Gabions for Water Erosion
Since the early 1800s, rock-filled gabion baskets have been used on river banks and shorelines to withstand the effect of wave action, turbulence, and the ever-present destructive erosion from running water. It takes the strength of interlocking rock to resist the relentless power of water. They have become the most effective solution in most erosion scenarios the world over.
There are 2 basic elements that make up a Gabion protective barrier. The first is the bulky Gabion Baskets which are immovable in most conditions weighing up to 8 tons and make of interlocking rock. These protect the edges of a flood line as the turbulent water rises in a storm event. The second is the flatter mattress which lines the water bed as lowers the energy and speed of running water. This is critical to prevent water undermining gabion toes and eroding riverbeds during floods and at weirs. Expert hydraulic design of Gabions is critical, as is the case for all erosion protection products. The rough surface of a gabion can slow down the water flow and can result in unexpected turbulence and erosion in other areas. It is generally best to get advice from an expert before proceeding with a Gabion design.
Galvanized and PVC Coatings
Gabion wire can be PVC to increase the resistance to corrosion from salt or acid in their environment. It also offers some protection to the galvanized coating which can be damaged by floating debris in water applications. The PVC adds approximately 0.5mm to the diameter of the wire with only a negligible increase in weight.
Over the years, new technologies have challenged the dominance of gabions against water erosion (link to erosion blocks). Gabion baskets and Mattresses tend to remain the preferred choice for the following reasons:
- They are heavy and immovable during flooding or under wave action.
- Their flexibility adds to their strength. Rather flex than break.
- The angular rock fill provides a strong interlocking action against movement.
- Class “A” galvanising keeps the structure resistant to corrosion for up to 50 years of service. PVC-coated wire further improves corrosion resistance in harsh environments.
- Double Twisted strands increase the strength against debris impact and corrosion at joints.
- Groundwater seeps through the rock, allowing for natural stability of embankments.
- The modular units can adopt any conceivable shape which will optimise the hydraulic flow of a water wall.
- The rough surface will slow the flow of rapidly moving stormwater. This will also encourage groundwater seepage which reduces destructive runoff volume.
- In areas where natural rock and pebbles are abundant, Gabions are easy and cheap to install.
- Local, unskilled or semiskilled labour can install gabions with minimal training, and without the need for special equipment.
- The appearance of natural stone will blend into the environment and can look quite breathtaking.