topic Re: ArcHydro in Water Resources Questions

ArcHydro

TimothyMaguire — Wed, 11 Jan 2012 19:32:13 GMT

I am working on delineating watersheds in a very flat spring driven system. NHD data only describes two of the major streams in the watershed, so I had to digitize the stream courses and use them as the Flowlines inthe analysis. I am able to build the catchments not problem but when I try to create the adjointcatchments something is amiss. Only two headwater streams are considered adjoint. This is not correct as several headwater sections should be included as parts of larger dowstream watersheds. Has anyone ran into this problem before? One other point is that I have had to manually update the HydroIDs throughout the process as ArcHydro is writing Hydro IDs as if the watershed outlet was a headwater stream - aka everything is backwards. Thanks in advance for any help you can offer.
Sincerely,
Tim

Re: ArcHydro

MattMead — Thu, 12 Jan 2012 11:52:48 GMT

I don't use ArcHydro but GeoRAS has a similar issue if you digitize the stream in the wrong direction. Check to see if all your stream segments go in the correct direction(ie end point of the line is the downstream end or however it is supposed to be). If that is the issue it might solve your other problem as well. Good luck

Re: ArcHydro

TimothyMaguire — Thu, 12 Jan 2012 14:54:48 GMT

Thanks for the reply. I am re-digitzing the streams in a downstream manner. I'll post how well it went when I am done.
Tim

Re: ArcHydro

MattMead — Fri, 13 Jan 2012 00:43:36 GMT

Thanks for the reply. I am re-digitzing the streams in a downstream manner. I'll post how well it went when I am done.
Tim

Just select "modify feature" instead of "Create feature" in the editor menu then right click on a vertex and click "flip"

Re: ArcHydro

TimothyMaguire — Fri, 13 Jan 2012 15:12:51 GMT

Just select "modify feature" instead of "Create feature" in the editor menu then right click on a vertex and click "flip"

Thanks Meadmw. I did not use the modify feature tip but will in the future. But, re-digitzing the streams starting at the top of the watershed and progressing downstream to the outlet worked. HydroIDs and nextdown IDs are all correct and watersheds are processing correctly.

Re: ArcHydro

MarkBoucher — Fri, 13 Jan 2012 17:05:36 GMT

There is also the Flip Line tool.

See under System Toolboxes>Editing Tools.tbx>Flip Line. You can go into Edit mode on the layer, select several lines and use this tool to flip all of them at once. It is nice to turn use the mid line "Arrow Right Middle" symbol so you can see which way the lines are "heading".

Re: ArcHydro

MarkBoucher — Fri, 13 Jan 2012 18:02:51 GMT

I just looked at a GeoHMS project that I worked on months ago. The agreestream layer has the line direction going all over the place and I had no problems using it back then. Line direction may not be critical in the agreestream layer with processing the DEM.