topic Re: Weighted Flow Accumulation not finishing in Water Resources Questions

Weighted Flow Accumulation not finishing

MS10 — Mon, 18 Apr 2016 21:57:55 GMT

Hi, I've seen posts with similar issues however i havent yet found a solution. Firstly, I've preprocessed my DEM (50m) and created Flow Direction in ArcMap. My weight raster is a floating point with values ranging from approx 0.004 - 0.3. However when i run Flow Accumulation using this as a weight it just runs and doesnt finish (i've left it for 8 hours and still nothing). I'm going to try a different computer tomorrow and fill the DEM, create flow direction etc again. I was wondering if the weight raster cell size (240, 240) is affecting it as the DEM and Flow Direction are 50,50?

Thanks

Re: Weighted Flow Accumulation not finishing

DanPatterson_Retired — Mon, 18 Apr 2016 22:03:30 GMT

don't know specifically, but it generally recommended practice to get your rasters lined up with regards to cell size, extent and snap raster before you begin the analysis to ensure that the resampling that would be needed to align all is in your hands and not within the software's. On top of this, it isn't just cell size but the overall number of rows and columns that is the key to processing speed. I would get everything in a common framework before you make any further assessments.

Re: Weighted Flow Accumulation not finishing

MS10 — Mon, 18 Apr 2016 22:39:18 GMT

Thanks i clipped my weight raster to my flow direction and flow direction to extent, snap raster etc.

Re: Weighted Flow Accumulation not finishing

curtvprice — Tue, 19 Apr 2016 01:00:55 GMT

How many rows and columns? I have run Flow Accumulation for 30 hours to complete on a large raster.

Make sure the environment for cellSize and snapRaster are set to match your flow direction grid. The default environment setting for cell size (Maximum of Inputs) could get you in big trouble!