Dekalb Method Model in HydroCAD

[DML-PE-LLC]

Hi All.

I help with small-scale land development projects (e.g., pools, additions, etc.) in Pennsylvania. We have some of the strictest stormwater regulations here and stormwater design is often a challenge. After doing this for 15+ years and observing real-world conditions, I have come to the conclusion that using the SCS method to model semi-urban runoff for areas less than 20,000 sf is not a great solution. I am curious if anyone has used the Dekalb Method in HydroCAD to model a pre- and post-development peak control comparison. If so, would you be open to sharing the model so I can review it?

Also, please, no need to respond about how the SCS method is more accurate than MRM / Dekalb. I do not need help understanding that.

Thanks,
dml

 

[psmart]

By way of background, here is some detail on using the Dekalb method in HydroCAD:

Dekalb Rational Method

 

[DML-PE-LLC]

By way of background, here is some detail on using the Dekalb method in HydroCAD:

Dekalb Rational Method

Thanks, Peter. I've had trouble following the instructions, so I was hoping to inspect an existing model to help me understand. I may contact you separately for additional help.

 

[backseatpockets]

I work in Pennsylvania as well doing land develoepment/ Stormwater. I typically use the Rational Method

The only downside is that for HydroCAD, in order to print hydrographs for BMP, you have to run the critical duration for each storm event. Depending on how you have your duration set up (I do 72 hours) it can take 2-4 minutes for each hydrograph.

 

[DML-PE-LLC]

Thank you. I was able to create a model using MRM and it seems to work OK. The critical duration can be pain when you are doing a significant number of iterations. I guess I'll try to understand it better as I use it more and maybe it will get easier.

 

[psmart]

There are lots of hidden complications with the Rational method, which is why we recommend the SCS/NRCS method instead.

www.hydrocad.net/rational.htm