This page contains a Flash digital edition of a book. Managing & Maintaining our water channels


value of this

approach becomes more and more evident with time,”

left: River Ebbw, with Tensar VMax P550 erosion control installed right: River Ebbw one year after erosion control and greening

Lower cost, higher sustainability

There is a strong economic benefit in many projects. Apart from the cost of concrete, shuttering, transporting aggregate and stone blocks, the actual riverside land can be difficult for the large scale construction plant needed for placing heavy materials.

“I have projects where I have demonstrated a 50% budget saving over traditional ‘hard’ measures, even before all the other benefits,” claims David. “But where we really need to convince is in pointing out that properly selected materials and systems, used in correctly designed schemes, have fully proven and tested performance criteria.

Established shear performance requirements

Salix uses Tensar’s RollMax™ range of materials, which are widely known in the USA under Tensar’s North American Green label, because they have fully accredited performance data stating their erosion resistance up to a specific maximum water velocity and permissible shear stress. This allows design and installation of erosion control measures schemes with confidence, fully backed by Professional Indemnity assurance.

The core Tensar RollMax products are the Vmax™ C350 and Vmax™ P550 permanent turf reinforcement mats used as revetments on critical flow channels, which comprise a permanent high strength three dimensional matting structure with an internal fibre matrix.

The Vmax™ C350 uses a 100% coconut fibre matrix which supplements the permanent matting to enhance the shear resistance of grass and vegetation growth for up to 36 months while it becomes established, before the coconut fibre biologically degrades. Vmax™ bolsters the shear resistance of vegetation up to 576 Pascal, suitable for a maximum flow velocity of 6m/sec.

Vmax™ P550 is an ultra high strength solution with a 100% high strength polypropylene matting and internal fibre as a complete alternative to hard revetments, and provides a permanent erosion protection enhancing vegetation shear resistance up to 672 Pascal, suitable for 7.6m/sec flow velocity.

While these figures are quoted at full vegetation maturity, both products offer immediate erosion protection for mulch and seeds and for growing vegetation. For example, tender stems and undeveloped

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 

root systems are prone to damage and removal at flow-induced shear stresses of only 29 Pascal. Even mature vegetation, if unreinforced, is susceptible to water erosion above 48 Pascal of shear.

Where immediate high shear stress resistance is required, each of these Tensar Vmax products can be supplied by Salix with precultivated turf, ready for unrolling down a bank for an ‘instant’ solution.

   


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