Crossings should be made as nearly as practical at a right angle to the direction of flow. Emphasis should be given to the direction of the flood flow where it is different from that of the low water. The direction, rate, and volume of flood flow at various stages in the location of bridge openings should always be considered. A highway built on the neck of a horseshoe bend that is subject to overflow is poorly located because the correct location of relief bridges sometimes varies with the flood stage.

Whenever practical, stream crossings should be at stable reaches of a stream. Meanders in the stream that are subject to shifting should be avoided. Meandering streams have inherent problems of having no stable place to cross because the sinusoidal pattern of the stream naturally tends to progress in a downstream direction.

The number of stream crossings and the disturbance of streambeds should be minimized. Crossing and then re-crossing the same stream should be avoided. Undue scour and erosion that might result in a complete change in the river channel should be avoided.

See Chapter 9, , for more details on planning and location.