Hydrological Sciences: Difference between revisions

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== Tutorials ==
* [[Creating watersheds]]
* [https://baharmon.github.io/watersheds-in-grass Watersheds in GRASS GIS] by Brendan Harmon
* [https://baharmon.github.io/hydrology-in-grass A tutorial on hydrological modeling and simulation in GRASS GIS] by Brendan Harmon
* [https://baharmon.github.io/flooding-in-grass Flooding in GRASS GIS] by Brendan Harmon
* [[R.basin]]
* [[R.stream.* modules]]
== Flow calculation ==
== Flow calculation ==


Line 6: Line 15:
* {{cmd|r.fill.dir}}: Filters and generates a depressionless elevation map and a flow direction map from a given elevation layer.
* {{cmd|r.fill.dir}}: Filters and generates a depressionless elevation map and a flow direction map from a given elevation layer.
* {{cmd|r.flow}}: Construction of slope curves (flowlines), flowpath lengths, and flowline densities (upslope areas) from a raster digital elevation model (DEM)
* {{cmd|r.flow}}: Construction of slope curves (flowlines), flowpath lengths, and flowline densities (upslope areas) from a raster digital elevation model (DEM)
* {{cmd|r.topidx}}: Creates topographic index [ln(a/tan(beta))] map from elevation map.
* {{cmd|r.topidx}}: Creates topographic index [ln(a/tan(beta))] map from elevation map (topographic wetness index).
* {{cmd|r.terraflow}}: Flow computation for massive grids.
* {{cmd|r.terraflow}}: Flow computation for massive grids.
* {{AddonCmd|v.breach}}: Creates vector maps of lines and points of continuosly lowering elevation down the input watercourses, based on the input raster DEM.
* {{AddonCmd|v.breach|version=64}}: Creates vector maps of lines and points of continuously lowering elevation down the input watercourses, based on the input raster DEM.
* {{AddonCmd|r.traveltime}}: Computes the travel time of surface runoff to an outlet.
* {{AddonCmd|r.traveltime}}: Computes the travel time of surface runoff to an outlet.
* {{AddonCmd|r.lfp}}: Calculates the longest flow path.
* {{AddonCmd|r.accumulate}}: Calculates weighted flow accumulation, stream networks, and the longest flow path using a flow direction map.


== Groundwater flow ==
== Groundwater flow ==
Line 15: Line 26:
* {{cmd|r.gwflow}}: Numerical calculation program for transient, confined and unconfined groundwater flow in two dimensions.
* {{cmd|r.gwflow}}: Numerical calculation program for transient, confined and unconfined groundwater flow in two dimensions.
* {{cmd|r3.gwflow}}: Numerical calculation program for transient, confined groundwater flow in three dimensions. See also [[Voxel]].
* {{cmd|r3.gwflow}}: Numerical calculation program for transient, confined groundwater flow in three dimensions. See also [[Voxel]].
Note: for the correct computation of tasks using {{cmd|r.gwflow}}, see the testsuite scripts [https://trac.osgeo.org/grass/browser/grass/trunk/raster/r.gwflow/testsuite/validation_7x7_grid.py validation_7x7_grid.py] and [https://trac.osgeo.org/grass/browser/grass/trunk/raster/r.gwflow/testsuite/validation_excavation.py validation_excavation.py]. Please be aware, that r.gwflow is a very simple groundwater computation tool. Many steps in groundwater modelling must be performed outside of r.gwflow, like calibration, temporally changing of boundary conditions, weather conditions and so on.
AGU Poster as an example: http://www.urbanmetabolism.asia/sites/default/files/mehta_etal_aguposter2_48x36_horz.pdf


