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Question 1
ప్రశ్న 1
Which expression represents the Rational Method for estimating peak runoff from a small drainage area when consistent units are used?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Method relates peak runoff discharge to a runoff coefficient, rainfall intensity and contributing drainage area. Its basic form is Qp = C i A when a consistent unit system is employed. The runoff coefficient C is dimensionless and represents the combined influence of runoff-producing characteristics. The rainfall intensity must correspond to the selected design frequency and an appropriate duration. Therefore Option A is correct.
వివరణ:
Question 2
ప్రశ్న 2
In Rational Method analysis, what is the time of concentration of a catchment?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Time of concentration is associated with travel through the drainage system. It represents the time required for runoff from the hydraulically most remote contributing location to reach the point of interest. When rainfall persists for approximately this duration, the entire drainage area can contribute simultaneously under the Rational Method assumptions. It is therefore important in selecting design rainfall intensity. Hence Option B is correct.
వివరణ:
Question 3
ప్రశ్న 3
Why is rainfall intensity corresponding approximately to the time of concentration commonly used in Rational Method design?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A storm shorter than the time of concentration may end before runoff from all portions of the catchment can contribute simultaneously. A much longer design duration generally has a lower average rainfall intensity for the same return period. The Rational Method therefore commonly uses an intensity associated with a duration equal to the time of concentration. This is consistent with the conceptual condition for the catchment-wide peak response. Therefore Option A is correct.
వివరణ:
Question 4
ప్రశ్న 4
If rainfall intensity i is expressed in mm/h and drainage area A in hectares, which SI form gives peak discharge Q in m³/s?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
One hectare equals 10,000 m². One millimetre per hour equals 0.001/3600 m/s. Their product is 10,000 × 0.001/3600 = 0.0027778 m³/s for C = 1 and i = 1 mm/h. Therefore the convenient metric form is Q = 0.00278 C i A when area is in hectares. Hence Option C is correct.
వివరణ:
Question 5
ప్రశ్న 5
A 20 ha drainage basin has runoff coefficient C = 0.60. If the design rainfall intensity corresponding to the time of concentration is 75 mm/h, what peak discharge is estimated by the Rational Method?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For area in hectares and intensity in mm/h, Q = 0.00278 C i A. Substitution gives Q = 0.00278 × 0.60 × 75 × 20. The result is 2.502 m³/s. Rounded suitably, the estimated peak discharge is 2.50 m³/s. Therefore Option B is correct.
వివరణ:
Question 6
ప్రశ్న 6
A catchment of area 1.5 km² has runoff coefficient 0.50 and design rainfall intensity 60 mm/h. Using Q = 0.278 C i A for A in km², what is the estimated peak discharge?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
When area is expressed in km² and rainfall intensity in mm/h, the metric conversion factor is approximately 0.278. Thus Q = 0.278 × 0.50 × 60 × 1.5. This evaluates to 12.51 m³/s. The calculation represents the idealized Rational Method peak under the stated assumptions. Therefore Option C is correct.
వివరణ:
Question 7
ప్రశ్న 7
A 20 ha catchment produces a Rational Method peak discharge of 4.17 m³/s under a design rainfall intensity of 100 mm/h. What runoff coefficient is implied?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Rearranging Q = 0.00278 C i A gives C = Q/(0.00278 i A). Substitution gives C = 4.17/[0.00278 × 100 × 20]. The denominator equals 5.56. Therefore C = 4.17/5.56 = 0.75. Hence Option C is correct.
వివరణ:
Question 8
ప్రశ్న 8
A 50 ha drainage area has runoff coefficient 0.60 and a design peak discharge of 8.34 m³/s. What rainfall intensity is implied by the Rational Formula?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Formula gives i = Q/(0.00278 C A) for the stated units. Substitution gives i = 8.34/[0.00278 × 0.60 × 50]. The denominator is 0.0834. Thus the required rainfall intensity is exactly 100 mm/h. Therefore Option C is correct.
