autodesk autocad civil 3d hydraflow hydrographs ext

This attempts to predict a more realistic runoff volume, which is characteristic of Moisture conditions of storms greater than those with a 25-year recurrence intensity Rational Method recommends that a coefficient be used in order to account for the antecedent Rainfall intensity for the entire rainfall period is assumed here. Method, this area is equal to the peak discharge rate times the duration of the storm. 'Theory: The area under a hydrograph equals the volume of runoff. I had found your attachement from Iowa and had read it earlier. I am not understanding of what the SDF factor is in the software. > My question is, is the SDF factor in Hydraflow Hydrographs 2009 the same as the antecedent precipitation factor? I can't connect the two factors together. Doing research on MRM, I find that you should only modify the 25, 50 & 100 year storms using an antecedent precipitation factor of 1.1, 1.2, & 1.25 respectively. The person used the SDF factor of 5 for all of the storms. > I am currently reviewing a site that was designed with the Modified Rational method using old Hydraflow. (20 + 2.25 x 20 = 65min).Īs an example, the APF will adjust the peak runoff UP (Y axis), while For example, the following hydrograph was produced usingĭuration Factor of 2.25. Multiplied by Tc and determines the total Storm Duration Factor - Modified Rational only. The SDF isn't defined in the help for Hydrographs, but it does appear in I would assume you could just modify your C values accordingly. (Think a factor of safety vs a true Antecedent Precipitation The Antecedent Precipitation Factor is an additional factor taken intoĪccount to estimate the true total volume of runoff the MRM triangle or I don't think the SDF and the APF are related in any way.

Autodesk autocad civil 3d hydraflow hydrographs ext