Application of Potentially Important Jute Geo-textiles for Erosion Control and Slope Stabilization

Abstract

Soil erosion is increasingly recognized as a problem in hilly regions which needs an effective and economic solution. Slope stabilization in hilly areas is now become a costly and tedious process since various human activities have led to land use changes which have indirectly affected the slope stability. Permanent structures are being used for slope stabilization which are costly and cannot be adopted on a larger scale. On other side, availability of area for construction of permanent structures in the road side is also a major constraint in many locations. Hence growing vegetation in these areas to cover and protect the soil is the wise choice for hill slope stabilization as it is sustainable as well as environmental friendly. However there are certain limitations which can hamper the establishment of vegetation in slopes as it is not able to resist severe scour or high runoff and takes time to establish (Abramson et al., 1995). Without immediate, appropriate and adequate protection, slopes can suffer from severe soil erosion and instability, which in turn makes vegetation establishment extremely difficult. Thus some mechanical protection at initial stage of the vegetation establishment is imperative on steep slopes which resists soil erosion, retains runoff and facilitates establishment of vegetation on the surface. Different ranges of natural and Synthetic Geo-textiles have been used for this purpose. Apart from conventional civil engineering applications, Geosynthetics play a major role even in environmental engineering applications including pollution control, landfills and erosion control. Alternatively natural fibre based Jute Geo Textiles (JGT) are also utilized effectively in road construction and slope stabilization to some extent. Recently, coir Geo-textiles have been evaluated for slope stabilization and rehabilitation of heavy metal contaminated soils. Its natural water absorbing capacity helps to conserve soil moisture and anchor soil firmly in sloppy areas. Keeping in view the erosion control characters of Jute Geo-textiles, two experiments were conducted to compare the performance of Jute Geo-textiles with Synthetic Geo-textiles as well as to identify the suitable Open Weave Jute Geo-textiles for hill slope stabilization with the following objectives. 1. Assess the impact of different Jute and Synthetic Geo Textiles on runoff and soil loss under various slopes. vii 2. Study the growth of tea and grass grown for soil binding under different Geo-textiles. 3. Evaluate the impact of Geo-textiles on soil moisture and nutrient losses. Two sets of field experiments were conducted at the Research Farm of ICAR - Indian Institute of Soil and Water Conservation (formerly known as Central Soil and Water Conservation Research and Training Institute), Research Centre, Udhagamandalam, Tamil Nadu which represents the geographical area of Nilgiris. Effect of different types of Geo-textiles on runoff, soil loss, nutrient loss, soil moisture retention, growth parameters of tea and grass has been evaluated. Results of three years field study on efficacy of various types of Open Weave Jute Geo-textiles namely 500, 600 and 700 GSM on slope stabilization showed that 700 GSM Open Weave JGT is more effective in reducing runoff, soil loss and nutrient loss and increasing soil moisture retention. However, plant height and growth of tea plants were better under 500 and 600 GSM JGT. Higher biomass of grass and other herbs in between tea plants was generated by 700 GSM JGT. Considering the scope of tea cultivation in sloppy regions, rehabilitation of land slide areas using tea plants, optimal moisture requirement and better plant growth of tea plants and economics, it is suggested that 500 GSM JGT will be more effective for slope stabilization with tea plants. Keeping in view of higher biomass production of grass and other herbs grown in between tea plants, 700 GSM JGT will be suitable for slope stabilization with grass. Results of three years field study on efficacy of various types of Jute Geotextiles and Synthetic Geo-textiles on 60 and 90 per cent slopes show that Jute Geo-textiles outperformed the Synthetic Geo-textiles in reduction of runoff and soil erosion. Among the Open Weave and Non Woven JGT, Open Weave JGT are more effective in reducing runoff, soil loss and nutrient loss and also increased soil moisture retention. Growth of the grass and root characters is vigorous in the plots covered by JGT as compared to Synthetic Geo-textiles. Application of Open Weave JGT increased the plant height, number of tillers, root density, surface area coverage and volume of soil binding in both the slope categories. The study concludes that the JGT can be effectively utilized for slope stabilization using the grass species as compared to Synthetic Geo-textiles. Open Weave JGT with grasses is recommended for slope stabilization in the degraded land having the slopes up to 90 %.