[ckatsoulas]

It looks like you are using 30minute time steps which is very large. If you have a large flow it is too much flow to push each step to each cell and therefore the software is crashing. You need to reduce the time step considerably until it becomes stable. usually seconds.

[ckatsoulas]

You need to do this in a GIS package like QGIS, ARCGIS or MAPINFO. HECRAS is limited at the moment.

[ckatsoulas]

What do you think of the following:
– split the 1D cross section into 2 separate channels/rivers side by side, one for the main channel/river and one for the overbank.
– send the upstream 1D to the main channel cross sections
– send the 2D area to the overbank 1D sections
– join the 2 rivers downstream with a junction
– use a lateral weir to allow flow between the main and overbank channels upstream of the junction.

[ckatsoulas]

ok, why don’t you use a culvert to transfer the flow.

I would place my inflow in a non flooded area and then collect the water with a large sized culvert. To ensure no loss/spillage of flow you could put an SA/2D connection to trap the flow at that location so it all gets into the culvert. The culvert should hopefully have positive momentum into the channel. Depending on the channel grade I think regardless of what you do you will always get some backwater effect until flows upstream start to combine.

[ckatsoulas]

why not add a wall behind it (using SA/2D connection) so that water does not push backwards. After adding the SA/2D connection change the weir elevations to be above the water levels and that way the flow will then proceed in downstream direction

[ckatsoulas]

can you post your 2D model showing the grid and boundary condition lines you used

[ckatsoulas]

I’m having trouble viewing the pictures because the forum doesn’t allow me to pan across. Are you sure you’re not having issues with the units. Are you using feet or meters? Also the picture below is showing cross sections so it’s not really a 2D model but a 1D model. how did you create the cross sections? did you extract them from the terrain?

[ckatsoulas]

can you send a picture of what the model looks like and the results

[ckatsoulas]

I have a situation where I have a building with roof that covers an open parking area. this area does not get rainfall however it can get flooded. If I delete the roof over the parking then I also allow direct rainfall over it but if I add the building as a blockage then I can’t model the flowpath through the parking. We need to turn off the 2D cells at this location to prevent rainfall but allow it to get flooded

[ckatsoulas]

I just answered my own question, when creating the merged terrain if you click on the box “merge inputs to single raster” it will then be recognized by HECRAS as a single raster not two rasters on top of each other with separate results.

[ckatsoulas]

can you provide a screenshot to show what is happening

[ckatsoulas]

This problem was fixed with the latest 5.0.6 release.

[ckatsoulas]

Since HECRAS doesn’t allow pits the only way you could do a stand pipe is to introduce a culvert with the invert set at the top level of the stand pipe and then apply a rating curve that coincides with the weir/orifice flow into the stand pipe for varying depths.

[ckatsoulas]

I am not 100% but with some of my runs where I also got this error code, I found that it usually occurred if my time step was way off the mark when I did a variable time step run. I think you need to play with the starting time step so that it is close enough to the calculated time step.

[ckatsoulas]

Paul

It is easier to use QGIScloud which provides free uploads. See link below for instructions

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