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An isolated 3 hour rainfall event on a small catchment produces a hydrograph peak and point of inflection on the falling limb of the hydrograph at 7 hours and 8.5 hours, respectively, after the start of the rainfall. Assuming no losses and no base flow contribution, the time of concentration (in hours) for this catchment is approximately
  • a)
    8.5 hours
  • b)
    7.0 hours
  • c)
    6.5 hours
  • d)
    5.5 hours
Correct answer is option 'D'. Can you explain this answer?
Most Upvoted Answer
An isolated 3 hour rainfall event on a small catchment produces a hyd...
Given information:
- Isolated 3-hour rainfall event
- Hydrograph peak occurs at 7 hours after the start of rainfall
- Point of inflection on the falling limb of the hydrograph occurs at 8.5 hours after the start of rainfall
- No losses and no base flow contribution

To find:
Time of concentration for the catchment

Solution:
The time of concentration (Tc) is the time taken for the water to travel from the furthest point of the catchment to the outlet. In this case, we need to determine the Tc based on the given information.

Step 1: Determining the time of peak (Tp)
The time of peak (Tp) is the time at which the maximum discharge occurs. In this case, the hydrograph peak occurs at 7 hours after the start of rainfall.

Step 2: Determining the time of inflection (Ti)
The time of inflection (Ti) is the time at which the slope of the falling limb of the hydrograph changes sign. In this case, the point of inflection on the falling limb occurs at 8.5 hours after the start of rainfall.

Step 3: Determining the time of concentration (Tc)
The time of concentration (Tc) can be calculated using the following equation:
Tc = Tp + 0.8(Tp - Ti)

Substituting the given values:
Tc = 7 + 0.8(7 - 8.5)
Tc = 7 + 0.8(-1.5)
Tc = 7 - 1.2
Tc = 5.8 hours

Therefore, the time of concentration for this catchment is approximately 5.8 hours.

Answer:
The correct option is (D) 5.5 hours.
Free Test
Community Answer
An isolated 3 hour rainfall event on a small catchment produces a hyd...
For small catchment, time of concentration is equal to lag time of peak flow.
Tc = 7 - 1.5 = 5.5 hours
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An isolated 3 hour rainfall event on a small catchment produces a hydrograph peak and point of inflection on the falling limb of the hydrograph at 7 hours and 8.5 hours, respectively, after the start of the rainfall. Assuming no losses and no base flow contribution, the time of concentration (in hours) for this catchment is approximatelya)8.5 hoursb)7.0 hoursc)6.5 hoursd)5.5 hoursCorrect answer is option 'D'. Can you explain this answer?
Question Description
An isolated 3 hour rainfall event on a small catchment produces a hydrograph peak and point of inflection on the falling limb of the hydrograph at 7 hours and 8.5 hours, respectively, after the start of the rainfall. Assuming no losses and no base flow contribution, the time of concentration (in hours) for this catchment is approximatelya)8.5 hoursb)7.0 hoursc)6.5 hoursd)5.5 hoursCorrect answer is option 'D'. Can you explain this answer? for Civil Engineering (CE) 2024 is part of Civil Engineering (CE) preparation. The Question and answers have been prepared according to the Civil Engineering (CE) exam syllabus. Information about An isolated 3 hour rainfall event on a small catchment produces a hydrograph peak and point of inflection on the falling limb of the hydrograph at 7 hours and 8.5 hours, respectively, after the start of the rainfall. Assuming no losses and no base flow contribution, the time of concentration (in hours) for this catchment is approximatelya)8.5 hoursb)7.0 hoursc)6.5 hoursd)5.5 hoursCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Civil Engineering (CE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An isolated 3 hour rainfall event on a small catchment produces a hydrograph peak and point of inflection on the falling limb of the hydrograph at 7 hours and 8.5 hours, respectively, after the start of the rainfall. Assuming no losses and no base flow contribution, the time of concentration (in hours) for this catchment is approximatelya)8.5 hoursb)7.0 hoursc)6.5 hoursd)5.5 hoursCorrect answer is option 'D'. Can you explain this answer?.
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