Irregular Weirs

Whenever the culvert headwater begins to rise above the minimum elevation of the roadway, overtopping will occur. The weir x-y structure can be used to model overtopping.

Overtopping flow is modeled as a special type of weir flow expressed by the general broad-crested weir equation.

Note: Do not use the irregular structure to model an overflow channel. The equations which define the irregular weir are different then channel equations and would result in significantly different flows.