[GRASS-user] r.stream.extract

[M S]

Great module!  I like the optional parameters to tweak the stream
extraction.  In my current situation, I have 20,000 acres modeled with
a 25ft cell DEM from relatively dense LiDAR data.  The project area is
very flat and has many wetlands.  The elevation range for the 20K
acres is only 30 to 170 feet.  What is nice, is that I have field
verified GPS data for the streams on the site to check against the
stream extraction results and tune the parameters.  Then, on a similar
area project, I can utilize this module where we have no GPS or field
data with confidence after tuning to known data.

That all being said, I'm looking for suggestions to tune the stream
extraction for flat areas with relatively low relief.  Additionally,
the component of many wetlands.

My first question is about the accumulation parameter.  As I
understand it, MFD is only available in GRASS 7 with r.watershed.  I'm
on 6.4RC5.  If I dont input accumulation with my elevation, will MFD
be used in r.stream.extract?

Looking at the weight parameter, it seems this may help tune the
results also.  For the project area, I have coded land use where I can
essentially input wet areas (water bodies & wetlands), and all else as
dry (uplands).  Would this help provide more accurate results, or is
there another intended use of this parameter?

For the mexp parameter, it seems to be applicable to helping with
results in flat areas such as this study area.  Is there caution
against using a higher mexp value if one's whole project area is
relatively flat?

Thanks for the contribution of this module.  I'm looking forward to
using the other r.stream.* modules after I have a good stream network
extracted.

Thanks,
Mark