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Slopes made of medium to high erosion
susceptibility, showing widespread erosion over its surface.
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After correcting the erosion, Strawmulch is applied
in sterile areas and two layers of anti-erosion biodegradable blankets are placed over the
surface..
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Same site three months after concluding the work;
there is no erosion and vegetation has established itself.
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Same site eight years after concluding the recovery
work with anti-erosion biodegradable blankets and sediment retainers. There is no erosion
and vegetation is lush..
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Building slopes and fill slopes requires surface or
deep protection, depending on the state of the material, the gradient and the geology,
among other factors. Surface protection is needed to avoid erosion gullies until
vegetation becomes established. Anti-erosion biodegradable blankets are used worldwide
for this type of protection. High quality hydrosowing should be applied prior to the
biodegradable blankets, including various species of grass and legumes with varying root
length and architecture to reach the deepest soil layers. These roots protect the slope at
deeper levels, as opposed to the use of a single grass species that only reaches - and
therefore protects - the upper soil layer.
PROBLEM
A recently built 45º gradient slope presenting initial gullies and erosion due
to a delay in surface protection, compromising the general slope stability. The silt-sandy
slopes are on average 15 meters high and are medium to highly erosion susceptible.
SOLUTION
The method adopted was to apply the unidimensional coconut/straw fiber
anti-erosion biodegradable blanket (Fibratextile Screen® 400UM) for surface protection
and a sediment retainer (Bermalonga® D40) to fill in erosion gullies and to anchor
sediments. A surface drainage system was built using concrete covered canals in
intermediate bermas directing water flow downwards over steps. There is irregular exposed
stone in the lower part of the slopes. In this case two anti-erosion biodegradable
blankets and soil layers were applied to form a substrate for vegetation growth.
RESULT
Results were immediate, as erosion gully progression and drainage canal silting
were halted soon after hydrosowing and application of the anti-erosion biodegradable
blanket. Vegetation developed three months following application of the anti-erosion
biodegradable blanket (Fibratextil Screen® 400UM).
This project was executed in 1996 and is still intact, with no erosion gullies. The slopes
are protected and do not require maintenance. The drainage system was efficient, with no
cracking or silting, demonstrating the efficiency of the technique and products used. |
