Hydraulic and Erosion
Control and Soil Bioengineering
An Introduction
Maccaferri Solutions;
Erosion of the earth occurs when the shear force
applied by water, ice or wind (or other external influence),
exceeds the shear resistance of the surface
it is in contact with.
Over time, the surface will gradually erode which can lead
to loss of land, habitat and infrastructure. The eroded particles
are transported in suspension, and deposited whenever the
fluid loses kinetic energy.
Water courses in particular, are polluted by suspended silts
created by erosion of the channels and river banks. The suspended
matter in the water limits light penetration and therefore
limits photosynthesis of riparian plants and habitats.
If pollution is allowed to continue, the water course
will become sterile as the water looses oxygen.
The erosion control industry offers a vast array of solutions
to limit erosion, which can be distilled into two approaches;
- Erosion Control: Improve the shear resistance
of the surface exposed to erosion, or reduce the kinetic
energy of the flow
- Sediment Control: Stop the particles
already in suspension from polluting water courses by filtration
Often the two approaches are used in conjunction to offer
comprehensive erosion protection.
Examples of Erosion Control are;
- Erosion control blankets, permanent (manmade) or temporary
(biodegradable)
- Establish vegetation
- Hard armor; rip-rap or Reno mattresses
- Weirs and drop structures
Examples of a Sediment Control are;
Erosion is a dynamic process with constantly changing conditions
and parameters. Therefore, in most circumstances, flexibility
is the key to long term erosion protection. Maccaferri’s
products are inherently flexible. They can accommodate large
differential settlements, and make ideal erosion control systems.
The great advantage of Maccaferri products is that by combining
them with soil bioengineering techniques,
vegetation can grow through the protection system and habitats
can be re-established. This is a more environmentally
friendly approach to solving construction problems
than the traditional hard armoring approach.
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Maccaferri is a pioneer of integrating soil
bioengineering techniques with bank protection. Soil
bioengineering brings together biological, ecological
and engineering concepts to produce living, functioning
systems for erosion and flood control, habitat enhancements
and water quality improvement. It uses living plant
material in combination with man-made structural elements
to provide long term strength. |
Our Soil Bioengineering CD Rom is packed with information
on the concepts and solutions for successful soil bioengineering
and ecological techniques. Please contact us for a free copy
- If you can’t wait, the "Soil Bioengineering
Manual" is in the download area under the Brochures section.
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Typical Performance Guide
Selection of the appropriate erosion control products can
be confusing.
If something sounds too good to be true, it probably
is, so take great care when comparing supposedly similar solutions.
Solution | Typical
Flow Condition | Approx.
Shear Resistance (Un-vegetated)* | Approx.
Shear Resistance (Vegetated)* | RECPs - Temporary | Low | 0.2
lb/ft 2 | 0.6 lb/ft 2 | RECPs - Permanent | Low - Medium | 3.9 lb/ft 2 | 7.3 lb/ft 2 | Rip rap | Medium - High | 6.2 lb/ft 2 | 7.3 lb/ft 2 | Reno mattress | High - Extreme | 7.1 lb/ft 2 | 9.4 lb/ft 2 |
* = Typical shear resistances for a 2 hour storm event and
the inclusion of a suitable safety factor. Vegetation can
improve the shear resistance significantly. However, can you
rely upon its performance year round? Will it die back or
become diseased? We recommend designing for the residual performance
of the product, not the maximum performance.
When designing erosion control solutions, it is vital to
consider not only the shear stresses applied, but the duration
for which that stress will be applied.
For example, although a RECP may have published data suggesting
it is capable of withstanding a shear stress of 10lb/ft2,
it may only do so for 15 minutes. After this, performance
will reduce.
Design checks should be carried out for the situation immediately
after installation, and after the establishment of vegetation.
Be sure that the appropriate design data is used, not simply
the data the manufacturer chooses to show you!
If in doubt, ask, ask and ask again - it’s
your project!
Maccaferri Solutions;
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