== Hydrological models ==
== Hydrological models ==
* [https://www.itzi.org/ Itzï] -  a dynamic, fully distributed hydrologic and hydraulic model that simulates 2D surface flows on a regular raster grid using simplified shallow water equations. It uses GRASS GIS as a back-end for reading entry data and writing results.
* {{cmd|r.topmodel}}: Simulates TOPMODEL which is a physically based hydrological model.
* {{cmd|r.topmodel}}: Simulates TOPMODEL which is a physically based hydrological model.
** How to run r.topmodel: [http://geni.ath.cx/r.topmodel.html tutorial]
** How to run r.topmodel: [http://idea.isnew.info/r.topmodel.html tutorial]
* {{AddonCmd|HydroFOSS}}: A distributed, physically based hydrological model.
* [[GRASS_AddOns#HydroFOSS|HydroFOSS]]: A distributed, physically based hydrological model.
* [http://swatmodel.tamu.edu/software/swat-model/swat981-interfaces SWAT]: a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds.
* [http://swatmodel.tamu.edu/software/swat-model/swat981-interfaces SWAT]: a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds.
* [http://grass.osgeo.org/gdp/hydrology/ r.water.fea] is an interactive program that allows the user to simulate storm water runoff analysis using the finite element numerical technique. Infiltration is calculated using the Green and Ampt formulation. r.water.fea computes and draws hydrographs for every basin as well as at stream junctions in an analysis area. It also draws animation maps at the basin level. The software is available within GRASS 4.x/5.x.
* [http://grass.osgeo.org/gdp/hydrology/ r.water.fea] is an interactive program that allows the user to simulate storm water runoff analysis using the finite element numerical technique. Infiltration is calculated using the Green and Ampt formulation. r.water.fea computes and draws hydrographs for every basin as well as at stream junctions in an analysis area. It also draws animation maps at the basin level. The software is available within GRASS 4.x/5.x.
* {{AddonCmd|GIPE}}: The GRASS Image Processing Environment (GIPE) has USLE, Energy-balance and radiance-reflectance correction models. (r.hydro.CASC2D - a physically-based, distributed, raster hydrological model which simulates the hydrological response of a watershed subject to a given rainfall field - is temporarily here waiting to return to main GRASS)
* [[GRASS_AddOns#GIPE|GIPE]]: The GRASS Image Processing Environment (GIPE) has USLE, Energy-balance and radiance-reflectance correction models. (r.hydro.CASC2D - a physically-based, distributed, raster hydrological model which simulates the hydrological response of a watershed subject to a given rainfall field - is temporarily here waiting to return to main GRASS)


== Sediment modules ==
== Sediment modules ==
* {{cmd|r.sim.sediment}}: Sediment transport and erosion/deposition simulation using path sampling method (SIMWE)
* {{cmd|r.sim.sediment}}: Sediment transport and erosion/deposition simulation using path sampling method (SIMWE)
* {{cmd|r.sim.water}}: Overland flow hydrologic simulation using path sampling method (SIMWE)
 
== Solute transport ==
* {{cmd|r.solute.transport}}: Numerical calculation program for transient, confined and unconfined solute transport in two dimensions


== Stream modules ==
== Stream modules ==
Line 32: Line 50:
For an overview, see [[R.stream.*]].
For an overview, see [[R.stream.*]].


* {{AddonCmd|r.stream.angle}}: Route azimuth, direction and relation to streams of higher order
In GRASS 7/8+:
* {{AddonCmd|r.stream.basins}}: Calculate basins according user input
 
* {{AddonCmd|r.stream.del}}: Calculate basins according user input
* {{AddonCmd|r.stream.basins}}: Delineates basins according stream network.
* {{AddonCmd|r.stream.distance}}: Calculate distance to and elevation above streams and outlets according user input. It can work in stream mode where target are streams and outlets mode where targets are outlets
* {{AddonCmd|r.stream.channel}}: Calculates local parameters for individual streams.
* {{AddonCmd|r.stream.extract}}: Stream network extraction
* {{AddonCmd|r.stream.distance}}: Calculates distance to and elevation above streams and outlet.
* {{AddonCmd|r.stream.order}}: Calculate Strahler's and Horton's stream order Hack's main streams and Shreeve's stream magnitude. It uses r.watershed or r.stream.extract output files: stream, direction and optionally accumulation. Output data can be either from r.watershed or r.stream.extract but not from both together
* {{AddonCmd|r.stream.order}}: Calculates Strahler's and more streams hierarchy.
* {{AddonCmd|r.stream.pos}}: Route azimuth, direction and relation to streams of higher order
* {{AddonCmd|r.stream.segment}}: Divides network into near straight-line segments and calculate its order.  
* {{AddonCmd|r.stream.stats}}: Calculate Horton's and optionally Hack's statistics according to user input
* {{AddonCmd|r.stream.slope}}: Calculates local parameters for slope subsystem.  
* {{AddonCmd|r.stream.snap}}: Snap point to modelled stream network.
* {{AddonCmd|r.stream.stats}}: Calculates Horton's statistics for Strahler and Horton ordered networks created with r.stream.order.


