online_wsprofiles_31: C_{1} watersurface profile
DESCRIPTION
General
 The php script [program] online_wsprofiles_31
calculates a C_{1} watersurface profile in a prismatic open channel using the directstep method (Chow, V. T.: Openchannel hydraulics, McGrawHill, 1959).
 The program calculates critical depth
based on the geometric and hydraulic input data. Newton's iteration is used to solve the nonlinear equations.
The program calculates critical slope based on the critical depth and the input Manning's n [see formula in onlinechannel04.php].
 A C_{1} profile is subnormal, subcritical, and the bottom slope is equal to critical slope (see figure).
The calculated gradually varied flow depth varies between the specified [or default] flow depth
at the downstream boundary y_{d} and the [calculated] critical depth y_{c} upstream.
Input
 There are four required input variables: discharge Q, bottom width B, side slope z, and Manning's n.
 For the downstream boundary condition, you can specify a suitable input flow depth.
Alternatively, if the input flow depth box is left blank,
the program will use a value equal to three times the critical depth (3 * y_{c}) instead.
 The program echoes the input data. Internally calculated downstream depth is echoed with fivedecimal (5) accuracy.
Defaults
 For the input flow depth, you can enter
any suitable [subcritical] subnormal flow depth, i.e., a flow depth greater than critical depth.
Leave this box blank if you want the program to use a value equal to three times
the sequent depth [ 3 * y_{2} ].
 You can enter the desired number of computational intervals n. The suggested range is 50200. A higher number
means higher computational accuracy.
Leave this box blank if you want the program to set the default value at 100.
 You can enter the desired number of tabular output intervals m. The suggested range is 10100. A higher number
means more detailed [longer] output.
Leave this box blank if you want the program to set the default value at 10.
Output
 A table with fourteen (14) columns: output interval index k, [flow] depth (m),
[flow] area (m^{2}), velocity (m/s), velocity head (m), specific head (m), wetted perimeter (m), hydraulic radius (m),
friction slope (m/m), average [friction] slope (m/m), specific head difference (m), length increment (m), depth gradient (m/m), and total [channel] length (m).
 The number of computational intervals n and the number of tabular output intervals m are printed for reference.
 The calculated critical depth, critical slope, and bottom slope (equal to critical slope) are printed for reference.
Units
 The current version is written in SI [metric] units.
Errors
 Enter only positive [nonzero] numbers for discharge and Manning's n.
Failure to do this will trigger an error message and halt execution (Error messages No. 1: A, and B, respectively).
 Enter only nonnegative [zero or greater] numbers for bottom width and side slope.
Failure to do this will trigger an error message and halt execution (Error messages No. 2: A and B, respectively).
 Bottom width and side slope cannot be zero at the same time.
Failure to do this will trigger an error message and halt execution (Error message No. 3).
 A Manning's n value outside of the range 0.0080.1
will trigger an error message and halt execution (Error message No. 4).
 An input flow depth greater than 100 [m] will trigger an error message and halt execution (Error message No. 5).
 An input flow depth less than or equal to the calculated critical depth [plus 0.01 m]
will trigger an error message and halt execution (Error message No. 6).
Thank you for running online_wsprofiles_31. Please call again. [Version 1.0.0, 070505]
