Breach flow formula (Water Overlay): Difference between revisions

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Where:
Where:
* Δw = The calculated water flow which takes place, based on the weir formula.
* Δw = The calculated water flow which takes place, based on the [[Weir formula (Water Overlay)|weir formula]].
* cell = Cell size
* cell = Cell size
* w<sub>e,t</sub> = The [[Surface water level formula (Water Overlay)|water level]] of the entry area at time t.
* w<sub>e,t</sub> = The [[Surface water level formula (Water Overlay)|water level]] of the entry area at time t.

Revision as of 08:16, 21 June 2023

Flow through breaches is calculated based on the weir formula, including the consideration between free flow and submerged flow situations. The weir formula is supplied with the breach width (as stand-in for the weir width), which is always calculated with the breach growth formula before calculating the weir flow. The downstream water level can optionally be measured with an additionally configured Breach Level Area, or an automatically placed

For the entry area, the area where the water originates from, the following also applies:

Each timestep, the external water level is changed based on the amount of water flowing in or out.

t=0 we,t = we,0
otherwise we,t = we,t-1 - ( (Δw * cell) / Ae )

Where:

  • Δw = The calculated water flow which takes place, based on the weir formula.
  • cell = Cell size
  • we,t = The water level of the entry area at time t.
  • we,0 = The water level of the entry area; In case of an external area: EXTERNAL_WATER_LEVEL of the breach.
  • Ae = The size of in the entry area; In case of an external area: EXTERNAL_AREA of the breach.

Notes

  • The water level we cannot become lower than the surface height se, defined by EXTERNAL_SURFACE_LEVEL in case of an external entry area. In case of an input area within the project, the surface height is determined per grid cell.

Related

The following topics are related to this formula.

Features
Breach
Formulas
Weir formula
Breach growth formula
Models
Surface model