Soil Erosion and Conservation Questions and Answers

Answer: B

The most effective, easy and economical method is re-vegetation.

Plant cover breaks the impact of raindrops, slows runoff, increases infiltration and binds the soil with roots, so re-vegetating bare slopes and gullies controls water erosion at its source at low cost and lasts on its own.

Fencing only keeps out grazing animals. Check dams are costly engineering structures that control gully erosion locally. Soil filling replaces lost soil without stopping the erosion.

Answer: D

The pair is Gujarat and Rajasthan.

Wind erosion is worst where the climate is arid, the soil is sandy and loose, vegetation is sparse and strong winds blow in the dry season. Western Rajasthan, in the Thar desert, and the Kutch and Saurashtra regions of Gujarat fit all of these conditions, with shifting sand dunes and dust storms.

Kerala and Tamil Nadu are humid, where water, not wind, erodes soil. Madhya Pradesh and Maharashtra, and Punjab and Uttar Pradesh, suffer mainly from water erosion and land degradation of other kinds rather than severe wind erosion.

Answer: A

The USLE predicts Annual soil loss in tonnes/ha.

The Universal Soil Loss Equation, developed by Wischmeier and Smith, estimates the long-term average annual loss of soil from sheet and rill erosion:

\[ A = R \times K \times L \times S \times C \times P \]

Here A is the soil loss in tonnes per hectare per year, R the rainfall erosivity, K the soil erodibility, L and S the slope length and steepness, C the cover-management factor and P the support-practice factor.

It is not designed for single storms; event-based estimates need its modification, the MUSLE. It does not produce a sedimentograph (sediment flow over time) or a land degradation index.

Answer: B

The structures are Drop inlet structures.

In a drop inlet spillway, water upstream rises to the crest of a vertical inlet (riser) before it can drop into a conduit that carries it under the embankment. The pool held upstream up to the crest can be used for lift irrigation or allowed to recharge groundwater, while peak flows pass safely through the conduit, which is the combination the question describes.

A drop structure (straight drop spillway) mainly lowers the stream bed in steps to control gully erosion, and a culvert simply carries water under a road. Gabion structures are loose-rock check dams that slow flow but are not designed to store water for lifting.

Answer: D

The Mitti Bachao movement started at Hoshangabad, Madhya Pradesh.

The Mitti Bachao Abhiyan (Save the Soil campaign) began in 1977 in Hoshangabad district, where farmers protested against the waterlogging and salinity caused by seepage from the Tawa dam's canal irrigation, which was ruining their fertile black soils.

It is remembered as one of India's early environmental movements on land degradation. Thane, Mysore and Darbhanga are not connected with it.

Answer: A

The practice is Strip cropping.

In strip cropping, long, narrow strips of erosion-permitting crops (row crops such as maize, sorghum or root crops) alternate with strips of erosion-resisting, close-growing crops (grasses, legumes, fodder crops) across the slope. The dense strips slow runoff, trap the soil washed from the open strips and help water soak in.

Regular and multiple cropping describe how many crops are grown in a year, not their arrangement for erosion control, so neither fits the definition.

Answer: A

The area described is a Watershed.

A watershed (catchment) is defined with respect to an outlet point: it is the area of land whose surface runoff all drains to and leaves through that single point, bounded by the ridge line that divides it from neighbouring watersheds. This makes it the natural unit for soil and water conservation planning.

A command area is the land that an irrigation system can serve, streams are the channels that carry the flow, and canopy cover is the vegetation over the soil. None of them is defined by drainage to an outlet.

Answer: A

The best combination is Contour bunds, farm ponds, and land smoothening/levelling.

In dry land areas the aim is to hold every drop of rain where it falls. Contour bunds run along the contour and hold runoff in the field so it soaks in, farm ponds harvest the excess for life-saving irrigation, and land smoothening spreads water evenly and prevents it collecting in low spots.

Graded bunds are meant to drain excess water safely in higher-rainfall areas, which is the opposite of what dry lands need. Bench terraces, big check dams, diversion bunds and deep reservoirs are costly structures for steep slopes or larger catchments, not the key in-field measures for dry lands.

Answer: B

The correct statement is that the elevation of each and every point on a contour line remains exactly same.

A contour is an imaginary line joining points of equal elevation on the ground surface, which is its definition.

That makes the other statements wrong. A contour is an imaginary line, drawn only on maps. Two contours of different elevation cannot cross, because a point cannot have two elevations at once; they merge only on a vertical cliff and appear to cross only at an overhang. Since those statements are false, "All of the above" is false too.

Answer: D

The answer is All of these.

All three plants belong to the grass family, Poaceae, and all three are used to hold soil. Vetiver (Chrysopogon zizanioides) is planted as hedges along contours; its dense, deep, vertical roots bind the soil and the hedge filters out silt. Cenchrus ciliaris (anjan or buffel grass) is a hardy pasture grass sown on bunds and degraded dry land to give quick cover.

Bamboo is also a grass, though a woody one, and its spreading rhizomes make it a standard choice for stabilising stream banks and slopes in the north-east. Since each of the three qualifies, choosing any one alone would be incomplete.