For a single structure, the flow will find its way to the opening until the roadway is overtopped. If two or more structures are available, the flow will divide and proceed to the structures offering the least resistance. The point of division is called a stagnation point.

In usual practice, TxDOT recommends that the flood discharge be forced to flow parallel to the highway embankment for no more than about 800 ft. If flow distances along the embankment are greater than recommended, a relief structure that will provide an additional opening is recommended. A possible alternative to the provision of an additional structure is a to control the turbulence at the header as discussed in Section 7.

Natural vegetation between the toe of slope and the right-of-way line is useful in controlling flow along the embankment. Therefore, make special efforts to preserve any natural vegetation in such a situation.