[GRASS-user] Strahler order starting from vector data?

[Hamish]

Hi,

I see v.strahler and r.stream.order in addons can assign
Strahler Order to a river network, but how to run that if you
are starting with an existing vector river network with no
raster DEM? could you cross with a matching coastline vector to
extract end nodes at the river mouths? will even a rough DEM
like SRTM data be better than nothing in that case? how good
does it have to be? would etopo1 be ok? (1 arc-minute ~ 2 km
cells)

also, how to get around attaching lake and swamp areas which
split the river vector line in two? convert their boundaries to
lines and treat it as a braided river? fill them in then r.thin
them somehow? otherwise topology would be clean.
how about if the river goes into a cave and out somewhere else? need to trace that gap by hand? (may be too big for the sloppy=
option)


thanks for any tips,
Hamish