[GRASS-user] r.flow: define contributing area
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 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.flow: define contributing area
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 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 > ___ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.flow: define contributing area
Rich, Maybe have a look at r.lake: https://grass.osgeo.org/grass70/manuals/r.lake.html. This module fills the area upstream a dam or a blocked stream. Cheers, Johannes Original message From: Thomas Adams Date:04/10/2016 04:32 (GMT+01:00) To: Rich Shepard Cc: grass-user@lists.osgeo.org Subject: Re: [GRASS-user] r.flow: define contributing area 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 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 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.flow: define contributing area
On Tue, 4 Oct 2016, Johannes Radinger wrote: Maybe have a look at r.lake: https://grass.osgeo.org/grass70/manuals/r.lake.html. This module fills the area upstream a dam or a blocked stream. Johannes/Thomas, I considered r.lake and r.damflood. What I will try to learn from the manual pages (and references thereon) is whether either of those modules require the blockage to be on a defined stream/river channel. Some lands can be on flat land without a stream running through it. These could be a suburban residential area, industrial/commercial area, or agricultural. Normally, when precipitation saturates the soils the excess runs off the surface and has a flow path to prevent flooding. When a drain, culvert, or swale is blocked the surface water accumulates where it's not wanted. This time of year this happens right outside my house where the storm drain grate in the street just off the curb between me and my neighbor is covered with dead leaves and the water backs up. Sweeping away the leaves clears this. But, this is the type of situation for which I need a solution: where will water back up and flood if drainage from flat land is blocked. So, I'll read what I can find about r.lake and r.damflood and see if they are suitable for this situation. Thanks both of you, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.flow: define contributing area
On Tue, 4 Oct 2016, Johannes Radinger wrote: Maybe have a look at r.lake ... fills the area upstream a dam or a blocked stream. Johannes, This module looks like it will do the job. The example of flooding along a small street somewhere in North Carolina is analogous to flooding of agricultural lands with blocked drainage. Yesterday I did not read all of the manual page and missed this. Thanks very much, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.flow: define contributing area
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 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.flow: define contributing area
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 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user