Creating IDF Curves for Different Durations and AEPs (Return Period) | Tutorial

hello to all welcome to the channel geoguru in this video we are going to learn about intensity duration frequency curve also known as IDF curve so this kind of curve look like this and it is a very important curve in the field of hydrology and hydraulics so let's see uh what is actually IDs curve is and what has its application so uh as it means such as it is intensity duration frequency that means it describes the relationship between the rainfall intensity the rainfall duration and the return period also known as frequency or probability of accidents so this Curve will Define the relation between these three things ah it is commonly used in the design of hydrologic hydraulic structure specifically in the Water Resource system and this curves can be obtained through the frequency analysis of rainfall distribution so we are going to learn how we are going to develop this iodf curve from the rainfall data set from the scratch so for that purpose we are going to use the Microsoft Excel so this is our rainfall data site it is a tri membraneful dataset those DRM user satellite rainfall data which provide the three hourly rainfall duration for entire world so it comes uh with the mm per hour for three hour duration so in order to convert mm per three hour or per six hour nine hour we are going to uh multiply this by 3 okay so now this intensity becomes three hour um uh in mm data set so in order to convert it three hour into six hour because we are focusing on getting the annual Maxima so we are not uh going to make from three hour to six hour in every six hour alternate duration we are but we are going to get that information for every three hours so for that purpose we are going to use the sum and add these two values and similarly for nine hours we are going to add three values from three hours that makes nine hour and similarly for 12 hours we will add the four values for 18 hours you are going to add the six values now we are interested in getting the IDF for up to 72 hours so please make sure that uh this is a three hourly duration so uh every duration is in the multiple of three if you are using hourly data set it can be like one hour two hour every single hour so if you are getting to using 24 hour of rainfall data set so for that uh you think that your get the IDF curve for every 24 hour interval that means 24 36 sorry not 24 48 72 Etc so after that we are going to extract the annual Maxima and in order to do that please make sure that one of the column head should have the date uh and the month inside that so what we will do we will go to the insert in the Microsoft Excel go to the pivot table and click on this from table to range and please make sure that all the rows and columns in which your data set have is selected which select OK and here we going to select the dates okay so now you can see that uh all the years in a single row have come up and uh we will add three hour so make sure that the date column should be in the rows and the value you are interested should be in the value cell so here it is the sum or three hour we are not interested in the sum but we are interested in the uh maximum so similarly for six hours if you just drop down click over here value field settings and click on maximum so similarly we are going to do this for 9 12 18 24 okay so in order to convert this sum to Max you can right click over here show summarize value as Max okay so we have get the annual Maxima for each and every year now we are going to copy this values and paste into a new worksheet okay so we will just copy this and open another so this is the sheet I have used going to use I'll just going to paste this and I'm going to paste it as a values okay so now you can see this uh all the data set that means annual Maxima for each and every duration has come up now we are going to I'll just zoom it little bit uh so next step is to get the IDF values okay so in order to get the idea values uh from literature which I'm going to go into cite in the read um description of this video the formula which we are going to use is the XT is equal to X bar plus kts so where x t is the precipitation depth for a calculator written period again for a specific duration and where X bar is the mean the average of all the annual maximum standard deviation and KT is the frequency factor and in order to calculate the frequency Factor we are going to use the gumball distribution formula okay and the gumball distribution formula is this where uh t a uh here is the year in which we are interested okay so in this case we are going to calculate like uh for one in two years one in five years up to one in Thousand Years okay so by using this formula we have calculated the value KT and write it over here that means for two uh written period two years return period five year return period we are getting the KT value as 0.720 this is the formula uh we are going to provide this Excel sheet for your reference purpose you can use this so next thing that we are going to require is the average of annual Maxima with the standard deviation so in order to get the average going to use the average formula we just tried and this we are going to do for every duration and similarly we are going to use the standard deviation okay so now uh mathematically if you just think that over the 20 years the average three hour Maxima is 52. so if you are going to talk about like 1 in 20 years so the maximum value in this maybe lie in between about uh maybe 30 or not the 20 years but one in 10 maybe like in uh near about 50 to with a standard deviation of 15 that's why if you see that for 10 years of written period the multiplication sector is 1.3 okay but how it may be slightly bit different because it totally