వివరణ:
Question 9
ప్రశ్న 9
A drainage system is designed for Q = 5.004 m³/s using C = 0.60 and i = 100 mm/h. What contributing area is implied?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Rearranging the metric Rational Formula gives A = Q/(0.00278 C i). Substitution gives A = 5.004/[0.00278 × 0.60 × 100]. The denominator is 0.1668. Dividing gives approximately 30 hectares. Therefore Option C is correct.
వివరణ:
Question 10
ప్రశ్న 10
A 30 ha catchment contains 10 ha with runoff coefficient 0.80 and 20 ha with coefficient 0.40. What area-weighted composite runoff coefficient should be used when the same design rainfall intensity applies to the whole catchment?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The composite coefficient is obtained by area weighting the component coefficients. Thus Cw = [0.80(10) + 0.40(20)]/30. The numerator is 8 + 8 = 16. Therefore Cw = 16/30 = 0.533 approximately. Hence Option C is correct.
వివరణ:
Question 11
ప్రశ్న 11
For the 30 ha composite catchment with C = 0.533 approximately, what peak discharge is obtained for a uniform design rainfall intensity of 70 mm/h?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The metric Rational Formula is Q = 0.00278 C i A. Using the unrounded weighted coefficient 16/30 gives Q = 0.00278 × (16/30) × 70 × 30. This gives 3.1136 m³/s. Rounded suitably, the peak discharge is approximately 3.11 m³/s. Therefore Option C is correct.
వివరణ:
Question 12
ప్రశ్న 12
For Rational Method design, which rainfall intensity should normally be obtained from the relevant intensity-duration-frequency information?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Design rainfall must represent both the selected frequency and an appropriate storm duration. The Rational Method commonly takes the relevant duration as the time of concentration. The corresponding intensity is then obtained from an IDF relationship or equivalent design-rainfall information. Using an unrelated short-duration or annual-average intensity would not satisfy the method's conceptual assumptions. Therefore Option A is correct.
వివరణ:
Question 13
ప్రశ్న 13
What is the principal problem with directly using a very short-duration rainfall intensity when that duration is substantially less than the catchment time of concentration?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Method peak concept assumes that all relevant portions of the drainage area are contributing at the design point. If storm duration is appreciably shorter than the time of concentration, remote parts may not yet be contributing when rainfall ends. Applying a very high short-duration intensity to the entire area can therefore violate the underlying assumption. More detailed hydrologic analysis may be appropriate when storm duration and spatial contribution are important. Therefore Option A is correct.
వివరణ:
Question 14
ప్రశ్న 14
For a fixed return period, rainfall intensity generally decreases as averaging duration becomes longer. What does this imply about choosing a storm duration much longer than the time of concentration in a standard Rational Method calculation?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Intensity-duration-frequency relationships generally show decreasing average intensity with increasing duration for a fixed return period. Once rainfall lasts at least as long as the time of concentration, the complete drainage area can participate under the Rational Method concept. Extending the duration substantially further generally reduces the corresponding design intensity. Thus the standard critical-duration choice is commonly near the time of concentration rather than arbitrarily much longer. Therefore Option A is correct.
వివరణ:
Question 15
ప్రశ్న 15
If a natural drainage area is extensively urbanized with roofs and pavement while area and design rainfall intensity remain unchanged, what Rational Method change is generally expected?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The runoff coefficient represents the tendency of rainfall to appear as rapid runoff. Impervious surfaces reduce infiltration and other local abstractions and frequently route water efficiently toward drainage systems. Urbanization therefore commonly increases the appropriate value of C. Since Rational Method discharge is directly proportional to C, the calculated peak also increases when i and A are unchanged. Therefore Option A is correct.
వివరణ:
Question 16
ప్రశ్న 16
Which statement about the Rational Method runoff coefficient is most accurate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Method coefficient summarizes several hydrologic influences in a simplified dimensionless parameter. Land cover, imperviousness, soil infiltration, slope and surface storage can all affect appropriate coefficient selection. Design manuals often provide ranges of C values for different surface conditions. The coefficient should therefore not be interpreted as an invariant fundamental constant for every event. Hence Option A is correct.
