Re: [GRASS-user] Re: Defining Partial Drainage Basin
In order for a basin to be delineated correctly, the pour point has to be in a high accumulation area (I once heard the expression synthetic river...) Well, put your pour point on top of the accumulation map and see if it's on top of the river. If not, change your easting and northing coordinates appropriately. If you come from ArcGIS world, they have a tool called Snap Pour Point that does that. I recall doing something similar in grass using v.distance and a stream raster... Good luck Daniel On Wed, Feb 10, 2010 at 4:22 PM, Rich Shepard rshep...@appl-ecosys.com wrote: On Wed, 10 Feb 2010, Micha Silver wrote: A quick tip regarding r.water.outlet (you may have noticed this already) The module creates a new raster covering the whole analysis region with two possible values: 1 for all cells draining into the outlet, and 0 everywhere else. If you do r.to.vect straightaway, you?l get a vector containing two polygons... I always run r.null setnull=0 on the r.water.outlet result first. This insures that r.to.vect leaves you with just the drainage area. Micha, I'm under a deadline to finish the current project, and nothing seems to be working correctly for me. I just ran r.water.outlet using the drainage (aspect) map created by r.watershed. The output is a yellow rectangle that the legend tells me represents '0'; that is, there're no cells in the calculated basin. g.region -p reports: projection: 99 (Lambert Conformal Conic) zone: 0 datum: nad83 ellipsoid: grs80 north: 1334420 south: 1279150 west: 769190 east: 819260 nsres: 10 ewres: 10 rows: 5527 cols: 5007 cells: 27673689 The command line was: r.water.outlet drain=aber10m.drain basin=lockie e=795542.95 n=1308323.52 --o I can send copies of aber10m.drain and lockie. It makes no sense to me that such a simple run fails to define the partial drainage basin. Any help or ideas you offer will be much appreciated. 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] Re: Defining Partial Drainage Basin
On Wed, 10 Feb 2010, Daniel Victoria wrote: In order for a basin to be delineated correctly, the pour point has to be in a high accumulation area (I once heard the expression synthetic river...) Daniel, Perhaps if I explain what I'm trying to do it will help everyone who's assisting me. There's a small parcel of land several hundred meters below a dam. On January 1, 2009, after almost 14 inches of rain in the past week (including 6.44 inches the day before), that property flooded, including the trailer house sitting there. This is the first flat spot below the dam (and the dam spillway operated properly); the creek is deeply incised with almost vertical walls below the dam. The bank on the other side from the property is higher so all the flooding was all on this one side. Of course, lower in the drainage basin flooding was more extensive (including a brand-new house that hasn't sold in two years because it was built on the floodplain.) What I want to show is where all that precipitation runoff came from, and that it's not all from the reservoir overflowing the spillway. Immediately west of the flooded property is a steep hill, so a lot of surface runoff came from there and augmented what was transported in the stream channel. Well, put your pour point on top of the accumulation map and see if it's on top of the river. If not, change your easting and northing coordinates appropriately. If you come from ArcGIS world, they have a tool called Snap Pour Point that does that. I recall doing something similar in grass using v.distance and a stream raster... The last time I used ARC/Info was 1989. :-) The pour point is on the stream channel. See the attached .png that I forgot to put on my response to Stephen. The topmost 'x' is the flooded property, the one below it is the center of the dam. Thanks, Richattachment: accum.png___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
Looking at the PNG it does not look like any of the pour points are on the channel. It has to be exactly on top of the lines in the flowacc map. By setting the pour point to the right place you can delineate the drainage area for each of them and see how much came from the reservoir. On Wed, Feb 10, 2010 at 5:47 PM, Rich Shepard rshep...@appl-ecosys.com wrote: On Wed, 10 Feb 2010, Daniel Victoria wrote: In order for a basin to be delineated correctly, the pour point has to be in a high accumulation area (I once heard the expression synthetic river...) Daniel, Perhaps if I explain what I'm trying to do it will help everyone who's assisting me. There's a small parcel of land several hundred meters below a dam. On January 1, 2009, after almost 14 inches of rain in the past week (including 6.44 inches the day before), that property flooded, including the trailer house sitting there. This is the first flat spot below the dam (and the dam spillway operated properly); the creek is deeply incised with almost vertical walls below the dam. The bank on the other side from the property is higher so all the flooding was all on this one side. Of course, lower in the drainage basin flooding was more extensive (including a brand-new house that hasn't sold in two years because it was built on the floodplain.) What I want to show is where all that precipitation runoff came from, and that it's not all from the reservoir overflowing the spillway. Immediately west of the flooded property is a steep hill, so a lot of surface runoff came from there and augmented what was transported in the stream channel. Well, put your pour point on top of the accumulation map and see if it's on top of the river. If not, change your easting and northing coordinates appropriately. If you come from ArcGIS world, they have a tool called Snap Pour Point that does that. I recall doing something similar in grass using v.distance and a stream raster... The last time I used ARC/Info was 1989. :-) The pour point is on the stream channel. See the attached .png that I forgot to put on my response to Stephen. The topmost 'x' is the flooded property, the one below it is the center of the dam. Thanks, 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] Re: Defining Partial Drainage Basin
