I'm using ArcGIS (Hydrology toolbox) for watershed delineation for a number of pour points, and I'm running into problems with very meandering rivers on extremely flat alluvial land (Amazon basin).
When I run the tool I get extremely small watershed rasters, or larger ones that break off at random points. I have used the exact same DEM, Flow Accumulation and Flow Direction raster files to successfully delineate other watersheds in more mountainous areas.
I'm assuming that the flat relief and meandering river path are to blame, but I'm not sure. The raster resolution is 90m, and I'm using a single point shapefile with the pour point manually placed dead centre on the river. (As I've successfully done previously.) I've tried with a raster pour point but there's no difference.
Does anyone have experience delineating watersheds for this type of river, or any suggestions?