వివరణ:
Question 17
ప్రశ్న 17
For which type of application is the Rational Method generally most appropriate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Method is widely used for relatively small drainage areas, particularly in storm-drain and urban drainage design. Its assumptions become increasingly restrictive as basin size and hydrologic complexity increase. Large watersheds usually have substantial spatial variation in rainfall, travel time, storage and routing. Hydrograph-based or distributed methods are therefore often more suitable for such cases. Hence Option A is correct.
వివరణ:
Question 18
ప్రశ్న 18
Which important output is not provided directly by the basic Rational Formula?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Formula produces a single peak-discharge estimate. It does not define the complete rising limb, peak duration, recession limb or time-varying discharge hydrograph. Consequently it does not directly provide total flood volume either. Methods such as unit-hydrograph or rainfall-runoff modeling are used when the full runoff hydrograph is required. Therefore Option A is correct.
వివరణ:
Question 19
ప్రశ్న 19
A standard Rational Method design commonly assumes that the return period of the calculated peak runoff is approximately the same as that of the design rainfall intensity. What type of assumption is this?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Method commonly assigns the selected rainfall frequency to the resulting design peak discharge. For example, a rainfall intensity associated with a selected return period is assumed to produce a peak flow of approximately that same design frequency. This is a simplifying assumption rather than an exact physical law. Variability in antecedent conditions and other runoff controls means real flood probabilities can be more complex. Therefore Option A is correct.
వివరణ:
Question 20
ప్రశ్న 20
A catchment has an overland travel time of 8 minutes, a shallow concentrated-flow travel time of 12 minutes and a channel travel time of 10 minutes along the hydraulically controlling path. What time of concentration should be used from these components?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Travel times along successive portions of the hydraulically controlling flow path are added. Thus tc = 8 + 12 + 10 minutes. The resulting time of concentration is 30 minutes. This value represents the total travel time along the stated remote-to-outlet path. Therefore Option C is correct.
వివరణ:
Question 21
ప్రశ్న 21
Rainfall intensity is 90 mm/h over a 0.20 km² catchment with runoff coefficient 0.70. Converting all quantities directly to base SI units, what Rational Method peak discharge is obtained?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The rainfall intensity is 0.090/3600 = 2.5 × 10^-5 m/s. The catchment area is 0.20 × 10^6 = 200,000 m². The full-runoff flow rate would therefore be 2.5 × 10^-5 × 200,000 = 5.0 m³/s. Applying C = 0.70 gives Q = 3.50 m³/s. Therefore Option B is correct.
వివరణ:
Question 22
ప్రశ్న 22
A drainage area is reported alternatively as 50 ha and 0.50 km². If C and i are unchanged, what should a correctly converted Rational Method calculation produce?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
One square kilometre equals 100 hectares. Therefore 0.50 km² is exactly equal to 50 hectares. The numerical coefficient in the Rational Formula changes according to the chosen area unit, but the physical discharge must not change. Correct dimensional conversion therefore produces the same peak discharge from either representation. Hence Option A is correct.
వివరణ:
Question 23
ప్రశ్న 23
For a selected return period, an IDF relation gives intensities of 70 mm/h for 10 minutes, 45 mm/h for 30 minutes and 30 mm/h for 60 minutes. If the catchment time of concentration is 30 minutes, which intensity is normally selected for a standard Rational Method calculation?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Rational Method commonly uses a design rainfall duration approximately equal to the catchment time of concentration. Here the time of concentration is 30 minutes. The selected return-period intensity corresponding to 30 minutes is 45 mm/h. The higher 10-minute intensity is associated with a duration too short for the whole catchment to contribute under the standard assumption. Therefore Option B is correct.
వివరణ:
Question 24
ప్రశ్న 24
For fixed rainfall intensity and catchment area, the runoff coefficient is reduced from 0.70 to 0.50. By approximately what percentage does the Rational Method peak discharge decrease?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For fixed i and A, Rational Method discharge is directly proportional to C. The ratio of the new discharge to the original discharge is 0.50/0.70 = 0.7143. Thus the fractional reduction is 1 - 0.7143 = 0.2857. Expressed as a percentage, the reduction is approximately 28.6 percent. Therefore Option B is correct.
