# Backwater curve for a rock-ramp fishpass

This module can be used to simulate the backwater curve of a simple macro-roughness fishway in order to determine the downstream flooding level of the fishway.

## Operating principle

The parameters of this module are :

- The choice of the "simple" rock-ramp fishpass module among those present in the work session which will be used to perform the calculation
- The water level downstream of the pass
- The space step used to discretise the curve calculation.

N.B. : As the backwater curve can only be calculated for one set of parameters, the simple rock-ramp fishpass module cannot contain varied parameters.

The theoretical calculation carried out in the macro-roughness channel corresponds to the calculation of the water line in a uniform regime where the slope of the water is equal to the slope of the bottom of the channel. The rock-ramp fishpass module is used here to calculate the slope of the water in the non-uniform case. The fluvial backwater curve is then calculated from the water level downstream using the trapezoid integration method.

This module is based on the module for calculating the backwater curve of a section to calculate and display the results.