Error in "Floodplain delineation"-HecGeoRas

[VanessaMartinez]

Hello,

I'm working with Hec-Ras and HecGeoRas extesion for ArcGis 9.3 version. I want generate inundation mapping for diferents  retorn periods. First of all, I create the streamcenterline, the flowpaths and the useland shape, in ArcGis. Then, I export this information to  HecRas, and I enter the flow values. Finally, I export the model to ArcGis.

But... When I select the "Floodplain delination using raster" (en Ras Mapping>Inundation Mapping), I get the following error:

"System.Runtime.InteropServices.COMException (0x80041098):ERROR 010067:Error en executing grid expresion. en ESRI.ArcGIS.GeoAnalyst.RasterConversionOpClass.RasterDataToPolygonFeatureData(IGeoDataset, IWorkspace pWorkspace, Sting name, Boolean weeding) en HECGeoRAS.clsMFloodGRIDIntersection.GridToPolygon1(Taster pRaster, IGeoDataset pGeoIn, IWorkspace pWS, String sName, Boolean sWeeding"


Sometimes, also, I get the other error: "Failed to convert TIN to GRID..."


I'm sure that the problem is about the TIN. But I dont' find it... I restar de computer, I change the ubication of folders direct on C:, I reinstal de extesion and the HecRas... I work in anothet computer.

I'm very lost.

If you can help me, I'd be greatfull, because I want throw out the computer for the window!!! :S


Lot of thanks!!! Excuse me for my english... :s

[MattMead]

The RAS mapper is more trouble than its worth most of the time.  It is much easier to do without it as debugging can be time consuming. 

1)create a copy of your georas cross sections(not 100% necessary, but its always bad to play around with your finished model files)
right click on the cross section file->Data->export data.

2)add field to the new cross section file attribute table for each RAS profile you want to map(the default "double" settings work just fine)

3) in an edit session,copy in your RAS output
if you have bridges you may need to copy the output to Excel or other database program first to remove the extra lines

4)In 3dAnalyst toolbar, Create/Modify Tin->Create Tin from features
Select your new cross section file and set it to the appropriate profile for the height data source

5)In 3dAnalyst toolbox->TIN Surface->Tin Difference
This will create a polygon of your floodplain with 3 values.  Above, below and same.  Delete the below as this is outside your floodplain.


Doing it this way allows you to have more control over the initial floodplain.  The RAS mapper only works with whatever was originally in the model instead of what would make sense for mapping.  A model cross section wont extend into backwater areas, or other areas where a linear interpolation from model cross sections would incorrectly map flood elevations.  This process allows you to modify the mapping cross sections however you want(which is another reason to export them an not use the georas files).

[JassyRivera_Solis]

The RAS mapper is more trouble than its worth most of the time.  It is much easier to do without it as debugging can be time consuming. 

1)create a copy of your georas cross sections(not 100% necessary, but its always bad to play around with your finished model files)
right click on the cross section file->Data->export data.

2)add field to the new cross section file attribute table for each RAS profile you want to map(the default "double" settings work just fine)

3) in an edit session,copy in your RAS output
if you have bridges you may need to copy the output to Excel or other database program first to remove the extra lines

4)In 3dAnalyst toolbar, Create/Modify Tin->Create Tin from features
Select your new cross section file and set it to the appropriate profile for the height data source

5)In 3dAnalyst toolbox->TIN Surface->Tin Difference
This will create a polygon of your floodplain with 3 values.  Above, below and same.  Delete the below as this is outside your floodplain.


Doing it this way allows you to have more control over the initial floodplain.  The RAS mapper only works with whatever was originally in the model instead of what would make sense for mapping.  A model cross section wont extend into backwater areas, or other areas where a linear interpolation from model cross sections would incorrectly map flood elevations.  This process allows you to modify the mapping cross sections however you want(which is another reason to export them an not use the georas files).

I'm having the same problem. I don't mind which way to use, I just want to delineate the floodplains. But I didn't understand everything you said.