agreed- the lower point does not look like it is on the stream. On Wed, Feb 10, 2010 at 1:56 PM, Daniel Victoria daniel.victo...@gmail.com wrote: Looking at the PNG it does not look like any of the pour points are on the channel. It has to be exactly on top of the lines in the flowacc map. By setting the pour point to the right place you can delineate the drainage area for each of them and see how much came from the reservoir. On Wed, Feb 10, 2010 at 5:47 PM, Rich Shepard rshep...@appl-ecosys.com wrote: On Wed, 10 Feb 2010, Daniel Victoria wrote: In order for a basin to be delineated correctly, the pour point has to be in a high accumulation area (I once heard the expression synthetic river...) Daniel, Perhaps if I explain what I'm trying to do it will help everyone who's assisting me. There's a small parcel of land several hundred meters below a dam. On January 1, 2009, after almost 14 inches of rain in the past week (including 6.44 inches the day before), that property flooded, including the trailer house sitting there. This is the first flat spot below the dam (and the dam spillway operated properly); the creek is deeply incised with almost vertical walls below the dam. The bank on the other side from the property is higher so all the flooding was all on this one side. Of course, lower in the drainage basin flooding was more extensive (including a brand-new house that hasn't sold in two years because it was built on the floodplain.) What I want to show is where all that precipitation runoff came from, and that it's not all from the reservoir overflowing the spillway. Immediately west of the flooded property is a steep hill, so a lot of surface runoff came from there and augmented what was transported in the stream channel. Well, put your pour point on top of the accumulation map and see if it's on top of the river. If not, change your easting and northing coordinates appropriately. If you come from ArcGIS world, they have a tool called Snap Pour Point that does that. I recall doing something similar in grass using v.distance and a stream raster... The last time I used ARC/Info was 1989. :-) The pour point is on the stream channel. See the attached .png that I forgot to put on my response to Stephen. The topmost 'x' is the flooded property, the one below it is the center of the dam. Thanks, 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 -- Stephen Sefick Let's not spend our time and resources thinking about things that are so little or so large that all they really do for us is puff us up and make us feel like gods. We are mammals, and have not exhausted the annoying little problems of being mammals. -K. Mullis ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
On Wed, 10 Feb 2010, Daniel Victoria wrote: Looking at the PNG it does not look like any of the pour points are on the channel. It has to be exactly on top of the lines in the flowacc map. By setting the pour point to the right place you can delineate the drainage area for each of them and see how much came from the reservoir. Daniel, OK. I'll read the exact point adjacent to the x's and re-run the analysis. I'm reading the TNT tutorial now and will then get back to GRASS. ESRI docs after that. Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
The easiest way that I have found to snap a point to a stream is to use Qgis to edit the vector. hth, Stephen On Wed, Feb 10, 2010 at 2:04 PM, Rich Shepard rshep...@appl-ecosys.com wrote: On Wed, 10 Feb 2010, Daniel Victoria wrote: Looking at the PNG it does not look like any of the pour points are on the channel. It has to be exactly on top of the lines in the flowacc map. By setting the pour point to the right place you can delineate the drainage area for each of them and see how much came from the reservoir. Daniel, OK. I'll read the exact point adjacent to the x's and re-run the analysis. I'm reading the TNT tutorial now and will then get back to GRASS. ESRI docs after that. Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user -- Stephen Sefick Let's not spend our time and resources thinking about things that are so little or so large that all they really do for us is puff us up and make us feel like gods. We are mammals, and have not exhausted the annoying little problems of being mammals. -K. Mullis ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
