DES 606 Watershed Modeling with HECHMS Troubleshooting HECHMS

DES 606: Watershed Modeling with HEC-HMS Troubleshooting HEC-HMS Projects Theodore G. Cleveland, Ph. D. , P. E. 16 OCT 11

Troubleshooting • Troubleshooting involves three kinds of “troubles” – Incomplete specifications, missing elements, etc. – Clobbered HEC-DSS files, bad paths, etc. – Poor conceptualization, data entry errors, etc.

Incomplete Specifications • Parts of HMS model are not connected – Sub-basins not connected to other elements – Data missing • Rainfall gages missing • Record lengths inconsistent • Troubleshooting these kinds of problems is really learning how to interpret the HMS message log

Incomplete Specifications

Incomplete Specifications

Incomplete Specifications The warning seems to be associated with missing data. We will need to import data into the project.

Incomplete Specifications Repair the data files, then re-run

Incomplete Specifications Fix again, and re-run – this run has no warnings.

Clobbered HMS-DSS files • As analyst changes components and reruns sometimes the DSS database gets clobbered. – This situation will usually throw errors that prevent the run form completing. – Easiest solution is to stop and restart HMS • Hopefully you have been saving files so recovery is possible.

• Previous model, attempted to save with new filename. – Did not save, however HMS does not report failed save outside of log file

• Previous model, attempted to save with new filename. – Attempted re-run of project (using new name) throws errors shown. – Solution is to import data from prior model, or start over.

How to Fix – Restart HMS

Import Prior Project

Select Prior Run 1

Select Run 1 The restart clears the computer memory And resets HEC-HMS paths There may be other ways to reset – this one is known to work

Poor Conceptualization • Hardest to detect and repair – If have data, then can use to guide repairs – Without data • use rules-of-thumb appropriate for locale – 3 cfs/acre/in-hr – Tlag(hrs) = SQRT(AREA(sq. mi. ) • use check-sums – Is loss what was anticipated? – Do flow peaks seem about correct?

Summary • Troubleshooting HEC-HMS projects needed to make simulation model what analyst thinks is modeling • Three modes of trouble – Incomplete specifications – Clobbered DSS file paths – Poor Conceptualization

Summary • Hints to help make troubleshooting easier – Name projects and components; avoid default naming • I didn’t follow for the course, but some examples show named components. – Maintain Excel data files as project • Use external (to HMS) preparation as a backup device. – Use HMS backup feature. – If recovery is needed, can use these files and cut-andpaste to recover work. – Maintain separate projects for substantial changes • This is my personal preference, the ANALYSIS tools in HMS are intended to perform such tracking for you

Summary • These hints should handle the bulk of the incomplete specification and DSS clobbering failure modes. • Conceptualization is harder

Summary • Conceptualization hints – Sketch (on paper) the watershed and components; keep a copy handy as build the project. – Parameter estimate external to HMS as much as practical; note estimates on the sketch. – Keep a simulation log (on paper) as you make minor changes; major changes should be separate project (my preference) or separate ANALYSIS (HMS tracking scheme)