Is it that I need to export the results from hecras and once I have it in ArcMap, export the shape containing the cross sections?
And then?

Could you please explain me a little bit more!!!


Thanks in advance

[MattMead]

I'm having the same problem. I don't mind which way to use, I just want to delineate the floodplains. But I didn't understand everything you said.

Is it that I need to export the results from hecras and once I have it in ArcMap, export the shape containing the cross sections?
And then?

Could you please explain me a little bit more!!!


Thanks in advance

You more or less have it right.  I would create the copy of the cross sections before copying in the Hec-ras output, but either way would work.  The only reason I would copy the cross sections first is that I have bad luck with geodatabases getting corrupted when I add fields to the files.  Basically the process I laid out has you manually do what the import process built into georas would do automatically.  Your end result is the cross sections with the appropriate water surface elevations in it.  How you get their is up to you.

Once you have your cross sections and elevations all you need to do is use the tools I identified in the previous post and you should be set.

[MattHinshaw]

The RAS mapper is more trouble than its worth most of the time.  It is much easier to do without it as debugging can be time consuming. 

1)create a copy of your georas cross sections(not 100% necessary, but its always bad to play around with your finished model files)
right click on the cross section file->Data->export data.

2)add field to the new cross section file attribute table for each RAS profile you want to map(the default "double" settings work just fine)

3) in an edit session,copy in your RAS output
if you have bridges you may need to copy the output to Excel or other database program first to remove the extra lines

4)In 3dAnalyst toolbar, Create/Modify Tin->Create Tin from features
Select your new cross section file and set it to the appropriate profile for the height data source

5)In 3dAnalyst toolbox->TIN Surface->Tin Difference
This will create a polygon of your floodplain with 3 values.  Above, below and same.  Delete the below as this is outside your floodplain.


Doing it this way allows you to have more control over the initial floodplain.  The RAS mapper only works with whatever was originally in the model instead of what would make sense for mapping.  A model cross section wont extend into backwater areas, or other areas where a linear interpolation from model cross sections would incorrectly map flood elevations.  This process allows you to modify the mapping cross sections however you want(which is another reason to export them an not use the georas files).

Matt,

Thanks for the information.  Is there any further guidance on this out there or instructions that you know of for a "work-around" like this?  Even this is a little difficult for novice ArcGIS users that only use the program as an input/output for HEC-RAS every now and then without much time to practice my skills.

I'm working with GRIDs from the get-go with my data since my LiDAR came from .img files.  So I was trying to avoid having to convert anything to a TIN at any time, but I guess that's a necessity with how GEO-RAS works - it creates a water surface TIN and then uses that to make a water surface GRID, subtracting that from your DTM surface (GRID already in my case) and that is the depth grid we are after in the end.  If we can just do all that manually (without GEO-RAS) and have it still look good then yes why even get caught on these GEO-RAS errors after all?

Matt H.

[RobertQueen]

Hi,

I know this is from a long time ago, but I just recently ran into this same error. I tried many different methods until I figured out a solution. I had my DEMs from a LiDAR and in a .img file. I converted these to a GRID file and it worked. This makes me think that Geo-RAS can't correctly read or deal with the .img file and it has to be a GRID file.

Thanks everybody for the replies and solutions as the different methods did work, it is just that my work wanted it done through RAS Mapping.

Best,

Robbie

[MarkBerry1]

Robbie,

How did you do that exactly? I'm kind new at GIS (ver 10.1) and need to delineate the floodplain as well.

Mark

[XanderBakker]

You may be interested in this thread too:

Re: Determine Floodplain: Based on known flood level

[RobertQueen]

For converting the .img file to a GRID, I just used the export feature (right click on the file in ArcGIS table of contents and Data to Export Data). This should give you the option to change the file type to GRID. The rest of it was just using the RAS Mapping tools in HEC-GeoRAS based on my results from HEC-RAS.

[XingZheng]

Perfect solution, THX!