how do I create a IDF (intensity duration frequency) cure of rainfall events in maplehow do I create a IDF (intensity duration f

Posted on 2008-10-31 17:15 By Wright_r (3)

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How do I ...? with Maple

I am new to maple and trying to create an IDF curve (intensity duration frequency curve) for rainfall. The fomula is quite simple I=A*T^c, where I-= rainfall intensity, A is the average rainfall in a given period and T is time of concentration (10 min) and C is a coeffecient developed from 40 year annual rainfall data

Now what i need to do is for a strom return period of 2, 5,10,25, 50 and 100 year storms, plot the I value for each of these years (I have 6 A values and 6 ^c values) that corespond to each year 2,5,10,25,50, 100

So ideally I would like to produce a plot that has Intensity as the Y value, time in 10 min intervals as the X value and shows me a cure for each of the storm return periods? any idea how to do this

too vague

Comment on 2008-11-01 16:12 from Axel Vogt ( Maple Rating 4

994)

I googled a longer time to find out what you may mean. Besides some Matlab code for plotting from Excel the most reasonable I got was public.deltares.nl/display/HYMOS/05+IDF+Relations and may be that helps to state a more precise question. I guess it is to estimate a continous density from occurencies, where some specific model is taken - it seems, that in Hydrology this is the Gumbel distribution (or log-Weibull as a dictionary says). May be that also helps for formulating ... may be it is about estimating parameters (which may depend on time or time frames).

Intensity duration frequency curves (hydrology)

Comment on 2008-11-01 17:05 from Wright_r (3)

I agree I was probably too vague. I know it can be done in excel and have in fact done it there. I was hoping as a new user to Maple that I could use the software to write a simple equation, in this case I=A*T^c for a number of values of A, T and C and then plot the distribution of all the values to generate the IDF curve. Maple hopefully would allow me to change some of the assumptions and to view the changes to the curve.

here I = Rainfall intensity (mm/hr), A rain fall coeffiecent (given), T is time (hour), and the coeffecient C is a given value

In my case where i know that the existing values for the imputs which in my case for Toronto are

return period (yr) A c T(hour - in 10 min increments up to 1 hour)

2 21.8 -0.78 .167 .25 .33 .416 .5 .583 .66 .75 .833 .916 1.00

5 32 -0.79 .167 .25 .33 .416 .5 .583 .66 .75 .833 .916 1.00

10 38.7 -0.8 .167 .25 .33 .416 .5 .583 .66 .75 .833 .916 1.00

25 45.2 -0.8 .167 .25 .33 .416 .5 .583 .66 .75 .833 .916 1.00

50 53.5 -0.8 .167 .25 .33 .416 .5 .583 .66 .75 .833 .916 1.00

100 59.7 -0.8 .167 .25 .33 .416 .5 .583 .66 .75 .833 .916 1.00

So my question as clearly as iI can state it is it possible to write an equation in Maple I=A*T^c which then uses the A, T and ^c for each return period (2, 5, 10, 25, 50, and 100 year storms) for each 10 minute increment and generates the points which I can plot. so far all I can do in maple is write one equation at a time for each set of imputs (I Idid this in excel the hard way by writing a formula for each cell and then calculated the result but it is difficult to dynamically change) If this works successfully I would have a plot with the Y axis being mm/hr (the I value) plotted against the X axis (the 10 min increments in decimal hours) with the corresponding points forming the IDF curves one for each storm return period (11 points in each curve) 6 curves in all......whew i hope I am clearer

clearer ...

Comment on 2008-11-01 17:12 from Axel Vogt ( Maple Rating 4

994)

clearer ... may be, I am too tiered :-) If it is not too ugly just upload your Excel sheet (you should 'zip' it to get it accepted), may be those days others or I find time to look into it

IDF curves

Comment on 2008-11-01 17:54 from Wright_r (3)

here is the fileDownload 9619_IDF curves toronto.zip
View file details