Low-Water Stream Crossing

What – Culverts are temporarily removed and replaced with natural fords, vented ford pipes, and low water bridges during extreme runoff events. 

Purpose – To prevent stream diversion and keep water in its natural channel.  This prevents erosion of the road fill, reduces adverse effects to water quality, and maintains access to areas once storm runoff rates diminish.

Effectiveness – Ford crossings effectively eliminate loss of water control at road/stream crossing.  However, poor design or implementation can result in damage to infrastructure and reduced water quality.  Informal monitoring indicates that flexible structures adjust to changes and are not prone to undercutting.  Boulder or riprap structures are long enough to avoid being outflanked by high flows.  Jersey barriers are less effective as an endwall material since they are not flexible.

Where

• Roads crossing ephemeral or seasonally flowing channels.
• Culverts that are at risk of plugging and diverting from increased runoff and bedload.
• Road crossings where high sediment delivery is expected.
• Roads where water overtops the road continuously or intermittently during and following mild floods.

Costs – $500–2500 for an unvented ford; costs increase for a vented ford or low-water bridge.  Additional factors include:

• Amount of material to be moved from stream channel
• Amount of riprap required to armor exposed and erodible slopes
• Location
• Depth of fill or embankment

How to Link – See USDA BAER Catalog page 122 (PDF page 122).