Use the following web address to download HEC-HMS 3.5 software.

Choose appropriate version depending on your computer system.

http://www.hec.usace.army.mil/software/hec-hms/download.html

01/11/2012

Question:

Hello-

Your website is very helpful. However, a question on calculating lag times for the SCS dimensionless hydrograph. Where percent slope is substituted in the formula, is that entered as the percentage value, e.g. 47.3%, or the equivalent decimal value in ft/ft or meters/meter, e.g. 0.473? The difference changes the answer for time of concentration or lag by a factor of 100. Thanks for clearing this up.

Response:

Thanks for your feedback. Please use the decimal value (e.g. ft/ft or m/m) when entering the slope value. I'll update the page to clarify this. Your questions help improve the webpage for providing clear understanding.

03/26/2014

Question:

Hi there. Thank you for your useful website. I have a question regarding the Curve Numbers. Everywhere I see people use the CN without decimal digits. Do we need to round the CN when we want to use it for example after calculation of composite CN?

Thanks

Response:

Hi Andrei,

Very good question!

I've seen documents with variety of CN values: Full rounding to integers and upto three decimal points.

Generally, most people round the rainfall and runoff values to 1 or 2 decimal points. Therefore, I would go with same for CN values. I would not recommend rounding to full integer value.

Hope this helps,

-Prof. Patel

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