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Problèmes avec Burn Stream slope et DEM Reconditioning

MargaretFisher

<\/HEAD>J'essaie de délimiter des bassins versants pour un projet en utilisant ArcHydro 10.1 beta. <\/SPAN>

Burn Stream Slope et DEM Reconditioning s'exécutent tous deux avec succès, mais le DEM résultant a à peine changé. Le cours d'eau que je traite passe sous un pont et donc lorsque je parcours tout le processus, les lignes de drainage finissent par suivre la route au lieu de suivre réellement le chemin du cours d'eau. Mais j'ai besoin que le cours d'eau soit intégré dans le DEM afin qu'il suive le chemin correct. Malheureusement, je ne vois pas cela se produire. J'ai essayé d'augmenter la zone tampon pour DEM Reconditioning et d'augmenter les taux de chute, mais rien ne semble faire de différence.<\/SPAN>

J'utilise NHDFlowline pour mon cours d'eau et un DEM de 1m. <\/SPAN>

Je serais vraiment reconnaissant si quelqu'un avait des idées sur la façon dont je peux intégrer le cours d'eau dans mon DEM.<\/SPAN><\/BODY><\/HTML>

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Accepted answers

DanPatterson_Retired

I hate to state the obvious, but are the X, Y and Z values in meters (or at least the same units)? or are the X,Y coordinates in decimal degrees?

All comments

MarkBoucher

Now the question is, which coordinate system should I use? Is it best to keep it all in meters?

My gut tells me that the data should be in the same coordinate system and units to work correctly.

MargaretFisher

I hate to state the obvious, but are the X, Y and Z values in meters (or at least the same units)? or are the X,Y coordinates in decimal degrees?

It would seem that my X, Y, and Z coordinates are all in meters for my 1m DEM, but the 10m DEM has the X, Y in decimal degrees. It would also seem that the NHDFlowline is in decimal degrees, so switching that to the same coordinate system as the 1m DEM works or vice versa. Now the question is, which coordinate system should I use? Is it best to keep it all in meters?

I'm pretty new to ArcGIS and especially ArcHydro, as well as delineating watersheds. So stating what might be obvious to most other people is completely not to me. A few of the tutorials I went though were using data from the same sources and used the same coordinate system from my DEM but didn't look at the coordinate system of the stream lines so it didn't even occur to me that it might be a problem.

Thanks for the help!

MarkBoucher

I am filling the reconditioned DEM, but it doesn't even look like the stream is burned into the reconditioned DEM to begin with.

Some thoughts:

Make sure the processing extent is set to include the area of your analysis. If not, the DEM Reconditioning. will run, but will do nothing. (see No. 5 in list linked at bottom of this post).

It seems like you are working in an area with lots of elevation change. If you are working in flat areas, make sure your most downstream agreestream feature extends beyond the DEM and that you internal agreestream features connect. If not, you may burn the stream, but the fill tool will just fill it up again. Burning "past" the edge of the DEM and making sure the internal features connect at the downstream ends avoids this. Having said that, you can burn a culvert or stream through an embankment; you just have to make sure the ends of the feature reside in the lower DEM grids of the creek/river. The burning will lower the embankment and the filling will fill it up again but just to the creek/stream bed.

You mentioned both a 10m DEM and a 1m DEM. To burn the roadside ditches in you will need a very fine DEM. It seems to me that a 10m DEM will not do that for you. Converting the 10m to a 1m would help. You can use the Resample command to go from 10m to 1m raster. (Data Management Tools.tbx\Raster\Raster Processing\Resample).

Make sure you burn the streams (DEM Reconditioning) and then fill.
See http://forums.arcgis.com/threads/48100-ArcHydro-Problem-Solvers?p=270146&viewfull=1#post270146 for more Arc Hydro set up tips.

DanPatterson_Retired

I hate to state the obvious, but are the X, Y and Z values in meters (or at least the same units)? or are the X,Y coordinates in decimal degrees?

MargaretFisher

Are you filling the reconditioned DEM? If you do, are your burnt in streams allowed to flow outside of the DEM? If they do not, then they will trap the water within the dem, be considered as sinks and filled in.

Christine Dartiguenave
Esri Water Resources Team

I am filling the reconditioned DEM, but it doesn't even look like the stream is burned into the reconditioned DEM to begin with. When I adjusted the AgreeDEM to be stretched and compared it to my original DEM I couldn't see any stream burned in. Both rasters looked almost identical. Even when I created a large buffer area and increased the smooth drop/raise I couldn't see any change along the stream path.

When I pulled the 10m DEM from the NED and ran the DEM Reconditioning I could see the stream burned in, but in the end it wasn't giving me watersheds that were very accurate when I looked at my contour lines. It just wasn't seeing most of the ditch lines running alongside roads that fed water into the streams or some of the small tributaries.

I really need to be able to get the stream to be burned into the 1m DEM, but it doesn't seem like the ArcHydro tools want to do that. The greater accuracy is important for the work we are doing.

In the end I'm having to spend a lot time editing the watersheds that is producing so they follow along more accurately with the contour lines and where the stream and ditches are actually located. It would probably be faster to just manually delineate the watersheds, but we are trying to add ArcGIS to our toolset.

ChristineDartiguenave

Are you filling the reconditioned DEM? If you do, are your burnt in streams allowed to flow outside of the DEM? If they do not, then they will trap the water within the dem, be considered as sinks and filled in.

Christine Dartiguenave
Esri Water Resources Team

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