What causes debris flows and shallow landslides?

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, glacier melt 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 clearance.

A likely future increase in these phenomena. Debris flows tend to be channelled by the topography. Left unchecked, debris flows can damage or disrupt infrastructure, or block watercourses, leading to significant destruction. Meteorologists predict that global climate changes will increase rainfall in many areas and is likely to influence the incidence of debris flow and shallow landslides.

Maccaferri long experience in tackling these phenomena

We have a long history in providing solutions to ‘debris flow’ phenomenon. Gabions and Reno mattresses are often used on slopes to construct weir-like structures, which are positioned across vulnerable slopes to limit the initiation of a debris flow and to restrain it when a flow event happens. Behaving in a manner similar to a weir for water flows, gabion structures built from double twisted wire mesh provide a long-term robust solution to debris flows. They have a high capacity and when the contained debris becomes too great, they can simply be emptied using excavation equipment.

Gabion structures are suitable when access and space is available for their implementation.

Our tailored solutions for challenging cases. However, where this is not possible, our specific Debris Flow Barriers can be considered. Our Debris Flow Barriers 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 customized to suit the dimensions of the project, the anticipated debris material and the expected volume of the flow.

Similarities and differences between debris flow and rockfall barrier solutions

Our debris flow barriers 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.

Solutions with fixed timeframes in mind. 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.


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