Your Answer : (Not Answered)

Correct Answer : A

The one that is not a runoff estimation method is the Logistic method.

The peak rate of runoff from a catchment is estimated by methods such as the Rational method (Q = CIA/360), the Curve Number method and the Soil Conservation Service (SCS) method, which uses the curve number to work out runoff volume and peak rate, together with empirical formulae such as Cook's method.

'Logistic method' refers to a statistical growth model and is not a hydrological method of estimating runoff, so it is the odd one out.

Your Answer : (Not Answered)

Correct Answer : B

The one that is not a form of water erosion is Fence.

Water erosion is described in stages of increasing severity: raindrop splash, sheet erosion, rill erosion, gully erosion and stream bank erosion.

A fence is a barrier, not an erosion process, so it is the odd one out. Sheet, rill and gully erosion are all standard forms of water erosion.

Your Answer : (Not Answered)

Correct Answer : B

It is Sheet erosion.

Sheet erosion is the removal of a thin, fairly uniform layer of soil from the whole surface by raindrop splash and shallow overland flow. It is hard to notice and often goes unchecked, yet it removes the most fertile topsoil.

Rill erosion cuts small channels a few centimetres deep, gully erosion forms large channels that cannot be crossed by tillage implements, and mass erosion (landslides, slumps) moves large masses of soil at once. None removes a uniform thin layer.

Your Answer : (Not Answered)

Correct Answer : D

The data not included is Load sampling data.

Planning a watershed improvement project needs hydrological information (rainfall, runoff, stream flow, groundwater), soil and land use data (soil types, depths, slopes, present use and capability) and economic and social data (land holdings, incomes, population and people's participation).

Load sampling refers to measuring sediment or pollutant loads in a stream, which is a monitoring activity rather than one of the standard categories of planning data, so it is the odd one out.

Your Answer : (Not Answered)

Correct 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.

Your Answer : (Not Answered)

Correct 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.

Your Answer : (Not Answered)

Correct Answer : C

The one that is not a type of farm pond is c only, dyke ponds.

Classified by the source of water and their position relative to the ground, farm ponds are excavated (dugout) ponds dug into the ground, creek or spring fed ponds, off-stream storage ponds filled from a nearby stream, and watershed (embankment) ponds formed by a dam across a depression that collects runoff.

A dyke is an embankment along a river or the coast that keeps water out. 'Dyke ponds' is not one of the recognised farm pond types, so only c fits the question.

Your Answer : (Not Answered)

Correct Answer : B

The key takes Surface water ponds as the most common type of farm pond.

Farm ponds are commonly classified by water source and position relative to the ground into four kinds: dugout ponds, surface (embankment) ponds, spring or creek fed ponds and off-stream storage ponds. In this classification, which many Indian soil and water conservation course notes follow, surface water ponds are called the most common type. They are formed by building an embankment across a depression or small stream so that runoff collects behind it, and this suits ordinary rolling farmland.

Dugout ponds are made by excavating the ground and suit flat land where there is no slope to build against. Spring ponds depend on a spring or creek being present, so they are site specific. Off-stream storage ponds are built beside seasonal streams and fed by conveyed water, which again needs special conditions. Note that other sources, such as prairie farm guides, call the dugout the commonest reservoir in their own regions, so the key reflects the course-note classification the paper follows.

Your Answer : (Not Answered)

Correct Answer : A

Both Statement I and Statement II are true.

Statement I: in contour cultivation, ploughing, sowing and interculture are done across the slope along the contour. Each furrow and row acts as a small barrier that slows overland flow, increases the time available for infiltration and so retards soil erosion.

Statement II: row crops such as sorghum and pearl millet are grown in lines and need repeated interculture, so the rows can follow the contour and give the barrier effect. They are the crops normally recommended for contour cultivation in dryland areas. Since both statements hold, the options that call either false are wrong.

Your Answer : (Not Answered)

Correct Answer : A

The short bouncing movement is saltation.

Wind moves soil in three ways. In saltation, particles of about 0.1 to 0.5 mm are lifted, carried a short distance and dropped, bouncing along the surface; it carries the major part of the soil moved, often 50 to 75%. In suspension, very fine particles are carried high and far by turbulence. In surface creep, larger particles roll and slide along the ground, pushed by the impact of saltating grains.

So suspension and surface creep are real modes but carry less soil and do not involve short bounces.

Your Answer : (Not Answered)

Correct Answer : C

Wind erosion is common in arid and semi-arid regions.

Wind erodes soil where the soil is dry, loose and finely divided, the surface has little vegetation, and winds are strong. These conditions occur together in regions of low rainfall: the deserts and semi-deserts. In India, western Rajasthan and parts of Gujarat and Haryana are the main areas.

