Detention Pond - Rational Method

[Structural Scott]

I did a simple design using the Rational Method. I created my own Rainfall Intensity Curve that looks like it came out right. When I look at the report it looks like if I set the intensity duration for 24 hours it only gives the the lowest peak flow, and if I the duration to 20 minutes I just get a sliver of a hydrograph. Am I doing something wrong? Also I looked for SCS information in the pull down menu and it's blank for all Oregon locations..

 

[psmart]

For the Rational method, you can use the critical duration analysis to determine the duration which produces the highest WSE in the pond. (See the Duration tab) However, the SCS method is better suited for pond modeling. For locations not included in the event lookup table, you can easily define the events by hand.

For further details see

http://www.hydrocad.net/rational.htm

Peter Smart
HydroCAD Software

http://www.hydrocad.net