Riverbank Gabion Baskets Compared with Riprap and Revetments

What is taking the bank

Flowing water shears the surface and carries the soil away. Waves from wind or boats hit the face. When the river drops, water leaving the bank can pipe soil out from inside. Scour at the toe digs under a revetment that otherwise looks sound.

Which of those matters, and how fast the water is, comes from the river study. A velocity or a shear stress copied from an article is how the wrong revetment gets built. Name the flood, the bend and the bed before you pick a product.

Gabion mattresses and gabion boxes

A gabion mattress is the shallow carpet on a slope or a bed. A gabion box is the deeper unit, used as a toe, a step or a low wall. Both hold stone in gabion mesh so the stone acts together instead of as loose rocks. A filter under them keeps the bank soil from leaving through the voids. The units are tied so a local dip does not open a bare gap.

They are flexible, which helps where the bank settles, and they drain, which helps when the river falls and a sealed face would trap water. They are not proof against every flood. The toe still has to be long enough for the scour you expect.

Steel-wire mattresses depend on the coating in wet ground. Polypropylene composite gabion mesh is the alternative with no steel-wire rust mechanism. It still has to resist abrasion from sediment and to use its own connections. Do not describe it as indefinite, and do not attach a replacement year to the steel wire from this page.

Riprap and concrete

Riprap is loose large stone. It is simple where the rock is nearby and the flow is moderate. It moves a little and can settle into a hole, which is sometimes called self-healing and is sometimes the start of a gap. It needs a filter. As the water gets faster, the stone has to get heavier. At some point the rock is impractical and a gabion, which holds smaller stone in a mesh, is the thing people compare.

Concrete, cast or as cabled blocks, is the rigid end of the range. It can take a harsher flow, and it cracks or lifts if the base moves or the water behind it cannot get out. It is not a habitat by default. Cost is a quotation question. This page does not say concrete costs a multiple of gabion, or the other way round.

Vegetation, stakes and rolls, can be enough on a quiet bank, often with a hard toe. It is the wrong headline for a bend that already fails in flood. The riverbank checklist is where the gabion version of that choice is written down as questions, not as a winner.

How to choose without a fake table

Start from the failure you are stopping: surface wash, toe scour, or a deep slip that a carpet will not fix. Then match a mattress, a box, riprap or concrete to that failure, the stone you can get, and the access. Ask the designer for the permissible velocity of the chosen section. Do not take 4 m/s or 6 m/s from a blog and put it on the drawing.

If the water or the soil is aggressive to zinc, put polypropylene composite mesh on the list of gabion options and compare it with coated wire on test reports and on price for the same basket schedule. The mesh does not change the need for a filter and a toe.