Only available for GRASS 7:
In GRASS 6 (old stable):


* [http://svn.osgeo.org/grass/grass-addons/grass7/raster/r.stream/r.stream.channel/ r.stream.channel]: Calculate some local properties of the stream network. It is supplementary module for r.stream.order and r.stream.distance to investigate channel subsystem.
* {{AddonCmd|r.stream.angle|version=64}}: Route azimuth, direction and relation to streams of higher order.
* [http://svn.osgeo.org/grass/grass-addons/grass7/raster/r.stream/r.stream.segment/ r.stream.segment]: The module is designed to inverstigate network lineaments and calculate angle relations between tributaries and its major streams.  
* {{AddonCmd|r.stream.basins|version=64}}: Calculate basins according user input.
* [http://svn.osgeo.org/grass/grass-addons/grass7/raster/r.stream/r.stream.slope/ r.stream.slope]: Calculates the difference between elevation of current cell and downstream cell, gradient and max curvature on the basis of a flow direction map. It can be used to calculate the directional slope using a flow direction map.
* {{AddonCmd|r.stream.del|version=64}}:  Calculates downslope length of first order streams and delete them if it length (in pixels) is lower than the treeshold.
* [http://svn.osgeo.org/grass/grass-addons/grass7/raster/r.stream/r.stream.snap/ r.stream.snap]: is a supplementary module for r.stream.extract and r.stream.basins to correct position of outlets or stream initial points as they do not lie on the streamlines.
* {{AddonCmd|r.stream.distance|version=64}}: Calculate distance to and elevation above streams and outlets according user input. It can work in stream mode where target are streams and outlets mode where targets are outlets.
* {{AddonCmd|r.stream.extract|version=64}}: Stream network extraction. It produces a vector network with the direction of the vector lines corresponding to the flow direction.
* {{AddonCmd|r.stream.order|version=64}}: Calculate Strahler's and Horton's stream order Hack's main streams and Shreeve's stream magnitude. It uses r.watershed or r.stream.extract output files: stream, direction and optionally accumulation. Output data can be either from r.watershed or r.stream.extract but not from both together.
* {{AddonCmd|r.stream.pos|version=64}}: Route azimuth, direction and relation to streams of higher order.
* {{AddonCmd|r.stream.stats|version=64}}: Calculate Horton's and optionally Hack's statistics according to user input.


== Watershed modules ==
== Watershed modules ==


* {{cmd|r.basin.fill}}: Generates a raster map layer showing watershed subbasins.
* {{cmd|r.basins.fill}}: Generates a raster map layer showing watershed subbasins.
* {{cmd|r.water.outlet}}: Generates a watershed basin from a drainage direction map (from r.watershed) and a set of coordinates representing the outlet point of watershed.
* {{cmd|r.water.outlet}}: Generates a watershed basin from a drainage direction map (from r.watershed) and a set of coordinates representing the outlet point of watershed.
* {{cmd|r.watershed}}: Watershed basin analysis program.
* {{cmd|r.watershed}}: Watershed basin analysis program.
* {{cmd|r.lake}}: Fills a lake to a target water level from a given start point.
* {{cmd|r.lake}}: Fills a lake to a target water level from a given start point.
* {{AddonCmd|r.basin}}: Generates the main morphometric parameters of the basin. Here a [[R.basin|tutorial]]
* {{AddonCmd|r.basin}}: Generates the main morphometric parameters of the basin. Here a [[R.basin|tutorial]]
* {{AddonCmd|r.threshold}}: Finds a first tentative value of upslope area to be used as input to extract the river network using r.stream.extract or r.watershed.  
* {{AddonCmd|r.threshold}}: Finds a first tentative value of upslope area to be used as input to extract the river network using r.stream.extract or r.watershed.
* {{AddonCmd|r.hydrodem}}: Applies hydrological conditioning (sink removal) to a required input elevation map.