Humid regions have moist soil and good plant cover, which hold soil against wind; erosion there is mainly by water. 'Arid region' alone is not wrong, but it leaves out the semi-arid regions, which also suffer badly, so the fuller option is the answer.

Your Answer : (Not Answered)

Correct Answer : D

The soil transported varies directly as the cube of the difference between the actual and threshold wind velocities and as the square root of the mean soil particle diameter.

Soil is moved only when the wind exceeds the threshold velocity at which particles start to roll and saltate, so it is the excess velocity \((V - V_{t})\) that drives transport. The relation used in soil conservation texts follows Bagnold's work on blown sand: the rate of soil movement grows with the cube of that excess and with the square root of the mean particle diameter, \(q \propto (V - V_{t})^{3}\sqrt{d}\).

The options using the threshold velocity alone or the actual velocity alone miss the fact that only the excess over the threshold does work, and they also wrongly make transport fall with particle size squared. The option with the square of the diameter has the right velocity term but the wrong power of \(d\).

Your Answer : (Not Answered)

Correct 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.

Your Answer : (Not Answered)

Correct 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.

Your Answer : (Not Answered)

Correct 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.

Your Answer : (Not Answered)

Correct 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.

Your Answer : (Not Answered)

Correct Answer : A

A concave vertical curve is provided.

Where the floor of a chute changes from a steeper slope to a milder one, the profile bends upwards, like the bottom of a valley. That change is made with a concave (sag) vertical curve, usually a circular arc of generous radius, so that the fast-moving water is turned gradually and the dynamic pressure on the floor stays within limits.

A convex vertical curve is needed in the opposite case, where the slope changes from milder to steeper; it must be flat enough (shaped to the jet trajectory) for the flow to stay in contact with the floor. A reverse curve is an S-shaped combination of the two, and a converging transition narrows the chute in plan, not in profile.

Your Answer : (Not Answered)

Correct Answer : B

The most suitable structure is the pipe drop structure.

A pipe drop (pipe outlet) carries runoff through a pipe laid in the bund, with its inlet on the higher side and its outlet on the lower side. The bund stays intact and is not overtopped, which is exactly what is needed to pass water across an earthen bund from a higher field to a lower one.

A drop structure (straight drop spillway) is a masonry weir with a free overfall, built across a gully or channel to control its bed, not through an earthen bund. A chute spillway carries large flows down a steep open channel over longer drops and is costly for this purpose. A gabion structure is a check dam of wire-mesh boxes filled with stone, used to stabilise gullies.

Your Answer : (Not Answered)

Correct Answer : A

Such areas should adopt bench terraces sloping inward.

An inward-sloping bench drops towards the hill, so runoff collects at the inner edge of each bench and is led away in a drain along the toe of the riser to a safe outlet. The outer edge and the riser stay dry and protected, which is what is needed in hilly regions of heavy rainfall where much of the rain must leave as surface runoff.

Level benches suit areas of moderate, evenly distributed rainfall on permeable soils, where water is to be held and absorbed. Outward-sloping benches suit low-rainfall areas, since they would send heavy runoff over the riser and erode it. Narrow width is a matter of land slope and use, not a drainage design.

Your Answer : (Not Answered)

Correct Answer : B

The most appropriate dimensions are a top width of 6 m and a depth of 0.4 m.

The flow area needed at the permissible velocity is \(A = Q/V = 2.85/1.78 = 1.60\ \text{m}^{2}\). Manning’s equation fixes the hydraulic radius:

\[ \begin{aligned} R^{2/3} &= \frac{Vn}{\sqrt{S}} = \frac{1.78 \times 0.04}{\sqrt{0.03}} = 0.411 \\ R &= 0.264\ \text{m} \end{aligned} \]

For a parabolic section with top width \(T\) and depth \(d\), \(A = \tfrac{2}{3}Td\) and \(R \approx T^{2}d/(1.5T^{2} + 4d^{2})\). With \(T = 6\) and \(d = 0.4\):

\[ \begin{aligned} A &= \tfrac{2}{3}(6)(0.4) = 1.60\ \text{m}^{2} \\ R &= \frac{36 \times 0.4}{54 + 0.64} = 0.264\ \text{m} \end{aligned} \]

Both match. The pair 4 and 0.6 gives the right area but \(R = 0.38\) m, too deep a section, so the velocity would exceed the permissible value. The pairs 7 and 0.5 and 5.5 and 0.6 give areas of 2.33 and 2.2 m², larger than needed.