Hello everyone!
I have 100 years of single station rainfall data and I need to compute 2D flow modelling in HEC-RAS. I need to design discharge at a different interval of 30 min for various return period i.e. 10yr, 25yr, 50yr, and 100yr. I tried to prepare the IDF curve but couldn't prepare the peak discharge to compute flow hydrograph and 2D flow in HEC-RAS.
Any help would be highly solicited. Thanks in anticipation.
First compute the frequency analysis of 30 min rainfall for each day. Then use rational method to get the discharge and then input data into the model.
I presume you are familiar with probability paper? A cumulative normal distribution (integral of the familiar bell-shaped curve) plots as a straight line on such paper. This is how 100-year, 500-year, 1000-year, etc. events are estimated. You fit a curve through the data and extrapolate. I have attached an example.
While Excel won't directly display a probability axis, you can use built-in functions to perform the calculations, as illustrated in the attached spreadsheet.
Dudley J Benton Thank you very much for answering the question. Yes, I am familier with cumulative normal distribution and also estimated the return periods through it in excel. But I want to prepare a flow hydrograph as provided in the attachement 1 (desired output) using the annual maximum rainfall data as shown in attachment 2 (input). I am sorry if I am missing any other parameter or step which need to be analysed before reaching to the desired stage cause I am relatively new in this field as compared to you guys. Hope you can understand the desired result, I require, by going through these two attachments.
Thanks!
Salah Hamad Thanks for your concern. I am using Excel and HEC-RAS applications. If you can suggest any better software or methodology to get the desired result, it would be a great help. You may take a look to the previous answer and can understand, I hope, what I require actually.
Kiprotich Kiptum Thanks for your suggestions. Can you please elaborate more about the suggested techniques to get the desired output? You may take a look at the previous answer and can understand, I hope, what I require actually.
I am familiar with HEC-RAS and have performed many rainfall/flooding simulations. The information you have provided is not sufficient to create the tables you need. Think of it like this… You have provided maximum daily sums, which are integrals. You want rates, which are integrated to obtain sums. There are an infinite number of rate patterns, which will produce the same sum. You can go from hourly to daily but you can't go from daily to hourly without presuming a pattern, which you have no basis for.
Dudley J Benton Thank you very much for your suggestions, it clears most of my doubt now. I will collect required data to perform the analysis and prepare the desired data/table accordingly.
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