Hello All,
I'm working on a 6 sq. mi. drainage study. I first ran HEC-HMS, then HydroCAD to get a quick sense of the storage volume required. The numbers were significantly different (2800 cfs vs. 2400 cfs) and I've set them up to use the same calculation methods. I'm using SCS unit hydrograph method, SCS Type 1A temporal distribution, NOAA 100-yr 24hr rainfall depth of 6.5", TR-55 for Tc (Hey HEC, how about incorporating the TR-55 equations?!)
The most curious is when I isolate one subshed and HMS and HydroCAD yield the same runoff depth (4.3") but have such different peaks (2200 cfs vs. 1900 cfs). 5% error I would still question, but 15% is very high, wouldn't you agree?
Thanks in advance for your thoughts!
Nate
I'm working on a 6 sq. mi. drainage study. I first ran HEC-HMS, then HydroCAD to get a quick sense of the storage volume required. The numbers were significantly different (2800 cfs vs. 2400 cfs) and I've set them up to use the same calculation methods. I'm using SCS unit hydrograph method, SCS Type 1A temporal distribution, NOAA 100-yr 24hr rainfall depth of 6.5", TR-55 for Tc (Hey HEC, how about incorporating the TR-55 equations?!)
The most curious is when I isolate one subshed and HMS and HydroCAD yield the same runoff depth (4.3") but have such different peaks (2200 cfs vs. 1900 cfs). 5% error I would still question, but 15% is very high, wouldn't you agree?
Thanks in advance for your thoughts!
Nate