If the weir flag is set, a unique name must be entered. The weir data is not shared with that from the Hydraulics layer and is also simplified. However, the weir flag is shared.

This dialog defines a Sanitary layer weir. Sanitary layer weirs are distinct from Hydraulics layer weirs and do not share data. Sanitary layer weirs are treated as flow diversion structures, as the data requirements of a threshold flow indicate.

The diagram represents the weir at the upstream node and is shown as a side weir. Flow enters the weir once a certain threshold flow is exceeded. This flow must correspond to a flow depth of the weir crest height at the node. Above the crest, the broad-crested weir equation is used:

Q = C * L * DH^1.5


Q = flow over weir, cfs [cms]

C = weir coefficient

L = weir length, ft [m]

DH = depth of flow over the weir crest, ft [m]

If multiple weirs exist along the link, the threshold flow calculations for higher weirs must take into account the diversions already occurring in lower weirs. These data entry requirements may seem tedious, but are required due to the simpler nature of Sanitary layer weirs as compared to Hydraulics layer weirs.

The data requirements for a TRANSPORT Weir are:

Crest Height. The height of the weir, before flow over the weir, ft [m].

Length. The length of a broad-crested weir, ft [m].

Discharge Coefficient. The discharge coefficient used to compute flow over a broad-crested weir.

Inflow before Weirflow. The total flow at the upstream node before flow occurs over the weir, cfs [cms]. This flow corresponds to a node flow depth equal to the weir crest height. You must perform this calculation yourself, since the Sanitary layer does not explicitly maintain node flow depths. The weir is thus treated as a flow diversion structure.

Gauged Data.Measured time series data can be entered directly at a node or link for comparison with model results. Visit the Gauged Data section for details on this parameter.