[GRASS-user] r.flow: define contributing area

[Rich Shepard]

   Reading the r.flow manual page suggests that the use of the '-u'
(upstream) option allows determination of flowlines and lengths that can be
used to delineate the area that would drain to a specific point. Is this
correct?

   To determine the area flooded if an outlet is plugged would require the
inverse of r.drain. That module calculates the area flooded with surface
water originating from a specific point; e.g., a hole in a dike or dam. The
closest I've seen to do the opposite seems to be r.flow. The quantity of
surface water and the rate of accumulation and infiltration into the vadoz
zone are not of interest, only the area flooded is needed.

   The modules listed under the Natural Hazards application page all appear
to delineate the area flooded from a point source. Can any of these be used
backwards to delineate the area flooded if an outlet is blocked?

   I'd appreciate pointers and suggestions based on cumulative experience
here for appropriate module(s).

TIA,

Rich