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HydroCAD to HEC-HMS Meterologic Models for TCEQ PMP rainfall events.

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Weimsguy

Civil/Environmental
Mar 1, 2017
19
I have been working on a Texas Comission on Enviromental Qualtiy (TCEQ) Dam Breach Hydrologic & Hydrologic Analysis and had modeled the area above the dam as a single sub-basin as a catchment, the lake as a pond, and the dam spillway and breach as outlets of the pond. Peter Smart added the TCEQ rainfall distributions to HydroCAD (thank you very much) that made coming up with the inflow/outflow hydrograph very easy. I was able to just export, cut and paste the hydrograph table into HEC-RAS as a boundary condition for the Unsteady Flow with dam breach. I also used the HydroCAD dam breach option to compare with the HEC-RAS dam breach. Having the TCEQ data in HydroCAD made that part easy and straight forward.

I am now having to use the FEMA model to do the same analysis. It is driven by HEC-HMS that divides the drainage basin above the dam into 8 sub-basins. I understand how to produce the hydrographs for the sub-basins. The HEC-RAS model outes through many reservoirs and lateral structures not in my original model. The flows are adjusted along the reaches at the various junctions. HEC-HMS has a user manual input option for the rainfall event in the form of a hyetograph. I want to use the HydroCAD hydrographs to generate those hyetographs from the exported hydrograph tables with its precipitation and excess rainfall values. I guess it is my lack of knowledge of working with the hyetograph phase of the process that is the crust of my problem. I have always just used the resulting hydrograph.

I'll keep researching and studying and perhaps answer my own question. Thought I would ask here if anyone had ever done this. I did not find any discussion searching through the forum.
 
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The TCEQ rainfall distribution is a hyetograph. (Rainfall depth vs time.) So you should be able to use this data as input to HEC-HMS. In this scenario you would be using HMS to generate the runoff hydrographs, rather than using the HydroCAD hydrographs.

The hyetograph is used to generate the runoff hydrograph, not vice versa.






Peter Smart
HydroCAD Software
 
Thanks for the explanation. Now I just need to figure out how to define the TCEQ distributions as a Precipitation Gage in HEC-HMS.
 
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