Rich Shepard wrote: On Wed, 10 Feb 2010, Micha Silver wrote: A quick tip regarding r.water.outlet (you may have noticed this already) The module creates a new raster covering the whole analysis region with two possible values: 1 for all cells draining into the outlet, and 0 everywhere else. If you do r.to.vect straightaway, you?l get a vector containing two polygons... I always run r.null setnull=0 on the r.water.outlet result first. This insures that r.to.vect leaves you with just the drainage area. Micha, I'm under a deadline to finish the current project, and nothing seems to be working correctly for me. I just ran r.water.outlet using the drainage (aspect) map created by r.watershed. The output is a yellow rectangle that the legend tells me represents '0'; that is, there're no cells in the calculated basin. The r.water.outlet module takes two parameters: first is the drainage *direction* raster, which I usually create first with r.watershed, like: r.watershed elev=dem drain=flow_dir accum=flow_acc basin=basin stream=str thresh= (At this stage you can go and make popcorn...) Next I do r.thin on the streams raster, and convert the thinned raster to a line vector: r.thin str out=str_thin r.to.vect -s str_thin out=streams feature=line Now you need the pour point which, as others have made abundantly clear ( ;-) ), must be exactly on a stream line. So zoom in *very* close to the flooded house, and identify the X-Y coords on the stream just below the house. Now try: r.water.outlet drain=flow_dir basin=house_catchment east=xxx north=yyy And finally the above trick to get your final vector drainage basin with: r.null house_catchment setnull=0 and r.to.vect -s house_catchment out=house_catchment feature=area Good luck... g.region -p reports: projection: 99 (Lambert Conformal Conic) zone: 0 datum: nad83 ellipsoid: grs80 north: 1334420 south: 1279150 west: 769190 east: 819260 nsres: 10 ewres: 10 rows: 5527 cols: 5007 cells: 27673689 The command line was: r.water.outlet drain=aber10m.drain basin=lockie e=795542.95 n=1308323.52 --o I can send copies of aber10m.drain and lockie. It makes no sense to me that such a simple run fails to define the partial drainage basin. Any help or ideas you offer will be much appreciated. Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user -- Micha Silver Arava Development Co. +972-52-3665918 http://surfaces.co.il ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
On Wed, 10 Feb 2010, Micha Silver wrote: r.null house_catchment setnull=0 and r.to.vect -s house_catchment out=house_catchment feature=area Micha, I have the coordinates correct now. When I get the house_catchment map I want the area encluded. Haven't found how to calculate that; v.build? Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
Rich Shepard pisze: On Wed, 10 Feb 2010, Jarek Jasiewicz wrote: try to use r.stram.basins from add ons it has solevd thsese prooblems Ah! Will do. Thanks, Jarek. Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user see it before: http://grass.osgeo.org/wiki/R.stream.* in general tutorial is out of date, (you do not need to patch dir map now), there are much more posibilites than there ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
On Wed, 10 Feb 2010, Jarek Jasiewicz wrote: http://grass.osgeo.org/wiki/R.stream.* Jarek, Will r.stream.stats calculate the basin area for the two sub-catchments? I see the input parameters as the raster maps for streams, flow direction, and DEM. Doesn't seem to calculate the areas of the two vector polygons. Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
On Wed, 10 Feb 2010, Micha Silver wrote: r.to.vect -s house_catchment out=house_catchment feature=area Micha, This process worked flawlessly ... once I corrected slightly off coordinates for the dam point. The last step I need is a way to calculate the areas of these two partial basins. They have no attribute information other than a category number. I tried v.overlay (intersecting the two maps) thinking that would calculate the area of the smaller (b) map from that of the larger (a) map. Doesn't work that way. My next try is to set the region to each of these partial basins, one-by-one, then calculate the area by multiplying the number of cells by 100 (10x10m resolution) and converting that to acres. This does not seem sufficiently precise to calculate the difference in drainage areas. r.stream.stats does not appear to help because that's working on the raster maps and not the vector versions. Isn't there a way to calculate areas of the vectors produced by the r.water.outlet-to-vector process? Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
On Wed, 10 Feb 2010, Rich Shepard wrote: Isn't there a way to calculate areas of the vectors produced by the r.water.outlet-to-vector process? Of course there is, silly me: v.report. Works like a charm. Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
Rich Shepard pisze: On Wed, 10 Feb 2010, Jarek Jasiewicz wrote: http://grass.osgeo.org/wiki/R.stream.* Jarek, Will r.stream.stats calculate the basin area for the two sub-catchments? I see the input parameters as the raster maps for streams, flow direction, and DEM. Doesn't seem to calculate the areas of the two vector polygons. Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user every cachmenet you can calculate using v.to.db what=area for polygons ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: Defining Partial Drainage Basin
On 02/10/2010 12:32 AM, Rich Shepard wrote: On Tue, 9 Feb 2010, Rich Shepard wrote: I want to limit my analyses to that portion of the basin that drains into a specified location along the main creek. Which module will allow me to define a partial basin with this point as the outlet? Got it. r.water.outlet, after running r.watershed. A quick tip regarding r.water.outlet (you may have noticed this already) The module creates a new raster covering the whole analysis region with two possible values: 1 for all cells draining into the outlet, and 0 everywhere else. If you do r.to.vect straightaway, youĺl get a vector containing two polygons... I always run r.null setnull=0 on the r.water.outlet result first. This insures that r.to.vect leaves you with just the drainage area. BTW. is there a readily available source for learning how to interpret the output maps of these various terrain/hydrological modules? Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user -- Micha Silver http://www.surfaces.co.il/ Arava Development Co. +972-52-3665918 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
