The multiple opening method within HEC-RAS is a one-dimensional flow approach to a complex hydraulic problem. The methodology has the following limitations: the energy grade line is assumed to be constant upstream and downstream of the multiple opening crossing; the stagnation points are not allowed to migrate past the edge of an adjacent opening; and the stagnation points between a conveyance area and any other type of opening must be fixed (i.e. can not float). The model is limited to a maximum of seven openings. There can only be up to two conveyance type openings, and these openings must be located at the far left and right ends of the cross sections. Given these limitations, if you have a multiple opening crossing in which the water surface and energy vary significantly between openings, then this methodology may not be the most appropriate approach. An alternative to the multiple opening approach is the divided flow approach. This method is discussed below.