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In EE8.4 a BC option has been which allows the use of an elevation specified flow but allows for a “free tangential”. Normally an open BC requires two cells at the border. In some models where there are tight boundaries, this can be restrictive. The Elevation Specified-Free Tangential option allows EFDC to only use one cell at the border.
Boundary Group Conditions frame
For open BC's, unlike flow BC's, the concentrations specified in the Constant Concentrations frame are always used for boundary assignments. The constant concentrations will be added to any time series concentrations defined. For example, if the user has a tidal time series of salinity that varies from 5 to 10 ppt and specifies a concentration for the salinity of 10 ppt in the Constant Concentrations frame, EFDC will apply time variable salinity concentrations ranging from 15 to 20 ppt.