1. DES 606 Watershed Modeling with HEC-HMS
Additional Topics

2. Additional Topics
This briefly covers some advanced features on HEC-HMS
These features are not often part of training, but for large production projects are likely to be useful
Reference is the User Manual

3. Analysis
HEC-HMS contains some analysis tools that can generate certain statistics from the program with greater ease then exporting results and analyzing externally
Documented in Chapter 14 of the user manual.

4. Multiple Runs
Some projects require the analyst to evaluate several different conditions.
Page 243 of the user manual mentions setting up multiple runs.
Utility is obvious; if change is being evaluated, there is some economy is preparing different scenarios before hand, and just running them in a single execution event.

5. Other Things
HEC-HMS has been illustrated as both a single element calculator and an integrated hydrology quasi-hydraulic modeling tool.
Most of the examples required external data preparation
Expect this step to be the time consuming activity in modeling, and also the most important.

6. Other Things Conceptualizing a watershed is important
Simple sketches, by-hand, external to the program are advised
External calculations are required
Esp. for storage-discharge tables, wiers, etc.
=> This means that diversion and detention models will involve substantial hydraulic considerations before modeling begins

7. Other Things
Sources of design rainfall are available from the internet, TxDOT Hydraulic Manual, etc.
Need to document (in a report or notebook) the source of values.
The results should be similar, but minor variations that could create arguments, could simply be users choosing different, but authoritative, sources. Cite your data sources.

8. Other Things Data management
Whether data are kept in DSS or in external files is a matter of personal preference in smaller projects (or one-of cases)
DSS undoubtedly exists for a good reason; larger projects, or projects that will be shared on a server or by should probably store all data in DSS and localize the data.

9. Other Things
Supervising a HEC-HMS study. At some point you are likely to supervise a HEC-HMS analysis either as a client, or contractor.

10. Supervising an HMS Study
Agree ahead of time on data sources. If a need arises, agree by consensus
Agree that data, even if stored in DSS, have externally readable mirrors maintained by the contractor and delivered with the final product
Verify that any files sent to you actually run on the recipient’s machines

11. Supervising an HMS Study
Collectively troubleshoot problematic HEC-HMS runs, there is desirable synergy
Carefully isolate calibration runs (I suggest entirely separate project files if at all feasible)
Require a modeling report and a simulation log

12. Supervising an HMS Study
Build the model using as few components and special features as practical.
Parsimony will go a long way in producing a better modeling study!
Don’t subdivide under the illusion of gaining accuracy, probably won’t.

13. Avoid Use as a Hydraulic ModelEM

14. Hydraulics
With experience HMS can do some hydraulics quite well, but the data preparation is not trivial.
If flow reversal is possible, should use a true hydraulics tool
HEC-RAS
SWMM

15. Staying Current HEC-HMS changes from time-to-time.
Look and feel will change
Icons move about
Recommend annual visit to website to check status

16. Geo-HMS
The course entirely ignores the GIS interface of HEC-HMS; however there has been substantial effort in the last two decades to directly integrate HEC-HMS and GIS
There is plenty of talent in Texas to help with GIS-HMS integrated modeling, bear in mind that troubleshooting gridded models is hard!

17. Geo-HMS Most H&H consulting firms can provide guidance
Many Universities can provide guidance
GeoHMS (and ArcHydro) were written with major contributions from faculty at UT and TAMU