unit hydrograph

[SETADS]

I had a reviewer make this comment:

"Please support the Unit Hydrograph and Peaking Factor of 484 assumed in pre-development conditions in both basins. The peaking factor assumed appears high. Please review and revise the peaking factor on pre-development conditions, as necessary, for consistency."

I've never used a different peaking factor for predevelopment and postdevelopment. I also don't have a masters degree. Could someone explain this to me like I'm a child?

 

[deucemanpoo]

If you are using the SCS method, the 484 shape factor value is built into the the equation that the NRCS developed after they analyzed multiple real world watersheds across the country. The SF-value can be changed depending on the topography, as it can over/underestimate peak flow. The unit hydrograph model you select should align with whatever local authorities require. The reviewer should be aware of how these models are built. If they are not, you should read up on it and help improve their understanding.

References:
https://learn.hydrologystudio.com/hydrology-studio/knowledge-base/nrcs-unit-hydrograph-peak-factors/

SCS Unit Hydrograph Model

www.hec.usace.army.mil