Computation Of Normal Depth In Open Channels

Abstract

Fixed-point iteration is an efficient technique for manual and machine calculation of normal depth. The method is applied to the solution of Manning's equation for two basic uniform flow problems in trapezoidal and circular channels. Computing normal depth when discharge and bed width, or diameter, are given, or computing bed width, or channel diameter, required to sustain a given discharge and normal depth. The iteration function has a standard form and uses only two variables, the area and hydraulic radius, for various channel geometries. It has been tested over a wide range of the variables. Convergence to the correct normal depth occurred in an average of three to four iterations regardless of the starting value used.