Steps to prevent soil erosion in hilly areas

Steps to prevent soil erosion in hilly areas in the context of overall soil conservation measures

    The need to conserve and build the country's land and soil resources, so that those serve the present as well as future generations, has assumed paramount importance in the wake of developing shortage of tillable land and water resources. Unplanned road construction in hilly areas has been identified as one of the causes contributing to loss of these resources.

    By its very nature, road construction in hills is a destructive process for the strata of the hill side, at least in the initial stages. Road cuttings through areas otherwise not susceptible to land-sides normally disturbed the natural inclination of the soil in such a way as to create conditions for large scale landslides in the first few years after construction. Even dense forests are not immune to this problem. With the removal of vegetative cover, destructive action of water gets further pronounced and accelerates the process of soil erosion and formation of deep gullies. End result of this is that enormous quantities of soil and rock move down the rivers, lakes and finally to the sea.

    It is, therefore, necessary that utmost care is taken during road construction, as regards planning of works and treatment of the catchment area of drainage so that soil erosion is prevented as far as possible. To combat this problem, the following measures are especially commended for adoption on National Highways as well as State Roads :

i) Roads should not be located through geologically unstable strata if this can be avoided.

ii) Road alignments should avoid large scale cuttings and fillings and follow the lie of the land (features or characteristics of an area) as far as possible. Use of tunnels to avoid deep cuts should be considered where feasible as also economical.

iii) Where necessary, provision of breast walls/Gabion walls/Geotextile application of suitable design should be considered to help achieve stability of the hill cuttings.

iv) To the extent feasible, roads should be aligned away from streams and torrents except where there are to be crossed. Since the greatest damage always occurs along water courses, special attention is necessary to "create protection belts of forests on both sides". Use of Geotextile liners is common nowadays for protection from erosion due to water streams.

v) Drainage of water from the roadside must be given top attention and necessary system of drains constructed to lead the runoff to natural water courses. In particular, suitable interceptor and catchwater drains must be provided above the cut slopes for speedy and safe disposal of rain water.

vi) Excavated material should not be thrown haphazardly but dumped at suitable places where it cannot got easily washed away by rain. It is other wise expected as a normal requirement of hill road design that the cross-section is either wholly in cutting, so that with the adoption of retaining walls of a suitable type, the cutting spoils can be utilised to the extent possible, guided of course by consideration of economy & best road stability.

vii) Depending upon the availability of land and other resources, afforestation of roadside land should be carried out to a sufficient distance on either side of the road. The selection of plant species will depend on climate, altitude and soil conditions, but preference should be given to deep rooted trees and plants. For preparing the detailed scheme of afforestation, persons having knowledge of soil conservation or forestry should desirably be associated.

viii) vegetative cover should be established on all cut/fill slopes through any one of techniques described in IRC Standard "Treatment of Embankment slopes for Erosion Control". The activity of establishing vegetation on barren slopes should be treated as part of the regular maintenance operations on all hill roads.