after code clean-up for use on UNIX workstations.DATA REQUIREMENTSInput for SEDDISCH is generated during an interactive session using the program DISDATA. DISDATA generates a direct access file that is read by SEDDISCH. The following data are prompted for by DISDATA to form the SEDDISCH data set: measurement location top width mean depth mean velocity water-surface slope water temperature particle size, in millimeters, at which the 35, 50, 65, and 90 percent by weight is finer (enter zero if not required) Bed-material particle size data are entered depending on the value of the option code selected at the start of the run. One option is that no size distribution data are to be entered. Zero values are given to the percent-in-class variables for the size fractions. The other two options are to enter the size data as percent-finer values or as percent-in-class values.SYSTEM REQUIREMENTSSEDDISCH is written in Fortran 77. Generally, the program is easily installed on most computer systems. The code has been used on UNIX- based computers and DOS-based 386 or greater computers having a math coprocessor and 1 mb of memory.DOCUMENTATIONStevens, H.H., and Yang, Chih Ted, 1989, Summary and use of selected fluvial sediment-discharge formulas: U.S. Geological Survey Water-Resources Investigations Report 89-4026, 121 p.CONTACTSOperation and Distribution: U.S. Geological Survey Hydrologic Analysis Software Support Program 437 National Center Reston, VA 20192 h2osoft@usgs.gov Official versions of U.S. Geological Survey water-resources analysis software are available for electronic retrieval via the World Wide Web (WWW) at: http://water.usgs.gov/software/ and via anonymous File Transfer Protocol (FTP) from: water.usgs.gov (path: /pub/software). The WWW page and anonymous FTP directory from which the SEDDISCH software can be retrieved are, respectively: http://water.usgs.gov/software/seddisch.html --and-- /pub/software/surface_water/seddischSEE ALSOdisdata(1) - Data entry program for seddisch mepdata(1) - Data entry program for modein modein(1) - Total sediment discharge program using modified Einstein procedure sedsize(1) - Particle-size statistics of fluvial sediments sizedata(1) - Data entry program for sedsize

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