Although, natural vegetation can provide a certain level of soil erosion protection, it is often inadequate on steep slops or areas pron to wave run up or intermittent high velocity flows. This can occur in coastal aeas, river lakes reservoirs, drainage ditches, floods bands and overspill it ponds.Riverbanks and coastinlines can be undermined and damaged by wave or tidal action.
The defensive elements that require for protection are. :
i) The in-situ soil
ii) The filter unit protecting the soil
iii) The rock armour protecting the filter
The Problem
River and canal banks are subject to wave action, i.e. Reversing flow conditions It is this dynamic erosive force that undermines bank stability and effects channel flow and/or navigability.
On coastlines, the three key agents of erosion are:
I) Waves and tides eroding the shoreline
ii) Waves and tidal scour take the eroded sendiment away from the coast.
Iii) Currents sweep the displaced material out to sea.
Traditional Methods
Defence structures for erosion control always require a filter to prevent soil washout.
Traditional filters usually consist of several layers of stone aggreate. Aggregater may be graded or single-sized but installation is always time- consuming and expensive. Furthermore, conventional layers are awkward to place on sleep slops, cannot always be installed in tidal zones and the laying proces
Benefits of Geotextile for Erosion Control
The Hydraulic and filtration properties of geotextile allows them to be used in place of some the traditional filter layers. Consequently, a single layer of goetextile fabric can replace a succession of stone filter layers. A single bedding layers of stone is laid on the geotextile, to carry the rocks that resist the movements caused by the hydraulic forces.
By usinfg Terram geosynthetics the filter system can be assembled above the water & lowered into position making it easier to install with less time being lost through bad weather or difficult water conditions. They can be pre - sewn or site sewn in to large sheet, reducing the number of overlapping joints, which is a particular benefit in tidal or fast flow conditions.
Other Benefits Includes
Geotextiles have built- in factory - controlled filter properties
Checking for correct installation is easier
Geotextile is easier to install, either by hand or mechanically
Geotextiles can be pre-sewn or site-sewn in to large sheets.
Working underwater is much easier because the filter system can be assembled above the water and lowered into position
Less time lost through bad weather or difficult water conditions
