How to control river erosion
Gabion river and stream erosion benfits are…
- Rapid construction and immediate use
- Dissipate flowing water energy
- Semi flexible building blocks for channel stabilisation.
- Have an irregular surface to diffuse and reduce river bank scouring
- Gabions are able to use smaller rock for river bank protection, when larger rip rap is unavailable
- Much cheaper, more flexible and greener than concrete
- Can be installed in wet or dry conditions
- Free draining with no hydrostatic pressure issues
How gabion erosion cages work
Gabion baskets placed on the outside of the river bend to prevent river bank erosion during floods. Geotech filter fabric is placed behind and underneath the gabion baskets to prevent the movement of soil material through the gabions.
Design for expected maximum scour depth
The base layer of gabions must be placed below the expected maximum scour depth, or the toe can be protected with gabion mattresses
Design for peak flood events
Gabion flood projection must be designed to cope with peak river flows often referred to to as 1 in 50yr, or 1 in 100yr floods. This often requires larger gabion walls and foundations, than envisaged. An engineer is able to examine historical weather data, and design for the expected flood events over the life time of the wall.
Gabions are ready for immediate use
Machine and hand filling gabions, is often possible without having to divert the river with a bund
Temporary bund
Building a temporary bund, to often done, to speed up construction
Scour protection
Placing large rocks, at the base of the gabion, provides added erosion protection. These rocks may need to be inspected and replaced after flood events
Purpose built lifting cradle
This allows gabions to be pre filled and lowered into place for immediate protection
Gabions can flex to ground movement
Gabions can flex to ground movement, dissipate energy from flowing water, and drain freely. Their strength and effectiveness may increase with time, as silt and vegetation fill the voids, and reinforce the structure.
Uses the strongest wire mesh
In locations where high flood water velocities are expected, carrying woody debris and gravels in suspension, the stronger 4ga or 5ga welded gabions are the preferred choice, to resist damage to the gabion structures during floods.
Rock grading
The rock grading for erosion control gabions must be .between 3″ to 8″ sizing
Non durable fine material is not acceptable
