Gully control and land stabilisation

Gully control and land stabilisation

A gully is a deep channel cut by concentrated surface flow on a slope. Gully control means stopping the growth of such channels and filling them, by reducing the flow velocity and trapping sediment. Land stabilisation means making the unstable slope or gully bank stable by engineering structures and vegetation (bio-engineering) so that erosion and landslides do not continue and endanger the road.

Gully control structures / methods (any four)

1. Check dams (gabion, stone masonry or brushwood) - small cross-barriers placed in the gully at intervals so that the toe of the upper dam is at the same level as the crest of the next lower dam. They reduce the bed slope, slow the flow, and trap sediment.
2. Drop structures / chutes - masonry or concrete stepped channels that lead the flow safely down a steep gully; energy is dissipated in stilling pools.
3. Diversion drains and catch drains - intercept and divert the runoff from the gully head, reducing the discharge entering it.
4. Vegetative and bio-engineering measures - planting grass (vetiver, napier), shrubs and trees on gully banks and bed; brush layering, live check dams, fascines and jute/coir netting hold the soil and bind the slope.
5. Gabion walls and re-grading of gully sides - regrade steep banks to a stable slope (1:1.5 to 1:2) and protect the toe.

  upper  ___           flow ->
        |   \__ check dam 1
         \       \___ 
           \  silt   check dam 2
 toe of dam 1 level with crest of dam 2

These works are used with proper drainage so that the road is not damaged by gully extension.