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time increment issue

time increment issue

time increment issue

I am doing some somewhat basic ditch routing and am having issues that my time of concentration < 8dt. (I am sure that someone has seen this message). Anyway, I havent been able to set my dt<0.01 hrs. Does anyone know a way to select a smaller dt than 0.01 hrs?  Maybe a by using a different routing method?

RE: time increment issue

Based on that message, I gather you're using the Rational method with a Tc less than 5 minutes?

Most IDF curves don't define durations that small, so most stormwater regulations generally define a minimum Tc of 5 minutes or so.  You can either increase the Tc manually, or you can set a minimum value that is automatically applied to each subcatchment.  You will find this on the Advanced tab of the Settings|Calculation screen.

If for some reason you REALLY need a smaller time-step, the limits and decimal places can be customized on the Settings|Units screen.  But I doubt this is required, and could raise other issues.

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