Problem in connecting river centerlines in HEC-GeoRAs

[AmirJavaheri]

Hi,

I digitized the river centerlines and I used snapping tools to connect reaches. But when I checked the attributes table, I saw that my reaches are not connected because in that table, FromNode, ToNode, ArcLength, FromSta and ToSta are <Null>.

I clicked on RAS Geometry -> Stream Centerline Attributes -> Topology. After that I met this error: "River nodes lie outside the terrain". I don't know how to solve this.

Thank you very much if you could help me.
Amir

[MattMead]

Amir,
Make sure to split your centerlines where ever they intersect.  GeoRAS will still run, but there is the chance that it will screw up your distances if you dont split them manually.  As long as you use the snap tool to overlap the vertices, HEC-RAS should still create the junction.

As for the node outside the terrain error, I assume you are using the DEM from your previous post as your terrain data?  If so, it seems there may be a bug when using georas with DEMs.  Several of my coworkers have experienced similar errors even though the spatial reference is correct and the lines are quite obviously within the DEM boundary.  It doesnt happen all the time though so we havent yet pinned down what the issue is.  You can get around this by clipping down your DEM and converting it to a TIN.

Hope this helps.

[AmirJavaheri]

Amir,
Make sure to split your centerlines where ever they intersect.  GeoRAS will still run, but there is the chance that it will screw up your distances if you dont split them manually.  As long as you use the snap tool to overlap the vertices, HEC-RAS should still create the junction.

As for the node outside the terrain error, I assume you are using the DEM from your previous post as your terrain data?  If so, it seems there may be a bug when using georas with DEMs.  Several of my coworkers have experienced similar errors even though the spatial reference is correct and the lines are quite obviously within the DEM boundary.  It doesnt happen all the time though so we havent yet pinned down what the issue is.  You can get around this by clipping down your DEM and converting it to a TIN.

Hope this helps.

Thank you! yes, I am using DEM. I could convert them to TIN. But I have another problem. I want to merge 3 maps. As I read in forum, first I should merge the DEM files and then convert it to TIN. But I don't know how to do that. I really appreciate if you can help me.

[MattMead]

I dont use Arc10 yet but our head GIS guy does and says to use Mosaic to combine your DEM datasets.  There are tutorials on doing so in the help files.

[RipenKaur]

Hi There,

When I export RAS files from ArcMap 10 to HECRAS and I do not see junctions in the HEC RAS , even though the attribute table for the stream line shows the correct nodes. I have tried using both RASTER and TIN formats for the surfaces but it does not help.

Please suggest solutions.

Thanks, RK

[MattMead]

It will only auto-generate the junctions if you turn on vertex snapping and snap the end vertices.  Double check to make sure you have those points snapped together.

Failing that, its just as easy to turn on "move object" in the HEC-RAS geometry window and just move the end vertex of your tributary stream to overlap the receiving stream.  This will split the reach at that location.  You will have to manually input the junction data though(distances and such).

[RipenKaur]

It will only auto-generate the junctions if you turn on vertex snapping and snap the end vertices.  Double check to make sure you have those points snapped together.

Failing that, its just as easy to turn on "move object" in the HEC-RAS geometry window and just move the end vertex of your tributary stream to overlap the receiving stream.  This will split the reach at that location.  You will have to manually input the junction data though(distances and such).

Thanks Meadmw, your suggestion worked.