Determine Flow Accumulation GRID: Using Python; Map Algebra and NumPy

Discussion created by Playa on May 12, 2013
Latest reply on May 12, 2013 by curtvprice
I'm currently busy with a hydrology study where I'm determining the location and structure requirements (culverts & bridges) for a proposed Railway Alignment. My initial assessment is based on the STRM 90m DEM and the size of my DEM is 34 651 X 24 934 cells = 863 988 034 cells. I can't afford to split my DEM or to increase the cells size as its already a coarse cell size. I've used the Flow Accumulation tool within Arc Hydro, the Flow Accumulation tool within the Spatial Analyst Extension; Hydrology Toolbox as well as tried running it from Python hoping for better processing time. The Flow Accumulation algorithm that is being used seems to be hard coded in that it doesn't use any more than 2 GB memory when processing the Flow Direction GRID to generate the Flow Accumulation GRID.

Is there a way to use Python; Map Algebra and Numpy to improve my processing time in generating the Flow Accumulation GRID for large DEM's.

The current Flow Accumulation GRID runs for almost 72 hrs.