Soil Erosion Types and Causes Questions and Answers

Answer: C

The match is P-3, Q-1, R-5, S-4, T-2.

• A flownet is drawn from streamlines and equipotential lines.
• The EI₃₀ index, storm energy times maximum 30-minute intensity, measures the erosivity of rainfall: soil erosion.
• Groynes are structures built out from a river bank to protect it.
• An isobath here is a line joining points of equal depth to groundwater.
• Runoff is estimated by the SCS curve number method.

The other options link the flownet to groundwater depth or the EI₃₀ index to the curve number, which misreads both terms.

Answer: C

Soil degradation takes place due to accelerated erosion.

Geologic (natural) erosion is the slow wearing of land by water, wind and gravity under natural vegetation; it is roughly balanced by soil formation. Accelerated erosion is erosion speeded up by human activity, such as deforestation, overgrazing and poor tillage, removing soil far faster than it forms. This is what degrades farmland.

Glacial erosion is the work of ice and is confined to glaciated mountains. Geologic erosion shapes landscapes over long periods without net degradation.

Answer: B

The removal of a thin, uniform top layer by overland flow is sheet erosion.

In sheet erosion, raindrop splash detaches soil and shallow overland flow carries it away more or less evenly over the field, so the topsoil thins without visible channels. It is the least noticeable form of water erosion but removes the most fertile layer.

Rill and gully erosion cut channels, and torrent erosion is channel erosion by fast mountain streams. Glacial erosion is caused by ice, not by overland flow.

Answer: C

Class IV land is partly suitable for cultivation.

In the USDA land capability classification used in India, Classes I to IV are suited to cultivation with increasing limitations, and Classes V to VIII are not suited to regular cultivation. Class IV land has very severe limitations, from steep slopes or erosion hazards, and can be cultivated only occasionally or with very careful management, so it is the last class that is partly suitable for cultivation.

'Suitable for cultivation' fits Classes I to III better. 'Not suitable for cultivation' describes Classes V to VIII.

Answer: B

A high intensity rain produces great splash.

Splash erosion depends on the kinetic energy of raindrops. High intensity storms have larger drops falling at higher terminal velocities, so their kinetic energy per unit of rain is greater. Each impact detaches and throws more soil, so splash increases with rainfall intensity. This is why the erosivity index EI₃₀ combines storm energy with intensity.

Less splash or no effect would mean intensity did not matter, which contradicts this relationship.

Answer: D

All three can deteriorate a watershed, so the answer is All above.

Rain falling on bare land and fires that strip vegetation leave the soil exposed to erosion. Industrial expansion clears land, seals surfaces and pollutes water. Unscientific mining and quarrying removes vegetation and topsoil, dumps loose spoil and silts up streams. Each reduces infiltration, increases runoff and sediment, and so degrades the watershed.

Picking only one of them ignores the others, which are equally recognised causes of watershed degradation.

Answer: A

It is considered a part of Watershed management.

Watershed management is the integrated management of land, water and vegetation within a watershed. Conservation farming practices such as contour cultivation, strip cropping, mulching and conservation tillage, adopted across the area to improve agriculture and reduce all kinds of erosion, are one of its core components, together with engineering works and afforestation.

Tillage is only one farming operation, surveying is a measurement activity, and gully making is the opposite of conservation, so none of them describes the overall programme the question refers to.

Answer: B

The one that is not a watershed development project is the National Flood Control Project.

India's watershed development efforts include the Drought Prone Areas Programme (1973-74), the Desert Development Programme (1977-78) and the National Watershed Development Project for Rainfed Areas (1990-91), all of which treat land, water and vegetation on a watershed basis.

Flood control in India was organised under the National Flood Control Programme, launched in 1954, which built embankments and drainage works on rivers. It is a flood management programme rather than a watershed development project, and the name in the option does not match any watershed scheme.

Answer: C

The one that is not a principle is Control of gravity.

Soil conservation measures work by reducing the impact of raindrops on bare soil (through cover and mulch), reducing splash erosion that follows from that impact, and controlling runoff by slowing it, spreading it and guiding it safely off the land.

Gravity is the force behind runoff and soil movement, but no conservation measure controls gravity itself; measures control the water and the soil it acts on, which is why this option is the odd one out.

Answer: A

The area is a Watershed.

A watershed (catchment or drainage basin) is the area of land from which all runoff from precipitation drains past a single outlet point into a larger stream, river, lake or the sea. It is bounded by the ridge line that separates it from neighbouring watersheds, and it is the unit of planning for soil and water conservation.

A farm pond stores water, a nadi is a village pond of western Rajasthan, and an anicut is a small weir across a stream. Each is a structure, not an area of land.