GATE — Agricultural Engineering (AG) · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papersEstimating erosion and designing the bunds, terraces, waterways, spillways, ponds and dams that control it.
In the exams: GATE AG Section 4 Soil & Water Erosion; ICAR AIEEA-PG Unit VII; ICAR AICE subject 40 Unit 5; NCEES PE erosion; PRC ABE land and water (32%); state PSCs
GATE — Agricultural Engineering (AG)
Section 4 Soil and Water Erosion as short numericals, often numerical-answer type: the effect of changing slope length or steepness in the USLE, VI and HI of bunds and terraces, bench-terrace earthwork, grassed waterway velocity and dimensions with Manning's equation, weir capacity of drop spillways, check-dam spacing, flow-net seepage through embankments, and shelterbelt protected distance and wind transport modes.
How our questions for GATE spread across the units of Soil & Water Conservation Engineering. Difficulty: 3 easy, 25 medium, 21 hard.
| Grassed waterways | 7 | |
| Soil loss estimation: USLE, RUSLE and MUSLE | 6 | |
| Bench and broad-base terraces | 5 | |
| Drop, drop-inlet and chute spillways | 5 | |
| Contour and graded bunds | 4 | |
| Earthen dams: seepage and stability | 4 | |
| Wind erosion mechanics | 4 | |
| Mechanics of water erosion | 3 | |
| Sediment yield | 3 | |
| Farm ponds | 3 | |
| Gully control | 2 | |
| Wind erosion control and shelterbelts | 2 | |
| Agronomic and biological conservation measures | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A storm has two uniform-intensity parts: 20 mm at 40 mm/h (30 minutes) followed by 10 mm at 10 mm/h (60 minutes). With e = 0.119 + 0.0873 log10 I (MJ/ha/mm), the storm's EI30 is closest to:
C. 289.6 MJ·mm/(ha·h)
Energy of part 1 = 20 × (0.119 + 0.0873 log10 40) = 5.177; part 2 = 10 × (0.119 + 0.0873 log10 10) = 2.063; E = 7.240 MJ/ha. The wettest 30 minutes delivered 20 mm, so I30 = 40 mm/h. EI30 = 7.240 × 40 = 289.6. Using the storm average intensity (20 mm/h) gives 144.8, treating all 30 mm as falling at 40 mm/h gives 7.766 × 40 = 310.6, and stopping at E gives 7.24.
Further reading: Wischmeier and Smith (1978), USDA Agriculture Handbook 537
A sediment rating curve for a stream is Qs = 2 Q^1.5, with Qs in t/day and Q in m³/s. The sediment discharge at a flow of 16 m³/s is:
A. 128 t/day
Qs = 2 × 16^1.5 = 2 × 64 = 128 t/day. Multiplying by 1.5 instead of raising to the power gives 48; raising (2 × 16) to 1.5 gives 181. Using the power 0.5 gives 2 × 4 = 8 t/day.
Further reading: Schwab et al. / Fangmeier et al., Soil and Water Conservation Engineering
For level bench terraces with vertical risers and a vertical interval of 1.2 m, the earthwork (cut) per hectare is:
C. 1,500 m³
Length of terrace per ha = 10,000/W; cut per metre = W·VI/8; so cut per ha = 10,000 × VI/8 = 1,250 × VI = 1,500 m³, independent of W. 3,000 m³ double-counts fill; 6,000 m³ uses the whole triangle under the original slope (W·VI/2 per metre). 1,042 m³ divides 1,250 by VI instead of multiplying.
Further reading: Suresh, R., Soil and Water Conservation Engineering
A broad-base terrace built by moving soil downhill from the upper side only, forming a relatively deep channel, is called a:
A. Nichols terrace
Nichols terraces take all soil from the upslope side. Mangum terraces take soil from both sides of the ridge. The conservation bench terrace is a runoff area plus a level storage bench.
Further reading: Schwab et al. / Fangmeier et al., Soil and Water Conservation Engineering
Check dams with an effective height of 0.9 m are placed in a gully with a bed slope of 6%, using the head-to-toe rule. The spacing between dams is:
B. 15 m
Head-to-toe: L = H / S = 0.9/0.06 = 15 m, so the crest of each dam is level with the toe of the next one upstream. Using S = 6 gives 0.15 m. H × S (0.9 × 6) gives 5.4 m, and reading 6% as 0.6 gives 1.5 m.
Further reading: Suresh, R., Soil and Water Conservation Engineering
A straight drop spillway discharges 1.5 m³/s per metre of crest over a drop of 2.0 m. Using the drop number D = q²/(g h³) and Rand's relation L_d = 4.30 h D^0.27, the distance from the drop wall to where the nappe strikes the apron is closest to:
B. 3.30 m
D = 1.5²/(9.81 × 2³) = 2.25/78.48 = 0.0287. D^0.27 = 0.3833. L_d = 4.30 × 2.0 × 0.3833 = 3.30 m. Omitting h gives 1.65 m; using q instead of q² in D gives 2.95 m. Dropping the 0.27 exponent gives 4.30 × 2.0 × 0.0287 = 0.247 m.
Further reading: Chow, V.T., Open-Channel Hydraulics
A pond must collect 4,000 m³ of runoff in a season with 500 mm of rain. If the seasonal runoff coefficient of the catchment is 0.2, the catchment area required is:
A. 4 ha
Runoff depth = 0.2 × 0.5 m = 0.1 m. Area = 4,000/0.1 = 40,000 m² = 4 ha. Forgetting the runoff coefficient gives 0.8 ha; using rainfall in mm without converting gives a tiny area. Working in mm without converting gives 40 m² = 0.004 ha, and multiplying by the coefficient gives 0.16 ha.
Further reading: Schwab et al. / Fangmeier et al., Soil and Water Conservation Engineering
The mode of transport that usually moves the largest share of soil in wind erosion is:
A. saltation
Saltation (short hops of particles about 0.1–0.5 mm) usually accounts for roughly 50–75% of movement. Suspension carries fine dust far but is usually a smaller share by mass; creep is driven by saltation impacts.
Further reading: Morgan, R.P.C., Soil Erosion and Conservation
Wind speed measured 2 m above a bare field is 8 m/s. The roughness length is 0.01 m and κ = 0.4. From the logarithmic profile u = (u*/κ) ln(z/z0), the friction velocity is closest to:
C. 0.604 m/s
u* = κ u / ln(z/z0) = 0.4 × 8 / ln 200 = 3.2/5.298 = 0.604 m/s. Using log10 gives 1.39; inverting κ gives 3.77.
Further reading: Morgan, R.P.C., Soil Erosion and Conservation
A shelterbelt is 12 m tall. If effective leeward protection is taken to extend 20 times the barrier height, the protected distance downwind is:
B. 240 m
Protected distance = 20 H = 20 × 12 = 240 m. 5 H (60 m) is closer to the windward-side effect; 10 H (120 m) is the zone of greatest reduction. 32 m adds 20 to the height.
Further reading: Morgan, R.P.C., Soil Erosion and Conservation
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