Indian Valley Gray - Low Water Crossing Rock

3-4 Inch Low Water Crossing Drain Rock

A low-water crossing provides a bridge when water flow is low. Under high-flow conditions, water runs over the roadway and precludes vehicular traffic.

The simplest type of low water crossing is called an unvented ford or drift. This type of low water crossing is used mainly for shallow waterways or dry streambeds. It consists of an improved surface of gravel, gravel-filled geotextile grid, paving blocks, or concrete slabs positioned to match the slope and elevation of the adjacent waterway and floodplain.

To cross somewhat deeper waterways, a type of low water crossing called a vented ford can be constructed with culverts. The size of the culverts is usually selected to allow the water to flow below the roadway and provide a dry crossing surface for most of the year. During periods of high-water flow (e.g., spring runoff or flash floods), water will flow over the top of the crossing, as the culverts are not large enough to carry these flood-type runoff events.