[[Image:Flowacc_nviz.png|center|thumb|640px|Flow accumulation with Multiple Flow Directions (using{{cmd|r.watershed}}, North Carolina sample dataset)]]
[[Image:Flowacc_nviz.png|center|thumb|640px|Flow accumulation with Multiple Flow Directions (using{{cmd|r.watershed}}, North Carolina sample dataset)]]


== Flooding areas ==
== Flooding areas ==


* {{AddonCmd|r.inund.fluv}}: Allows to obtain a fluvial potentially inundation map given a high-resolution DTM of the area surrounding the river and a water surface profile calculated through an 1-D hydrodinamic model.
* {{cmd|r.sim.water}}: Overland flow hydrologic simulation using path sampling method (SIMWE)
* [[AddOns/GRASS_6#r.inund.fluv|r.inund.fluv]]: Allows to obtain a fluvial potentially inundation map given a high-resolution DTM of the area surrounding the river and a water surface profile calculated through an 1-D hydrodinamic model.
* {{AddonCmd|r.hazard.flood}}:  Is an implementation of a fast procedure to detect flood prone areas. It may help in the delineation of flood prone areas especially in basins with marked topography. The use of the modified topographic index should not be considered as an alternative to standard hydrological-hydraulic simulations for flood mapping, but may represent a tool for a preliminary delineation of flooding areas.
* {{AddonCmd|r.hazard.flood}}:  Is an implementation of a fast procedure to detect flood prone areas. It may help in the delineation of flood prone areas especially in basins with marked topography. The use of the modified topographic index should not be considered as an alternative to standard hydrological-hydraulic simulations for flood mapping, but may represent a tool for a preliminary delineation of flooding areas.


== Tutorials ==
== User hints ==
 
=== Sink filling: why not needed in GRASS GIS ===
 
Traditionally, contour lines created by land surveying provided more detail than available DEMs. Nowadays (e.g., since SRTM of 2001), DEMs provide more detail than contour lines and contour lines are meanwhile derived from a DEM. Therefore creating a DEM from contour lines which (if in doubt) have been created using a DEM is no longer recommended, rather use any DEM instead.
 
'''Remarks on altering a DEM by filling sinks''':
 
The ArcGIS reference for sink filling is Goodchild and Mark (1987), ignoring the literature of the past 27+ years. According to the [http://resources.arcgis.com/en/help/main/10.1/index.html#//009z0000007m000000 ArcGIS 10 documentation, "The program assumes that all unidentified sinks are errors"].
 
Identified sinks are those supplied by the user. Unfortunately for ArcGIS, unidentified sinks are not errors but usually true terrain elevation, particularly in the year 1987 when LIDAR was not yet available and DEMs were derived from radar. That means that the elevation values surrounding sinks are erroneous rather than the sinks themselves. Two (of several) methods to deal with sinks in a more realistic way are the minimum impact approach of Lindsay & Creed (2005) which alters the DEM (implemented in GRASS as [http://svn.osgeo.org/grass/grass-addons/grass7/raster/r.hydrodem/ r.hydrodem] Addon) and {{cmd|r.watershed}} which does not alter the DEM.
 
In short, you should carefully choose your hydrological software (e.g., RiverTools/Whitebox/TauDEM/GRASS GIS).
 
