*4.1.1 Vegetative barrier*

*Slope Engineering*

**Land capability class**

**Table 2.**

a certain regular order with well-defined side slopes, bed width and depth. In the upper reaches of the drainage system the gullies are wide and shallow with varying side slopes. The middle part of the drainage system usually has relatively deeper, wider and has uniform side slopes normally up to about 25%. The lower portion of the drainage system usually happens very deep, has steep side slopes and associated with intricate branched gullies. The ravine management depends on extent of gully bank deformation, slope, soil quality and vegetation cover. The ravines are classified in six classes based on the extent of gully bank deformation and erosion vulnerability under varying slopes. The shallow gullies up to 3.0 m depths are classified under land capability class I and II and recommended for cultivation of seasonal crops with moderate land leveling. The land capability class III has deeper and narrow gullies and more limitations for cultivation of seasonal crops. The land capability class IV has severe limitations of soil texture, gully size, steeper side slopes, and deeper and narrower gully beds for cultivation of seasonal crops and recommended for perennial horticulture plantations. The Class V and VI lands are not recommended for high value plantations or cultivation due to limitations of seasonal backflows from an adjoining river system, waterlogging, development of soil salinity due to irrigation, or due to extreme slope of gully bank. Hence, Class V and VI lands are recommended for perennial vegetation avoiding uncontrolled grazing activities. The ravine management is location-specific and should be undertaken

**Slope (%) Distance from gully** 

(G4)

*Land capability classification for soil and water conservation measures in ravine land.*

VII (brown) Varies Gully sides and beds

VIII (purple) Varies Gully sides and beds

**rim and land form**

(G4) with rock on the surface.

**Recommended soil and water conservation** 

(i) Staggered contour trenching for moisture conservation and afforestation, (ii) Gully plugging and easing of the rapids along the gully beds, (iii) Development of pasture and

Complete closure to grazing and felling of

**measures**

afforestation.

trees.

Several workers have classified the gullies based on their cross section, forms, gully head characteristics, length, width and depth of catchment. Classification of the gullies, evolved at the ICAR-Indian Institute of Soil and Water Conservation, Research Centre, Vasad, Gujarat, India after critically observing ravine landscape developed along most of the river banks in Western India. The different types of gullies classified based on depth from adjacent marginal lands, width of the gully and side slopes given below in **Table 1** and the land capability classification and recommended conservation measures for ravine land is given in **Table 2** [9].

The agricultural activity with land leveling is preferred for slope stabilization and its management in shallow ravines due to presence of deep and alluvial soil. The increased cost of land leveling operation is a major constraint and key factor in making decision for management of medium and deep ravines. The appropriate ways for management of ravines is reducing runoff intensity and safe disposal of runoff in ravines. The runoff generated from the adjacent marginal land is managed

based on the above classification and limitations.

**4. Measures for management of ravine land**

**182**

Vegetative barriers are used either for supplementing or substituting earthen bunds. The *Dichanthium annulatum, Cenchrus ciliaris, Vetiveria zizanioides, Eulaliopsis binata, Saccharum munja* and *Aloe barbadensis* vegetative barriers were evaluated for their effectiveness in reducing runoff, soil and nutrients losses from 2% slope of marginal shallow ravines. Vegetative barriers were grown across the slope at 45 m horizontal interval, in paired rows of 10 cm slip to slip spacing. The cultivation of pigeon pea (BDN-2) was done at 120 × 30 cm spacing in all plots. These vegetative barriers reduced the annual runoff by 19.7 to 50.1% and soil loss by 51.1 to 80.3% over the control plot [10].

The Napier, Guinea and Para fodder grasses strips of 1 m and 2 m were grown as vegetative barrier in 2% slope in shallow ravines. The lowest sediment yield was observed in 2 m width of Napier grass strip (1.43 t/ha) followed by 2 m width of Guinea and Para grass strips as compared to control (4.07 t/ha), respectively. The 2 m width of Napier grass strips has lowest nutrient loss of (N-5.64 kg/ha, P-3.1 kg/ ha, K-5.4 kg/ha) followed by Guinea and Para were found almost equally efficient in reducing nutrient losses from crop field which is 28 to 30% of nutrient losses from control (N-20.01 kg/ha, P-8.3 kg/ha, K-17.00 kg/ha). The equivalent yield of 2 m width of Napier grass strip and cotton crop (1293.5 kg/ha) has highest yield followed by others. The economic analysis shows that Napier grass strips of 2 m width was found best in reducing runoff, soil loss, nutrient losses and net return from crop field [10].

#### *4.1.2 Grassed waterway*

Grassed waterways are important for preventing the scouring of channel bed in shallow ravines. The *Para* grass strips in waterways were optimized for grass cover to check runoff velocity and reduce sediment concentration in downstream water bodies. The different *Para* grass cover (0–100%) in waterways was studied at 2% slope. The different grass covers are 100%, 75%, 50%, 25% and no grass cover. These *Para* grass strips were able to produce green grass yield of 14.5 kg/m2 . The *para* grass strips in waterways is able to reduce the outflow up to 22% with 100%

grass cover. The grass filter strips is able to reduce the sediment concentration in runoff water by 5 times (from 3.6 to 0.72 g/lit). The *Para* grass filter in waterways is able to reduce the flow velocity of runoff water by converting the super critical flows into sub critical flows [10].
