On a more basic note, to answer your question as to file differences between the .rf and .idf files. The .rf files are the average rainfall values for different year storms for a particular area. I have copied this file and edited it to include only the counties in which I work. Unfortunately, LDD will only recognize the original "County.rf" name. Therefore, rename the original to "County_orig.rf" and your copy to "County.rf". Be sure to leave in the same directory as that's where the program is going to look. Keep a copy of your edited file (now named "county.rf") in another location as every new upgrade or install will wipe this out and you'll have to recreate it. I keep a hardcopy in my CAD binder.
Now, the .idf is an Intensity, Duration, Frequency file that can be developed manually or as output of storm data from another program. Either is viable, you just have to tell the program which one you're using.
Finally, make sure your paths are correct for your data sources. When you tried to save the .rf file, where was it trying to save to? Make note of that directory, and make sure your data support paths match under "options".
I have tested the TR-55 portion of the LDD package against manual calculations and was pleased with the results. With careful output file editing, you can create a number of "storms" to test your design.
Mark D. Premo, P.E., Civil Engineer II
Onondaga County Department of Transportation
421 Montgomery Street
Syracuse, New York 13202
Phone: 315-435-3176
Fax: 315-435-5744
markpremo@ongov.net
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