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
Rich,
The only way to -correctly- do this is with hydrodynamic modeling, such as with HEC-RAS. It can be very crudely approximated with r.damflood (https://grass.osgeo.org/grass70/manuals/addons/r.damflood.html).
Tom
···
On Mon, Oct 3, 2016 at 7:39 PM, Rich Shepard <rshepard@appl-ecosys.com> wrote:
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
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On Mon, 3 Oct 2016, Thomas Adams wrote:
The only way to -correctly- do this is with hydrodynamic modeling, such as
with HEC-RAS. It can be very crudely approximated with r.damflood (
https://grass.osgeo.org/grass70/manuals/addons/r.damflood.html).
Tom,
I had tried using HEC-RAS long ago and found it required too much input
data for use with existing environmental data. It's great for research but
not so much in a regulatory context.
Six years ago this would have been a great module for me to use for a
project had I been aware of it.
For current need, it is the opposite of what r.flood does and the latter
is the appropriate one for the current purpose.
Thanks for making me aware of this,
Rich
On Tue, 4 Oct 2016, Rich Shepard wrote:
For current need, it is the opposite of what r.flood
^^^^^
Er, make that r.lake instead.
Rich