If rainfall occurs between 2 P.M. and 3 P.M. and runoff reaches the basin outlet starting at 3 P.M., what is the time of concentration_____________________?
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Answer: D. 60 minutes
Explanation
Time of concentration measures the travel duration from the most hydraulically remote watershed point to the outlet. Runoff begins reaching the basin outlet sixty minutes after the rainfall event starts. The elapsed time between rainfall onset and initial outlet runoff defines the time of concentration. Watershed response time depends on flow path length, basin slope, and surface roughness characteristics. Rational method peak discharge calculations require determining the catchment time of concentration. Flow velocity across overland, shallow channel, and pipe network segments determines total travel time.
Drainage engineers use time of concentration to estimate peak stormwater discharge rates for urban sewers. Designing highway culverts requires accurate watershed travel time calculations to prevent road flooding. Land development increasing impervious surfaces shortens the time of concentration and worsens flash floods. Option A fifteen minutes underestimates watershed travel time for typical medium sized catchments. Option B twenty minutes represents an arbitrary duration inconsistent with the given time difference. Option C thirty minutes incorrectly splits the sixty minute elapsed duration between rainfall and runoff.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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