Debris Flow Fence
Barriers for debris flow
Debris flows and shallow landslides are highly mobile liquefied landslides containing a variety of material from fine particles to large boulders and tree branches. They are caused by excessive water on and within slopes, caused by rainfall, glaciers melting or similar. The likelihood of debris flows is increased when vegetation and other surface protection has been removed from vulnerable slopes, perhaps by wildfire or clearing.
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Our Debris Flow Fences are positioned within the anticipated path of the debris flow or shallow landslide, often in natural gullies, channels or chutes on the slope. They are customised to suit the dimensions of the project, the anticipated debris material and the expected volume of the flow. Upon impact by the debris flow, the Debris Flow Fence progressively deforms with the compression brakes and systems absorbing the energy. The hydrostatic pressure within the flow rapidly dissipates once the debris flow has been arrested leaving the volume of debris within the barrier.
Our Debris Flow Fences are similar to our rockfall barriers (catch fences) but incorporate additional energy absorption elements and variable geometries. In addition, combinations of different diameter ring nets are often used as the containment mesh. Ring nets are ideal in these structures as they have inherent energy absorption capacity, before loads are transferred to the compression brakes. Larger diameter ring nets are placed along the bottom of the structure to enable water and small material flow to continue through the barrier. Our smaller diameter ring nets are used at the top of the debris flow structures.
- The barriers are normally designed to be in place until vegetation is re-established on the vulnerable slopes above
- The barrier can then be removed leaving the foundation intact
- They can be reinstalled if risks from debris flows increase in the future
Depending on the site topography, these fences are often custom made to suit design and site conditions. Among others, the essential information to enable a preliminary assessment of a debris flow fence design includes:
- Density of mass
- Constant height of debris
- Impact velocity
- Up slope gradient