Définition du flux - sortie vide

Question

<\/HEAD>Je lance la définition du flux et j'obtiens un raster avec des valeurs de 1 à 255 au lieu d'un simple 1 pour toutes les cellules faisant partie d'un flux. Le raster est également complètement vide (voir pièce jointe). J'utilise une grille d'accumulation de flux entière en entrée qui a été créée en utilisant l'outil d'accumulation de flux dans spatial analyst. ArcGIS se bloque chaque fois que j'essaie de créer une grille d'accumulation de flux avec ArcHydro, ou de créer une grille à virgule flottante avec spatial analyst. Je ne comprends pas pourquoi celle en entier ne devrait pas fonctionner, cependant.<\/P> Quelqu'un a-t-il déjà rencontré ce problème ?<\/P> <\/P> Merci,<\/P><\/BODY><\/HTML>

LornaMurison · Answer

I figured out that the issue was with my flow accumulation grid. While it looked fine at first glance, I noticed that the maximum value was way higher than it should be and that these high value cells tended to occur at the headwaters of my stream network.

It turns out that the issue was with "Create Drainage Line Structures" and "Adjust Flow Direction in Streams" tools. The former created a flow direction grid underlying my streams assigning flow according to the digitized direction of the stream network which, in my case, does not correspond to actual flow direction. So I ran flow accumulation on the flow direction grid without running "Adjust Flow Direction in Streams" and it worked.

I'm now stuck on one of the following steps, but I'll find a better place to discuss that.

Thanks for looking into this with me.

IanMurray · Answer

First off, I'll direct you to a thread where they were troubleshooting a large number of ArcHydro issues, as well as some recommendations for making sure things run pretty smoothly when using ArcHydro.

https://community.esri.com/thread/43771

Your versions of ArcMap and ArcHydro should both be compatible so no problem there.

File sizes shouldn't be an issue either.

You should be able to do a stream delineation using the Conditional Raster Tool without ArcHydro, returning 1 if the flow accumulation is over your threshold limit, and 0 if it does not.  This however doesn't help the fact that ArcHydro isn't working for you properly.

http://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-analyst-toolbox/con-.htm

Tagging a few people for input:

MBoucher21‌
curtvprice‌

Dan_Patterson‌

LornaMurison · Answer

Hi Ian,

I am using ArcMap 10.2.0.3348 and ArcHydro 10.2.

The uncompressed size of the raster files are 376.39 MB (which seems small to me) with 10,753 x 9,176 cells. Everything is based off a 1m resolution Lidar DEM for an area of just over 50 km2.

When I run flow accumulation with ArcHydro (from either the toolbar or the toolbox) it appears to keep running indefinitely. I have left it for a maximum of 2.5 days and when I open task manager I can see that memory usage is unchanging which makes me think that it crashed.

When I ran the flow accumulation tool from Spatial Analyst with integer as the output format, it took 11 minutes and created a flow accumulation grid that looks totally fine to me. When I run the Spatial Analyst flow accumulation tool with float as the output format it also appears to run indefinitely although I haven't left it for more than maybe an hour.

When I try to run the stream definition tool using the integer flow accumulation grid created with Spatial Analyst it tells me it has successfully completed  and I get an empty raster that has values of 1 to 255. I have tried this with multiple different flow accumulation thresholds with the same result. I haven't seen this issue on any forums. The closest I've found is this one: https://community.esri.com/message/385236

Thanks,