Flow analyses produce straight flow lines

Discussion created by jcbrewster on Feb 19, 2013
Latest reply on Feb 26, 2013 by MBoucher21
Hi All,

I've been running some tools from the SA hydrology toolset (NOT ArcHydro) for a variety of areas, to estimate surface runoff flow onto and out from specific parcels. Some areas produce logical flow networks, others produce straight flow lines that are clearly incorrect. I've tried this from both bare earth and hydro-enforced DEMs, and they both do the same thing. My workflow is:
- Fill sinks (from .5m DEM)
- Flow Direction
- Flow Accumulation
- Raster Calculator: StreamLink(SetNull(FlowAcc < x, FlowAcc), FlowDir) -- "x" being the cell threshold
- Stream to Feature tool for the result from the Raster Calculator

Attached is an aerial of a wetland area with the derived stream network overlaid -- the drainages are fairly accurate until they go straight, and then clearly deviate from the actual streams seen in the aerial. Are these errors from my processes, or does this analysis sometimes produce these kinds of results? Has anyone experienced this before?  Any thoughts would be greatly appreciated. Thanks!

ps -- I'm using 10.1 SP1