== See also ==


* [[Creating watersheds]]
* [http://www.surfaces.co.il/flow-direction-from-grass-to-arcgis/  Flow Directions from GRASS to ArcGIS]
* [http://www.surfaces.co.il/?p=241 Watershed Analysis with GRASS]
* [[R.basin]]
* [[R.stream.*]]


== References ==
== References ==


* Bhowmik, AK, Metz, M. and Schäfer RB, 2014: Reproducible, Automated and Objective Stream Threshold Selection and Upstream Riparian Corridor Delineation from Digital Elevation Models  ([http://semanticommunity.info/@api/deki/files/30406/4321a043.pdf PDF])
* Metz, M. et al 2009: Fast Stream Extraction from Large, Radar-Based Elevation Models with Variable Level of Detail ([http://www.geomorphometry.org/system/files/metz2009geomorphometry.pdf PDF])
* Metz, M. et al 2009: Fast Stream Extraction from Large, Radar-Based Elevation Models with Variable Level of Detail ([http://www.geomorphometry.org/system/files/metz2009geomorphometry.pdf PDF])
* Metz, M. et al 2010: Accurate stream extraction from large, radar-based elevation models ([http://www.hydrol-earth-syst-sci-discuss.net/7/3213/2010/hessd-7-3213-2010.pdf PDF])
* Metz, M. et al 2010: Accurate stream extraction from large, radar-based elevation models ([http://www.hydrol-earth-syst-sci-discuss.net/7/3213/2010/hessd-7-3213-2010.pdf PDF])
* J Jasiewicz, M Metz, 2011: A new GRASS GIS toolkit for Hortonian analysis of drainage networks, Computers & Geosciences. [http://dx.doi.org/10.1016/j.cageo.2011.03.003 DOI]
* J Jasiewicz, M Metz, 2011: A new GRASS GIS toolkit for Hortonian analysis of drainage networks, Computers & Geosciences. [http://dx.doi.org/10.1016/j.cageo.2011.03.003 DOI]
* Di Leo M., Di Stefano M., Claps P., Sole A. Caratterizzazione morfometrica del bacino idrografico in GRASS GIS (Morphometric characterization of the catchment in GRASS GIS environment), Geomatics Workbooks n.9, 2010 (In Italian). ([http://geomatica.como.polimi.it/workbooks/n9/GW9-FOSS4Git_2010.pdf PDF]).  
* Di Leo M., Di Stefano M., Claps P., Sole A., Caratterizzazione morfometrica del bacino idrografico in GRASS GIS, Geomatics Workbooks n.9, 2010 (89-100). ([http://geomatica.como.polimi.it/workbooks/n9/GW9-FOSS4Git_2010.pdf PDF]). (In Italian)
 
* Di Leo M., Manfreda S., Fiorentino M., An automated procedure for the detection of flood prone areas: r.hazard.flood, Geomatics Workbooks n.10, 2011 (83-89). ([http://geomatica.como.polimi.it/workbooks/n10/GW10-FOSS4Git_2011.pdf PDF]).
* Manfreda S., Di Leo M., Sole A., 2011: Detection of Flood Prone Areas using Digital Elevation Models, Journal of Hydrologic Engineering, (10.1061/(ASCE)HE.1943-5584.0000367).


[[Category: Applications]]
[[Category: Applications]]
[[Category: Documentation]]
[[Category: Documentation]]
[[Category: Hydrology]]
[[Category: Hydrology]]

Latest revision as of 16:47, 1 March 2024

Tutorials

Flow calculation

  • r.carve: Takes vector stream data, transforms it to raster and subtracts depth from the output DEM.
  • r.drain: Traces a flow through an elevation model on a raster map.
  • r.fillnulls: Fills no-data areas in raster maps using v.surf.rst splines interpolation
  • r.fill.dir: Filters and generates a depressionless elevation map and a flow direction map from a given elevation layer.
  • r.flow: Construction of slope curves (flowlines), flowpath lengths, and flowline densities (upslope areas) from a raster digital elevation model (DEM)
  • r.topidx: Creates topographic index [ln(a/tan(beta))] map from elevation map (topographic wetness index).
  • r.terraflow: Flow computation for massive grids.
  • v.breach: Creates vector maps of lines and points of continuously lowering elevation down the input watercourses, based on the input raster DEM.
  • r.traveltime: Computes the travel time of surface runoff to an outlet.
  • r.lfp: Calculates the longest flow path.
  • r.accumulate: Calculates weighted flow accumulation, stream networks, and the longest flow path using a flow direction map.