వివరణ:
Question 25
ప్రశ్న 25
Consider the following statements about the Rational Method: I. Peak discharge is proportional to runoff coefficient, design rainfall intensity and contributing area. II. Design rainfall intensity is commonly selected for a duration approximately equal to the time of concentration. III. The basic method is best suited to relatively small drainage areas and does not directly generate a complete flood hydrograph. IV. Correct unit conversion is essential when rainfall intensity and drainage area are expressed in units such as mm/h, hectares or km². Which option is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement I correctly describes the structure of the Rational Formula. Statement II gives the standard design-duration concept associated with full catchment contribution. Statement III correctly identifies both the typical application and an important limitation of the method. Statement IV is essential because the numerical conversion factor depends on the units selected for intensity and area. Therefore all four statements are correct and Option D is the valid answer.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: A. Qp = C i A సమాధానం: A.
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Question 2 ప్రశ్న 2Answer: B. The travel time from the hydraulically most remote contributing point of the catchment to the design outlet సమాధానం: B.
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Question 3 ప్రశ్న 3Answer: A. Because rainfall lasting for about the time of concentration permits runoff from the entire catchment to contribute at the outlet while retaining a relatively high design intensity సమాధానం: A.
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Question 4 ప్రశ్న 4Answer: C. Q = 0.00278 C i A సమాధానం: C.
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Question 5 ప్రశ్న 5Answer: B. 2.50 m³/s సమాధానం: B.
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Question 6 ప్రశ్న 6Answer: C. 12.51 m³/s సమాధానం: C.
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Question 7 ప్రశ్న 7Answer: C. 0.75 సమాధానం: C.
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Question 8 ప్రశ్న 8Answer: C. 100 mm/h సమాధానం: C.
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Question 9 ప్రశ్న 9Answer: C. 30 ha సమాధానం: C.
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Question 10 ప్రశ్న 10Answer: C. 0.533 సమాధానం: C.
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Question 11 ప్రశ్న 11Answer: C. 3.11 m³/s సమాధానం: C.
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Question 12 ప్రశ్న 12Answer: A. The intensity for the selected return period and a duration approximately equal to the time of concentration సమాధానం: A.
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Question 13 ప్రశ్న 13Answer: A. The rainfall may cease before runoff from the whole catchment can contribute simultaneously at the outlet సమాధానం: A.
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Question 14 ప్రశ్న 14Answer: A. Although the whole catchment can contribute, the lower longer-duration intensity may produce a smaller calculated peak than the intensity associated with the time of concentration సమాధానం: A.
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Question 15 ప్రశ్న 15Answer: A. The appropriate runoff coefficient generally increases, increasing the calculated peak discharge సమాధానం: A.
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Question 16 ప్రశ్న 16Answer: A. It is a lumped empirical coefficient representing runoff-producing characteristics and should be selected for the land cover, soil, slope and design conditions of interest సమాధానం: A.
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Question 17 ప్రశ్న 17Answer: A. Estimating design peak runoff from relatively small drainage areas such as urban storm-drain or minor drainage catchments సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: A. A complete discharge hydrograph and flood volume through time సమాధానం: A.
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Question 19 ప్రశ్న 19Answer: A. A simplifying frequency assumption of the Rational Method సమాధానం: A.
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Question 20 ప్రశ్న 20Answer: C. 30 min సమాధానం: C.
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Question 21 ప్రశ్న 21Answer: B. 3.50 m³/s సమాధానం: B.
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Question 22 ప్రశ్న 22Answer: A. The same peak discharge from either area representation సమాధానం: A.
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Question 23 ప్రశ్న 23Answer: B. 45 mm/h సమాధానం: B.
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Question 24 ప్రశ్న 24Answer: B. 28.6% సమాధానం: B.
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Question 25 ప్రశ్న 25Answer: D. I, II, III and IV సమాధానం: D.