Field instrumentation and monitoring of soil erosion in coir geotextile stabilised slopes - A case study

Soil erosion along degraded hill slopes has been a problem of serious concern throughout the world. In India, about 5330 million tones (16.4t/ha) of soil is being lost every year. Conventional methods of bench terracing coupled with dry rubble packed bunds are being used on steep slopes of plantation area situated along the Western Ghats, to reduce surface erosion. But these conventional methods prove unsuitable in many of the steep slopes which are highly susceptible to erosion. A permanent and self-propagating vegetal cover is found to be an ideal solution to 90% of the erosion problems. Stabilisation of soil along the hill slopes using natural and locally available materials such as coir is a recent technique. Natural and biodegradable fibres such as coir and jute in the form of nettings can aid in vegetative turfing along the slopes. These nettings are intended to protect the seeds and the soil until. the sites are permanently stabilised with vegetal cover, by providing a physical barrier between the soil particles and rainwater. The coir netting spread over seeded slopes shields the soil and seeds from the impact of rain drops, minimise runoff and slows down its velocity, maintains the capacity of soil to absorb water, holds the soil particles and seeds in place and retains soil moisture. When seeds germinate, they grow through the gaps in the fabric and achieve a cover all over as the biodegradable coir netting begins to degrade. This technology is applicable to highly erodable slopes where mechanical methods such as tillage or terracing prove unsuitable. This paper. presents the methodology followed in monitoring soil erosion in a hill slope stabilised by coir geotextile aided vegetative turfing. Improvement in various soil parameters in such a protected slope is analysed by a comparison of results from a similar unprotected slope. (C) 2004 Elsevier Ltd. All rights reserved.