HEC-RAS has numerous optional capabilities that allow the user to model unique situations. This chapter describes some of the optional capabilities available for performing a hydraulic analysis. For additional steady flow computational options, see "Modeling Culverts". For information on Unsteady Flow computational options, see "Modeling Multiple Bridge and/or Culvert Openings". Some of the more commonly used option capabilities include (but not limited to): multiple profile analysis; multiple plan analysis; optional friction loss equations; cross section interpolation; mixed flow regime calculations; modeling stream junctions; flow distribution calculations; split flow optimization; pressurized pipe flow; estimating ungaged area inflows.