HEC-RAS Known Issues

HEC-RAS has two methods for computing the maximum Courant number used for the adaptive time stepping. One is based on the face velocities while the other is based on the cell outflows and volume (i.e. residence time). The default method is the face velocity method, but in 6.1 there was a bug in which the residence time method is always used no matter what method is selected by the user. 

If the Depth Blocked setting for culverts is left empty, the culvert may crash or be completely blocked. The simple workaround is to ensure the Depth Blocked has a value specified (not blank), even if it is zero. 

One of the inlet coefficients ('submerged Y') for a box culvert for flared wingwalls (chart #8) flared 30 to 75 degrees (scale #1) was using 0.86 when it should have been using 0.81 according to HDS No. 5.  This will only effect the culvert hydraulics for this particular box culvert when flowing under inlet conditions.  (Outlet control is more typical).

The stage boundary condition for 2D areas can produce instability problems when the user-specified water level is below the boundary face invert elevations. 

The Shallow Water Equation Solver with the explicit Eulerian advection scheme (SWE-EM) had a bug in which the values for the face areas were incorrect. This produced only slightly different results. The bug has been resolved and the new results of the SWE-EM solver are closer to those of the Eulerian-Lagrangian solver (SWE-ELM). 

The 2D Implicit Weighting Factor is not being set correctly for the warmup or simulation and is defaulting to the value 1.0. Therefore, this is only an issue if the user enters a value less than the default value of 1.0. There is currently no workaround for this issue. 

The River-Reach-RS drop down does not repopulate the correct reaches if a new River is selected

The sediment subcell bed elevation plot does not produce correct subcell areas when running in SI units. Spatial maps of bed elevations are correct in both SI and US English unit systems. Only the subcell bed elevation plots are affected. The work around is to convert the project to US English units. 

The morphologic acceleration was not being considered in the calculation of consolidation. Therefore, Morphologic Acceleration Factor values other than 1.0 do not yield correct results. The work around is to use a Morphologic Acceleration Factor of 1.0 when consolidation is needed. 

If the model contains river reaches with the same name, For example: River A, Reach A; and River B, Reach A, a 1D bridge may be assigned the wrong river after saving in RAS Mapper.  Work-around is to not have reaches with the same name

If the model contains interpolated cross sections and 1D bridges, then there is a chance an unhandled exception will occur in RAS Mapper on save.  Work-around is to remove all *'s from the RiverStationName column for cross-sections. 

The optional precipitation ratio specified in the Unsteady Flow Data editor is not being applied. The only work around is to modify the precipitation data directly. 

Sometimes adding a boundary condition line using RAS Mapper will assign the wrong Storage Area or the wrong 2D area.  The ability to reassign with a right click menu will be added for version 6.2.  To assign a boundary condition line to a different Storage Area or 2D Area, follow these steps:

1. Start editing the geometry
2. Click and drag the line so it is closer to the perimeter of the intended 2D area/ Storage area
3. Double click the line to open it for editing
4. Add a point to the line
5. Ctrl+Z or click undo to undo adding the point to the line
6. Double click to close the line.  At this point the BC line will reassign itself, hopefully it assigns to the intended 2D area/Storage Area
7. Ctrl+Z to undo moving the line, this undos the movement done in step 2.
8. Stop editing and save if the boundary condition line is assigned properly.

If you change the Reference XS in the riprap calculator it does not update the hydraulics until something else in the editor is changed.

Work around: When you update the reference XS in the riprap calculator, change something else (and then change it back) to get the hydraulics to update.  This has been fixed for version 6.2.

Some users are reporting longer than usual times for computing face profiles when their terrain has polygon modifications with control points.  A possible work around is:

For each polygon mod:

    clip the terrain using the steps described here

    The clipped terrain will have the same terrain mods as the source terrain.  The clip routine works on terrain tiles, a terrain tile may contain more than just the one polygon mod.  Remove mods that are outside the tile.

    Resample the clipped terrain to a single terrain so the mod gets burned into the terrain.

Remake the original terrain, using the new layers from clipping each polygon mod as inputs for the new RAS terrain.

At this point, your terrain should look the same as before, but not have any polygon modifications in it.  This will make RAS use the standard rasterized terrain approach for computing face profiles.

Datasets containing gates will sometimes not plot in Hydrograph Plot

After an unsteady run, and trying to open the hydrograph plotter, the hydrograph plotter may show an error box "Sequence has no elements."  The hydrograph plotter will open correctly if the user clicks the hydrograph plot button again. 

RipRap calculator not loading with unsteady datasets

The riprap calculator will not launch when a project with a project with unsteady data is loaded. Launch it with a steady dataset or with no dataset at all (to run it headless).

3D Viewer not launching from main RAS window

The 3D Viewer will no longer launch from HEC-RAS main window.  Can launch 3D Viewer from RAS Mapper. Details on launching the 3D Viewer are here.

Renaming a 2D area in RAS Mapper Breaks the Connection with Boundary Conditions Lines

If a 2D area is renamed in RAS Mapper, the boundary conditions for the 2D area are lost and the user has to reenter the boundary conditions in the Unsteady Flow Data editor.

Coupled 1D/2D Sediment Simulations

It is not possible to run coupled 1D/2D sediment simulations. However, a possible work around which may feasible in some situations is to run 1D and 2D sediment decoupled. For example, a 1D sediment model can be run and used to specify sediment time series for a downstream 2D sediment model. 

Unable to plot Initial Condition Points

Initial Condition Points will show "No Data for Plot" in the new Hydrograph Plotter.  Work around is make an identical reference point at the initial condition point and plot that instead.

Advanced Rules SI Reference Points

When using 2D Area Reference Points with Advanced Rules with a SI dataset, the value of the Reference Points was being evaluated using incorrect units [inside of the rules].

Advanced Rules Lateral Weirs/2D Connectors Gate 'not set'

When using the Advanced Rules with a Lateral Weir or a 2D connector, the ability to set the gate opening to 'not set' was not working correcting.

General non-English Language issues

"Error in Loading Geometry Data" in the Geometry Schematic.

GDAL Conflict when Opening RAS Mapper

"Error initializing the GDAL path variables. Please check HEC-RAS installation" error message is displayed when attempting to open RAS Mapper.