Groundwater flow

  • r.gwflow: Numerical calculation program for transient, confined and unconfined groundwater flow in two dimensions.
  • r3.gwflow: Numerical calculation program for transient, confined groundwater flow in three dimensions. See also Voxel.

Note: for the correct computation of tasks using r.gwflow, see the testsuite scripts validation_7x7_grid.py and validation_excavation.py. Please be aware, that r.gwflow is a very simple groundwater computation tool. Many steps in groundwater modelling must be performed outside of r.gwflow, like calibration, temporally changing of boundary conditions, weather conditions and so on.

AGU Poster as an example: http://www.urbanmetabolism.asia/sites/default/files/mehta_etal_aguposter2_48x36_horz.pdf

Hydrological models

  • Itzï - a dynamic, fully distributed hydrologic and hydraulic model that simulates 2D surface flows on a regular raster grid using simplified shallow water equations. It uses GRASS GIS as a back-end for reading entry data and writing results.
  • r.topmodel: Simulates TOPMODEL which is a physically based hydrological model.
  • HydroFOSS: A distributed, physically based hydrological model.
  • SWAT: a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds.
  • r.water.fea is an interactive program that allows the user to simulate storm water runoff analysis using the finite element numerical technique. Infiltration is calculated using the Green and Ampt formulation. r.water.fea computes and draws hydrographs for every basin as well as at stream junctions in an analysis area. It also draws animation maps at the basin level. The software is available within GRASS 4.x/5.x.
  • GIPE: The GRASS Image Processing Environment (GIPE) has USLE, Energy-balance and radiance-reflectance correction models. (r.hydro.CASC2D - a physically-based, distributed, raster hydrological model which simulates the hydrological response of a watershed subject to a given rainfall field - is temporarily here waiting to return to main GRASS)

Sediment modules

  • r.sim.sediment: Sediment transport and erosion/deposition simulation using path sampling method (SIMWE)

Solute transport

  • r.solute.transport: Numerical calculation program for transient, confined and unconfined solute transport in two dimensions

Stream modules

For an overview, see R.stream.*.

In GRASS 7/8+:

  • r.stream.basins: Delineates basins according stream network.
  • r.stream.channel: Calculates local parameters for individual streams.
  • r.stream.distance: Calculates distance to and elevation above streams and outlet.
  • r.stream.order: Calculates Strahler's and more streams hierarchy.
  • r.stream.segment: Divides network into near straight-line segments and calculate its order.
  • r.stream.slope: Calculates local parameters for slope subsystem.
  • r.stream.snap: Snap point to modelled stream network.
  • r.stream.stats: Calculates Horton's statistics for Strahler and Horton ordered networks created with r.stream.order.

In GRASS 6 (old stable):

  • r.stream.angle: Route azimuth, direction and relation to streams of higher order.
  • r.stream.basins: Calculate basins according user input.
  • r.stream.del: Calculates downslope length of first order streams and delete them if it length (in pixels) is lower than the treeshold.
  • r.stream.distance: Calculate distance to and elevation above streams and outlets according user input. It can work in stream mode where target are streams and outlets mode where targets are outlets.
  • r.stream.extract: Stream network extraction. It produces a vector network with the direction of the vector lines corresponding to the flow direction.
  • r.stream.order: Calculate Strahler's and Horton's stream order Hack's main streams and Shreeve's stream magnitude. It uses r.watershed or r.stream.extract output files: stream, direction and optionally accumulation. Output data can be either from r.watershed or r.stream.extract but not from both together.
  • r.stream.pos: Route azimuth, direction and relation to streams of higher order.
  • r.stream.stats: Calculate Horton's and optionally Hack's statistics according to user input.

