DES 606 Watershed Modeling with HEC- HMS Advanced Topics

This last module before one more set of exercises and the course examination briefly covers some additional topics of 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

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.

Multiple Runs Exercise 8 will 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.

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.

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

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.

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.

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. – 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

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. – 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

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

Avoid Temptation to Use as a Hydraulic Model – EM

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

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

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!

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 – Most consulting firms can also provide guidance