# Channel geometry

### Description

Compute geometry relations for trapezoidal channels.

### Usage

1 | ```
channel_geom(y, B, SS)
``` |

### Arguments

`y` |
Flow depth [ |

`B` |
Channel bottom width [ |

`SS` |
Channel sideslope [ |

### Details

Channel geometry relations are routinely calculated in numerical solutions of steady, gradually-varied and unsteady flows. This function is used extensively by internal procedures and is made accessible to the user for convenience.

### Value

Named vector:

`A` |
Flow area [ |

`P` |
Wetted perimeter [ |

`R` |
Hydraulic radius [ |

`dAdy` |
Water surface width [ |

`dPdy` |
First derivative of wetted perimeter w.r.t. flow depth. |

`dRdy` |
First derivative of hydraulic radius w.r.t. flow depth. |

`DH` |
Hydraulic depth [ |

`ybar` |
Vertical distance from water surface to centroid of flow area [ |

### Examples

1 2 | ```
channel_geom(1.71, 100, 0) # rectangular channel
channel_geom(5.79, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V
``` |