Watershed modules

  • r.basins.fill: Generates a raster map layer showing watershed subbasins.
  • r.water.outlet: Generates a watershed basin from a drainage direction map (from r.watershed) and a set of coordinates representing the outlet point of watershed.
  • r.watershed: Watershed basin analysis program.
  • r.lake: Fills a lake to a target water level from a given start point.
  • r.basin: Generates the main morphometric parameters of the basin. Here a tutorial
  • r.threshold: Finds a first tentative value of upslope area to be used as input to extract the river network using r.stream.extract or r.watershed.
  • r.hydrodem: Applies hydrological conditioning (sink removal) to a required input elevation map.


Flow accumulation with Multiple Flow Directions (usingr.watershed, North Carolina sample dataset)

Flooding areas

  • r.sim.water: Overland flow hydrologic simulation using path sampling method (SIMWE)
  • r.inund.fluv: Allows to obtain a fluvial potentially inundation map given a high-resolution DTM of the area surrounding the river and a water surface profile calculated through an 1-D hydrodinamic model.
  • r.hazard.flood: Is an implementation of a fast procedure to detect flood prone areas. It may help in the delineation of flood prone areas especially in basins with marked topography. The use of the modified topographic index should not be considered as an alternative to standard hydrological-hydraulic simulations for flood mapping, but may represent a tool for a preliminary delineation of flooding areas.

User hints

Sink filling: why not needed in GRASS GIS

Traditionally, contour lines created by land surveying provided more detail than available DEMs. Nowadays (e.g., since SRTM of 2001), DEMs provide more detail than contour lines and contour lines are meanwhile derived from a DEM. Therefore creating a DEM from contour lines which (if in doubt) have been created using a DEM is no longer recommended, rather use any DEM instead.

Remarks on altering a DEM by filling sinks:

The ArcGIS reference for sink filling is Goodchild and Mark (1987), ignoring the literature of the past 27+ years. According to the ArcGIS 10 documentation, "The program assumes that all unidentified sinks are errors".

Identified sinks are those supplied by the user. Unfortunately for ArcGIS, unidentified sinks are not errors but usually true terrain elevation, particularly in the year 1987 when LIDAR was not yet available and DEMs were derived from radar. That means that the elevation values surrounding sinks are erroneous rather than the sinks themselves. Two (of several) methods to deal with sinks in a more realistic way are the minimum impact approach of Lindsay & Creed (2005) which alters the DEM (implemented in GRASS as r.hydrodem Addon) and r.watershed which does not alter the DEM.

In short, you should carefully choose your hydrological software (e.g., RiverTools/Whitebox/TauDEM/GRASS GIS).

See also

References

  • Bhowmik, AK, Metz, M. and Schäfer RB, 2014: Reproducible, Automated and Objective Stream Threshold Selection and Upstream Riparian Corridor Delineation from Digital Elevation Models (PDF)
  • Metz, M. et al 2009: Fast Stream Extraction from Large, Radar-Based Elevation Models with Variable Level of Detail (PDF)
  • Metz, M. et al 2010: Accurate stream extraction from large, radar-based elevation models (PDF)
  • J Jasiewicz, M Metz, 2011: A new GRASS GIS toolkit for Hortonian analysis of drainage networks, Computers & Geosciences. DOI
  • Di Leo M., Di Stefano M., Claps P., Sole A., Caratterizzazione morfometrica del bacino idrografico in GRASS GIS, Geomatics Workbooks n.9, 2010 (89-100). (PDF). (In Italian)
  • Di Leo M., Manfreda S., Fiorentino M., An automated procedure for the detection of flood prone areas: r.hazard.flood, Geomatics Workbooks n.10, 2011 (83-89). (PDF).
  • Manfreda S., Di Leo M., Sole A., 2011: Detection of Flood Prone Areas using Digital Elevation Models, Journal of Hydrologic Engineering, (10.1061/(ASCE)HE.1943-5584.0000367).