The Hindu Business Line : Coir geo-textiles can control soil erosion: Study

STUDIES conducted by the State Government to develop a uniform standard on coir geo-textiles for soil erosion control as part of its development programme have proved that irrespective of the weaving pattern and spinning methods it is good for erosion control.

The studies were conducted as part of the watershed management projects along the Western Ghats in Kerala and proved that coir geo-textiles of any weaving pattern as well as coir yarns made of any spinning methods are equally good for erosion control, Dr K. Balan, Director, Centre for Development of Coir Technology (C-DOCT), Thiruvananthapuram.

Pilot projects were taken up to study the efficacy of weaving pattern of geo-textiles and also the spinning methods adopted for making yarn.

Coir geo-textiles of different mesh opening sizes as well as yarns of different spinning were utilised in two sites in Idukki and one in Thiruvananthapuram district, he said.

He said that all the different mesh mattings have performed equally well in the soil erosion control of natural slopes of 35 degrees. Observations have shown that all mesh mattings have controlled more than 80 per cent of the erosion compared to bare soil.

Vegetation growth was also equally good. Woven coir geotextiles of MMV2 (H2M6) of 400 gsm (gram per sq metre) with vycome coir yarn and MMA4 (H2M9) of 900 gsm with angengo an Aratory yarns were used to stabilise a steep slope having degrees along the Western Ghats in the State in 1994.

The woven geo-textiles of 400 gsm was found to be effective in controlling the erosion and subsequent growth of vegetation, even on previously exposed rock surfaces along slopes having 45 degrees and that of 900 gsm was found to be effective along 60 degree slopes, he pointed out. Owning to land slide, the area was previously abandoned by the rubber plantation authorities. Now they are using this area for plantation after the successful trial with coir geo-textiles, he said.

After visualising the efficacy of woven coir geo-textiles in controlling the erosion, the efficacy of needle-punched coir geo-textiles in controlling erosion in the same plantation area was tried in 1996. Non-woven coir geo-textiles with medium thick PP net on top and bottom and having a mass per unit area of 1000 gsm were tried along the slope.

After seven months of application of the non-woven coir geo-textiles, vegetation has started taking place and the slope has stabilised within one and a half years time.

The only major problem encountered with the non-woven coir geo-textile is that it takes much more time for the vegetation, he said. Hence it can be recommended that non-woven coir geo-textiles of lesser mass per unit area will be more ideal than heavier varieties for erosion control purposes, he said.

The results that emerged from the pilot projects are that coir geo-textiles of MMV2 is ideal and cheaper for erosion control for moderate slopes, while MMV1 ideal for any slope and sandy silt type of soil. Both woven and non-woven are equally effective as soil bio-engineering products.

For the protection of mine waste dumps, coir geo-textiles are found to be the best and cheaper solution compared to any other conventional solutions. This has been proved in an erosion control project at the iron ore mine waste dumps in Goa, which was executed in August 2001. Here erosion control blankets (needle punched non-woven coir geo-textiles with medium thick PP net on top and bottom) of 600 gsm were tried, he said.

Woven coir geo-textiles made of conventionally/machine made yarns are equally good in erosion control applications. Thus, the method of yarn spinning is not influencing the erosion control effectiveness of the geo-textile as a whole, he added.

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