Beta release:   

Final release:  

New Features

Global temperature-index snow editors

Global temperature-index snow editors were added to facilitate rapid calibration of large temperature-index snow models. Global editors can be accessed from the Parameters | Snowmelt menu, whenever a meteorologic model with temperature-index snowmelt is selected in the Watershed Explorer. A filter was added to the global editor to allow users to quickly filter elements by computation point or zone. 

The global temperature-index snow editors were funded by the Corps Water Management System (CWMS) National Implementation Program. The initial code implementation was done by Thomas Brauer with testing by Matthew Fleming, Michael Bartles, and Gregory Karlovits.

Time-variable wet-meltrate

Capability was added to model the temperature-index wet-meltrate parameter as variable in time. This capability supports dam safety studies that might want to adjust the wet-meltrate during highly dynamic storms. This capability also allows the the wet-meltrate parameter to change seasonally.

The time-variable wet meltrate was funded through an agreement with California Department of Water Resources (DWR), Division of Safety of Dams (DSOD). The initial code implementation was done by Thomas Brauer with testing by Matthew Fleming and Thomas Brauer.

Debris yield methods

It is now possible to evaluate debris yield/flow under post-wildfire situations within the watershed. Subbasin elements have three debris yield methods based on precipitation, topography, and soil burn severity information for event and continuous simulation. Reach and reservoir elements are being further developed for debris/hyper-concentration flow routing analysis.

Meanwhile existing sediment features (reach and reservoir elements) can be used to evaluate debris flow effects throughout the watershed with certain limitations. The results of the analysis can also be used upstream as inflow boundary conditions to non-Newtonian numerical modeling capabilities within HEC-RAS in order to evaluate complex debris/mud flow problems.

The debris yield methods were funded by the USACE Arid Regions work unit within the Flood and Coastal Systems Research and Development program. The initial code implementation was done by Jay Pak and Paul Ely with testing by Jay Pak. 

Number of cores user interface selection

A number of cores selection was added to the user interface in Tools | Program Settings, Defaults tab. This selection allows users to adjust the number of cores used in native processes, which is currently limited to the GIS raster and delineation processes. Increasing the number of cores should result  in better performance for Preprocess Sinks, Preprocess Drainage, Identify Streams, and Delineate Elements menu items. It is anticipated that this setting will be used to control the default number of cores for other native processes in the future. Note: there are many instances in the code where parallelization is handled by Java based on the resources available to the Java Runtime Environment; The default number of cores setting will have no effect in this situation.

Java 11

For v.4.5, HEC-HMS was migrated from Java 8 to Java 11. Java 11 has shown much better performance on highly-scaled and high-resolution displays. A previous known issue guided users through overriding the DPI scaling behavior when attempting to use HEC-HMS on a highly-scaled display. Java 11 should help eliminate the need to make any scaling adjustments.

Bug Fixes

Error 14703: No data source is specified for unit hydrograph when attempting to use a user-specified unit hydrograph

An issue was found in the DSS Pathname validation logic for the unit hydrograph paired data curve. This caused a No data source is specified for unit hydrograph error during the pre-run validation check, even though valid DSS file and pathname were provided. The validation was updated to correct the false negative.

Unit hydrograph interval and duration are not saved in the Paired Data editor

An issue was found where the unit hydrograph interval and duration were overridden by defaults in the Paired Data editor upon save. This issue was corrected so that the interval and duration can be updated by the user, and the updates are persisted during save.

Failed copy + paste in the unit hydrograph Paired Data editor

An issue was found where attempting to copy + paste in the unit hydrograph paired data editor failed. The issue was traced back to the underlying write logic for storing time patterns. The time pattern write logic was updated fixing the copy + paste functionality.

Missing or reduced-area mod Clark grid cells when generating a grid cell file with target projection differing from the basin model coordinate referencing system

An issue was observed during testing where some mod Clark grid cells were missing or reduced in area when the target projection was different from the basin model coordinate referencing system, and the projected grids were highly-oblique, e.g. UTM 17N basin model coordinate system to Standard Hydrologic Grid (SHG) target projection. The missing or reduced-area cells were limited to a subset of the perimeter cells. Interior grid cells and most perimeter grid cells were unaffected. There was no issue when the basin model coordinate system and target coordinate system were the same, or, the same but used different linear units, e.g. SHG Feet vs SHG Meters. The grid cell file creation logic was updated to use a vector-geometry-based intersection which eliminates the issue. The vector geometry approach may take slightly more processing time than the previous raster-based approach.

General Acknowledgments

Many engineers, computer specialists, and student interns have contributed to the success of this project. Each one has made valuable contributions that enhance the overall success of the program. Nevertheless, the completion of this version of the program was overseen by Matthew Fleming while Christopher N. Dunn was Director of the Hydrologic Engineering Center. Thomas Brauer led the HEC-HMS team during the Version 4.5 release cycle. HEC-HMS team members include Thomas Brauer, Michael Bartles, David Ho, Gregory Karlovits, Jang (Jay) Pak and Alejandro Sanchez.