This code defines a function called "getSurfaceOutflowRate" which calculates the outflow rate from a LID's surface layer. The function takes in a depth of ponded water on the surface layer (in feet) and returns the outflow from the surface layer (in feet per second) as output. The function starts by initializing two variables, "delta" and "outflow", to 0.0. Then, it checks if the depth of ponded water is below the storage depth and if it is, it immediately returns 0.0.

Otherwise, the function calculates the outflow from overland flow Manning equation, which is the product of surface layer's alpha, the fifth root of delta, full width of the LID, and the area of the LID. The function also checks if the outflow is greater than the change in time step and if it is, it limits the outflow to the change in time step.

Variable | Description |
---|---|

delta | The difference between the depth of ponded water and the thickness of the surface layer |

outflow | The outflow rate from the surface layer |

theLidProc->surface.thickness | The thickness of the surface layer |

theLidProc->surface.alpha | The alpha value used in the overland flow Manning equation |

theLidUnit->fullWidth | The full width of the LID |

theLidUnit->area | The area of the LID |

Tstep | The change in time step |

Note that this function should not be applied to swales or rain barrels.