depends on the number of years of data which you are using so it is normally suggested that it should be more than 20 years or maybe 15 to 20 or more than that the more data set to use the more accuracy you will get okay so now uh we are going to apply this formula in order to calculate the XC that means our rainfall depth so we are going to use the Plus bracket it's standard deviation multiplied by KT and bracket close so we are going to drag this formula but before that we are going to put the dollar sign and I hope everyone here know the importance of this dollar sign in the Microsoft Excel I'll just drag this and practice and let's check in one of the formula for yes this multiplied by this and into this so uh this is we have got the rainfall tip in order to create the ITF curve so when I say rainfall tab that means for this area if we talk about uh one in Thousand Years 24 hour rainfall the rainfall depth is equal to 73.1 okay so in order to make this uh in a beautiful graphical presentation I'll just use any two columns and go to the insert you have this lot okay and just drag all other durations okay so now in the x axis we have the number of return periods and in the y axis we have a rainfall in MN okay so we are going to uh uh put this value as a log axis and the base of 10 so now it is looking more nice so this is your final IDF curve but here the x axis is in the sorry Y axis in the mm that means okay uh in the millimeters not in the mm per hour okay it might happen then some of the literature might give you this the rainfall uh this IDF curve because the name intensity is there so this is should not be sometimes it's not been the mm but in the mm per hour so what you can do you you can just simply uh I'll just uh uh before that uh it can also be represented by some other manners like you can just select this two rows and go to the insert and go to this 2D line okay so now in the accesses we have duration in the y-axis with the rainfall mm you can drag it over here or before that if you go to the form chart design select data and in the name we are going to give to okay so similarly we are going to track this graph but I can see that this graph is not looking right because this duration should not be like increasing and decreasing so let's check what we have done anything wrong so in order to check this make sure that this value should be in in the increasing order as we increase the division so we can see the 76 91 93 oh so here we can see that for bigger duration we are getting the smaller values uh let's just cross check uh with the previous pivot table so industry base table also we are getting the similar value if we go to the rainfall okay we'll just cross check the formula okay for six hours we are getting good for nine hours the formula is okay oh so you can see that for 12 hours and maybe for other hour we are actually edit the mm per hour we should add the three hour uh that means the value in the mm so we will just Rectify it and for I think for all of the duration we have to do this similar thing so it's a good habit to create uh your own formula or your own Excel sheet so that you can debug it very easily okay you can use this Excel sheet as a reference I'll just go to the pivot table and if you go to the pivot table so go to analyze and click on refresh so now you can see that we have updated but yes for 72 and for 18 we haven't updated and for 72 also we fit update now if we go to the viewer table and let's just refresh it once again oh now we are getting the result is good okay so now it may happen that this value might not increase in the next duration but it should not decrease so we will just copy this once again and go to the IDS with this as a value now our average has been changed now our graph is looking much nicer okay so the next thing that what I was telling that sometimes it is not necessary that uh you may get a IDs curve in the rainfall mm you might get X Y axis in the mm per hour so for that purpose uh we can this is a similar sheet and we can use this average and divide this for a specific duration okay so for example this is the mm per three hours so in order to convert this mm per three hour into MM per hour we are going to divided by 3. okay and and similarly we are going to new dollar sign and let's just cross check we have done something mistake okay so this dollar sign I have to talk putting dollar sign over here and now you can use this similar formula so now you can see that now graph is in the mm per hour so this is also uh your IDF curve look likes if you are using the mm per hour and if you are using not the intensity but detect your graphics look like this so and how to use this graph suppose if you want to design a structure which is a lag time of like four hour okay or maybe it's at 12 hour okay so you can see that for 12 hour and if you want to design for the 100 years so for 12 hour 100 year we are getting the rainfall as approximity 137.5 so this is be your should be design strong value and this value is going to be uh you uh used for creating the design flood hydrographs and for any other purpose or maybe modeling purpose flood marketing purpose so that's it for the day uh hope you like the video and find this video informative if so then please hit the like button share this video And subscribe to the channel thank you

Channel: Geo Guru

Views: 7,663

Keywords: IDF curves, rainfall analysis, hydrological design, TRMM data, rainfall intensity, frequency analysis, infrastructure design, data analysis, tutorial, meteorology, hydrology, stormwater management, drainage systems, annual exceedance probability, rainfall patterns, engineering, research, data preprocessing, statistical techniques

Id: dUo1fVGTDUc

Length: 16min 59sec (1019 seconds)

Published: Fri Jul 14 2023