Gabion Check Dam

What a gabion check dam does

A check dam is a low barrier across a gully or small stream. It slows the water, lets silt settle behind it, reduces erosion of the bed and banks, and helps water soak into the ground. Built from gabions it is permeable, flexible and quick to construct from local stone.

Parts of a check dam

• Body — gabion boxes across the channel, keyed into the bed.
• Wings — the body extends and is keyed into both banks, so water cannot go round it.
• Notch (spillway) — a lower section in the middle of the crest that keeps the flow away from the banks.
• Apron — a revet mattress or gabion layer downstream that absorbs the energy of the falling water, so it cannot scour out the foundation.
• Filter — under the apron and against the soil, so fine material is not washed out.

Layout along a channel

Check dams are usually built as a series. A common rule is to space them so that the crest of one is roughly level with the base of the next one upstream, which keeps each reach of the channel gentle. Start where erosion is worst and work with the natural shape of the gully.

Construction notes

• Excavate a key trench into the bed and both banks before placing units.
• Lace every unit to its neighbours so the dam acts as one structure.
• Pack the stone by hand, larger faces horizontal, with no voids at the exposed faces.
• Use PVC coated wire where the dam will be wet for long periods.

Maintenance

Inspect after heavy rain and floods: check the apron for scour, the wings for bypassing, and the mesh for damage from floating debris. Repair individual units early.

Questions