Convert Precipitation to IDF
Convert Precipitation to IDF
(OP)
Dear all experts,
I'm civil engineer an have very basic understanding of hydrology. In my past with hydrology/hydraulic cals, IDF were given. This time, I work on a project oversea that requires some basic drainage cals but all I have is precipitation data from this website: http://www.mandalay.climatemps.com/precipitation.p...
My question is from looking at the data do you think I can create IDF curve for 1 yr, 5,10,100 yr? or do you think I can use the precipitation and divide certain time period to get intensity? And how do you interpretate some of the probability, dry and wet month...
Thanks.
I'm civil engineer an have very basic understanding of hydrology. In my past with hydrology/hydraulic cals, IDF were given. This time, I work on a project oversea that requires some basic drainage cals but all I have is precipitation data from this website: http://www.mandalay.climatemps.com/precipitation.p...
My question is from looking at the data do you think I can create IDF curve for 1 yr, 5,10,100 yr? or do you think I can use the precipitation and divide certain time period to get intensity? And how do you interpretate some of the probability, dry and wet month...
Thanks.





RE: Convert Precipitation to IDF
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Convert Precipitation to IDF
Thanks
RE: Convert Precipitation to IDF
http://www.nws.noaa.gov/oh/hdsc/currentpf.htm
The entire discussion of this paper would be useful for you to read and understand, as well as the discussions in TP-40 and some other documents at that link about how they processed rainfall data into information useful for design engineers.
Hopefully that gives you enough material to go on. Then it comes down to what data is available. In the end, you may have to make some assumptions.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Convert Precipitation to IDF
1. The data is 1-yr storm event
2. Heaviest rain is in Oct of 7.3 inch, 7 rainy days in the month -> 7.3/7 = 1.1 inch -> 1-Yr storm, 24 hr storm duration
Thanks
RE: Convert Precipitation to IDF
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Convert Precipitation to IDF
In a very general sense, in order to establish the 100 year 24 hour storm, you need 100 years worth of daily (24-hr) storm data.
Likewise, in a very general sense, in order to establish the 100 year 30 minute storm, you need 100 years worth of tipping bucket rain gage data at 30 minute intervals. If you don't have that, which nobody does, you have to interpret it using some pretty sophisticated stochastics.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Convert Precipitation to IDF
RE: Convert Precipitation to IDF
For instance, NOAA has used as little as 13 years of data, however that results in significantly higher error in the estimated rainfall. In NOAA-14, the average station used in the analysis is about 37 years and none have 100 years of data
http://www.nws.noaa.gov/oh/hdsc/PF_documents/Atlas...
RE: Convert Precipitation to IDF
What the big boys do, if I'm recalling properly, is grab as much data as possible and then fit it to a Gumbel distribution.
https://en.wikipedia.org/wiki/Gumbel_distribution
Your statistics pencil needs to be very sharp when attempting this, and it's thankfully not something most design engineers have to fool with. We trust that NOAA's pencils were sharp when they did it. I would probably have to spend days reviewing the appropriate textbooks before I would feel confident tackling this problem in a comprehensive way. I might be tempted to cheat in some manner, like saying for instance, "Well, Foreign Country X has a climate about like Arizona, sooo......"
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Convert Precipitation to IDF
RE: Convert Precipitation to IDF
While I did not find the exact information you are requesting in the few documents I viewed, I suspect one could contact some of the references in the documents and obtain some decent data.
RE: Convert Precipitation to IDF
Thanks
RE: Convert Precipitation to IDF
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com