Problem with DEM in a flat area

Dear group,
Have a problem on hand. I am trying to use SWAT-ArcView to study an
area, so the first thing needed is DEM, which I have already.
The problem is that one area is very flat, so the SWAT-ArcView
stream extraction function couldn't get the stream line right.
Basically, it thinks one stream should be draining one direction, but
actually it should be draining the opposite direction, also there is
some breakage in stream line that exists on the ground (like ditches
etc).
I 've tried to use our correct stream layer to burn in during the
SWAT-ArcView stream line extraction process, but it still failed to
get it right.
There have to be people dealing with this type of situations on a
daily basis, could someone give me some suggestions? I figure either
mess with the DEM (but how) or edit the extracted stream and joints
layer in SWAT-ArcView environment (also how?), please help.
Many thanks.