Describe briefly the principle of the Rational method and the limitation of this method for runoff...

80.2K

Verified Solution

Question

Civil Engineering

Describe briefly the principle of the Rational method and thelimitation of this method for runoff estimation. A sub-catchment ofarea 0.1km² is built on gently sloping land. The averageslope of the land is 0.001. The length of the longest natural flowpath L is 276.3m. The flow time t_f in the drainagesystem is 3min. Determine the 50yr design discharge for thesubdivision using the rational method, given that the averagerunoff coefficient of the subdivision is C=0.7.
The above sub-catchment is drained by a pipe system which isalso used to drain the second sub-catchment. The secondsub-catchment is of area 0.2km², average slope 0.002,L=300m, and t_f=3min, C=0.5. If the pipe system isdesigned for the 50-yr rainfall event, what is the appropriateduration to be used? Explain briefly. Hence determine the 50yrdesign discharge of the drainage system.

The 50-yr rainfall intensity i can be calculated fromi(mm/hr)=a/(td+b)^c, where a=687, b=4.2, c=0.42,t_d(min)=duration.

Answer & Explanation Solved by verified expert

4.3 Ratings (793 Votes)

Ans In rational method it is assumed that rainfall duration issame as the time of concentration and return period of rainfallintensity is same as the peak runoff The basic principle ofrational method is that the time of concentration of drainage areashould be less than peak rainfall intensity This method is has See Answer

Get Answers to Unlimited Questions

Join us to gain access to millions of questions and expert answers. Enjoy exclusive benefits tailored just for you!

Membership Benefits:

Unlimited Question Access with detailed Answers
Zin AI - 3 Million Words
10 Dall-E 3 Images
20 Plot Generations
Conversation with Dialogue Memory
No Ads, Ever!
Access to Our Best AI Platform: Flex AI - Your personal assistant for all your inquiries!

Become a Member