Occasionally you may need to model a river crossing that cannot be modeled adequately as a single bridge opening or culvert group. This often occurs in wide floodplain areas where there is a bridge opening over the main river channel, and a relief bridge or group of culverts in the overbank areas. There are two ways you can model this type of problem within HEC-RAS. The first method is to use the multiple opening capability in HEC-RAS, which is discussed in detail in the following section. A second method is to model the two openings as divided flow. This method would require the user to define the flow path for each opening as a separate reach. This option is discussed in the last section of this chapter.